Experimental Analysis on Sinking Time of Littoral Submarine
in Various Trim Angle
Luhut Tumpal Parulian SINAGA1,a*
1Senior Researcher at PTRIM, BPPT Laboratorium Hydrodinamika Indonesia, Surabaya
[email protected]
*corresponding author
Keyword: Littoral submarine, dive, sink, experiment.
Abstract. A submarine must conform to Archimedes’ Principle, which states that a body immersed
in a fluid has an upward force on it (buoyancy) equal to the weight of the displaced fluid,
(displacement). Submarines are ships capable of being submerged. The history of submarines and
their operation have largely revolved around being able to alter the density of the vessel so that it
may dive below the surface, maintain a depth, and return to the surface as needed. The way modern
submarines accomplish this task is to bring in and remove water from tanks in the submarine called
ballast tanks. Ballast tanks fit into two categories: those used for major adjustment of mass (main
ballast tanks); and those used for minor adjustments (trim tanks). The effect of each tank is plotted
and this is compared with the changes in mass and trimming moment possible during operations
using a trim polygon to determine whether the ballast tanks are adequate. On the water surface,
metacentric height (GM) is important, whereas below the surface it is the distance between the
centre of buoyancy and the centre of gravity (BG) which governs the transverse stability of a
submarine.
Introduction
A submarine or a ship can float because the weight of water that it displaces is equal to the
weight of the ship. This displacement of water creates an upward force called the buoyant force and
acts opposite to gravity, which would pull the ship down. Unlike a ship, a submarine can control its
buoyancy, thus allowing it to sink and surface at will [1].
As with any object in a fluid, a submarine must conform to Archimedes’ Principle, which states
that a body immersed in a fluid has an upward force on it (buoyancy) equal to the weight of the
displaced fluid, (displacement). This applies whether the submarine is floating on the water surface,
or deeply submerged [2, 3].
To control its buoyancy, the submarine has ballast tanks and auxiliary, or trim tanks, that can be
alternately filled with water or air (see Fig. 1). When the submarine is on the surface, the ballast
tanks are filled with air and the submarine's overall density is less than that of the surrounding
water. As the submarine dives, the ballast tanks are flooded with water and the air in the ballast
tanks is vented from the submarine until its overall density is greater than the surrounding water and
the submarine begins to sink (negative buoyancy) [4, 5].
A supply of compressed air is maintained aboard the submarine in air flasks for life support and
for use with the ballast tanks. In addition, the submarine has movable sets of short "wings" called
hydroplanes on the stern (back) that help to.
In view of the desire to prevent vessel grounding at port and channel entry thus, maintaining
ship’s continued trading, this research work presents how Maximum squats and the remaining under-keel
clearances can be predictedfor two vessel categories (Container and General Cargo) along two prominent
channels (BONNY ACCESS and the BONNY TO ONNE JUNCTION) in Nigeria using empirical models
developed for maximum squat in the open water and confined channels conditions. The results obtained show
that maximum squat increase with increasing vessel speed as the ratio of water depth to vessel draft (H/T)
reduces for any particular channel or vessel. However, an opposite trend was observed with the remaining
under-keel-clearances as they zero up and even cross to negatives, indicating vessel grounding; both of which
agree with the results of previous researchers. Further analysis revealed that for optimal vessel safety the
cruising speed within these channels should be between 0.5 knots to 5knots for the open water conditions,(H/T
between1.10 -1.40),investigated. Hence, if pilots should cruise at the speed limit for the critical H/T ratio where
the remaining under-keel clearance is not lower than the channel designed minimum, safety is guaranteed along
either channel even with changing depths.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
This work presents hydrodynamic characterization and comparative analysis of high speed crafts
(HSCs). HSCs performance characterizing is a serious concern to Hydrodynamicists because of the wide
variation of total resistance with hull-form, trim, draft and speed. Conversely, these parameters are not duly
analyzed during design due to inadequate theories. Therefore, this research investigates total resistance, wetted
surface and effective trim of four different HSC hull-forms. An interactive computer-program is developed based
on Savitsky and CAHI algorithms, and the results compared against test-data. The analysis correctly predicts
quantitatively the resistances of the four hull-forms at high speeds but with some discrepancies at speeds below
12 knots. The average standard-deviation for resistance predictions by CAHI = 4.69 kN and Savitsky= 6.13 KN.
Also, the results indicate that the transition from bow-wetting to full-planing occurs at 12 knots, and beyond
which the effective trim is fairly constant. Again, the wetted length-beam ratio (λm) drops rapidly from bowwetting
speeds to a plateau at speeds >12knot where hydrodynamic lift prevails. Standard-deviations of λm by
Savitsky’s and CAHI are 1.07 and 1.41, respectively. In conclusion, model-predictors are reasonably in good
agreement with measurement.
In view of the desire to prevent vessel grounding at port and channel entry thus, maintaining
ship’s continued trading, this research work presents how Maximum squats and the remaining under-keel
clearances can be predictedfor two vessel categories (Container and General Cargo) along two prominent
channels (BONNY ACCESS and the BONNY TO ONNE JUNCTION) in Nigeria using empirical models
developed for maximum squat in the open water and confined channels conditions. The results obtained show
that maximum squat increase with increasing vessel speed as the ratio of water depth to vessel draft (H/T)
reduces for any particular channel or vessel. However, an opposite trend was observed with the remaining
under-keel-clearances as they zero up and even cross to negatives, indicating vessel grounding; both of which
agree with the results of previous researchers. Further analysis revealed that for optimal vessel safety the
cruising speed within these channels should be between 0.5 knots to 5knots for the open water conditions,(H/T
between1.10 -1.40),investigated. Hence, if pilots should cruise at the speed limit for the critical H/T ratio where
the remaining under-keel clearance is not lower than the channel designed minimum, safety is guaranteed along
either channel even with changing depths.
Welcome to International Journal of Engineering Research and Development (IJERD)IJERD Editor
journal publishing, how to publish research paper, Call For research paper, international journal, publishing a paper, IJERD, journal of science and technology, how to get a research paper published, publishing a paper, publishing of journal, publishing of research paper, reserach and review articles, IJERD Journal, How to publish your research paper, publish research paper, open access engineering journal, Engineering journal, Mathemetics journal, Physics journal, Chemistry journal, Computer Engineering, Computer Science journal, how to submit your paper, peer reviw journal, indexed journal, reserach and review articles, engineering journal, www.ijerd.com, research journals,
yahoo journals, bing journals, International Journal of Engineering Research and Development, google journals, hard copy of journal
This work presents hydrodynamic characterization and comparative analysis of high speed crafts
(HSCs). HSCs performance characterizing is a serious concern to Hydrodynamicists because of the wide
variation of total resistance with hull-form, trim, draft and speed. Conversely, these parameters are not duly
analyzed during design due to inadequate theories. Therefore, this research investigates total resistance, wetted
surface and effective trim of four different HSC hull-forms. An interactive computer-program is developed based
on Savitsky and CAHI algorithms, and the results compared against test-data. The analysis correctly predicts
quantitatively the resistances of the four hull-forms at high speeds but with some discrepancies at speeds below
12 knots. The average standard-deviation for resistance predictions by CAHI = 4.69 kN and Savitsky= 6.13 KN.
Also, the results indicate that the transition from bow-wetting to full-planing occurs at 12 knots, and beyond
which the effective trim is fairly constant. Again, the wetted length-beam ratio (λm) drops rapidly from bowwetting
speeds to a plateau at speeds >12knot where hydrodynamic lift prevails. Standard-deviations of λm by
Savitsky’s and CAHI are 1.07 and 1.41, respectively. In conclusion, model-predictors are reasonably in good
agreement with measurement.
Time History Analysis of Circular and Rectangular Elevated Water Storage Tank...Dr. Amarjeet Singh
In the world, there are large number of storage tanks which are used as water and oil storage facilities. Elevated water tank is one of the most important structures in earthquake event. As known from very upsetting experiences, elevated water tanks were heavily damaged or collapsed during earthquake Hence different configurations of liquid storage tanks have been constructed. Water tanks are play an important role in municipal water supply and firefighting systems. Due to post earthquake useful desires, seismic safety of water tanks is most important. In the current study time history analysis of rectangular and circular elevated water storage tank were analyzed using SAP 2000 software. In this study the concrete baffle wall was used to reduce sloshing effect of the water tank. The tank responses such as maximum nodal displacement, base shear and result were compared for empty and full tank water fill condition. From IS 11682:1985provision when seismic loading is considered only two cases may be taken one is tank empty condition and other is tank full condition. Finally, study discloses the importance of suitable supporting baffle wall to remain withstand against heavy damages of circular and rectangular elevated water tanks during earthquake. As per IITK-GSDMA guidelines for seismic design of liquid storage tanks, hydrodynamic pressure for impulsive and convective mode was calculated.
Diving and propulsion system of modern diesel-electric submarineALWYN ARJUN ANTONY
The objective of the project was to identify the various components and necessary calculations involved in diving and propulsion of a modern diesel-electric submarine. An analysis was done on a model submarine to verify the resistance, powering and propulsive efficiency of the vessel.
Analysis of The Propulsion System Towards The Speed Reduction of Vessels Type...IJERA Editor
(PC-43) is an Indonesian navy vessel type limited patrol craft made in Indonesian. The vessel was designed using a steel material with a maximum speed of 27 knots and using engine power by 3 x 1800 HP, T = 1.40 at the empty draft and T = 1.70 at full draft. The speed is decreased in the current conditions by 22 knots at 1.50 meters draft within 1 year after its launching. This fact is very interesting to be used as a paper project by analyzing the effect of changes in vessel’s draft to the resistance and analyze the current installed engine power, This paper carried two methods of calculation, namely: resistance and power calculation numerically along with resistance and power calculation using software maxsurf. The results from the manual calculations of power at T = 1.65 meters in 27 knots, the power needed is BHPscr = 4245.04 HP. From the data of power installed in the vessel, it was stated that the power is 3 x 1800 = 5400 HP, means a mathematical/theoretical speed of 27 knots can be achieved. Thus, the resistance and power is not one of the causes of speed reduction in Vessel Type PC- 43.
In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion).
Strictly speaking, the liquid must have a free surface to constitute a slosh dynamics problem, where the dynamics of the liquid can interact with the container to alter the system dynamics significantly. Liquid sloshing strongly influences the directional dynamics and safety performance of highway tank vehicles in a highly adverse manner. Hydrodynamic forces and moments arising from liquid cargo oscillations in the tank under steering and/or braking maneuvers reduce the stability limit and controllability of partially-filled tank vehicles. Anti-slosh devices such as baffles are widely used in order to limit the adverse liquid slosh effect on directional performance and stability of the tank vehicles.
Propeller cavitation is a major problem in ship operation and the costs of repair and maintenance is high for ship-owners. Proper design of propeller plays a very important role in life cycle and the performance of a vessel. The use of simulation to observe various parameters that affect cavitations can be helpful to optimize propeller performance. This project designs and simulates cavitations flow of a Kaplan series, Fixed Pitch Propeller (FPP) of a 48-metres Multipurpose Deck Ship at 11 knots. Simulation test was carried out for laminar and turbulent flow using Computational Fluid Dynamics (CFD) approach to observe cavitations occurrence at selected radius. The parameters considered are pitch angle, angle of attack, viscosity of sea water, operating vapour pressure in the sea water, engine power, lift and drag vectors of each of the blade sections, and resultant velocity of the fluid flow. Comparison of performance is made and it compares well with the theory. Thrust coefficient (KT), torque coefficient (KQ), thrust (T), advance coefficient (J), and cavitations number (σ), were calculated to deduce efficiency and validate the model. The study can be used to build a prototype physical model that could be beneficial for future additional experimentation investigation.
Key words: Simulation, cavitation, performance, propeller, CFD
Review on Design Optimization of Liquid Carrier Tanker for Reduction of Slosh...IOSR Journals
Abstract: This Paper Reviews Briefly The Current Research On Sloshing And Its Effect In Liquid Carrier
Tanker. The Aim Of This Paper To Study The Basics Of Sloshing And Its Prevention (Mainly In Liquid Carrier
Tanker) The Liquid Sloshing Is Free Surface Fluctuation Of Liquid When Its Container Is Excited By External
Vibrations Such As Earthquakes. The Liquid Sloshing May Cause Various Engineering Problem, For Example
Instability Of Ships In Aero Engineering And Ocean Engineering, Failures On Structural Systems Of The
Liquid Container. The Tanker Used For The Transportation Of Liquid Over The Road-Ways Is An Integral
Part Of The Carrier/Vehicle. The Tanker Is Expected To Withstand The Unbalanced Forces On Account Of
Transit Over Uneven And Irregular Surfaces/Contours Of The Road As Also Due To Sudden Acceleration Or
Deceleration (Due To Application Of Brakes).
Keywords-Sloshing, Impact, Baffle, Simulation
It is hard to imagine how far we would be if we had just listen to the true masters of the Game Kaj Lavender & Jens Kappel these 2 men would have saved our world and oceans, here is just one of Oskar's examples his is Kajs son, SeaBus was and is so real it is truly a question of treason ..!
Development of a floating tow body for shallow water bottom and sub bottom im...eSAT Journals
Abstract
A floating tow body which can be towed at a speed range of 2-6 knots with a pay load of 50 kg is designed and tested as part of the development of a Buried Object Location Sonar (BOLS) for shallow water imaging application. In this paper the results of extensive towing tank measurements of a floating tow body with the diamond and a cross shaped bow are presented and compared. A cross shaped bow with a stream lined body shape is adopted for the floating tow body for minimizing the drag as well as the turbulence during the tow. Both the bow shape as well as the dimensions of the body is optimized based on the towing tank experimental results so that the body can be towed smoothly with minimum turbulence to avoid acoustic noise generation during the SONAR tests. An iterative experimental procedure is carried out in finalizing the dimensions and the shape of the tow body.
Keywords: Floating tow body, bow shape, towing test.
Comparative Study on Dynamic Analysis of Elevated Water Tank Frame Staging an...IOSRJMCE
This paper presents comparative study of elevated water tanks subjected to dynamic loading supported on RC framed structure and concrete shaft structure with different capacities and placed in different seismic zones. History of earthquake reveals that it have caused numerous losses to the life of people in its active time, and also post earthquake time have let people suffer due to damages caused to the public utility services. Either in urban or rural areas elevated water tanks forms integral part of water supply scheme, so its functionality pre and post earthquake remains equally important. These events showed that importance of supporting system is uncompromising for elevated tank as compared to any other type of tank. Damages caused are the results of unsuitable design of supporting system; wrong selection of supporting system, etc. These structures have heavy mass concentrated at the top of slender supporting system hence these structures are especially vulnerable to horizontal forces due to earthquakes. This paper presents the dynamic analysis of elevated water tanks with respect to the latest IS code published for liquid retaining structures by Bureau of Indian Standards i.e. IS 1893 (Part 2) : 2014. Comparison of elevated tanks with different supporting system, capacities and seismic zones states that these parameters may considerably change the seismic behaviour of tanks.
FIN 336 Milestone Two Guidelines and Rubric Economic Envir.docxnealwaters20034
FIN 336 Milestone Two Guidelines and Rubric
Economic Environments and Risk Mitigation
Overview: This milestone will help you complete Sections II and III of the final project.
Prompt: Develop a report that analyzes one company’s approach to multinational expansion. Include financial factors such as economic environments and
market conditions, risk mitigation strategies, and ethical and legal practices.
Specifically, the following critical elements must be addressed:
II. Economic Environments and Market Conditions
C. Explain the role of international financial markets and institutions in global environments in evaluating their impact on the company’s risk
management strategies.
D. Analyze impacts of exchange rate on the company’s performance for determining if a loss occurred because of fluctuations or devaluations of
foreign currencies. Provide examples from the past year to support your claims.
III. Risk Mitigation: Examine sources of risk and risk reduction methods available to multinational corporations. Use the 2007–2008 annual report and the
most current annual report to support responses in this section.
B. Discuss risks and financial factors associated with exchange rates and interest rates for assessing how they inform the company’s financial
management approaches.
C. Discuss diversification in the company’s expansion model for examining advantages or disadvantages, and provide examples and financial
information from the past year to support claims.
D. Discuss company strategies before and after the 2007–2008 crisis for determining possible reasons for the company’s current financial
performance. Provide examples to support your claims.
Rubric
Guidelines for Submission: Your paper must be submitted as a 1- to 2-page Microsoft Word document with double spacing, 12-point Times New Roman font,
and one-inch margins. Cite appropriate academic references as necessary.
Critical Elements Proficient (100%) Needs Improvement (75%) Not Evident (0%) Value
Economic
Environments and
Market Conditions:
Financial Markets
and Institutions
Explains the role of international financial
markets and institutions in global
environments in evaluating their impact on
the company’s risk management strategies
Explains the role of international financial
markets and institutions in global
environments in evaluating their impact on
the company’s risk management strategies,
but explanation is cursory, illogical, or
missing key elements
Does not explain the role of international
financial markets and institutions in global
environments
18
Critical Elements Proficient (100%) Needs Improvement (75%) Not Evident (0%) Value
Economic
Environments and
Market Conditions:
Impacts of Exchange
Rate
Analyzes impacts of exchange rate on the
company’s performance for determining if a
loss occurred because of fluctuations or
devaluations of foreign currencies, and
provides examples from .
files may help with writing paperEvaluation Essay Topic Sho.docxnealwaters20034
files may help with writing paper
Evaluation Essay Topic: Should world leaders use a pandemic crisis brought about by a killer virus to boost their own popularity?
Write a 1.5-2-page Evaluation Argument Essay in response the assigned topic. (Note: Write essay in third person.
DO NOT USE
“I,” “me,” “my,” “we,” “our,” “you,” or “your”).
.
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Time History Analysis of Circular and Rectangular Elevated Water Storage Tank...Dr. Amarjeet Singh
In the world, there are large number of storage tanks which are used as water and oil storage facilities. Elevated water tank is one of the most important structures in earthquake event. As known from very upsetting experiences, elevated water tanks were heavily damaged or collapsed during earthquake Hence different configurations of liquid storage tanks have been constructed. Water tanks are play an important role in municipal water supply and firefighting systems. Due to post earthquake useful desires, seismic safety of water tanks is most important. In the current study time history analysis of rectangular and circular elevated water storage tank were analyzed using SAP 2000 software. In this study the concrete baffle wall was used to reduce sloshing effect of the water tank. The tank responses such as maximum nodal displacement, base shear and result were compared for empty and full tank water fill condition. From IS 11682:1985provision when seismic loading is considered only two cases may be taken one is tank empty condition and other is tank full condition. Finally, study discloses the importance of suitable supporting baffle wall to remain withstand against heavy damages of circular and rectangular elevated water tanks during earthquake. As per IITK-GSDMA guidelines for seismic design of liquid storage tanks, hydrodynamic pressure for impulsive and convective mode was calculated.
Diving and propulsion system of modern diesel-electric submarineALWYN ARJUN ANTONY
The objective of the project was to identify the various components and necessary calculations involved in diving and propulsion of a modern diesel-electric submarine. An analysis was done on a model submarine to verify the resistance, powering and propulsive efficiency of the vessel.
Analysis of The Propulsion System Towards The Speed Reduction of Vessels Type...IJERA Editor
(PC-43) is an Indonesian navy vessel type limited patrol craft made in Indonesian. The vessel was designed using a steel material with a maximum speed of 27 knots and using engine power by 3 x 1800 HP, T = 1.40 at the empty draft and T = 1.70 at full draft. The speed is decreased in the current conditions by 22 knots at 1.50 meters draft within 1 year after its launching. This fact is very interesting to be used as a paper project by analyzing the effect of changes in vessel’s draft to the resistance and analyze the current installed engine power, This paper carried two methods of calculation, namely: resistance and power calculation numerically along with resistance and power calculation using software maxsurf. The results from the manual calculations of power at T = 1.65 meters in 27 knots, the power needed is BHPscr = 4245.04 HP. From the data of power installed in the vessel, it was stated that the power is 3 x 1800 = 5400 HP, means a mathematical/theoretical speed of 27 knots can be achieved. Thus, the resistance and power is not one of the causes of speed reduction in Vessel Type PC- 43.
In fluid dynamics, slosh refers to the movement of liquid inside another object (which is, typically, also undergoing motion).
Strictly speaking, the liquid must have a free surface to constitute a slosh dynamics problem, where the dynamics of the liquid can interact with the container to alter the system dynamics significantly. Liquid sloshing strongly influences the directional dynamics and safety performance of highway tank vehicles in a highly adverse manner. Hydrodynamic forces and moments arising from liquid cargo oscillations in the tank under steering and/or braking maneuvers reduce the stability limit and controllability of partially-filled tank vehicles. Anti-slosh devices such as baffles are widely used in order to limit the adverse liquid slosh effect on directional performance and stability of the tank vehicles.
Propeller cavitation is a major problem in ship operation and the costs of repair and maintenance is high for ship-owners. Proper design of propeller plays a very important role in life cycle and the performance of a vessel. The use of simulation to observe various parameters that affect cavitations can be helpful to optimize propeller performance. This project designs and simulates cavitations flow of a Kaplan series, Fixed Pitch Propeller (FPP) of a 48-metres Multipurpose Deck Ship at 11 knots. Simulation test was carried out for laminar and turbulent flow using Computational Fluid Dynamics (CFD) approach to observe cavitations occurrence at selected radius. The parameters considered are pitch angle, angle of attack, viscosity of sea water, operating vapour pressure in the sea water, engine power, lift and drag vectors of each of the blade sections, and resultant velocity of the fluid flow. Comparison of performance is made and it compares well with the theory. Thrust coefficient (KT), torque coefficient (KQ), thrust (T), advance coefficient (J), and cavitations number (σ), were calculated to deduce efficiency and validate the model. The study can be used to build a prototype physical model that could be beneficial for future additional experimentation investigation.
Key words: Simulation, cavitation, performance, propeller, CFD
Review on Design Optimization of Liquid Carrier Tanker for Reduction of Slosh...IOSR Journals
Abstract: This Paper Reviews Briefly The Current Research On Sloshing And Its Effect In Liquid Carrier
Tanker. The Aim Of This Paper To Study The Basics Of Sloshing And Its Prevention (Mainly In Liquid Carrier
Tanker) The Liquid Sloshing Is Free Surface Fluctuation Of Liquid When Its Container Is Excited By External
Vibrations Such As Earthquakes. The Liquid Sloshing May Cause Various Engineering Problem, For Example
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Liquid Container. The Tanker Used For The Transportation Of Liquid Over The Road-Ways Is An Integral
Part Of The Carrier/Vehicle. The Tanker Is Expected To Withstand The Unbalanced Forces On Account Of
Transit Over Uneven And Irregular Surfaces/Contours Of The Road As Also Due To Sudden Acceleration Or
Deceleration (Due To Application Of Brakes).
Keywords-Sloshing, Impact, Baffle, Simulation
It is hard to imagine how far we would be if we had just listen to the true masters of the Game Kaj Lavender & Jens Kappel these 2 men would have saved our world and oceans, here is just one of Oskar's examples his is Kajs son, SeaBus was and is so real it is truly a question of treason ..!
Development of a floating tow body for shallow water bottom and sub bottom im...eSAT Journals
Abstract
A floating tow body which can be towed at a speed range of 2-6 knots with a pay load of 50 kg is designed and tested as part of the development of a Buried Object Location Sonar (BOLS) for shallow water imaging application. In this paper the results of extensive towing tank measurements of a floating tow body with the diamond and a cross shaped bow are presented and compared. A cross shaped bow with a stream lined body shape is adopted for the floating tow body for minimizing the drag as well as the turbulence during the tow. Both the bow shape as well as the dimensions of the body is optimized based on the towing tank experimental results so that the body can be towed smoothly with minimum turbulence to avoid acoustic noise generation during the SONAR tests. An iterative experimental procedure is carried out in finalizing the dimensions and the shape of the tow body.
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FIN 336 Milestone Two Guidelines and Rubric Economic Envir.docxnealwaters20034
FIN 336 Milestone Two Guidelines and Rubric
Economic Environments and Risk Mitigation
Overview: This milestone will help you complete Sections II and III of the final project.
Prompt: Develop a report that analyzes one company’s approach to multinational expansion. Include financial factors such as economic environments and
market conditions, risk mitigation strategies, and ethical and legal practices.
Specifically, the following critical elements must be addressed:
II. Economic Environments and Market Conditions
C. Explain the role of international financial markets and institutions in global environments in evaluating their impact on the company’s risk
management strategies.
D. Analyze impacts of exchange rate on the company’s performance for determining if a loss occurred because of fluctuations or devaluations of
foreign currencies. Provide examples from the past year to support your claims.
III. Risk Mitigation: Examine sources of risk and risk reduction methods available to multinational corporations. Use the 2007–2008 annual report and the
most current annual report to support responses in this section.
B. Discuss risks and financial factors associated with exchange rates and interest rates for assessing how they inform the company’s financial
management approaches.
C. Discuss diversification in the company’s expansion model for examining advantages or disadvantages, and provide examples and financial
information from the past year to support claims.
D. Discuss company strategies before and after the 2007–2008 crisis for determining possible reasons for the company’s current financial
performance. Provide examples to support your claims.
Rubric
Guidelines for Submission: Your paper must be submitted as a 1- to 2-page Microsoft Word document with double spacing, 12-point Times New Roman font,
and one-inch margins. Cite appropriate academic references as necessary.
Critical Elements Proficient (100%) Needs Improvement (75%) Not Evident (0%) Value
Economic
Environments and
Market Conditions:
Financial Markets
and Institutions
Explains the role of international financial
markets and institutions in global
environments in evaluating their impact on
the company’s risk management strategies
Explains the role of international financial
markets and institutions in global
environments in evaluating their impact on
the company’s risk management strategies,
but explanation is cursory, illogical, or
missing key elements
Does not explain the role of international
financial markets and institutions in global
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Critical Elements Proficient (100%) Needs Improvement (75%) Not Evident (0%) Value
Economic
Environments and
Market Conditions:
Impacts of Exchange
Rate
Analyzes impacts of exchange rate on the
company’s performance for determining if a
loss occurred because of fluctuations or
devaluations of foreign currencies, and
provides examples from .
files may help with writing paperEvaluation Essay Topic Sho.docxnealwaters20034
files may help with writing paper
Evaluation Essay Topic: Should world leaders use a pandemic crisis brought about by a killer virus to boost their own popularity?
Write a 1.5-2-page Evaluation Argument Essay in response the assigned topic. (Note: Write essay in third person.
DO NOT USE
“I,” “me,” “my,” “we,” “our,” “you,” or “your”).
.
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FIN 402 Week 3 Case Problems
Case Problem 6.1 Sara Decides to Take the Plunge
1. LG 1
2. LG 6
Sara Thomas is a child psychologist who has built a thriving practice in her hometown of Boise, Idaho. Over the past several years she has been able to accumulate a substantial sum of money. She has worked long and hard to be successful, but she never imagined anything like this. Even so, success has not spoiled Sara. Still single, she keeps to her old circle of friends. One of her closest friends is Terry Jenkins, who happens to be a stockbroker and who acts as Sara’s financial advisor.
Not long ago Sara attended a seminar on investing in the stock market, and since then she’s been doing some reading about the market. She has concluded that keeping all of her money in low-yielding savings accounts doesn’t make sense. As a result, Sara has decided to move part of her money to stocks. One evening, Sara told Terry about her decision and explained that she had found several stocks that she thought looked “sort of interesting.” She described them as follows:
· North Atlantic Swim Suit Company. This highly speculative stock pays no dividends. Although the earnings of NASS have been a bit erratic, Sara feels that its growth prospects have never been brighter—“what with more people than ever going to the beaches the way they are these days,” she says.
· Town and Country Computer. This is a long-established computer firm that pays a modest dividend yield (of about 1.50%). It is considered a quality growth stock. From one of the stock reports she read, Sara understands that T&C offers excellent long-term growth and capital gains potential.
· Southeastern Public Utility Company. This income stock pays a dividend yield of around 5%. Although it’s a solid company, it has limited growth prospects because of its location.
· International Gold Mines, Inc. This stock has performed quite well in the past, especially when inflation has become a problem. Sara feels that if it can do so well in inflationary times, it will do even better in a strong economy. Unfortunately, the stock has experienced wide price swings in the past. It pays almost no dividends.
Questions
a. What do you think of the idea of Sara keeping “substantial sums” of money in savings accounts? Would common stocks make better investments for her than savings accounts? Explain.
Answer: It is not a smart idea for Sara to retain substantial sums of money in her savings account for the reason that she could potentially make more money by investing in stocks. For example, the average rate for a savings account is 0.06%, and if you invest in stock, you can make anywhere from 0-15% depending on the amount of risk you is willing to take.
b. What is your opinion of the four stocks Sara has described? Do you think they are suitable for her investment needs? Explain.
Answer: Three out of the four stocks are ok investments to make since there is so little information provided. I do not think the NASS is a good i.
Film Review Select a contemporary English film of your choice that .docxnealwaters20034
Film Review: Select a contemporary English film of your choice that includes significant content about social issues. Review and analyze the film in an essay of 3-5 pages (double-spaced). The review will include a short summary of the content and mostly focus on sociological analysis. You should use very few outside sources (or none) and instead focus on your own analysis.
.
Fieldwork Research Primary SourcesThis assignment assumes 4.docxnealwaters20034
Fieldwork Research: Primary Sources
This assignment assumes 4 steps:
Attend a live music making opportunity, a concert, or watch an entire music concert on YouTube. It can be of any music genre (see instructions below).
Interview an insider of that culture
Write a
Fieldwork Concert Report
Transcribe and arrange the
interview
(in the same paper)
this the concert https://www.youtube.com/watch?v=lxjgqVsYu0g&feature=youtu.be ( kpop music is korean music )
first you have to make about concert report/ participant observation :
Students will attend minimum one live or online music performance. The preferred ethnographic writing is that of a participant observation – meaning, you take part in the music making next to the performers, so that you can live their experiences. Sometimes this is not possible, and you will have to experience music making from the fan’s perspective, or just that of the spectator’s perspective – in the case of Western classical concerts, or if you are viewing a concert on YouTube. Your goal is to capture the performance, event, and situation, and meaning of the event to the people involved (insider’s point of view). In order to do this, please describe as accurately as possible:
• The physical setting (stage, concert hall, audience) – you can draw a plan of the hall and/or take pictures, if allowed
• The behavior of individuals and groups of people – both the artists on the stage, as well as the audience
• Conversation and interactions between people • Sequence of events (before the concert, during the concert, after the concert)
• Demographic survey (count or approximate how many people are there; offer information about their gender, age, professional background, education level – if possible). In trying to assume the audience’s socio-economic status, you can look at their fashion style, cars, etc.
• Rationale of the event: for WHOM is the event held, WHERE was it held, WHEN did it happen, and WHY did it happen
• People’s emotions, meanings, and beliefs (if possible)
the second part is to make interview with 2 persons individually ( create 2 persons from your imagination introduce them and ask them these questions):
Upon gaining access in a live performance event or an online music-genre specific chatroom, students will follow the steps below to conduct one interview with a participant in the specific culture/performance:
1- what is your reaction of songs?
2- do you like it? and why do you like it?
3- why do people like these songs or concert?
4- Identify the most expert participant member that you can have access to interview (“key informant”): for some concerts, it would be hard or almost impossible to interview the performer. In such case, interview an audience member/participant/fan that has most knowledge of the culture/genre performed or strong ties to the particular music tradition.
5. Inform them of the purpose of your research, and gain acceptance for interviewing. If the su.
Field TripAssist the cooperating teacher for the age you are obs.docxnealwaters20034
Field Trip
Assist the cooperating teacher for the age you are observing in planning a field trip. The site you use may be as simple as a walk to a park or to the fire/police station. Other options include: zoo, museum, library, farm, etc.
Please type the answers to the following questions regarding the field trip:
1. Explain why this site was chosen. Be sure to state what subject or them is covered and provide the MDE CCRS that supports your reason for this rip and what is studied.
2. Describe/explain safety concerns about the chosen field trip site.
3. How does the field trip relate to what the children are currently learning?
4. List and explain your duties involved in planning this field trip (permission slip, contacting bus, etc.).
*Include a sample permission slip that would be given to the parents before the field trip and a brochure of the field trip site.
.
Field of study ( Interdisciplinary studies)Choose a piece of w.docxnealwaters20034
Field of study ( Interdisciplinary studies)
Choose a piece of writing for your field (journal article, news or magazine article, lab report, etc.).
Using either the insert comment feature on Word or Adobe, or handwriting and scanning/posting images, annotate the piece.
Annotations should highlight what you think is important, ask questions, make comments.
Your annotations should show an awareness of the argument of the piece, whether or not it is effective.
Part II: You will create an infographic (poster, brochure, webpage, etc.) that uses images and text to present on what writing in your field looks like.
.
Feminist & Empowerment TheoriesFeminist theory can be applie.docxnealwaters20034
Feminist & Empowerment Theories
Feminist theory can be applied with Peter and Fernando to promote self-determination and problem-solving skills for their current and future challenges. Feminist theory states that patriarchal culture is concerned with power and oppression over minority populations (Adams et al., 2013). Specific feminist techniques include: an analysis of oppression and power, exploring client self-esteem and interdependence, and empowering clients (Sommers-Flanagan & Sommers-Flanagan, 2014). Patriarchy is damaging to males in society (Sommers-Flanagan & Sommers-Flanagan, 2014) and teaches ‘manhood’ where the dominant heterosexual culture views homosexual men and women as ‘others’ (Adams et al., 2013). This can be seen with Fernando’s father who has disapproval of his son’s sexual identity. In addition, Peter has taken on the responsibility of head of household while Fernando has taken on the role of stay-at-home caretaker to Jose. Feminist theory brings together personal and political thinking to increase the client’s power (Turner, 2017).
When applying feminist theory within a relationship there is an emphasis on the concept of mutuality wherein there is a sense of respect, interest, empathy, and responsiveness experienced by both parties (Turner & Maschi, 2015). This fosters resilience through a two-way relational dynamic (Turner & Maschi, 2015). The use of this approach within the case of Peter and Fernando would help to foster resilience in the family dynamic through this emphasis on mutuality. By fostering empathy, respect, and responsiveness within the relationship dynamic will help Peter and Fernando improve communication through empathy and respect for each other’s perspective.
Empowerment is a concept that is strongly supported by evidence in social work practice (Turner, 2017). Empowerment theory and feminist theory both provide social workers with the expertise to validate client experiences, support client strengths, and promote collectivism through mutual aid and support (Turner, 2017). Three dimensions of empowerment theory include: (1) a development of a more positive identity and sense of self, (2) build knowledge and critical thinking to connect personal and political realities, and (3) build resources and strategies to achieve personal and collective goals (Turner, 2017). Empowerment theory assumes that the client(s) are the expert on the issue at hand and have within them the strengths to overcome the given problem (Turner & Maschi, 2015). It is then the job of the social worker to connect the client to resources within their community and assist them in utilizing those resources in keeping with their identified strengths (Turner & Maschi, 2015).
.
Feminist Family TherapyPresentation originally given by Allen.docxnealwaters20034
Feminist Family Therapy
Presentation originally given by Allen Mallory
1
In-Class Journal Feminism and Family Therapy
What do you typically think of when you hear the word “feminism?”
How do you define feminism?
Do you think feminism is a useful concept for marriage and family therapy?
Why or why not?
For those who do use ideas from feminism in therapy what might that look like?
Three (of many facets) of feminist theory importance of history, context, reflexive
2
The Who’s Who of Family Therapy
Jay Haley
Cloe Madanes
Strategic “ power and control as central to family patterns ….symptoms result from repetitive, unproductive attempts to control or influence other family members”
Madanes “ revers hierarchies are not bad in certain situations. They become problematic when there is incongruence in those hierarchies. Problems arise from dilemmas between love and violence
3
The Who’s Who of Family Therapy
Salvador Minuchin
Focus on changing interactional patterns and moving clients in the room, alliances, boundaries, and coalitions
Interesting that Minuchin worked with low income population were traditional gender roles likely look different, enactments
4
The Who’s Who of Family Therapy
Murray Bowen
Differentiation/fusion, genograms/family of origin, intergenerational patterns, family life stages,
5
The Who’s Who of Family Therapy
Ivan Boszormenyi-Nagy
Ethical considerations, fairness, trust, ledger of entitlement/indebtedness, invisible loyalties, integration of interpersonal and intra-psychic (the context), multidirectional pariality
6
The Who’s Who of Family Therapy
Carl Whitaker
Enter into the family system and use self to change patterns, co-therapy, atheoretical, battle for stucture, battle for initiative (fatherly figure), goal is to give the family new experience through craziness, creativity, humor, fantasy, treat children as children, and use of self.
7
The Who’s Who of Family Therapy
Virginia Satir
Nurturance, strength/growth focused, when one person has pain the whole family experiences, sculpting, holistic growth (different aspects of the self), use of self
8
Feminisms
Liberal
Radical
Marxist/Socialist
Eco
Postmodern
Women of Color
Postcolonial
Intersectionality
Liberal – equality through legal means and social reform (most commonly used in MFT)
Radical – oppression of women most fundamental form of oppression (what people are referring to when they say feminazi/haters
Marxist/Socialist- capitalism and patriarchy as root of women's oppression public and private sphere change
Eco – mainly focused on domination and oppression o.
Felicia makes fabulous fried foods that she sells to family and .docxnealwaters20034
Felicia makes fabulous fried foods that she sells to family and friends. Felicia’s friend, Fergus, is interested in selling her fried foods using the name “Felicia’s Fabulous Food Company.” Felicia is flattered but does not have enough time to fry any more foods; so Felicia charges Fergus $125,000 to allow Fergus to use her recipes and market the food using her name. On March 10, 2001, Fergus and Felicia enter into a written agreement that provides:
1. Felicia will market and advertise the fried foods.
2. All food is to be prepared with no deviation from Felicia’s recipes.
3. Fergus will manage sales and accounts receivables.
4. Felicia and Fergus will each pay 50 percent of the expenses of the business, such as electricity, water, telephone, heat, insurance and advertising.
5. Felicia will keep two-thirds of the gross receipts and Fergus one-third.
Ten years later, Fergus and Felicia had a number of disagreements and Fergus decides to leave the business. At the time, the business’s net worth was $857,000. Felicia argues that she owns the business and that Fergus, if not an employee, was no more than a franchisee. Fergus argues that he is Felicia’s partner. Were Felicia and Fergus partners? Explain and discuss the factors that lead to your conclusion.
.
Federalism Comparing Government Response in Hurricane Katrina vs..docxnealwaters20034
Federalism: Comparing Government Response in Hurricane Katrina vs. Coronavirus
Submissions must be a minimum of 2 pages, in length. This does not include your bibliography or works cited. This should be attached and added on as the last page of your essay. Y ou will only have one attempt to upload and submit your paper. Your bibliography or works cited page, and your paper, must be uploaded as a single file. They cannot be uploaded separately. No e-mailed assignments will be accepted.
Your response should be your own thoughts and analysis. Research and resources should be incorporated with scholarly application. I.e. used as examples or evidence to support your analysis. Citations may be formatted in APA, MLA or Chicago style, as long as they are consistent throughout. You must include in-text (parenthetical) citations, as well as a bibliography.If you have questions about citation formatting, please ask me, or utilize the tool easybib.com. You must provide in-text citations, to show ownership of any information that you include, in your essay, which is either
1. Not considered common knowledge
2. Paraphrased
3. Directly quoted
Failure to cite information, properly, will result in students receiving an automatic zero. Furthermore, to not do so is considered plagiarism.
Make sure to use complete sentences, and proper grammar. Your response to the prompt should focus on analyzing the information you gather and use to complete the constitutional chart through application. Incorporate the information you gathered by using it to provide examples and support for your response to the prompt.
Essay Topic and Objective:
You will be watching two 50 minute documentaries: The Storm and Coronavirus Pandemic in order to complete this essay.
1. The Storm: Hurricane Documentary (Links to an external site.)
2. Coronavirus Pandemic Documentary (Links to an external site.)
Federalism Overview: Considered together, Hurricane Katrina and Covid-19 both produced policy disasters in the United States that were both unnecessary and linked to federalism. These challenges produced by nature raise the question of whether certain disasters are beyond the capacities of state and local government.
Objective: While watching these films, the central theme to take away from these videos is a better and more comprehensive understanding of Federalism, through real life evidence and explanation. Critically analyze each of the elements and consequences of each different national disaster, based on different level of government’s responses, actions. Leadership, communication processes, and decision-making. Despite, both Hurricane Katrina and Corona Virus being deemed as “national emergencies”, the power organization resulted in vastly different responses by each level of government’s leadership (across all levels: federal, state and local).
Introduction to Federalism: State and Local governments are the first line responders to crisis. The institutions encompass not only the na.
Federalism Comparing Government Response in Hurricane Katrina v.docxnealwaters20034
Federalism: Comparing Government Response in Hurricane Katrina vs. Coronavirus
You will be watching two 50 minute documentaries: The Strom and Coronavirus Pandemic in order to complete this essay.
Topic Overview
: Considered together, Hurricane Katrina and Covid-19 both produced policy disasters in the United States that were both unnecessary and linked to federalism. These challenges produced by nature raise the question of whether certain disasters are beyond the capacities of state and local government.
Objective
: While watching these films, the central theme to take away from these videos is a better and more comprehensive understanding of Federalism, through real life evidence and explanation. Critically analyze each of the elements and consequences of each different national disaster, based on different level of government’s responses, actions. Leadership, communication processes, and decision-making. Despite, both Hurricane Katrina and Corona Virus being deemed as “national emergencies”, the power organization resulted in vastly different responses by each level of government’s leadership (across all levels: federal, state and local).
Introduction to Federalism:
State and Local governments are the first line responders to crisis. The institutions encompass not only the national government and the American states, each with their own distinctive histories, but extend down to the local level of counties, cities, smaller communities, and special-purpose entities such as school districts. Support and opposition for Federalism rests on government leadership, power, decision-making, and response to national disasters. Response is a geographic and constitutional matter of design. The principles underlying federalism create a power system where multiple levels of government (local, state, and federal) coexist in an organization of power that is both exclusive and shared, depending on the event at hand. Though the federal government has a vital role to play in advancing national priorities through the powers enumerated to it by the U.S. Constitution, our founders recognized long ago that many of the challenges our citizens face can best be addressed at the state level. The Constitution set forth means for strengthening national government’s power, intended to establish a more perfect union (Preamble). Federalism would be the new organization of power, between local, state and federal U.S. government, in order to the remedy weaknesses caused by the Articles of Confederation.
Principles of Federalism
Limited government
States’ rights (10th amendment)
Goals of Federalism:
Foster cooperation
Prevent Federal Intrusion into State
Protect State’s utility as “laboratories” of democracy
Central Themes to Focus on and Think About
comparisons and discussion of struggles between local,
state and federal levels of government according to how federalism has manifested into a power tug-of-war in authority
division of power
division .
Feedback for 4 Milestone Two Research and SupportPlease addre.docxnealwaters20034
Feedback for 4 Milestone Two: Research and Support
Please address Milestone two’s feedback and include these changes when working on your Milestone 3 assignment.
1)Proposal Care Support
The data you cite in this section supports that there is a nursing shortage. However, I would have liked to see you add more insight into what research shows on the impact this shortage has on patient safety and quality care. What does the research say about the nursing shortage and its connection with quality care, thus leading you to believe a change was necessary?
2) Value-Based Support
While you discussed financial impacts of your proposal, you did not touch on value based reimbursement. How does short staffing effect patient care and then ultimately reimbursement rates received by your institution?Top of Form
Bottom of Form
3) Data Evidence
You listed an example of a quality indicator that MAY be effected by the nrusing shortage. However, you need to include data that the nursing shortage itself is an issue. How many nurses is your facility short? What is the nurse to patient ratio? How many openings are there? etc.
4) Strategies
While you gave great examples of strategies that could be used to help improve the nursing shortage, are there any interprofessional strategies currently in use that would also be helpful?
5) Strategy Defense
So what nursing indicators will be affected with the implementation of your proposal? See http://ojin.nursingworld.org/MainMenuCategories/ANAMarketplace/ANAPeriodicals/OJIN/TableofContents/Volume122007/No3Sept07/NursingQualityIndicators.html for a list of the Nursing Sensitive Indicators Additionally, while you wrote your own professional insight, I would have liked to see you utilize research to add support to these views and ideas.
6) Articulation of Response
Submission has errors related to citations, grammar, spelling, or syntax
Running head: RESEARCH & SUPPORT 1
Research and support 2
Nursing Shortage and the Need for More Nurses
Research and Support
Proposal Care Support
Nurses are a very critical part of a health care facility. Nursing shortage is not just a problem experienced in the United States but globally. The shortage is as a result of high turnover, unavailability of potential educators and unfair distribution of the workforce. Healthcare organizations are therefore competing to acquire the scarce nurses in order to improve their delivery of quality care. According to the US Bureau of Labor Statistics, more than 1.1 million additional nurses are required to address the shortage problem (Haddad, 2019). For an organization to effectively compete for the scarce nurses, acquire top talent and reduce employee turnover, it must offer an enticing compensation and benefits package. Organizations that offer great wages and benefits easily attract applicant and maintain the nurses they already have. My proposal to offer a better compensation and benefits package would therefore lead to an i.
Federal Budget SpeechDo you want to know who you are Don.docxnealwaters20034
Federal Budget Speech
"
Do you want to know who you are? Don't ask. Act! Action will delineate and define you
." - Thomas Jefferson
The federal budget spends close to four trillion dollars a year and is split between mandatory spending (what the federal government has to spend due to congressional legislation) and discretionary spending (what the federal government spends as a result of congressional allotment). Roughly speaking, mandatory spending accounts for two-thirds of the federal budget and discretionary spending accounts for one-third of the federal budget.
Every year the executive and legislative branches debate budgetary priorities for the federal bureaucracies such as the Department of Defense, the Pentagon, the Environmental Protection Agency, Veteran Affairs, the Department of Education, and others. Many of these debates occur within congressional committee meetings as members of Congress, federal employees, outside interests, and individual citizens articulate funding requests.
For the Unit 9 Assignment you will compose a speech advocating why your chosen department, administration, or agency within the federal bureaucracy should receive additional funding.
Because the “world is a stage,” let us establish the setting, plot, and the ensuing action for your speech.
Setting:
Exterior: Washington D.C. State Capitol Building.
Interior: Room 221B. Congressional Hearing Room.
Plot:
Imagine that you are in a cavernous room. You sit before a large table facing twenty one senators from the Budget Committee. Photographers, more than you can imagine, squeeze between the space that separates you from the members of Congress. Behind you in the gallery, public policy wonks and regular citizens sit, awaiting your presentation.
You are a featured speaker from a citizen group that advocates a particular public policy funding concern for your federal department, administration, or agency. Prior to the meeting you have already read the president’s proposed federal budget for the upcoming year from the
Office of Management and Budget
and you have some budgetary concerns. You read in alarm how the upcoming federal budget request from the White House reduces funding for your federal department, administration, or agency. But, as you know, it is up to Congress to fund the executive bureaucracy. The executive branch requests funding and the legislative branch allocates funding. This is your chance to request more funding for your federal department, administration, or agency of choice.
Action:
Equally eager and nervous you stand in front of a lectern. “Now,” you think, “now I am ready…” You click on the microphone, examine your prepared speech about your funding request, and you begin to speak with eloquence and passion!
Directions
: Compose a 400 word transcript of your public policy speech.
Select a specific example of public policy from one of the following fields:
Economic policy – for example, U.S. budget deficit spending.
.
February is Black History Month. In great honor of this month, y.docxnealwaters20034
February is Black History Month. In great honor of this month, your project will be to make a PowerPoint or Microsoft Word document depicting a notable African American figure. Please follow the guidelines below. This is an independent project which means you cannot work with a partner. Period!
Choose an African American to research and have your person approved today.
Begin your research. Do not use Wikipedia. You may use books, encyclopedias, and the internet. Gather information that will thoroughly answer the following questions:
1. Name of person 2. Where he or she was born and when 3. 10 detailed facts about the person or persons (1-2 Sentences per fact.) 4. Fully discuss why he/she is a prominent figure in society (4-6 sentences) 5. Discuss why you believe this person made a significant contribution to African American history. (4-6 sentences) 6. Must include a picture
****This will count as project and class participation grade****
All of the topics MUST be addressed to receive full credit. Your responses can be written or typed preferably, but it must be neat! Your research must be in your OWN words, otherwise you will receive a 0 for plagiarizing. All projects will be ran through turnitin.com. It is a website that shows if someone plagiarized.
Your facts can be in paragraph or outline form.
Spelling, grammar, and neatness counts!
.
Feedback developed by Estee Beck, PhD
General strategies for peer response attribution to an unknown author
The Good, the Bad, and the Ugly of Peer Feedback
Research in writing studies show evidence that undergraduate student writers are not familiar
with providing adequate peer feedback, and instead rely upon mildly pleasant comments as a
way to not offend a fellow student. At the same time, getting feedback is a crucial step in
writing. Feedback provides insight from a detached reader, who may provide overall direction
for the works-in-progress. Learning how to give feedback requires practice, patience, good
reading skills, and sensitivity toward relations. But, students need training with how to give
good peer feedback.
How to give not-so-great feedback:
Here’s a sample paragraph from a friend who has asked for some feedback on the scope of the
paragraph. He’s concerned that the summary paragraph does not provide enough detail to
conclude a section of the paper.
for working within electronic computer
Although computers & writing and digital rhetoric employ different methodologies
benefits apply to classroom based writing practices along with research and
scholarship, the ultimate quest provides insight into a knowledge and information
exchange economy through and with digital technologies. As people make
-mediated spaces, both fields form around a
sense of searching for how people and machines interact with each other. While the
advancements with digital technologies, especially with movement in the multi-
million dollar Internet of Things industry, the relationship of not just human-to-
machine interaction, but also machine-to-machine interaction will become
important for rhetoricians to address. Again, understanding the function of rhetoric
in algorithmic processes is just one step in support of positioning a rhetorical code
studies as central to rhetorical scholarship.
Comment [BE1]: I have no idea what this means!
Comment [BE2]: Long
Comment [BE3]: Who cares?
Comment [BE4]: This is a horrible paragraph.
The comments in the margins show a few traits: An uncaring critique, ignorance, inadequate
explanation, and a final comment that’s not too pleasant to read. What’s missing from the four
comments?
Here’s the same paragraph, with some alterations:
Although computers & writing and digital rhetoric employ diferent methodologies
Comment [BE6]: Punctuation
Comment [BE5]: Spelling error
for working with electronic computer mediated spaces both fields form a sense of
searching for people and machines interact with each other. While the benefits
apply to classroom based writing practices along with research and scholarship, the
ultimate quest provides insight into a knowledge and information exchange
economy through and with digital technologies. As people mke advancements with Comment [BE7]: Spelling error
digital technologies, especially with mov.
FC305 Essay’s Guidelines March Start cohort Deadline Mond.docxnealwaters20034
FC305 Essay’s Guidelines March Start cohort
Deadline: Monday 15th of June 2020 by 09.00am
First Draft Deadline: Monday 11th of May 2020 by 09.00am
1000 words (+/- 10% – i.e. 900-1100)
Read all instructions very carefully
1. Your assignment needs to be submitted via VLE Turnitin App on the date given above. Submit both versions in their respective Turnitin portals.
2. You should observe the word count stated on the assignment brief. A 10% margin is allowed above or below the limit. You will lose marks if this is not followed.
3. Penalties apply for late submissions.
4. If you failed to submit on time due to an Exceptional Extenuating Circumstance (EEC), you should submit an EEC form within three days of the assessment deadline. These are available from Student Service and may, depending on your circumstances, affect your final mark.
Choose ONE of the UN Global Issues from the selection available on your VLE (and as instructed in a separate email) and discuss it critically.
Marking criteria
Total Mark for each criterion
Content and Understanding30%
· Relevance
· Appropriate detail
· Depth of knowledge (evidence of understanding of the topic)
· Evidence of research
Critical Thinking20%
· Understanding of the debates relating to the topic
· Evidence of original thought
· Analysis
· Construction of a coherent argument
Structure20%
· Logical and coherent structure
· Clear introduction and conclusion
· Overall presentation
Citation of authority and Bibliography20%
· Accurate referencing
· Variety of sources (at least 5 academic references)
· In text References
Overall style10%
· Overall style ranging from impressive to confusing, inaccurate, or poor
Academic Referencing
A good place to start is with academic sources, also called scholarly sources. These sources can include books, academic journal articles, and published expert reports. Whatever the exact form, academic sources all have in common the fact that they are peer-reviewed. Peer reviewed sources are written by an expert in the field and have passed review by other experts who judged the source for quality and accuracy. If a source is peer-reviewed, you know it is a good choice for high-quality, accurate information about your topic.
Not all sources show whether they are scholarly relevant or peer-reviewed, but there are some clues you should check.
· Look at the author's credentials. They should have an advanced degree and/or an affiliation with a scholarly organization like a university or a science foundation.
· Look as well for a list of references or a bibliography. Most high-quality research is based on other research, so a good source will have a list of works the author studied as he or she was writing it. Check this list to make sure.
· Finally, you can tell a lot about a source by looking at the publisher who publishes it. Scholarly sources should be published by a professional association like the American Medical Association; by a university, for example the Oxford Unive.
Faster Computing has contacted Go2Linux and requested a brief p.docxnealwaters20034
Faster Computing has contacted Go2Linux and requested a brief proposal presentation for migrating its systems from Windows to Linux. The company is specifically interested in seeing the following information:
Based on your current understanding of Faster Computing's business, what are some potential benefits of Linux?
The company is aware that many different Linux derivatives exist. Which would Go2Linux recommend, and why?
Are there graphical interfaces available for the Linux workstations that would provide similar functionality to Windows? Some users are concerned about working with a command-line interface.
What steps will be required to migrate the systems from Windows to Linux?
What tools are available on Linux for the servers to provide file sharing, web servers, and email servers?
The deliverable for this phase of the project is a three- to five-slide PowerPoint narrated presentation. For each slide, you will embed your own audio recording as if you were presenting the content to the Faster Computing team. Faster Computing has not yet committed to the project, so this should be presented as a proposal.
The presentation should be visually appealing; inclusion of at least one image that supports the content and adds value to the proposal is required. You must cite at least two quality sources.
.
Faster Computing was impressed with your presentation. The compa.docxnealwaters20034
Faster Computing was impressed with your presentation. The company is interested in moving forward with the project, but the senior management team has responded to the presentation with the following questions and concerns:
How will security be implemented in the Linux systems—both workstations and servers?
End users have expressed some concern about completing their day-to-day tasks on Linux. How would activities such as web browsing work? How would they work with their previous Microsoft Office files?
The current Windows administrators are unsure about administering Linux systems. How are common tasks, such as process monitoring and management, handled in Linux? How does logging work? Do we have event logs like we do in Windows?
Some folks in IT raised questions about the Linux flavor that was recommended. They would like to see comparisons between your recommendation and a couple of other popular options. What makes your recommendation the best option?
How does software installation work on Linux? Can we use existing Windows software?
How can Linux work together with the systems that will continue to run Windows? How will we share files between the different system types?
The deliverable for this phase of the project is a memo. There is no minimum or maximum page requirement, but all of the questions must be fully answered with sufficient detail. The recommended format is to respond to the questions in a bulleted format. Provide sufficient detail to fully address the questions. You must cite at least two quality sources.
Template
Go2Linux, Inc.
Provide a brief summary of your recommendation
of a specific version of Linux. Explain how your choice meets the business need of Faster
Computing, Inc.
The bold text questions below represent the specifics you need to focus on. For
each question, refer to your Implementation Proposal (Assignment #1) for consistency. In this
assignment you will provide technical details for Information Technology personnel.
Any example Linux commands should be properly displayed (e.g., in lower case)
and any acronyms explained on first use (e.g., Secure Shell (SSH)).
·
How will you implement security in the Linux systems?
o
Start by outlining how you plan to migrate the existing Windows
Servers to Linux. Ho
w will users authenticate? What technologies will be used? What
kind of access controls will be used?
o
Will you recommend simple authentication mechanisms or employ
multiple factors? For passwords, what policy(ies) will you recommend?
needed>
o
How will you handle data-at-rest and data-in-transit?
needed>
o
How will you enforce software installations and control which
applications may run on the network?
·
End users have expressed some concern about completing their day-to-day tasks on
Linux. How would activities such as email/web browsing work? How would they work
with their previous Microsoft Office files?
o
Th.
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
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Experimental Analysis on Sinking Time of Littoral Submarine .docx
1. Experimental Analysis on Sinking Time of Littoral Submarine
in Various Trim Angle
Luhut Tumpal Parulian SINAGA1,a*
1Senior Researcher at PTRIM, BPPT Laboratorium
Hydrodinamika Indonesia, Surabaya
[email protected]
*corresponding author
Keyword: Littoral submarine, dive, sink, experiment.
Abstract. A submarine must conform to Archimedes’ Principle,
which states that a body immersed
in a fluid has an upward force on it (buoyancy) equal to the
weight of the displaced fluid,
(displacement). Submarines are ships capable of being
submerged. The history of submarines and
their operation have largely revolved around being able to alter
the density of the vessel so that it
may dive below the surface, maintain a depth, and return to the
surface as needed. The way modern
submarines accomplish this task is to bring in and remove water
from tanks in the submarine called
ballast tanks. Ballast tanks fit into two categories: those used
for major adjustment of mass (main
ballast tanks); and those used for minor adjustments (trim
tanks). The effect of each tank is plotted
and this is compared with the changes in mass and trimming
moment possible during operations
using a trim polygon to determine whether the ballast tanks are
adequate. On the water surface,
2. metacentric height (GM) is important, whereas below the
surface it is the distance between the
centre of buoyancy and the centre of gravity (BG) which
governs the transverse stability of a
submarine.
Introduction
A submarine or a ship can float because the weight of water that
it displaces is equal to the
weight of the ship. This displacement of water creates an
upward force called the buoyant force and
acts opposite to gravity, which would pull the ship down.
Unlike a ship, a submarine can control its
buoyancy, thus allowing it to sink and surface at will [1].
As with any object in a fluid, a submarine must conform to
Archimedes’ Principle, which states
that a body immersed in a fluid has an upward force on it
(buoyancy) equal to the weight of the
displaced fluid, (displacement). This applies whether the
submarine is floating on the water surface,
or deeply submerged [2, 3].
To control its buoyancy, the submarine has ballast tanks and
auxiliary, or trim tanks, that can be
alternately filled with water or air (see Fig. 1). When the
submarine is on the surface, the ballast
tanks are filled with air and the submarine's overall density is
less than that of the surrounding
water. As the submarine dives, the ballast tanks are flooded
with water and the air in the ballast
tanks is vented from the submarine until its overall density is
greater than the surrounding water and
the submarine begins to sink (negative buoyancy) [4, 5].
4. (a) Surface
(b) Dive
Figure 1. Submarine diving process.
Figure 2. Location ballast tank of submarine.
As the righting moment at an angle of heel must be the same for
these two definitions of
displacement, the relationship between the centres can be
obtained from Eq. 1.
BFGF x ΔF = BH x GH x ΔH (1)
Therefore,
��������
��������
= ����
∆��
(2)
where
���� = Total mass Hydrostatic displacement, other than free
flood water
∆�� = Total mass Form displacement, including free flood
water
���� = Centre of gravity Hydrostatic displacement
���� = Centre of gravity Hydrostatic displacement
���� = Centre of buoyancy Form displacement
���� = Centre of buoyancy Form displacement
The Main Ballast Tanks (MBTs), are usually ballast tanks
5. external to the pres- sure hull, which
are free flooding when the submarine is submerged, as shown in
Fig. 3.
The purpose of the MBTs is to allow major adjustment of the
submarine mass to enable it to
operate submerged as well as on the water surface. Water and
air enter and leave the MBTs through
flooding holes at the bottom and vents at the top of the tanks.
Applied Mechanics and Materials Vol. 874 129
Figure 3. Schematic of typical main ballast tank system.
During operations the mass and longitudinal centre of gravity of
a submarine will change due to
use of consumables including fuel, and weapons discharge. In
addi- tion, changes in seawater
density, hull compressibility and surface suction when operating
close to the surface will all result
in the need to be able to make small changes to the submarine
mass and longitudinal centre of
gravity.
The trim and compensation ballast tanks are used to make these
small adjust- ments. A
schematic of such a typical system is shown in Fig. 4.
Figure 4. Schematic of typical trim and compensation ballast
tanks.
6. At the design stage it is necessary to determine whether the trim
and compensation ballast tanks
are adequate to cope with all possible changes in submarine
mass and longitudinal centre of gravity.
To do this, the effect of each tank is plotted as a function of
mass and trimming moment as shown
in Fig. 5 [6].
In this figure, the point with zero mass and zero trimming
moment is where all the tanks are
empty. The forward trim tank (FTT) is then filled. In this case,
the tank is a soft tank, not open to
the sea, so there is no change in mass, just a move- ment of the
centre of gravity forward from the
aft trim tank (ATT) to the forward trim tank. Thus, the effect is
a forward trimming moment with no
change in mass. This is shown by a horizontal line.
To perform a quick dive, the front ballast is filled with water
and then forms the angle required
to perform the dive, so the submarine has an effective range, see
Fig. 6. Once the boat is trimmed to
more or less neutral buoyancy, the depth of the boat is
controlled with the hydroplanes. To use the
hydroplanes the boat requires speed to create a force on the
tilted planes. At slow speeds, the fore
hydroplanes are exclusively used to keep the boat at the
required depth
The dive technology was shown that the bulk buoyancy of the
boat is changed with the MBT
followed by fine tuning with the MBT and finally the correct
depth is maintained using the
hydroplanes. Due to the application of the real submarine
technology is not always possible. In the
following, some of the available model diving technologies will
7. be treated [7].
This research focuses on the study of the influence of sloshing
against the coupling movement
heave the ship while the ship conducted a quick dive using
Physical Tests in Indonesia
Hydrodynamics Laboratory.
130 Marine Systems and Technologies
Figure 5. Polygon showing the effect of trim and compensation
ballast tanks.
Figure 6. Quick dive submarine.
Methodology
The investigation was carried out experimentally. The
experimental work was conducted using
towing tank and tested at various angle of trim. Physical models
of the submarine are shown in
Fig.7. The model is made from FRP (fibreglass reinforced
plastics) in order to obtain appropriate
displacement as scaled from full ship mode in accordance with
Froude law of similarity. Principal
particulars of the submarine given in Table 1.
Table 1. Main dimension submarines model.
Dimension SHIP (m) MODEL (mm)
LOA 22.00 700.00
8. B Total 4.29 136.30
D Total 5.13 163.30
T 2.60 82.70
dim. Press Hull 3.00 95.50
JR. FS 1.10 35.00
JR. WL 1.00 31.80
JR. BL 0.30 9.50
Scala 31.43
Applied Mechanics and Materials Vol. 874 131
Figure 7. Design of submarine.
Results and Discussion
To get a angle dive effective when quick dive at model of litoral
submarine, has obtained the
water depth in Cavitation Tunnel = 0.6 m a summary of the test
results that can be seen from the
Table 2 below:
Table 2. Angle of Attack Pitch Ballast Water Depth.
Volume of ballast
in Fwd. Tank (gr.)
Angle of Trim Sinking time (sec.) Sinking velocity
(V m / sec)
150 5⁰ 3.2 0.188
300 7.5⁰ 3.0 0.200
400 10⁰ 2.8 0.214
9. 500 12.5⁰ 2.7 0.220
550 15⁰ 2.5 0.240
In Table 2 was obtained dives fastest ship that is for 2.5
seconds at an angle of 150 trim. This is
due to the angle trim large enough so that the size of the area
aboard the front facing the water flow
becomes tighter. It is also their ballasts volume large enough to
add to the weight of the model
submarine. As shown in Fig. 8, the addition of ballast resulted
in a bigger angular change also.
However, the time it takes to sink even less.
Furthermore by addtion 150 gr ballast at forward ballast tank,
submarine can be have trim 50.
But, Litorral submarin have 3.2 sec in singking time. This is
due to wide cross section and blocking
into the water, causing longer sinking time.
The conditions of trim described apply of submarine operations
by flooding the forward ballast
tank. However, these buoyancy conditions always be considered
with respect to the law of the lever
on each side of the center of gravity of the boat. The trimming
of the submarine is accomplished by
varying, or adjusting, the amount of water in the variable ballast
tanks. The trim system is the
means by which this adjustment is made. However, the trim has
been so carefully adjusted that by
flooding the main ballast tanks and adding the required amount
of water to the special ballast tanks,
the submarine can be made to submerge at the desired rate [8].
132 Marine Systems and Technologies
10. Figure 8. Sinking time for submarine.
Conclusions
Ship model testing was conducted to determine the model to the
required time to dive to the
bottom. From the tests of models with angle of attack 150 has
the fastest time in the amount of
2.5 seconds or has a speed of 0.24 m/sec to reach the bottom of
the pool of test.
In general the vessel can sink due to a sharp angle so that the
area of the bow that is exposed to
water is smaller so that the resistance becomes small and the
weight gain due to the addition of the
front ballast. As the next stage should be calculated
comprehensively on navigation vessels arising
from the movement of the ship.
References
[1] Dmitri Kuzmin, Introduction to Computational Fluid
Dynamics, Institute of Applied
Mathematics University of Dortmund,
http://www.mathematik.uni-dortmund.de /_kuzmin/ cfdintro/
cfd.html (2000).
[2] M. Mackay, The Standard Submarine Model: a Survey of
Static Hydrodynamic Experiments
and Semi empirical Predictions, Defence R&D, TR 2003-079,
2003.
[3] Erwandi, T.S. Arief, C.S.J. Mintarso, The study on
hydrodynamic performances of ihl-mini-
submarine, In: Proc. The Second International Conference on
Port, Coastal, and Offshore
11. Engineering (2nd ICPCO), Bandung, 12-13 November 2012.
[4] S.W. Lee, H.S. Hwang, C.M. Ryu, H. I. Kim, S.M. Sin, A
Development of 3000-ton class
submarine and the study on its hydrodynamic performances, In:
Proc. the Thirteenth (2003)
International Offshore and Polar Engineering Con-Prosiding
InSINas 2012 HK-6 0026: Erwandi
dkk. ference Honolulu Hawaii, USA May 2003.
[5] L.T.P. Sinaga, Theoretical Analysis Of Sloshing Effect On
Pitch Angel To Optimize Quick
Dive On Litoral Submarine 22 M. In: The 8th International
Conference on Physics and Its
Applications (ICOPIA 2016), August 23, 2016, Denpasar,
Indonesia, 2016.
[6] A. F. Molland, S.R. Tunock, D.A. Hudson, 2011, Ship
Resistance and Propulsion, Cambridge
University Press, New York, 2001.
[7] A. Prisdianto, A. Sulisetyono, Perancangan ROV dengan
Hydrodinamic Performance yang
Baik untuk Misi Monitoring Bawah Laut, ITS, Surabaya, 2012.
[8] A. Sulisetyono, D. Purnomo, The Mini-Submarine Design
for Monitoring of the Pollutant and
Sewage Discharge in Coastal Area, In: Proc. 5th International
Conference on Asian and Pacific
Coasts, NTU, Singapore, 2009.
0
0,5
1
1,5
2
13. Forward Ballast (gr)
Trim
Sinking Time
Sinking tim
e (s)
Applied Mechanics and Materials Vol. 874 133
Reproduced with permission of copyright owner. Further
reproduction
prohibited without permission.
Reproduced with permission of the copyright owner. Further
reproduction prohibited without permission.
TURTLE: David Bushnell's Revolutionary Vessel
Taylor, Blaine
Sea Classics; Nov 2010; 43, 11; ProQuest
pg. 66
Ocean Engineering 72 (2013) 441–447
Contents lists available at ScienceDirect
Ocean Engineering
0029-80
14. http://d
n Corr
E-m
jgpelaez
journal homepage: www.elsevier.com/locate/oceaneng
On a submarine hovering system based on blowing and venting
of ballast tanks
Roberto Font a,n, Javier García-Peláez b
a Departamento de Matemática Aplicada y Estadística, ETSI
Industriales, Universidad Politécnica de Cartagena, 30202
Cartagena, Spain
b Direction of Engineering, DICA, Navantia S. A., Cartagena
30205, Spain
a r t i c l e i n f o
Article history:
Received 27 July 2012
Accepted 27 July 2013
Available online 19 August 2013
Keywords:
Manned submarines
Underwater hovering
Variable buoyancy
Sliding control
18/$ - see front matter & 2013 Elsevier Ltd. A
x.doi.org/10.1016/j.oceaneng.2013.07.021
esponding author. Tel.: +34 968 338 947; fax:
ail addresses: [email protected], robertojav
@navantia.es (J. García-Peláez).
a b s t r a c t
15. A submarine hovering system based on the blowing and venting
of a set of dedicated tanks is
investigated. We review the mathematical models involved and
propose a sliding mode controller for
the input–output linearized system. Numerical simulation
results support the idea that this could be a
promising hovering strategy for manned submarines,
autonomous underwater vehicles or other plat-
forms.
& 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Underwater hovering, the ability to statically keep a desired
depth, is at the same time a challenge, due to many uncertainties
associated with the underwater environment, and a very impor-
tant feature for both small size autonomous underwater vehicles
(AUVs) and large manned submarines. In the last years several
hovering AUVs have been developed (see Vasilescu et al., 2010
for
a survey on the subject). The hovering facility expands the
capabilities of AUVs allowing them to perform more complex
missions that previously could only be carried out through
Remotely Operated Vehicles (ROVs). For manned submarines,
accurate hovering can be an invaluable tool, for example, for
safe
swimmer delivery, cover supply replacement or the deployment
and recovery of AUVs, a subject that has recently raised an
extraordinary interest (see for example Hardy and Barlow,
2008;
Martínez-Conesa and Oakley, 2011).
From the technological point of view, AUVs usually hover by
using thrusters (Choi et al., 2003; Li et al., 2011). Due to the
large
16. energy requirements of this approach, however, buoyancy
control
by pumping seawater in or out of ballast tanks can be used to
save
energy (Vasilescu et al., 2010) or in larger designs (Tangirala
and
Dzielski, 2007). In manned submarines, hovering is
traditionally
performed using hydraulic pumps (Yang and Hao, 2010; Ying
and
Jian, 2010), although not very much information about hovering
ll rights reserved.
+34 968 338 916.
[email protected] (R. Font),
systems is available in the literature due to the military nature
of
these vehicles.
The aim of this work is to investigate the feasibility of a
hovering system in which dedicated tanks are blown and vented
similarly to the way the main ballast tanks are traditionally
operated in manned submarines.
In these vehicles, a variable number of main ballast tanks are
distributed along the hull. In case of emergency the main ballast
tanks can be emptied by blowing into them air from high
pressure
bottles. This way the water is expelled from the tanks, the
vehicle
gains buoyancy and can rise more quickly. To fill the tanks with
water, air is vented out of the ballast tanks. In the previous
works
(Font et al., to appear, 2013) we proposed mathematical models
for
the blowing and venting of ballast tanks and showed that the
17. implementation of a control system for these processes, usually
performed manually, can improve in a significant way the
perfor-
mance and stability in emergency rising manoeuvres. Our objec-
tive is to extend the approach used with the main ballast tanks
to a
set of dedicated hovering tanks (see Section 2 for details) in
order
to test the feasibility of a hovering system based on blowing and
venting of tanks. Although throughout this paper we will use a
manned submarine as test platform, it is worth noting that the
use
of blowing and venting of tanks as hovering control is not
limited
to these vehicles nor is our intention to carry out the discussion
of
conceptual designs for the compromise between efficiency and
stealth in a hovering system ready for military applications.
Indeed, this technology could be applicable to manned submar-
ines, AUVs, ROVs or any offshore platform requiring variable
buoyancy control.
The rest of the paper is organized as follows. In Section 2
we formulate the problem and describe the mathematical models
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18. mailto:[email protected]
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Table 1
Summary of symbols introduced in Section 2.1.
Av Vent pipe cross-section (m
2)
hwc(t) Height of water column in the tank (m)
mB(t) Mass of air in ballast tank (kg)
mF(t) Mass of air in pressure bottle (kg)
mF0 Initial mass of air in pressure bottle (kg)
_mFðtÞ Mass flow rate from pressure bottle (kg/s)
_m ðtÞ Mass flow rate through venting valve (kg/s)
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447442
for blowing and venting processes, vehicle motion and external
disturbances. In Section 3 we propose a feedback control
scheme
for the hovering submarine consisting of a sliding mode
controller
acting on a previously input–output exactly linearized system.
Section 4 is devoted to the results of numerical simulations
testing
the performance of the proposed hovering system. Finally, in
Section 5 we discuss the obtained results and present some
conclusions.
v
pB(t) Pressure in ballast tank (Pa)
pext(t) Pressure outside the venting valve (Pa)
19. pF(t) Pressure in bottle (Pa)
pF0 Initial pressure in bottle (Pa)
pSEA(t) Pressure outside the outlet hole (Pa)
qB(t) Water flow through outlet hole (m
3/s)
Rg Gas constant for air (J/kg K)
TB Water temperature (K)
VB0 Initial air volume in ballast tank (m
3)
VB(t) Volume of air in ballast tank (m
3)
VF Pressure bottle volume (m
3)
γ Isentropic constant
ρ Density of water (kg/m3)
2. Problem formulation. Mathematical models
As we said above, we will consider a manned submarine,
particularly the Navantia P-650 design, as the test platform for
our hovering system. Details about the hydrodynamic character-
istic and the blowing/venting system can be found in García et
al.
(2011) and Font et al. (to appear) respectively.
Our objective is to maintain a desired depth with no propulsion
(and thus without any help from the control surfaces) in the face
of external disturbances like changes in water density or forces
induced by the sea state. In the next sections we review the
mathematical models for the blowing/venting system, vehicle
motion and external disturbances.
2.1. Blowing/venting system
20. The blowing and venting system is composed of the tank, the
pressure bottle, the blowing and venting valves and the outlet/
inlet hole located at the bottom of the tank. When the blowing
valve is opened, air flows into the tank from the bottle
increasing
the pressure and forcing the water to flow out through the outlet
hole. When the venting valve is opened, air can flow out from
the
tank letting the water flow back into the tank. Fig. 1 shows
a schematic view of these processes. The subindex F denotes
conditions in the bottle, the subindex B denotes conditions in
the
tank, _mF and _mv are respectively the mass flow rates through
blowing and venting valves, qB is the water flow through the
tank
hole, hwc is the height of the water column in the tank and
pSEA,
pext are respectively the hydrostatic pressures outside the flood
port and venting outlet (they differ in the depth at which each
one
is evaluated). We will use 3 variables for each tank to
completely
describe its state: mass of air in the bottle, mF, mass of air in
the
tank, mB, and pressure in the tank, pB. We refer the reader to
Font
et al. (to appear) and Font and García (2011) for a more detailed
description of the model presented below. The symbols
introduced
in this section are summarized in Table 1.
Due to the high pressure difference between bottle and tank,
the flow from the bottle will usually be supersonic. As the
bottle
empties, however, this difference decreases and the flow can
21. become subsonic if the pressure ratio is below the critical
pressure
Fig. 1. Blowing and venting processes.
ratio Pc ¼ ððγ þ 1Þ=2Þγ=ðγ�1Þ, with γ the isentropic constant.
Let s
denote the variable aperture of the blowing valve, the equation
for
the mass of air in the bottle in both the supersonic and the
subsonic cases is
_mF tð Þ ¼ s tð ÞA
mFðtÞγþ1pF0
mγF0VF
!1=2
μ pB tð Þ; mF tð Þ
� �
ð1Þ
where A ¼ _mFmaxðð2=ðγ þ
1ÞÞ�ðγþ1Þ=ðγ�1ÞVF=γpF0mF0Þ1=2, with _mFmax
the maximum mass flow rate from the bottle, experimentally
measured, VF is the bottle volume, pF0, mF0 are respectively
the
initial pressure and mass of air in the bottle and
μ pB; mF
� �
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ffiffiffiffiffiffiffiffiffiffiffiffiffi
γ
23. � �γ
0
[email protected]
1
CCA
ðγþ1Þ=γ0
[email protected]
1
CCA
vuuuuut ; 1opFpB oPc
0;
pF
pB
r1:
8>>>>>>>>>>>>>><
>>>>>>>>>>>>>>:
The mass flow through the venting valve is obtained similarly.
The variation in the mass of air in the tank is the difference
between the mass flow rate from the bottle and the mass flow
rate
through the venting valve. Let s denote the aperture of the
venting
valve. Then, the equation for the mass of air in the tank is
_mB tð Þ þ _mF tð Þ ¼ �μ
pextðtÞ
pBðtÞ
� �
sðtÞAvpBðtÞffiffiffiffiffiffiffiffiffiffi
24. RgTB
p ; ð2Þ
where Av is the venting pipe system cross-section, Rg is the gas
constant for air, TB is the temperature in the tank and
μðpextðtÞ=pBðtÞÞ
is a function of the tank and outside pressures obtained by curve
fitting from experimental measures.
Finally, the variation in the tank pressure is obtained from the
perfect gas equation as
mBðtÞ
pBðtÞ
_pB tð Þ� _mB tð Þ ¼ �
pBðtÞqBðtÞ
RgTB
; ð3Þ
where qB(t) is the water flow through the flood port.
We will consider two hovering tanks, bow and aft, with their
respective bottles and blowing and venting valves. The
geometric
characteristics of the blowing and venting system have been
adapted from the characteristics of the main ballast tanks
blowing
and venting system which can be found in Font et al. (to
appear).
Table 2
25. Hovering system characteristics.
Parameter Stern tank Bow tank
Flood port area, Ah ðm2Þ 0.1 0.1
Venting pipe system cross-section, Av ðm2Þ 9.62 � 10�4 9.62
� 10�4
Tank height, Htk (m) 1.5874 1.5874
Maximum mass flow rate, _mF;max ðkg=sÞ �2 �2
Initial bottle pressure, pF0 (Pa) 2.5 � 107 2.5 � 107
Initial bottle temperature, TF0 (K) 4 4
Tank volume, VBB ðm3Þ 293 293
Bottle volume, VF ðm3Þ 0.8 0.8
Tank location (m)
xb �28.6 23.7
yb 0 0
zb 0.595 0.595
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447 443
However, since the size of the main ballast tanks is not
adequate
for the hovering system requirements, the size of the hovering
tanks has been considerably reduced with respect to the main
ballast tanks. Precisely, each hovering tank has a volume of 4
m3
and is initially filled up to half of its capacity. In the same way,
the
maximum mass flow rate from the bottle has been reduced to
2 kg/s. The main characteristics of the hovering system are
summarized in Table 2. We note that these are tentative values
in the context of this preliminary study. Of course, the
implemen-
tation in a real ship would require the careful selection of the
26. most
appropriate values.
2.2. Vehicle motion
Vehicle motion is given, as usual, by Feldman's (1979) 6 degree
of freedom equations of motion. The final form of these
equations
adapted to the particular vehicle we are considering can be
found
in García et al. (2011).
These equations assume the mass of the submarine to be
constant. In our case, however, water flowing in or out of the
hovering tanks will cause mass variations at several points of
the
vehicle. We will therefore need to write vehicle mass, weight,
moments and products of inertia and location of center of
gravity
as a function of the amount of water in the tanks.
Let m0 be the initial mass of the vehicle and Δmstern, Δmbow
the
mass variations in the stern and bow tanks respectively (positive
when mass is added). This mass variation can be obtained by
multiplying the increase in the volume occupied by water with
respect to the initial condition by the density of water, ρ. It is
easy
to see that this increase coincides with the decrease in the
volume
of air, i.e. the difference between the initial and momentary
volume of air in the tank. This way
Δmfstern;bowg tð Þ ¼ ρ VB0�VBfstern;bowg tð Þ
� �
27. ¼ ρ VB0�
mBfstern;bowg ðtÞRgTB
pBfstern;bowg
!
;
and the momentary mass of the vehicle is given by
mðtÞ ¼ m0 þ ΔmsternðtÞ þ ΔmbowðtÞ:
The rest of parameters can be obtained analogously (Font et al.,
to
appear).
It is worth noting that coefficient based models can lead to
inaccurate results in certain situations. In movements at high
angles of incidence, like hovering, vortices generated by
crossflow
separation of the hull boundary layer and the trailing wakes
from appendages can produce significant loads (Watson et al.,
1993). We do think, however, that this standard model is
enough
for the purposes of this preliminary study. Up to our best
knowl-
edge, it is not easy to account for these phenomena without
using
computationally intensive techniques that are not suitable for
control system design (see for instance Bettle et al., 2009). Our
objective (see Section 3) is to design a robust controller that
can
maintain consistent performance in the presence of large
external
disturbances and/or modelling uncertainties. This approach has
been successfully used in the design of a variety of hovering
AUVs.
28. We refer the reader to, for example, Riedel et al. (2005) where a
sliding mode controller is used to address a similar problem.
2.3. Complete model in affine form
Let the state vector be
x ¼ ½x; y; z; ϕ; θ; ψ; u; v; w; p; q; r; …
mFstern ; mBstern ; pBstern ; mFbow ; mBbow ; pBbow � ð4Þ
composed of the state variables for the stern and bow tanks, the
vehicle position and orientation, x, y, z and ϕ (roll), θ (pitch)
and
ψ (yaw) respectively, and the linear and angular velocities, u, v,
w
and p, q, r. Let u ¼ ½sstern; sstern; sbow; sbow� be the control
vector. The
state law is composed of the equations of motion (see Section
2.2)
plus a set of Eqs. (1)–(3) for each of the two hovering tanks.
This
state law can be expressed in compact form as
AðxÞ _x ¼ Φðx; uÞ ð5Þ
where A (x) is the mass matrix of the system.
As we will see in Section 3, it is convenient, from the point of
view of control system design, to express (5) in the affine form
_x ¼ fðxÞ þ ∑
m
i
giðxÞui: ð6Þ
29. This expression can be obtained from (5) as follows. It is easy
to
see that the state law (5) can be expressed as
AEMðxÞ 012�6
06�12 ABV ðxÞ
" #
_x ¼
ΦEMðxÞ
ΦBV ðx; uÞ
" #
where AEM (x) and ΦEMðxÞ are respectively the mass matrix
and the
right hand side of the equations of motion, depending only on
the
state variable, ΦBV ðx; uÞ is the right hand side of Eqs. (1)–
(3), and
ABV xð Þ ¼
1 0 0 0 0 0
1 1 0 0 0 0
0 �1 mBstern
pBstern
0 0 0
0 0 0 1 0 0
0 0 0 1 1 0
0 0 0 0 �1 mBbow
30. pBbow
2
6666666666664
3
7777777777775
Since both AEM (x) and ABV (x) take non-singular values for
any
x (Font et al., to appear), the state law can be expressed in
explicit
form as
_x ¼
A�1EMΦEMðxÞ
A�1BV ΦBV ðx; uÞ
" #
It is immediate to separate the terms where the control input
appears to obtain the desired form (6) with
f xð Þ ¼ A�1EMΦEM; 0; 0;
pBstern qBstern
mBstern RgTB
; 0; 0;
pBbow qBbow
mBbow RgTB
T
31. R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447444
and gi; 1rmr4, the columns of the matrix
012�4
αstern 0 0 0
�αstern βstern 0 0
�pBstern
mBstern
αstern
pBstern
mBstern
βstern 0 0
0 0 αbow 0
0 0 �αbow βbow
0 0 �
pBbow
mBbow
αbow
pBbow
mBbow
βbow
2
6666666666666664
3
7777777777777775
32. with
αfstern;bowg ¼ μfstern;bowgA
mγþ1Ffstern;bowg pF0
mγF0VF
0
@
1
A
1=2
;
βfstern;bowg ¼ �μfstern;bowg
AvpBfstern;bowgffiffiffiffiffiffiffiffiffiffi
RgTB
p :
2.4. External disturbances
The main disturbances that a submerged submarine must face
are the wave induced forces and the changes in its buoyancy
caused by seawater density changes and hull compressibility.
2.4.1. Wave induced forces
The surface elevation of a long-crested irregular sea can be
modelled as a sum of N regular wave components. The
amplitude
of each regular wave is given by a wave energy spectrum, in
this
case the Pierson–Moskowitz spectrum. A detailed description of
this approach can be found in Fossen (1994).
33. To model the effect of an irregular sea over the vehicle it is
usual to consider 1st and 2nd order wave disturbances. Using
the
superposition principle the 1st order forces (in this work we
will
consider a heave force and a pitching moment) can be modelled
as
the sum of the forces caused by each individual regular compo-
nent, i.e. a wave with the same frequency and different
amplitudes
and phase angles.
For this work, the amplitude and phase angle of the vertical
force and pitching moment, Fi; Mi; ΦF;i; ΦM;i, have been
obtained
experimentally using captive tests on a scale model. The ampli-
tudes and phase angles under regular waves of different wave-
lengths were measured for several heading directions. These
data
were then adjusted using a least-squares fit. Fig. 2 shows the
results for the vertical force and pitching moment at 1801 wave
Fig. 2. Non-dimensional force (left) and moment (right) vs non-
dimensional wave leng
solid line.
heading. In this case the fitted curves are
F
ρgHL2
¼
0:01161
λ
L
34. λ
L
� �2
�3:898λ
L
þ 5:046
M
ρgHL3
¼
0:001932
λ
L
λ
L
� �2
�2:398λ
L
þ 1:917
where L is the vehicle length, λ the wave length, H the wave
height
and g the acceleration due to gravity. A similar methodology
was
used in Byström (1988).
The 2nd order force, or suction force, is an upward force,
35. usually small in comparison with 1st order forces. Under an
irregular sea, this is a slowly varying force (Booth, 1983). For
the
purpose of this work, however, it suffices to consider a mean
constant value. The series of captive tests mentioned above
provided a mean value for the suction force under Sea State 5 of
0.8 ton.
Both the 1st and 2nd order forces are assumed to decay
exponentially with depth in the form e�kiðzðtÞ�z0Þ where ki
is the
wave number of each component. For the suction force, k was
taken corresponding to the peak of the spectrum.
2.4.2. Compressibility and water density
Vehicle buoyancy can be expressed as B ¼ ρg∇ fd, where ρ is
the
water density and ∇ fd is the form displacement, i.e. the total
displaced volume in submerged condition. In trim condition the
vehicle buoyancy is equal to its weight. If the submarine moves
down from the equilibrium position, however, the outside pres-
sure will compress the hull and other materials reducing the
vehicle buoyancy, which will result in a downward acceleration.
In
the same way, moving the submarine up from its equilibrium
position will result in an upward acceleration (see, for instance,
Booth, 1983). The displacement variation caused by pressure
hull
compressibility can be considered linear with depth in the form
ΔVcðzÞ ¼ αðz�z0Þ, where α is a compression coefficient that
can be
easily determined for each particular vehicle.
Similarly, changes in seawater density will modify the vehicle
buoyancy also causing a destabilizing effect. The seawater
density
36. as a function of temperature and salinity can be obtained using
the
algorithms described in Fofonoff and Millard (1983). Let us
assume
that, for a certain temperature/salinity vertical profile, the water
density can be expressed as a function of depth. Let ρðzÞ
denote
this variable density (we will continue to denote the nominal
value by ρ). The vehicle buoyancy is given by
BðzÞ ¼ ρðzÞgð∇ fd�ΔVcðzÞÞ: ð7Þ
th for wave heading 1801. Measured values are shown as circles
and fitted curve as
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447 445
3. Sliding mode controller
Sliding mode control (Slotine and Li, 1991) has been success-
fully applied in several AUV designs and has been identified as
one
of the most promising control strategies to account for large
disturbances or model uncertainties (Lea et al., 1999). Although
sliding mode control is often applied over a linearized model
(Demirci and Kerestecioğlu, 2004; Riedel et al., 2005), our
previous
experience with the dynamic model of the submarine leads us to
think that in this case, due to high coupling and severe
nonlinea-
rities, this could be inaccurate. Instead, we propose an exact
input–output feedback linearization (Isidori, 1995). The sliding
control of a nonlinear system using input–output linearization is
discussed more generally in Fossen and Foss (1991).
37. For the hovering control we will consider a single output, the
depth z, and 4 inputs, the apertures of the blowing and venting
valves. This way, the system can be expressed (see Section 2.3)
as
_x ¼ fðxÞ þ ∑
m
i
giðxÞui
y ¼ hðxÞ ¼ z: ð8Þ
Let Lfh, Lgi h denote the Lie derivatives of h with respect to f
and
gi respectively. The repeated Lie derivatives are recursively
defined
as Ljf h ¼ Lf ðL
j�1
f hÞ. In the same way, Lgi L
j
f h ¼ Lgi ðL
j
f hÞ. The computa-
tion of Lgi L
j
f h; j ¼ 1…r, shows that the system has a well defined
relative degree r¼3. We refer the reader to Isidori (1995) for
more
detail on this subject.
38. Define FðxÞ ¼ Lrf h and GðxÞ ¼ ½Lg1 L
r�1
f h ⋯ Lgm L
r�1
f h�. This way (8)
can be expressed as
yðrÞ ¼ FðxÞ þ GðxÞ
u1
⋮
um
2
64
3
75 ð9Þ
that can be reduced to
yð3Þ ¼ v ð10Þ
Fig. 3. Evolution of depth for Scenario 1.
Fig. 4. Flooded volume in stern (left) an
using the control law
u ¼ GnðxÞðv�FðxÞÞ ð11Þ
where GnðxÞ is a vector such that GðxÞGnðxÞ ¼ 1.
Once the input–output relation in system (8) has been reduced
to the linear form (10) it is easy to use linear control techniques
to
stabilize (10). The exact cancellation of the nonlinear terms,
39. however, relies on the perfect knowledge of fðxÞ and giðxÞ,
some-
thing that can hardly be achieved due to modelling errors or
unknown external disturbances. We propose the use of sliding
mode control to account for this issue.
Let y ¼ ½y _y ⋯ yðr�1Þ� be the output vector, yd ¼ ½yd _yd
⋯ yðr�1Þd � a
desired output vector and ~y ¼ y�yd ¼ ½~y _~y ⋯ ~yðr�1Þ�
the tracking
error vector. For r¼3 the sliding surface can be defined as
s ¼ €~y þ 2λ _~y þ λ2 ~y:
Taking the derivative with respect to time in the above equation
and taking into account that in our case yð3Þd ¼ 0 and in the
absence
of uncertainties yð3Þ ¼ v, the equivalent control is veq ¼ �2λ
€~y�λ2 _~y .
Let F̂ ðxÞ; ĜðxÞ be the estimates of FðxÞ and GðxÞ,
respectively. If
the signum function is linearly smoothed inside a boundary
layer
of thickness Φ (Slotine and Li, 1991), then the proposed control
law
is
u ¼ ĜnðxÞð�2λ €~y�λ2 _~y�k satðs=ΦÞ�F̂ ðxÞÞ ð12Þ
with satð�Þ the saturation function.
If we consider no errors in the modelling of the hovering
system, then ĜðxÞ ¼ GðxÞ. Let ΔZjFðxÞ�F̂ ðxÞj be an upper
bound of
the error in the estimation of FðxÞ, then it suffices to choose
40. k4Δ.
Considering extreme values for seawater density, the value of Δ
for changes in water density can be obtained. In the case of
wave
induced forces the value of Δ cannot be explicitly obtained due
to
the random nature of these forces. However, for a given sea
state,
upper bounds can be estimated. The choice of k¼0.001 is
enough
to account for both the density changes and the wave induced
forces in Sea State 5. For the rest of parameters we have taken
d bow (right) tanks for Scenario 1.
Fig. 5. Depth evolution for Scenario 2.
Fig. 6. Blowing valve aperture (top) and venting valve aperture
(bottom) for Scenario 2.
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447446
λ ¼ 0:05, Φ ¼ 0:001. If modelling uncertainties, like those
discussed
in Section 2.2, were considered, an upper bound of the
associated
error should also be estimated and taken into account in the
choice of k.
4. Numerical simulations
The aim of this section is to test the performance of the
proposed hovering system against the disturbances treated in
Section 2.4. Two different scenarios are considered. In both
cases
41. the submarine starts at straight and level flight at 4 kn and at
t¼0
the propeller is stopped and the vehicle progressively loses
forward speed (it is around 0.4 kn at the end of simulation
time).
In the first scenario (Figs. 3 and 4) the submarine is at 50 m
depth
under the action of sea wave disturbances (Sea State 5, with
H1/3¼3.25 m, Tz¼6.2 s). Additionally, the hovering system has
to
compensate for sudden changes in water temperature. For
0rtr1250 s temperature varies with depth as TðzÞ ¼ 20�0:05z
1C.
At t¼1250 s, the temperature gradient is changed to TðzÞ ¼
5 þ 0:05z 1C. The vehicle buoyancy is affected by these
gradients
according to (7).
Flooded volume in stern and bow tanks is plotted in Fig. 4. We
can see how the buoyancy variation is rapidly compensated by
emptying the tanks. Depth evolution is plotted in Fig. 3.
Although
depth keeping is satisfactory for both temperature gradients, we
can see how, after the instability caused by the density jump,
the
second gradient, where the density increases with depth, is more
favourable. Indeed, density increasing with depth tends to com-
pensate the effect of hull compressibility while decreasing
density
adds up to …
Ocean Engineering 72 (2013) 441–447
Contents lists available at ScienceDirect
42. Ocean Engineering
0029-80
http://d
n Corr
E-m
jgpelaez
journal homepage: www.elsevier.com/locate/oceaneng
On a submarine hovering system based on blowing and venting
of ballast tanks
Roberto Font a,n, Javier García-Peláez b
a Departamento de Matemática Aplicada y Estadística, ETSI
Industriales, Universidad Politécnica de Cartagena, 30202
Cartagena, Spain
b Direction of Engineering, DICA, Navantia S. A., Cartagena
30205, Spain
a r t i c l e i n f o
Article history:
Received 27 July 2012
Accepted 27 July 2013
Available online 19 August 2013
Keywords:
Manned submarines
Underwater hovering
Variable buoyancy
Sliding control
18/$ - see front matter & 2013 Elsevier Ltd. A
x.doi.org/10.1016/j.oceaneng.2013.07.021
esponding author. Tel.: +34 968 338 947; fax:
ail addresses: [email protected], robertojav
43. @navantia.es (J. García-Peláez).
a b s t r a c t
A submarine hovering system based on the blowing and venting
of a set of dedicated tanks is
investigated. We review the mathematical models involved and
propose a sliding mode controller for
the input–output linearized system. Numerical simulation
results support the idea that this could be a
promising hovering strategy for manned submarines,
autonomous underwater vehicles or other plat-
forms.
& 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Underwater hovering, the ability to statically keep a desired
depth, is at the same time a challenge, due to many uncertainties
associated with the underwater environment, and a very impor-
tant feature for both small size autonomous underwater vehicles
(AUVs) and large manned submarines. In the last years several
hovering AUVs have been developed (see Vasilescu et al., 2010
for
a survey on the subject). The hovering facility expands the
capabilities of AUVs allowing them to perform more complex
missions that previously could only be carried out through
Remotely Operated Vehicles (ROVs). For manned submarines,
accurate hovering can be an invaluable tool, for example, for
safe
swimmer delivery, cover supply replacement or the deployment
and recovery of AUVs, a subject that has recently raised an
extraordinary interest (see for example Hardy and Barlow,
2008;
Martínez-Conesa and Oakley, 2011).
From the technological point of view, AUVs usually hover by
44. using thrusters (Choi et al., 2003; Li et al., 2011). Due to the
large
energy requirements of this approach, however, buoyancy
control
by pumping seawater in or out of ballast tanks can be used to
save
energy (Vasilescu et al., 2010) or in larger designs (Tangirala
and
Dzielski, 2007). In manned submarines, hovering is
traditionally
performed using hydraulic pumps (Yang and Hao, 2010; Ying
and
Jian, 2010), although not very much information about hovering
ll rights reserved.
+34 968 338 916.
[email protected] (R. Font),
systems is available in the literature due to the military nature
of
these vehicles.
The aim of this work is to investigate the feasibility of a
hovering system in which dedicated tanks are blown and vented
similarly to the way the main ballast tanks are traditionally
operated in manned submarines.
In these vehicles, a variable number of main ballast tanks are
distributed along the hull. In case of emergency the main ballast
tanks can be emptied by blowing into them air from high
pressure
bottles. This way the water is expelled from the tanks, the
vehicle
gains buoyancy and can rise more quickly. To fill the tanks with
water, air is vented out of the ballast tanks. In the previous
works
(Font et al., to appear, 2013) we proposed mathematical models
45. for
the blowing and venting of ballast tanks and showed that the
implementation of a control system for these processes, usually
performed manually, can improve in a significant way the
perfor-
mance and stability in emergency rising manoeuvres. Our objec-
tive is to extend the approach used with the main ballast tanks
to a
set of dedicated hovering tanks (see Section 2 for details) in
order
to test the feasibility of a hovering system based on blowing and
venting of tanks. Although throughout this paper we will use a
manned submarine as test platform, it is worth noting that the
use
of blowing and venting of tanks as hovering control is not
limited
to these vehicles nor is our intention to carry out the discussion
of
conceptual designs for the compromise between efficiency and
stealth in a hovering system ready for military applications.
Indeed, this technology could be applicable to manned submar-
ines, AUVs, ROVs or any offshore platform requiring variable
buoyancy control.
The rest of the paper is organized as follows. In Section 2
we formulate the problem and describe the mathematical models
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Table 1
Summary of symbols introduced in Section 2.1.
Av Vent pipe cross-section (m
2)
hwc(t) Height of water column in the tank (m)
mB(t) Mass of air in ballast tank (kg)
mF(t) Mass of air in pressure bottle (kg)
mF0 Initial mass of air in pressure bottle (kg)
_mFðtÞ Mass flow rate from pressure bottle (kg/s)
_m ðtÞ Mass flow rate through venting valve (kg/s)
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447442
for blowing and venting processes, vehicle motion and external
disturbances. In Section 3 we propose a feedback control
scheme
for the hovering submarine consisting of a sliding mode
controller
acting on a previously input–output exactly linearized system.
Section 4 is devoted to the results of numerical simulations
testing
the performance of the proposed hovering system. Finally, in
Section 5 we discuss the obtained results and present some
conclusions.
v
47. pB(t) Pressure in ballast tank (Pa)
pext(t) Pressure outside the venting valve (Pa)
pF(t) Pressure in bottle (Pa)
pF0 Initial pressure in bottle (Pa)
pSEA(t) Pressure outside the outlet hole (Pa)
qB(t) Water flow through outlet hole (m
3/s)
Rg Gas constant for air (J/kg K)
TB Water temperature (K)
VB0 Initial air volume in ballast tank (m
3)
VB(t) Volume of air in ballast tank (m
3)
VF Pressure bottle volume (m
3)
γ Isentropic constant
ρ Density of water (kg/m3)
2. Problem formulation. Mathematical models
As we said above, we will consider a manned submarine,
particularly the Navantia P-650 design, as the test platform for
our hovering system. Details about the hydrodynamic character-
istic and the blowing/venting system can be found in García et
al.
(2011) and Font et al. (to appear) respectively.
Our objective is to maintain a desired depth with no propulsion
(and thus without any help from the control surfaces) in the face
of external disturbances like changes in water density or forces
induced by the sea state. In the next sections we review the
mathematical models for the blowing/venting system, vehicle
motion and external disturbances.
48. 2.1. Blowing/venting system
The blowing and venting system is composed of the tank, the
pressure bottle, the blowing and venting valves and the outlet/
inlet hole located at the bottom of the tank. When the blowing
valve is opened, air flows into the tank from the bottle
increasing
the pressure and forcing the water to flow out through the outlet
hole. When the venting valve is opened, air can flow out from
the
tank letting the water flow back into the tank. Fig. 1 shows
a schematic view of these processes. The subindex F denotes
conditions in the bottle, the subindex B denotes conditions in
the
tank, _mF and _mv are respectively the mass flow rates through
blowing and venting valves, qB is the water flow through the
tank
hole, hwc is the height of the water column in the tank and
pSEA,
pext are respectively the hydrostatic pressures outside the flood
port and venting outlet (they differ in the depth at which each
one
is evaluated). We will use 3 variables for each tank to
completely
describe its state: mass of air in the bottle, mF, mass of air in
the
tank, mB, and pressure in the tank, pB. We refer the reader to
Font
et al. (to appear) and Font and García (2011) for a more detailed
description of the model presented below. The symbols
introduced
in this section are summarized in Table 1.
Due to the high pressure difference between bottle and tank,
the flow from the bottle will usually be supersonic. As the
49. bottle
empties, however, this difference decreases and the flow can
become subsonic if the pressure ratio is below the critical
pressure
Fig. 1. Blowing and venting processes.
ratio Pc ¼ ððγ þ 1Þ=2Þγ=ðγ�1Þ, with γ the isentropic constant.
Let s
denote the variable aperture of the blowing valve, the equation
for
the mass of air in the bottle in both the supersonic and the
subsonic cases is
_mF tð Þ ¼ s tð ÞA
mFðtÞγþ1pF0
mγF0VF
!1=2
μ pB tð Þ; mF tð Þ
� �
ð1Þ
where A ¼ _mFmaxðð2=ðγ þ
1ÞÞ�ðγþ1Þ=ðγ�1ÞVF=γpF0mF0Þ1=2, with _mFmax
the maximum mass flow rate from the bottle, experimentally
measured, VF is the bottle volume, pF0, mF0 are respectively
the
initial pressure and mass of air in the bottle and
μ pB; mF
� �
¼
ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
51. mF0
� �γ
0
[email protected]
1
CCA
ðγþ1Þ=γ0
[email protected]
1
CCA
vuuuuut ; 1opFpB oPc
0;
pF
pB
r1:
8>>>>>>>>>>>>>><
>>>>>>>>>>>>>>:
The mass flow through the venting valve is obtained similarly.
The variation in the mass of air in the tank is the difference
between the mass flow rate from the bottle and the mass flow
rate
through the venting valve. Let s denote the aperture of the
venting
valve. Then, the equation for the mass of air in the tank is
_mB tð Þ þ _mF tð Þ ¼ �μ
pextðtÞ
pBðtÞ
52. � �
sðtÞAvpBðtÞffiffiffiffiffiffiffiffiffiffi
RgTB
p ; ð2Þ
where Av is the venting pipe system cross-section, Rg is the gas
constant for air, TB is the temperature in the tank and
μðpextðtÞ=pBðtÞÞ
is a function of the tank and outside pressures obtained by curve
fitting from experimental measures.
Finally, the variation in the tank pressure is obtained from the
perfect gas equation as
mBðtÞ
pBðtÞ
_pB tð Þ� _mB tð Þ ¼ �
pBðtÞqBðtÞ
RgTB
; ð3Þ
where qB(t) is the water flow through the flood port.
We will consider two hovering tanks, bow and aft, with their
respective bottles and blowing and venting valves. The
geometric
characteristics of the blowing and venting system have been
adapted from the characteristics of the main ballast tanks
blowing
and venting system which can be found in Font et al. (to
appear).
53. Table 2
Hovering system characteristics.
Parameter Stern tank Bow tank
Flood port area, Ah ðm2Þ 0.1 0.1
Venting pipe system cross-section, Av ðm2Þ 9.62 � 10�4 9.62
� 10�4
Tank height, Htk (m) 1.5874 1.5874
Maximum mass flow rate, _mF;max ðkg=sÞ �2 �2
Initial bottle pressure, pF0 (Pa) 2.5 � 107 2.5 � 107
Initial bottle temperature, TF0 (K) 4 4
Tank volume, VBB ðm3Þ 293 293
Bottle volume, VF ðm3Þ 0.8 0.8
Tank location (m)
xb �28.6 23.7
yb 0 0
zb 0.595 0.595
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447 443
However, since the size of the main ballast tanks is not
adequate
for the hovering system requirements, the size of the hovering
tanks has been considerably reduced with respect to the main
ballast tanks. Precisely, each hovering tank has a volume of 4
m3
and is initially filled up to half of its capacity. In the same way,
the
maximum mass flow rate from the bottle has been reduced to
2 kg/s. The main characteristics of the hovering system are
summarized in Table 2. We note that these are tentative values
in the context of this preliminary study. Of course, the
54. implemen-
tation in a real ship would require the careful selection of the
most
appropriate values.
2.2. Vehicle motion
Vehicle motion is given, as usual, by Feldman's (1979) 6 degree
of freedom equations of motion. The final form of these
equations
adapted to the particular vehicle we are considering can be
found
in García et al. (2011).
These equations assume the mass of the submarine to be
constant. In our case, however, water flowing in or out of the
hovering tanks will cause mass variations at several points of
the
vehicle. We will therefore need to write vehicle mass, weight,
moments and products of inertia and location of center of
gravity
as a function of the amount of water in the tanks.
Let m0 be the initial mass of the vehicle and Δmstern, Δmbow
the
mass variations in the stern and bow tanks respectively (positive
when mass is added). This mass variation can be obtained by
multiplying the increase in the volume occupied by water with
respect to the initial condition by the density of water, ρ. It is
easy
to see that this increase coincides with the decrease in the
volume
of air, i.e. the difference between the initial and momentary
volume of air in the tank. This way
Δmfstern;bowg tð Þ ¼ ρ VB0�VBfstern;bowg tð Þ
55. � �
¼ ρ VB0�
mBfstern;bowg ðtÞRgTB
pBfstern;bowg
!
;
and the momentary mass of the vehicle is given by
mðtÞ ¼ m0 þ ΔmsternðtÞ þ ΔmbowðtÞ:
The rest of parameters can be obtained analogously (Font et al.,
to
appear).
It is worth noting that coefficient based models can lead to
inaccurate results in certain situations. In movements at high
angles of incidence, like hovering, vortices generated by
crossflow
separation of the hull boundary layer and the trailing wakes
from appendages can produce significant loads (Watson et al.,
1993). We do think, however, that this standard model is
enough
for the purposes of this preliminary study. Up to our best
knowl-
edge, it is not easy to account for these phenomena without
using
computationally intensive techniques that are not suitable for
control system design (see for instance Bettle et al., 2009). Our
objective (see Section 3) is to design a robust controller that
can
maintain consistent performance in the presence of large
external
disturbances and/or modelling uncertainties. This approach has
56. been successfully used in the design of a variety of hovering
AUVs.
We refer the reader to, for example, Riedel et al. (2005) where a
sliding mode controller is used to address a similar problem.
2.3. Complete model in affine form
Let the state vector be
x ¼ ½x; y; z; ϕ; θ; ψ; u; v; w; p; q; r; …
mFstern ; mBstern ; pBstern ; mFbow ; mBbow ; pBbow � ð4Þ
composed of the state variables for the stern and bow tanks, the
vehicle position and orientation, x, y, z and ϕ (roll), θ (pitch)
and
ψ (yaw) respectively, and the linear and angular velocities, u, v,
w
and p, q, r. Let u ¼ ½sstern; sstern; sbow; sbow� be the control
vector. The
state law is composed of the equations of motion (see Section
2.2)
plus a set of Eqs. (1)–(3) for each of the two hovering tanks.
This
state law can be expressed in compact form as
AðxÞ _x ¼ Φðx; uÞ ð5Þ
where A (x) is the mass matrix of the system.
As we will see in Section 3, it is convenient, from the point of
view of control system design, to express (5) in the affine form
_x ¼ fðxÞ þ ∑
m
i
57. giðxÞui: ð6Þ
This expression can be obtained from (5) as follows. It is easy
to
see that the state law (5) can be expressed as
AEMðxÞ 012�6
06�12 ABV ðxÞ
" #
_x ¼
ΦEMðxÞ
ΦBV ðx; uÞ
" #
where AEM (x) and ΦEMðxÞ are respectively the mass matrix
and the
right hand side of the equations of motion, depending only on
the
state variable, ΦBV ðx; uÞ is the right hand side of Eqs. (1)–
(3), and
ABV xð Þ ¼
1 0 0 0 0 0
1 1 0 0 0 0
0 �1 mBstern
pBstern
0 0 0
0 0 0 1 0 0
0 0 0 1 1 0
58. 0 0 0 0 �1 mBbow
pBbow
2
6666666666664
3
7777777777775
Since both AEM (x) and ABV (x) take non-singular values for
any
x (Font et al., to appear), the state law can be expressed in
explicit
form as
_x ¼
A�1EMΦEMðxÞ
A�1BV ΦBV ðx; uÞ
" #
It is immediate to separate the terms where the control input
appears to obtain the desired form (6) with
f xð Þ ¼ A�1EMΦEM; 0; 0;
pBstern qBstern
mBstern RgTB
; 0; 0;
pBbow qBbow
mBbow RgTB
T
59. R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447444
and gi; 1rmr4, the columns of the matrix
012�4
αstern 0 0 0
�αstern βstern 0 0
�pBstern
mBstern
αstern
pBstern
mBstern
βstern 0 0
0 0 αbow 0
0 0 �αbow βbow
0 0 �
pBbow
mBbow
αbow
pBbow
mBbow
βbow
2
6666666666666664
3
60. 7777777777777775
with
αfstern;bowg ¼ μfstern;bowgA
mγþ1Ffstern;bowg pF0
mγF0VF
0
@
1
A
1=2
;
βfstern;bowg ¼ �μfstern;bowg
AvpBfstern;bowgffiffiffiffiffiffiffiffiffiffi
RgTB
p :
2.4. External disturbances
The main disturbances that a submerged submarine must face
are the wave induced forces and the changes in its buoyancy
caused by seawater density changes and hull compressibility.
2.4.1. Wave induced forces
The surface elevation of a long-crested irregular sea can be
modelled as a sum of N regular wave components. The
amplitude
of each regular wave is given by a wave energy spectrum, in
this
61. case the Pierson–Moskowitz spectrum. A detailed description of
this approach can be found in Fossen (1994).
To model the effect of an irregular sea over the vehicle it is
usual to consider 1st and 2nd order wave disturbances. Using
the
superposition principle the 1st order forces (in this work we
will
consider a heave force and a pitching moment) can be modelled
as
the sum of the forces caused by each individual regular compo-
nent, i.e. a wave with the same frequency and different
amplitudes
and phase angles.
For this work, the amplitude and phase angle of the vertical
force and pitching moment, Fi; Mi; ΦF;i; ΦM;i, have been
obtained
experimentally using captive tests on a scale model. The ampli-
tudes and phase angles under regular waves of different wave-
lengths were measured for several heading directions. These
data
were then adjusted using a least-squares fit. Fig. 2 shows the
results for the vertical force and pitching moment at 1801 wave
Fig. 2. Non-dimensional force (left) and moment (right) vs non-
dimensional wave leng
solid line.
heading. In this case the fitted curves are
F
ρgHL2
¼
0:01161
λ
62. L
λ
L
� �2
�3:898λ
L
þ 5:046
M
ρgHL3
¼
0:001932
λ
L
λ
L
� �2
�2:398λ
L
þ 1:917
where L is the vehicle length, λ the wave length, H the wave
height
and g the acceleration due to gravity. A similar methodology
was
used in Byström (1988).
63. The 2nd order force, or suction force, is an upward force,
usually small in comparison with 1st order forces. Under an
irregular sea, this is a slowly varying force (Booth, 1983). For
the
purpose of this work, however, it suffices to consider a mean
constant value. The series of captive tests mentioned above
provided a mean value for the suction force under Sea State 5 of
0.8 ton.
Both the 1st and 2nd order forces are assumed to decay
exponentially with depth in the form e�kiðzðtÞ�z0Þ where ki
is the
wave number of each component. For the suction force, k was
taken corresponding to the peak of the spectrum.
2.4.2. Compressibility and water density
Vehicle buoyancy can be expressed as B ¼ ρg∇ fd, where ρ is
the
water density and ∇ fd is the form displacement, i.e. the total
displaced volume in submerged condition. In trim condition the
vehicle buoyancy is equal to its weight. If the submarine moves
down from the equilibrium position, however, the outside pres-
sure will compress the hull and other materials reducing the
vehicle buoyancy, which will result in a downward acceleration.
In
the same way, moving the submarine up from its equilibrium
position will result in an upward acceleration (see, for instance,
Booth, 1983). The displacement variation caused by pressure
hull
compressibility can be considered linear with depth in the form
ΔVcðzÞ ¼ αðz�z0Þ, where α is a compression coefficient that
can be
easily determined for each particular vehicle.
Similarly, changes in seawater density will modify the vehicle
64. buoyancy also causing a destabilizing effect. The seawater
density
as a function of temperature and salinity can be obtained using
the
algorithms described in Fofonoff and Millard (1983). Let us
assume
that, for a certain temperature/salinity vertical profile, the water
density can be expressed as a function of depth. Let ρðzÞ
denote
this variable density (we will continue to denote the nominal
value by ρ). The vehicle buoyancy is given by
BðzÞ ¼ ρðzÞgð∇ fd�ΔVcðzÞÞ: ð7Þ
th for wave heading 1801. Measured values are shown as circles
and fitted curve as
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447 445
3. Sliding mode controller
Sliding mode control (Slotine and Li, 1991) has been success-
fully applied in several AUV designs and has been identified as
one
of the most promising control strategies to account for large
disturbances or model uncertainties (Lea et al., 1999). Although
sliding mode control is often applied over a linearized model
(Demirci and Kerestecioğlu, 2004; Riedel et al., 2005), our
previous
experience with the dynamic model of the submarine leads us to
think that in this case, due to high coupling and severe
nonlinea-
rities, this could be inaccurate. Instead, we propose an exact
input–output feedback linearization (Isidori, 1995). The sliding
control of a nonlinear system using input–output linearization is
65. discussed more generally in Fossen and Foss (1991).
For the hovering control we will consider a single output, the
depth z, and 4 inputs, the apertures of the blowing and venting
valves. This way, the system can be expressed (see Section 2.3)
as
_x ¼ fðxÞ þ ∑
m
i
giðxÞui
y ¼ hðxÞ ¼ z: ð8Þ
Let Lfh, Lgi h denote the Lie derivatives of h with respect to f
and
gi respectively. The repeated Lie derivatives are recursively
defined
as Ljf h ¼ Lf ðL
j�1
f hÞ. In the same way, Lgi L
j
f h ¼ Lgi ðL
j
f hÞ. The computa-
tion of Lgi L
j
f h; j ¼ 1…r, shows that the system has a well defined
relative degree r¼3. We refer the reader to Isidori (1995) for
more
66. detail on this subject.
Define FðxÞ ¼ Lrf h and GðxÞ ¼ ½Lg1 L
r�1
f h ⋯ Lgm L
r�1
f h�. This way (8)
can be expressed as
yðrÞ ¼ FðxÞ þ GðxÞ
u1
⋮
um
2
64
3
75 ð9Þ
that can be reduced to
yð3Þ ¼ v ð10Þ
Fig. 3. Evolution of depth for Scenario 1.
Fig. 4. Flooded volume in stern (left) an
using the control law
u ¼ GnðxÞðv�FðxÞÞ ð11Þ
where GnðxÞ is a vector such that GðxÞGnðxÞ ¼ 1.
Once the input–output relation in system (8) has been reduced
to the linear form (10) it is easy to use linear control techniques
67. to
stabilize (10). The exact cancellation of the nonlinear terms,
however, relies on the perfect knowledge of fðxÞ and giðxÞ,
some-
thing that can hardly be achieved due to modelling errors or
unknown external disturbances. We propose the use of sliding
mode control to account for this issue.
Let y ¼ ½y _y ⋯ yðr�1Þ� be the output vector, yd ¼ ½yd _yd
⋯ yðr�1Þd � a
desired output vector and ~y ¼ y�yd ¼ ½~y _~y ⋯ ~yðr�1Þ�
the tracking
error vector. For r¼3 the sliding surface can be defined as
s ¼ €~y þ 2λ _~y þ λ2 ~y:
Taking the derivative with respect to time in the above equation
and taking into account that in our case yð3Þd ¼ 0 and in the
absence
of uncertainties yð3Þ ¼ v, the equivalent control is veq ¼ �2λ
€~y�λ2 _~y .
Let F̂ ðxÞ; ĜðxÞ be the estimates of FðxÞ and GðxÞ,
respectively. If
the signum function is linearly smoothed inside a boundary
layer
of thickness Φ (Slotine and Li, 1991), then the proposed control
law
is
u ¼ ĜnðxÞð�2λ €~y�λ2 _~y�k satðs=ΦÞ�F̂ ðxÞÞ ð12Þ
with satð�Þ the saturation function.
If we consider no errors in the modelling of the hovering
system, then ĜðxÞ ¼ GðxÞ. Let ΔZjFðxÞ�F̂ ðxÞj be an upper
68. bound of
the error in the estimation of FðxÞ, then it suffices to choose
k4Δ.
Considering extreme values for seawater density, the value of Δ
for changes in water density can be obtained. In the case of
wave
induced forces the value of Δ cannot be explicitly obtained due
to
the random nature of these forces. However, for a given sea
state,
upper bounds can be estimated. The choice of k¼0.001 is
enough
to account for both the density changes and the wave induced
forces in Sea State 5. For the rest of parameters we have taken
d bow (right) tanks for Scenario 1.
Fig. 5. Depth evolution for Scenario 2.
Fig. 6. Blowing valve aperture (top) and venting valve aperture
(bottom) for Scenario 2.
R. Font, J. García-Peláez / Ocean Engineering 72 (2013) 441–
447446
λ ¼ 0:05, Φ ¼ 0:001. If modelling uncertainties, like those
discussed
in Section 2.2, were considered, an upper bound of the
associated
error should also be estimated and taken into account in the
choice of k.
4. Numerical simulations
The aim of this section is to test the performance of the
proposed hovering system against the disturbances treated in
69. Section 2.4. Two different scenarios are considered. In both
cases
the submarine starts at straight and level flight at 4 kn and at
t¼0
the propeller is stopped and the vehicle progressively loses
forward speed (it is around 0.4 kn at the end of simulation
time).
In the first scenario (Figs. 3 and 4) the submarine is at 50 m
depth
under the action of sea wave disturbances (Sea State 5, with
H1/3¼3.25 m, Tz¼6.2 s). Additionally, the hovering system has
to
compensate for sudden changes in water temperature. For
0rtr1250 s temperature varies with depth as TðzÞ ¼ 20�0:05z
1C.
At t¼1250 s, the temperature gradient is changed to TðzÞ ¼
5 þ 0:05z 1C. The vehicle buoyancy is affected by these
gradients
according to (7).
Flooded volume in stern and bow tanks is plotted in Fig. 4. We
can see how the buoyancy variation is rapidly compensated by
emptying the tanks. Depth evolution is plotted in Fig. 3.
Although
depth keeping is satisfactory for both temperature gradients, we
can see how, after the instability caused by the density jump,
the
second gradient, where the density increases with depth, is more
favourable. Indeed, density increasing with depth tends to com-
pensate the effect of hull compressibility while decreasing
density
adds up to this destabilizing effect (see Section 2.4).
For the second scenario we consider a more unfavourable
situation, with a depth of 35 m and Sea State 5. Fig. 5 shows the
70. evolution of vehicle depth. We can see how, again, the system
shows excellent performance with maximum error around 1.5 m.
The control inputs over a 250 s interval are shown in Fig. 6. In
all
cases there is no appreciable chattering and the oscillations are
smooth and compatible with the physical restrictions
considered.
The autonomy of the air bottles is around 30 min in this
operating condition and above 90 min at the same depth and
Sea State 4.
5. Conclusions
The performance of a hovering system based on blowing and
venting of ballast tanks has been investigated using a manned
submarine as test platform. Simulation results show that this
system has the ability to maintain a desired depth in the
presence
of significant external disturbances.
The blowing and venting of tanks, alone or in conjunction with
another control mechanism, like pumping, seems to be a promis-
ing hovering strategy to be used in manned submarines, AUVs
or
other submarine platforms.
Accuracy and fast response are the potential advantages of this
approach. On the other hand, the dependence on air bottles with
their associated payload and limited autonomy are the main
disadvantages for small platforms like AUVs. In the case of
manned
submarines, the main limitation is the noise generation
associated
with the blowing process. However, since the needed flow rates
are considerably lower than the flow rates used when blowing
the
main ballast tanks, we do believe that this problem could be
71. mitigated with an appropriate design of the blowing system.
This
will be the subject of our future work.
Acknowledgements
This work was supported by projects 2989/10MAE from
Navantia S.A. and 08720/PI/08 from Fundación Séneca,
Agencia
de Ciencia y Tecnología de la Región de Murcia (Programa de
Generación de Conocimiento Científico de Excelencia,
IIPCTRM
2007-10).
References
Bettle, M.C., Gerber, A.G., Watt, G.D., 2009. Unsteady analysis
of the six DOF motion
of a buoyantly rising submarine. Computers and Fluids 38,
1833–1849.
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447 447
Booth, T.B., 1983. Optimal depth control of an underwater
vehicle under a seaway.
In: RINA International Symposium on Naval Submarines,
London, UK.
Byström, L., 1988. Adaptive control of a submarine in a
snorting condition in waves.
In: Warship 88, London.
Choi, H.T., Hanai, A., Choi, S.K., Yuh, J., 2003. Development
72. of an underwater robot,
ODIN-III. In: International Conference on Intelligent Robots
and Systems, Las
Vegas, USA.
Demirci, U., Kerestecioğlu, F., 2004. A re-configuring sliding-
mode controller with
adjustable robustness. Ocean Engineering 31, 1669–1682.
Feldman, J., 1979. Revised Standard Submarine Equations of
Motion. Report
DTNSRDC/SPD-0393-09. David W. Taylor Naval Ship
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Fofonoff, …
486 IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
NOV-DEC 2011
A Review Note for Position Control of an
Autonomous Underwater Vehicle
Ahmed Rhif
Department of Electronics, High Institute of Applied Sciences
and Technologies, Sousse, Tunisia
(Institut Supérieur des Sciences Appliquées et de Technologie
de Sousse)
Abstract
A new autonomous underwater vehicle (AUV) called H160 is
described in this article. The first prototype of
73. this AUV has been realized through collaboration between two
partners, which are the Laboratory of Data
processing, Robotics and Micro electronic of Montpellier
(LIRMM) and the ECA‑HYTEC (specialist in the de‑
sign and manufacture of remote controlled systems in “hostile”
environments). This paper shows a general
presentation of the vehicle, its hardware and software
architecture including the process modeling and the
control law used. Simulation results presented are based on the
AUV mathematical model.
Keywords
Autonomous underwater vehicle, Position control, Sliding mode
control, Underwater vehicle.
1. Introduction
The concept of underwater vehicle is not a recent idea.
The first proposal was designed by William Bourne
in 1578. In 1664, Cornelis Van Drebbel proposed the
first underwater vehicle advancing using 12 oarsmen
equipped with special oars that could be actuated in
order to carry out vertical movements. This ovoid boat
was built of wood and had been tested experimentally.
In 1776, David Bushnell and his brother introduced the
first submarine “Turtle” built out of steel. Its principle
operation was similar to that of the current submarines.
This mobile used a propeller for its propulsion. The
machine was immersed by actuating a valve, allowing
the water admission in a tank which was used as bal-
last. It went up thanks to a pump which expelled water.
Oxygen autonomy was of 30 min (Pararas‑Carayannis,
1976). Nowadays, the submarines have strongly evolved
from a technological point of view. A classification of the
underwater vehicles in two groups is proposed: Manned
vehicles and unmanned vehicles [1].
74. Under the manned vehicles, we can distinguish two
categories of underwater vehicles:
• The large‑sized submarines operated by a crew which
can reside on during long periods. This category
belongs to the military submarines.
• The small‑sized submarines intended for the great
depths’ exploration. The crew of this kind of machine
is reduced (two to three persons) and the oxygen quan-
tity is limited. For example, Nautile was conceived by
Ifremer 1 in 1984 and can immerse up to 6000 m with
three passengers. Its main missions were the search
for hydrothermal sources in the Pacific Ocean.
The unmanned vehicle was specially the interest of the
navy. In 1866, the Austrian navy asked Robert Whitehead
to develop a new weapon for the warships. He showed
the effectiveness of a system propelled at a speed of
3 m/s to a distance of 700 m transporting an explosive
load: The torpedo was born. However, this machine
did not have any monitoring system. Those underwater
vehicles exist in three different technology: those con-
nected to the surface by a cable, vehicle connected by
an acoustic bond, and finally completely autonomous
vehicles [2‑4].
Actually, the first autonomous underwater vehicles
(AUVs) developed during 1960s–1970s were as fol-
lows:
• The Self‑propelled Underwater Research Vehicle
(SPURV, USA, 1977): It weighed 480 kg and could
operate at a speed of 2.2 m/s during 5 hours until
a depth of 3000 m. The vehicle was acoustically
75. controlled from the surface. The researchers used it
to make conductivity and temperature measures to
perfect the theoretical wave modeling.
• Remotely Operated Vehicles (ROVs): Machines
equipped by a camera operated by an operator,
connected to surface via a cable, called umbilical,
by which the orders, energy and/or measurement
are provided. The principal disadvantage of these
robots is the presence of the umbilical which makes
their movements complicated and especially the
extent of their fields of application.
• Unmanned Underwater Vehicles (UUVs): Uninhabited
underwater machines which are equipped with
sophisticated systems for their navigation and their
work according to their degree of autonomy. The
487IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
NOV-DEC 2011
principal constraint lies in the energy necessary to
embark for mission realization. There exist two types
of UUVs:
• The AUV can be defined as a machine knowing
its position and which surfs toward an objective
[ Figure 1]. For this, we have to draw an operation list
to be carried out beforehand. The operators do not
intervene under nominal operation; the machine is
completely autonomous.[5]
• The Untethered Underwater Vehicle (UUV) func-
tions like the AUV, but there exists an acoustic bond
76. between the surface and the machine, allowing the
verification and the data exchange. In the event of
problems, the operator can order the system to be
in an emergency situation implying its return to the
surface. It is important to note that the redundancy
of term UUV poses a problem. In fact, UUVs are also
called AUVs.
2. Autonomous Underwater Vehicle Description
The AUVs can be classified into two types depending
on the immersion depth, i.e. AUVs coastal and AUVs
deep seas. From a few hundred meters of depth, the
dimensions, structure and the characteristics of the AUVs
change. This limit of depth makes difference between the
deep seas vehicles from the coastal one [2].
Today, the underwater robots are an integral part of
the scientific equipment for sea and ocean exploration.
Many examples show that ROVs and AUVs are used in
many fields and for various applications like the inspec-
tion, the cartography or bathymetry [1]. However, we
can distinguish a limiting depth for the various types
of existing autonomous underwater machines. Indeed,
starting from 300 m, the structure, dimensions and the
characteristics of these vehicles change. We have, on one
side, AUVs Hugin 3000 type of Kongsberg Simrad, the
Sea Oracle of Bluefin Robotics or Alistar 3000 of ECA,
which can reach depths of 3000 m, have a very great
autonomy, considerable dimensions and a weight which
requires important logistics. On the other side, AUVs
of Remus Hydroid or Gavia Hyfmind types, with much
less autonomy, but of reduced dimensions and logistics
and with good modularity capacities, seem to be the per-
fect tool for the exploration of not very deep water [2].
77. In this context, the Laboratory of Data processing,
Robotics and Micro electronic of Montpellie (LIRMM)
and the ECA‑HYTEC company became partners to
develop the first prototype of the AUV H160. This
prototype was developed to surf and position with the
using a global positioning system (GPS). On the surface,
the torpedo must be able to transmit the mission’s data.
The applications concerned are the inspection, bathym-
etry, the chemical data acquisition or sonar and video
images. The machine also has the possibility of surfing
between 1 and 2 m of depth with no angle of immersion.
H160 is a torpedo type vehicle of small size and low cost,
dedicated to the applications in not very deep water (up
to 160 m). The vehicle measures 1.80 m in length with a
diameter of 20 cm and a weight of 50 kg. Thanks to its
small size, the tests on the sea require a logistics reduced
to the minimum to two people and a motor boat. The
prototype is able to accomplish a mission of at least
3 hours, maintaining its speed of 3 knots. Its positive
floatability makes it possible for the torpedo to go back
to surface after the end of each mission. H160 is fed by
a battery 48 V/16 Ah of the NiMH type, has an actuator
with DC current 230 W and 430 N cm servo‑motors for
the riders control. The torpedo immersion capacity with
no angle of pitching is due to its pair of surface riders
that constitutes the main feature of this machine [2‑5].
The torpedo is a cylindrical vehicle form as shown in
Figure 2. Its structure is mainly made up of aluminum.
We can detail the prototype in seven parts:
1. The principal part is the electronic section, composed
of two stages. The first stage accommodates the
battery, while the second one is composed of all the
78. embarked charts (sensors, power, PC, etc.). This part
is obviously tight.
2. Section made by the antennas for GPS, Radio and
Wifi, also by the riders’ control of the front immersion.
3. The sensor Conductivity Temperature Depth (CTD)
and sidescan sonar are in a wet part.
4. The Doppler Log is located in a tight part.
5. The nose of the vehicle composed of a CCD camera
and two sounders.
6. Behind the principal part, we find the pressure
Figure 1: Schematic of an AUV.
Figure 2: Different components of the H160.
Rhif A: AUV Position Control
488 IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
NOV-DEC 2011
pick‑ups and an emergency acoustic pinger in a wet
part.
7. Finally, the propeller and the riders constitute the
engine back part.
3. Autonomous Underwater Vehicle
Modeling and Control
3.1 Mathematical Model
79. For the modeling of this system, two referentials are
defined [Figure 3] [6]: One fixed referential related to
the vehicle which is defined in an origin point: R
0
(x
0
, y
0
,
z
0
) and the second one related to the Earth R(x, y, z) [1].
The referential related to the mobile R0 could be formu-
lated using the referential R as shown in Equation (1):
r r r
r r r
r r r
U U U
U U U
U U
x x z
y y x
80. z z
0
0
0
= +
= +
= +
cos sin
cos sin
cos sin
φ φ
θ θ
ψ ψ UUx
89. K
M
N
(3)
z) reference, u represents the robot speed related to
R
0
(x
0
, y
0
, z
0
), and Γ is the forces vector applied to the
mobile.
The dynamic equation is represented by:
M C v D v gη η η η ηη η η η η η η τ( ) ( , ) (( , ) ( )&& & &+ +
+ =
(4)
and th is the input control vector.
90. In order to control the behavior of an underwater vehicle
in the immersion phase, we must be able to vary its
buoyancy. The buoyancy of a vehicle in immersion is
the difference between the Archimedes pressure and
the gravity. Buoyancy (denoted as Φ
1
) depends on the
vehicle mass (m), its volume (V) and the density of water
-m (5)
The AUV presents a strong nonlinear aspect that appears
when we describe the system in three dimensions (3D), so
the state function will present a new term of disturbances
as shown in Equation (6).
where | |j (X, u)| | ≤ MX, M > 0.
As we consider only the linear movement in immer-
sion phase, we need only four degrees of freedom. For
this, we describe the system only in two dimensions
(2D). With all the developments done, the result-
ing state space describing the system is given by
Equation (7):
X = AX + Bu (7)
where
&
93. =
andB
.
.
where ω is the linear velocity, q the angular velocity, θ
the inclination and z is the depth.
Figure 3: AUV engine referentials.
u Xo
X
94. Y
Z
Origin referential
Yo
Zo
q
r
v w
p
Fix referential
O
Rhif A: AUV Position Control
489IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
NOV-DEC 2011
3.2 Autonomous Underwater Vehicle Controller
Design
3.2.1 The Sliding Mode Control
The AUV position control is ensured by the sliding mode
approach. The choice of such a controller is imposed by
the strong nonlinear aspect of the AUV, thanks to the
95. robustness of this approach [7].
The development of the sliding mode approach
occurred in the Soviet Union in the sixties with the
discovery of the discontinuous control and its effect
on the system dynamics. This approach is classified in
the monitoring with Variable System Structure (VSS)
[8,9]. The sliding mode is strongly requested due to
its facility of establishment, its robustness against
the disturbances and model uncertainties [10]. The
principle of the sliding mode control is to force the
system to converge toward a selected surface and then
to evolve there in spite of the uncertainties and the
disturbances. The surface is defined by a set of rela-
tions between the state variables of the system. The
synthesis of a control law by sliding mode includes
two phases:
• The sliding surface is defined according to the control
objectives and to the wished performances in closed
loop.
• The synthesis of the discontinuous control is carried
out in order to force the trajectories of the system state
to reach the sliding surface, and then to evolve in spite
of uncertainties, of parametric variations, etc. The
sliding mode exists when commutations take place
in a continuous way between two extreme values
u
max
and u
min
[11]. To ensure a good commutation,
96. we choose a relay type control and get the desired
result when commutations are sufficiently high [12].
The sliding mode control [13] has largely proved its
effectiveness in the reported theoretical studies. Its
principal scopes of application are robotics [13‑17]
and the electrical motors [12,18,19].
For any control device which has imperfections such as
delay, hystereses, which impose a frequency of finished
commutation, the state trajectory oscillates in the vicinity
of the sliding surface. A phenomenon called chattering
appears [20].
3.2.2 The High Order Sliding Mode Control
The high order sliding mode consists of the sliding
variable system derivation [21,22]. This method allows
the total rejection of the chattering phenomenon while
maintaining the robustness of the approach. For this, two
algorithms could be used:
• The twisting algorithm: The system control is
increased by a nominal control ue; the system error,
on the phase plane, rotates around the origin until it
has been canceled. If we derive the sliding surface
(S) n times, we see that the convergence of S is even
more accurate when n is higher [23].
• The super twisting algorithm: The system control is
composed of two parts u1 and u2 with u1 being the
equivalent control and u2 the discontinuous control
used to reject disturbances. In this case, there is no
need to derive the sliding surface [6]. To obtain a
sliding mode of order n, in this method, we have to
derive the error of the system n times.
97. In [24], a comparison between the two algorithms was
achieved. In conclusion, we note that the super twisting
algorithm is more reliable than the twisting algorithm,
despite the approximate results, since it does not ensure
the same robustness to perturbations. Indeed, in his
arti cle [24], the author used the second‑order sliding
mode to improve the performances of a turbine torque.
Notice that the conventional control approaches of
double‑fed asynchronous generator is incapable to
make the torque convergence to the desired value, then,
the choice. Then, the choice of the high order sliding
mode approach was based on its robustness against
disturbances. On the other hand, the use of linear
surfaces in the control laws synthesis by sliding mode
was considered satisfactory by the author in terms of
stability. However, the dynamics imposed by this choice
is relatively slow. To overcome this problem, we may
use nonlinear sliding surfaces. In the same direction, to
work on the speed and position regulation or power of
asynchronous machines, we often limit the stator cur-
rent (torque) that can damage the system. In this case,
the author suggested the use of the high order sliding
mode approach considering a nonlinear switching law
that consists of two different sliding surfaces S1+ and
S1− using two switched positions. Thus, we get two
limits bands, a lower band and a higher one that reduces
the chattering phenomenon.
In the literature, different approaches have been pro-
posed for the synthesis of nonlinear surfaces [6,10,23‑
27]. In [25], the proposed area consists of two terms,
a linear term that is defined by the Herwitz stability
criteria and a nonlinear term used to improve transient
performance.
98. In [10], to measure the armature current of a DC motor,
Zhang Li used the high order sliding mode since it is
faster than the traditional methods such as vector control.
To eliminate the static error that appears when measur-
ing parameters, we use a Proportional Integrator (PI) con-
troller [23,28‑30]. Thus, the authors have chosen to write
the sliding surface in a transfer function of a proportional
integral form while respecting the convergence proper-
ties of the system to this surface. The same problem of
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490 IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
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the static error was treated by adding an integrator block
just after the sliding mode control [31‑34].
The tracking problem of an AUV is treated by using
sliding mode control [Figure 4] with nonlinear sliding
surface as shown in Equation (8).
s(t)=k
1
e(t)+k
2
e
.
(t) (8)
where e(t) is the system error, k
1
> 0 and k
99. 2
> 0.
To ensure the state convergence to the sliding hyper-
plane, we have to verify the Lyaponov stability criterion
(Equation (9)) [35‑37].
ss. ≤ ‑h|s| (9)
where h>0.
The control law can be then composed of two parts:
u=u
0
+u
1
(10)
• u
0
the nominal control
• u
1
the discontinuous control allowing to reject the
disturbances.
4. Simulation Results and Discussion
Simulation results were accomplished using the MATLAB
software for both the first‑ and second‑order sliding modes
of the state function (Equation (7)) that represent the process
100. in the immersion phase using four degrees of freedom. In
Rhif A: AUV Position Control
2.5
2.0
1.5
1.0
0.5
0
-0.5
0.15
0.10
0.05
0
-0.05
-0.10
2.0
1.5
1.0
102. 0 2 4 6 8 10 12 14 16 18 20
0 5 10 15 20 25 30 35 40 45 50
Z
(m
)
ta
ta
(d
eg
)
w
(d
eg
/s
ec
)
U
t(s) t(s)
(a) (b)
(c) (d)
t(s) t(s)
Figure 4: Sliding mode control bloc representation.
Equivalent
103. control
∑
∑ Switching
control
Surface
Transducer
AUV
ueq
uc
xd e+
-
+
+S
u x
Figure 5: First‑order sliding mode control.
491IETE TECHNICAL REVIEW | VOL 28 | ISSUE 6 |
NOV-DEC 2011
this simulation, we need to study the system output evolu-
tion (the depth z), the linear control (u), the inclination θ
and the angular velocity q that ensures this output.
104. The sliding surface parameters used are k
1
=1 and k
2
=3.
The desired immersion point was fixed on 2m. For the
first‑order sliding mode, the simulation shows that the
system output [Figure 5a] reaches its desired value in a
short time (about 5 s) with good precision. But we notice
the presence of the chattering phenomenon (oscilla-
tions on the steady state). Moreover, the variations in
the inclination θ [Figure 5c] and in the angular velocity
q [Figure 5d] are due to this chattering phenomenon.
Other ways, the control level and the frequency of
switching of this control [Figure 5b] are not very sharp
that gives good operating conditions to actuators. By
using high order sliding mode control, the chattering
phenomenon has disappeared, the output evolution
[Figure 6a] is more stable and the tracking process is
more precise. The control level of the process is now less
than the first solution but its commutation frequency is
sharper [Figure 6b]. The inclination θ [Figure 6c] and
the angular velocity q [Figure 6d] are now very close to
0 which means that the system reaches the steady state.
5. Conclusion
An extensive review of the literature of AUVs and
tracking process by sliding mode has been carried out.
In this work, major components like actuators, sensors,
amplifier, etc. have been listed. AUVs’ controllers have
105. been presented, detailed and justified by the simulation
results. This paper could be a ready study for those who
want to start research with AUVs and sliding mode
control.
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31. M. Hanmandlu, “An Al based Governing Technique for
Automatic
Control of small …
The experiment research of high-pressure air blowing ballast
tanks
Liu Ruijie,Xiao Changrun,Liu Yihan
Naval University of Engineering,Wuhan 430033,China
Naval University of Engineering,Wuhan 430033,China
114. PetroChina Oil and Gas Pipeline Control Center,Beijing
100007,China
[email protected]
[email protected]
[email protected]
Key words: submarine self-propelled model;CFD;ballast
tanks;high-pressure gas
Abstract.In order to test and verify the accuracy and reasonable
of the mathematical model of the
high-pressure air blowing the main ballast tanks, the paper
design a submarine self-propelled model
with the system of high-pressure air blowing the ballast
tanks.Through the experiment without
propulsion, the paper obtains drainage performance and key
performance parameters of
motion.Through the comparing of CFD, the result shows the
ability to describe correctly the process