This study examined operator workload in 18 wheel loader operators using psychophysiological measurements under different machine settings that limited engine speed and traction force. The findings did not support using these measurements to easily assess operator workload for machine testing, as other factors strongly influence workload. While workload-adaptive assistance could help with complex machines, different workload measurements may be needed for practical use by test engineers. The machine settings aimed to study the impact of limited traction force on workload during bucket filling, which requires simultaneously controlling multiple motions and is the most fuel-consuming part of the loading cycle. However, the results indicated operability is affected by many other machine and task factors beyond the settings tested.
A study to compare trajectory generation algorithms for automatic bucket fill...Reno Filla
In this paper we study how automatic bucket filling can be realised in wheel loaders. Based on observations of how experienced operators use their machines in bucket applications, four algorithms for parametric generation of bucket trajectories are investigated. The algorithms have been developed and tuned using a simplistic static integration-based approach.
The Discrete Element Method is used to validate the predictive capability of the aforementioned algorithms. Results and limitations of the simplistic approach in comparison to the numerical results, as well as specific simulation-related challenges and findings are reported and discussed.
Study of a method for assessing operability of working machines in physical a...Reno Filla
In this study of eighteen wheel loader operators, test-driving a machine in three different traction force settings, we found strong support for the hypothesis that the operator’s control commands can be used to assess the machine’s operability, at least in form of ease of bucket filling.
The methods chosen to derive the control effort worked well and were computationally efficient.
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-70392
IRJET- Finite Element Simulation of Pressurized FluidIRJET Journal
1) The document describes a finite element simulation of a pressurized fluid using the Smoothed Particle Hydrodynamics (SPH) method in ABAQUS software.
2) It specifically models a typical landing gear shock absorber system for a re-entry vehicle undergoing a simulated landing with 3g acceleration.
3) The analysis determines the optimal orifice diameter and fluid to air volume ratio for maximum shock absorption based on the SPH simulation results. An orifice diameter of 10mm showed the best performance.
Modeling, Simulation and Body Height Adjustment Control of Full Car Laterally...IRJESJOURNAL
Abstract:- In this paper, the working principles, the dynamic performance, and the static characteristics of full car interconnected air suspension are investigated and verified using established real physical test benches and simulations. Also, the physical and mathematical models of the suspension are established to help study the vehicle‟s roll, pitch, bounce and other relevant motions. PID and Fuzzy controllers are built using matlab/simulink to simulate and control the body vertical height adjustment of the interconnected air suspension. Two two-dimensional fuzzy controllers are applied respectively to control the front and rear air springs. To improve height adjustment precision, a target height of 20 mm is used as input to the front controller; while the actual body height in front air spring is used as an input to the rear controller. The results of the simulation clearly demonstrate that compared with the open-loop switch control, PID and fuzzy controllers are found to effectively suppress the overshoot during the process of body height adjustment. Again, by setting the front wheels as the target height, the designed controllers quickly and accurately adjust body height to the target height and significantly stabilized and improved the performance of the system as compared to the openloop switch control.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online
This document summarizes research on improving the stability of hydraulic pipes in axial piston pump systems. It first provides background on previous studies modeling axial piston pumps and their control systems. It then discusses the objective of investigating a novel single PID controller for the pump and how it impacts overall pump performance, including hydraulic system smoothness and vibration reduction. The results of simulations and experiments show promising results for implementing the new control strategy to improve pipe stability in axial piston pumps.
Investigation on Chassis Dynamometer with Capability to Test Regenerative Bra...IJPEDS-IAES
An investigation-based approach to a bidirectional power flow method for
testing regenerative braking function on a chassis dynamometer is presented.
The requirements and specifications for capability to test regenerative
braking function of Electric Vehicle (EV) emulated by using a bidirectional
chassis dynamometer are discussed. The dynamometer emulates road load
conditions during testing, and regenerative braking is able to test their
function while the vehicle is in deceleration condition. Performances of
power requirement are illustrated and translated into sequence diagram. It is
shown that the proposed topology is particularly advantageous in generating
and regenerating power for energy consumption. The overview of
conventional chassis dynamometer and the proposed chassis dynamometer is
compared to investigate the parameter in the development of regenerative
braking test.
Modeling And Simulation Swash Plate Pump Response Characteristics in Load Sen...IJMERJOURNAL
ABSTRACT: Fluid Power is widely employed in applications required high loads such as tractors, cranes, and airplanes. In load sensing hydraulic systems, loads are controlled by adjusting a pump-valve arrangement. In this paper, the swash plate pump hydraulic characteristics will be determined, the pump and its fluid gains will be derived to obtain the pump overall transfer function. Firstly, the swash plate pump mechanism is analyzed and its dynamic model is constructed; the pump pressure and flow rate are plotted and the possible improvement is introduced. The load sensing unit parameters such as orifice width, orifice area, maximum passage area, and piston area at X and Y will be examined to identify their influence on the pump characteristics; and the optimum parameters will be introduced. All results are developed and simulated numerically.
A study to compare trajectory generation algorithms for automatic bucket fill...Reno Filla
In this paper we study how automatic bucket filling can be realised in wheel loaders. Based on observations of how experienced operators use their machines in bucket applications, four algorithms for parametric generation of bucket trajectories are investigated. The algorithms have been developed and tuned using a simplistic static integration-based approach.
The Discrete Element Method is used to validate the predictive capability of the aforementioned algorithms. Results and limitations of the simplistic approach in comparison to the numerical results, as well as specific simulation-related challenges and findings are reported and discussed.
Study of a method for assessing operability of working machines in physical a...Reno Filla
In this study of eighteen wheel loader operators, test-driving a machine in three different traction force settings, we found strong support for the hypothesis that the operator’s control commands can be used to assess the machine’s operability, at least in form of ease of bucket filling.
The methods chosen to derive the control effort worked well and were computationally efficient.
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-70392
IRJET- Finite Element Simulation of Pressurized FluidIRJET Journal
1) The document describes a finite element simulation of a pressurized fluid using the Smoothed Particle Hydrodynamics (SPH) method in ABAQUS software.
2) It specifically models a typical landing gear shock absorber system for a re-entry vehicle undergoing a simulated landing with 3g acceleration.
3) The analysis determines the optimal orifice diameter and fluid to air volume ratio for maximum shock absorption based on the SPH simulation results. An orifice diameter of 10mm showed the best performance.
Modeling, Simulation and Body Height Adjustment Control of Full Car Laterally...IRJESJOURNAL
Abstract:- In this paper, the working principles, the dynamic performance, and the static characteristics of full car interconnected air suspension are investigated and verified using established real physical test benches and simulations. Also, the physical and mathematical models of the suspension are established to help study the vehicle‟s roll, pitch, bounce and other relevant motions. PID and Fuzzy controllers are built using matlab/simulink to simulate and control the body vertical height adjustment of the interconnected air suspension. Two two-dimensional fuzzy controllers are applied respectively to control the front and rear air springs. To improve height adjustment precision, a target height of 20 mm is used as input to the front controller; while the actual body height in front air spring is used as an input to the rear controller. The results of the simulation clearly demonstrate that compared with the open-loop switch control, PID and fuzzy controllers are found to effectively suppress the overshoot during the process of body height adjustment. Again, by setting the front wheels as the target height, the designed controllers quickly and accurately adjust body height to the target height and significantly stabilized and improved the performance of the system as compared to the openloop switch control.
International Journal of Engineering and Science Invention (IJESI)inventionjournals
International Journal of Engineering and Science Invention (IJESI) is an international journal intended for professionals and researchers in all fields of computer science and electronics. IJESI publishes research articles and reviews within the whole field Engineering Science and Technology, new teaching methods, assessment, validation and the impact of new technologies and it will continue to provide information on the latest trends and developments in this ever-expanding subject. The publications of papers are selected through double peer reviewed to ensure originality, relevance, and readability. The articles published in our journal can be accessed online
This document summarizes research on improving the stability of hydraulic pipes in axial piston pump systems. It first provides background on previous studies modeling axial piston pumps and their control systems. It then discusses the objective of investigating a novel single PID controller for the pump and how it impacts overall pump performance, including hydraulic system smoothness and vibration reduction. The results of simulations and experiments show promising results for implementing the new control strategy to improve pipe stability in axial piston pumps.
Investigation on Chassis Dynamometer with Capability to Test Regenerative Bra...IJPEDS-IAES
An investigation-based approach to a bidirectional power flow method for
testing regenerative braking function on a chassis dynamometer is presented.
The requirements and specifications for capability to test regenerative
braking function of Electric Vehicle (EV) emulated by using a bidirectional
chassis dynamometer are discussed. The dynamometer emulates road load
conditions during testing, and regenerative braking is able to test their
function while the vehicle is in deceleration condition. Performances of
power requirement are illustrated and translated into sequence diagram. It is
shown that the proposed topology is particularly advantageous in generating
and regenerating power for energy consumption. The overview of
conventional chassis dynamometer and the proposed chassis dynamometer is
compared to investigate the parameter in the development of regenerative
braking test.
Modeling And Simulation Swash Plate Pump Response Characteristics in Load Sen...IJMERJOURNAL
ABSTRACT: Fluid Power is widely employed in applications required high loads such as tractors, cranes, and airplanes. In load sensing hydraulic systems, loads are controlled by adjusting a pump-valve arrangement. In this paper, the swash plate pump hydraulic characteristics will be determined, the pump and its fluid gains will be derived to obtain the pump overall transfer function. Firstly, the swash plate pump mechanism is analyzed and its dynamic model is constructed; the pump pressure and flow rate are plotted and the possible improvement is introduced. The load sensing unit parameters such as orifice width, orifice area, maximum passage area, and piston area at X and Y will be examined to identify their influence on the pump characteristics; and the optimum parameters will be introduced. All results are developed and simulated numerically.
Cavitation Effects in Centrifugal Pumps- A ReviewIJERA Editor
Cavitation is one of the most challenging fluid flow abnormalities leading to detrimental effects on both the
centrifugal pump flow behaviors and physical characteristics. Centrifugal pumps’ most low pressure zones are the
first cavitation victims, where cavitation manifests itself in form of pitting on the pump internal solid walls,
accompanied by noise and vibration, all leading to the pump hydraulic performance degradation. In the present
article, a general description of centrifugal pump performance and related parameters is presented. Based on the
literature survey, some light were shed on fundamental cavitation features; where different aspects relating to
cavitation in centrifugal pumps were briefly discussed.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
This document provides a review of research on using turbocharging to improve diesel engine performance and reduce exhaust emissions. It discusses how turbochargers work by using the engine's exhaust gases to power a turbine, which spins a compressor to increase the density of intake air entering the engine. This allows the engine to operate with higher volumetric efficiency. The document reviews several studies that have investigated how non-adiabatic (heat transfer) effects within the turbocharger can impact engine volumetric efficiency and increase turbo lag. Insulating the turbine is suggested as a way to reduce these impacts. The review examines models developed to represent heat transfer between turbocharger components and experimental work analyzing its effects on the engine charging process.
The document summarizes the air brakes system used in railways. It begins by introducing the importance of braking systems for controlling vehicle movement. It then discusses how modern trains rely on George Westinghouse's fail-safe air brake system design. The rest of the document details the components and working of the railway air brake system, including the distributor valve, auxiliary reservoir, brake cylinder, and others. It explains the charging, application and release stages. Limitations include potential issues if brakes are applied before full recharging. The conclusion states air brakes are more efficient than older vacuum brakes.
This document summarizes a numerical study on the effect of discharge coefficient on the performance of a six jet Pelton turbine model. Computational fluid dynamics (CFD) was used to analyze the turbine's performance at design and off-design discharge conditions. The CFD results for efficiency were compared to available model test data and found to be in close agreement. Pressure distribution, water velocity, and water distribution within the turbine were also obtained from the CFD simulations and discussed. The study aims to provide a cost-effective tool for detailed flow analysis and performance evaluation of Pelton turbines at different operating conditions.
This document discusses methods for assessing the energy performance of water pumps. It describes how to measure key parameters like flow, head, and power to determine a pump's efficiency. Flow can be measured using tracer methods, ultrasonic meters, or by filling a tank. Total head is the difference between suction and discharge heads. Pump efficiency is the fluid power divided by the power input. The document also explains how to construct a system resistance curve and compare it to the pump curve to evaluate performance and identify efficiency losses over time.
Development of Hill Chart diagram for Francis turbine of Jhimruk Hydropower u...Suman Sapkota
The study is expected to provide a milestone for the study of performances of Francis Turbine at different loading conditions. It can also serve as a reference for the study of CFD analysis on Francis turbine for the development of performance characteristics curve and Hill chart.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.t
This document discusses various gas power cycles used in engines. It describes the Otto, Diesel, dual, and Brayton cycles. The Otto cycle models spark ignition engines using four processes: isentropic compression, constant volume combustion, isentropic expansion, and constant volume exhaust. The Diesel cycle also uses four processes but replaces constant volume combustion with constant pressure combustion. The dual cycle combines aspects of the Otto and Diesel cycles. The Brayton cycle models gas turbines using constant pressure processes. Real examples of engines using these cycles are also provided.
A Review Paper on Effects of Different Intake Manifold Designs on Diesel Engi...ijsrd.com
One of the objectives of car manufacturers is to improve engine performance, reduce consumption and reduce emissions. To achieve this objective, it is important to understand the phenomena involved in the combustion chambers of engines. There are various factors that influence the engine performance such as compression ratio, atomization of fuel, fuel injection pressure, and quality of fuel, combustion rate, air fuel ratio, intake temperature and pressure and also based on piston design, inlet manifold, and combustion chamber designs etc. Geometrical design of intake manifold is one such method for the better performance of an I.C. Engine. Air swirl motion in CI engine influences the atomization and distribution of fuel injected in the combustion chamber. Intake manifolds provides Air motion to the chamber. So, to get the maximum output with the least input on Diesel engine researchers are experimentally and computationally working on construction of the intake manifold configurations for increase in engine performance and reduction of Exhaust Emissions. In this paper i have studied few papers and also gone through basics of my topic from various books to understand the phenomena.
Thermo coupled stress analysis of exhaust manifold assemblage using abaqusINFOGAIN PUBLICATION
Comprehension of the basic conduct in the beginning period of outline can help to lessen the quantity of virtual models and the time taken for their assessment. For an engine development program, the engine exhaust manifold system is a mind boggling framework subjected to thermo mechanical burdens. The investigation of such a framework is discriminating because of the many-sided quality of meeting the basic and stream prerequisites. In this paper the Thermal Stress Index (TSI) is created for down to earth reason. Especially the TSI is appeared to be extremely powerful in discovering an ideal shape with imperatives in outline of the exhaust manifold system. Therefore, the objective for discovering an ideal state of the exhaust manifold system is to minimize the TSI, and philosophy received to address a failure of an Exhaust complex amid physical testing on an engine test bed. A non-linear thermo-auxiliary quality investigation of the exhaust manifold system gathering of the four cylinder four stroke engine is done. The FE model comprises of the exhaust manifold system get together, head and mounting bolts. The contact interaction between the parts is likewise modeled. The assembly is subjected to bolt preloads, for reproducing the mechanical assembly. The thermal loads utilized as a part of the reenactment are computed through CFD (Input). The model considers a temperature reliance of a heat exchange coefficient on wall temperature in cooling sections. For the structural analysis temperature subordinate non-linear material properties and contact non-linearity is considered.
1. The document describes the fabrication of an electro hydraulic jack to lift vehicles without requiring large physical force.
2. It works on the principle of Pascal's law, using a hydraulic system including a pump, cylinder, and reservoir to transmit pressure throughout the fluid.
3. The electro hydraulic jack is powered by an electric motor and can be operated automatically by a button in the vehicle's dashboard, making lifting easier than conventional screw jacks.
1) The document describes a study investigating the effects of variable intake plenum length on the performance of a spark-ignition engine with electronically controlled fuel injectors.
2) Engine tests were conducted with additional plenum lengths of 16mm, 32mm, 48mm, and 64mm added to the original intake manifold.
3) The results showed that a 32mm plenum extension improved engine thermal efficiency, especially at lower engine speeds up to 3000rpm, while also reducing fuel consumption at high loads and low speeds.
performance of the four strokes diesel engineSaif al-din ali
This document describes an experiment to test the performance of a four-stroke diesel engine at varying speeds. It includes sections on the objective, engine performance, test procedure, calculations, results, and discussion. The objective is to study the effect of engine speed on performance parameters. The test procedure involves varying the engine speed using a water dynamometer and recording speed, torque, temperatures, and fuel consumption. Calculations are presented for power, specific fuel consumption, air-fuel ratio, efficiencies, and heat losses. Results are reported for two engine speeds.
Knowledge Based Design of Axial Flow CompressorIJERA Editor
In the aerospace industry with highly competitive market the time to design and delivery is shortening every day. Pressure on delivering robust product with cost economy is in demand in each development. Even though technology is older, it is new for each customer requirement and highly non-liner to fit one in another place. Gas turbine is considered one of a complex design in the aircraft system. It involves experts to be grouped with designers of various segments to arrive the best output. The time is crucial to achieve a best design and it needs knowledge automation incorporated with CAD/CAE tools. In the present work an innovative idea in the form of Knowledge Based Engineering for axial compressor is proposed, this includes the fundamental design of axial compressor integrated with artificial intelligence in the form of knowledge capturing and programmed with high level language (Visual Basis.Net) and embedded into CATIA v5. This KBE frame work eases out the design and modeling of axial compressor design and produces 3D modeling for further flow simulation with fluid dynamic in Ansys-Fluent. Most of the aerospace components are developed through simulation driven product development and in this case it is established for axial compressor.
Dynamic Stability of Zaghloul Drainage Pumping Station, Kafr El Shiekh, EgyptIJERA Editor
Zaghloul Pumping Station located at El-Moheet drainage in Kafr El Sheikh Governorate. The station consists of four axial pumping units. The operating system depends on running not more than three pumping units. The old station is replaced by new one and the old sump is reused with some modifications. Each pump takes 20 second to start and takes 300 second to reach steady state. Activation more than two units lead to decrease the suction water level, disturbance of velocity distribution in suction intake and increase vibration and noise levels. The disturbance in velocity distribution generates dynamic instability of pumping units which leads to failure, damage and other operation and maintenance difficulties. Field measurements and numerical simulation were done to investigate dynamic stability of the station. The Solid Works flow simulation software, Computational Fluid Dynamics (CFD) is used to simulate the flow conditions at different water levels to predict the hydraulic problem at the suction side. The field measurements are used to investigate the dynamic problem. Measurements are used to measure pump flow rate, pump head and vibration levels. The (MVP2C OneproD/ ACOEM) two channel vibration analyzer and data collector was used to prepare dynamic balancing for each unit with different weights. In general, the results indicated that with the decrease of water level; approach velocity increases, swirl and vortices induce vibrations and excessive bearing loads. From simulation results the geometry of suction intake is proper for running three parallel axial flow pumps with the designed flow rate. The input data to simulation model were taken from the filed measurements and this data is validating to simulation model. The dynamic balancing as a solution leads to reduce vibration level and save bearing life. It is very important to investigate the dynamic stability and check the dynamic balancing for pumping units at the primary operation of the new stations as mentioned in the bidding
This paper describes the operating principle and the constructive solution for a rotating volumetric pump with two profiled rotors. Calculation relations are established for the flow rate and the driving power of the rotating pump. An example of a calculation for determining the pump driving power according to the conveyed flow rate is presented; the flow rates were chosen for the case when the pump would be used in an irrigation pumping station. The pump can carry different categories of fluids such as: (1) Fluids with suspended particles (water + ash, water + sand), (2) Viscous fluids (oil, diesel, oil), (3) Multi-phase fluids (water + air, water + steam).
Nonlinear integral control for dc motor speed controlSaif al-din ali
This document discusses nonlinear integral control for DC motor speed control with unknown and variable external torque. It begins with an introduction to DC motors and common speed control techniques. It then provides the basic model of a DC motor and derives the transfer function. It discusses nonlinear control systems and elements like saturation, deadband, and friction. It describes methods for solving nonlinear transient responses, nonlinear system stability, and provides a Simulink model example comparing PI and P controller performance for speed and error. References for DC motor speed control and optimization of PI controllers are also provided.
Variable speed operation of hydraulic turbines has been researched for over two decades. It provides advantages such as improved performance at off-design heads and discharges. Variable speed allows turbines to operate at higher efficiencies over a wider range of flows and heads. This increases energy production and reduces operational issues like cavitation. Commercially available variable speed turbine systems include Turbinova, the DIVE turbine, VLH turbine, and systems from Kawasaki Plant Systems which use permanent magnet generators and water lubrication for high efficiency without oil requirements.
This document reports on a numerical investigation of a jet pump with twisted tapes. Water and air were used as the primary and secondary fluids, respectively. Computational fluid dynamics software was used to simulate flow through nozzles with diameters of 4mm and 6mm, both with and without single or double twisted tapes. Results found that double twisted tapes increased efficiency the most by enhancing momentum exchange and pressure drop after the nozzle through increased vorticity. Velocity, turbulent kinetic energy, and vorticity profiles along the length supported these findings. The maximum 10% efficiency increase was with a double twisted tape compared to no tape.
Slavery In America by Rachel CooperriderRachelCoop3
Slavery was established in America between 1700-1770 to meet labor needs as indentured servants became unreliable. Slaves were captured in Africa through bartering, kidnapping, and warfare. They endured a brutal months-long journey to America where they were auctioned off and forced into plantation labor. Though some African traditions were preserved, slave life was unpredictable and families could be separated. The slave population grew rapidly despite rebellions and resistance. By 1750, African Americans comprised 4/5 of the population in some colonies. Slavery resulted in increasing legal restrictions and racism against slaves.
As a follow up to the May webinar on IT Planning & Budgeting, we organized a joint webinar with Nonprofit Roundtable to share case studies and best practices. While everyone agrees that technology is an essential resource, organizations often underestimate technology costs and overlook critical conversations with their IT team/partners.
In this webinar Johan Hammerstrom, COO at Community IT Innovators, talked about the essential elements of an annual IT budget, IT considerations in a project budget, and key personnel in building the budget and managing it.
We also had a guest speaker, Norwin Herrera, IS Manager at La Clinica del Pueblo who shared his organization’s experience around IT Planning & Budgeting.
Cavitation Effects in Centrifugal Pumps- A ReviewIJERA Editor
Cavitation is one of the most challenging fluid flow abnormalities leading to detrimental effects on both the
centrifugal pump flow behaviors and physical characteristics. Centrifugal pumps’ most low pressure zones are the
first cavitation victims, where cavitation manifests itself in form of pitting on the pump internal solid walls,
accompanied by noise and vibration, all leading to the pump hydraulic performance degradation. In the present
article, a general description of centrifugal pump performance and related parameters is presented. Based on the
literature survey, some light were shed on fundamental cavitation features; where different aspects relating to
cavitation in centrifugal pumps were briefly discussed.
International Journal of Engineering Research and Applications (IJERA) is a team of researchers not publication services or private publications running the journals for monetary benefits, we are association of scientists and academia who focus only on supporting authors who want to publish their work. The articles published in our journal can be accessed online, all the articles will be archived for real time access.
Our journal system primarily aims to bring out the research talent and the works done by sciaentists, academia, engineers, practitioners, scholars, post graduate students of engineering and science. This journal aims to cover the scientific research in a broader sense and not publishing a niche area of research facilitating researchers from various verticals to publish their papers. It is also aimed to provide a platform for the researchers to publish in a shorter of time, enabling them to continue further All articles published are freely available to scientific researchers in the Government agencies,educators and the general public. We are taking serious efforts to promote our journal across the globe in various ways, we are sure that our journal will act as a scientific platform for all researchers to publish their works online.
This document provides a review of research on using turbocharging to improve diesel engine performance and reduce exhaust emissions. It discusses how turbochargers work by using the engine's exhaust gases to power a turbine, which spins a compressor to increase the density of intake air entering the engine. This allows the engine to operate with higher volumetric efficiency. The document reviews several studies that have investigated how non-adiabatic (heat transfer) effects within the turbocharger can impact engine volumetric efficiency and increase turbo lag. Insulating the turbine is suggested as a way to reduce these impacts. The review examines models developed to represent heat transfer between turbocharger components and experimental work analyzing its effects on the engine charging process.
The document summarizes the air brakes system used in railways. It begins by introducing the importance of braking systems for controlling vehicle movement. It then discusses how modern trains rely on George Westinghouse's fail-safe air brake system design. The rest of the document details the components and working of the railway air brake system, including the distributor valve, auxiliary reservoir, brake cylinder, and others. It explains the charging, application and release stages. Limitations include potential issues if brakes are applied before full recharging. The conclusion states air brakes are more efficient than older vacuum brakes.
This document summarizes a numerical study on the effect of discharge coefficient on the performance of a six jet Pelton turbine model. Computational fluid dynamics (CFD) was used to analyze the turbine's performance at design and off-design discharge conditions. The CFD results for efficiency were compared to available model test data and found to be in close agreement. Pressure distribution, water velocity, and water distribution within the turbine were also obtained from the CFD simulations and discussed. The study aims to provide a cost-effective tool for detailed flow analysis and performance evaluation of Pelton turbines at different operating conditions.
This document discusses methods for assessing the energy performance of water pumps. It describes how to measure key parameters like flow, head, and power to determine a pump's efficiency. Flow can be measured using tracer methods, ultrasonic meters, or by filling a tank. Total head is the difference between suction and discharge heads. Pump efficiency is the fluid power divided by the power input. The document also explains how to construct a system resistance curve and compare it to the pump curve to evaluate performance and identify efficiency losses over time.
Development of Hill Chart diagram for Francis turbine of Jhimruk Hydropower u...Suman Sapkota
The study is expected to provide a milestone for the study of performances of Francis Turbine at different loading conditions. It can also serve as a reference for the study of CFD analysis on Francis turbine for the development of performance characteristics curve and Hill chart.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.t
This document discusses various gas power cycles used in engines. It describes the Otto, Diesel, dual, and Brayton cycles. The Otto cycle models spark ignition engines using four processes: isentropic compression, constant volume combustion, isentropic expansion, and constant volume exhaust. The Diesel cycle also uses four processes but replaces constant volume combustion with constant pressure combustion. The dual cycle combines aspects of the Otto and Diesel cycles. The Brayton cycle models gas turbines using constant pressure processes. Real examples of engines using these cycles are also provided.
A Review Paper on Effects of Different Intake Manifold Designs on Diesel Engi...ijsrd.com
One of the objectives of car manufacturers is to improve engine performance, reduce consumption and reduce emissions. To achieve this objective, it is important to understand the phenomena involved in the combustion chambers of engines. There are various factors that influence the engine performance such as compression ratio, atomization of fuel, fuel injection pressure, and quality of fuel, combustion rate, air fuel ratio, intake temperature and pressure and also based on piston design, inlet manifold, and combustion chamber designs etc. Geometrical design of intake manifold is one such method for the better performance of an I.C. Engine. Air swirl motion in CI engine influences the atomization and distribution of fuel injected in the combustion chamber. Intake manifolds provides Air motion to the chamber. So, to get the maximum output with the least input on Diesel engine researchers are experimentally and computationally working on construction of the intake manifold configurations for increase in engine performance and reduction of Exhaust Emissions. In this paper i have studied few papers and also gone through basics of my topic from various books to understand the phenomena.
Thermo coupled stress analysis of exhaust manifold assemblage using abaqusINFOGAIN PUBLICATION
Comprehension of the basic conduct in the beginning period of outline can help to lessen the quantity of virtual models and the time taken for their assessment. For an engine development program, the engine exhaust manifold system is a mind boggling framework subjected to thermo mechanical burdens. The investigation of such a framework is discriminating because of the many-sided quality of meeting the basic and stream prerequisites. In this paper the Thermal Stress Index (TSI) is created for down to earth reason. Especially the TSI is appeared to be extremely powerful in discovering an ideal shape with imperatives in outline of the exhaust manifold system. Therefore, the objective for discovering an ideal state of the exhaust manifold system is to minimize the TSI, and philosophy received to address a failure of an Exhaust complex amid physical testing on an engine test bed. A non-linear thermo-auxiliary quality investigation of the exhaust manifold system gathering of the four cylinder four stroke engine is done. The FE model comprises of the exhaust manifold system get together, head and mounting bolts. The contact interaction between the parts is likewise modeled. The assembly is subjected to bolt preloads, for reproducing the mechanical assembly. The thermal loads utilized as a part of the reenactment are computed through CFD (Input). The model considers a temperature reliance of a heat exchange coefficient on wall temperature in cooling sections. For the structural analysis temperature subordinate non-linear material properties and contact non-linearity is considered.
1. The document describes the fabrication of an electro hydraulic jack to lift vehicles without requiring large physical force.
2. It works on the principle of Pascal's law, using a hydraulic system including a pump, cylinder, and reservoir to transmit pressure throughout the fluid.
3. The electro hydraulic jack is powered by an electric motor and can be operated automatically by a button in the vehicle's dashboard, making lifting easier than conventional screw jacks.
1) The document describes a study investigating the effects of variable intake plenum length on the performance of a spark-ignition engine with electronically controlled fuel injectors.
2) Engine tests were conducted with additional plenum lengths of 16mm, 32mm, 48mm, and 64mm added to the original intake manifold.
3) The results showed that a 32mm plenum extension improved engine thermal efficiency, especially at lower engine speeds up to 3000rpm, while also reducing fuel consumption at high loads and low speeds.
performance of the four strokes diesel engineSaif al-din ali
This document describes an experiment to test the performance of a four-stroke diesel engine at varying speeds. It includes sections on the objective, engine performance, test procedure, calculations, results, and discussion. The objective is to study the effect of engine speed on performance parameters. The test procedure involves varying the engine speed using a water dynamometer and recording speed, torque, temperatures, and fuel consumption. Calculations are presented for power, specific fuel consumption, air-fuel ratio, efficiencies, and heat losses. Results are reported for two engine speeds.
Knowledge Based Design of Axial Flow CompressorIJERA Editor
In the aerospace industry with highly competitive market the time to design and delivery is shortening every day. Pressure on delivering robust product with cost economy is in demand in each development. Even though technology is older, it is new for each customer requirement and highly non-liner to fit one in another place. Gas turbine is considered one of a complex design in the aircraft system. It involves experts to be grouped with designers of various segments to arrive the best output. The time is crucial to achieve a best design and it needs knowledge automation incorporated with CAD/CAE tools. In the present work an innovative idea in the form of Knowledge Based Engineering for axial compressor is proposed, this includes the fundamental design of axial compressor integrated with artificial intelligence in the form of knowledge capturing and programmed with high level language (Visual Basis.Net) and embedded into CATIA v5. This KBE frame work eases out the design and modeling of axial compressor design and produces 3D modeling for further flow simulation with fluid dynamic in Ansys-Fluent. Most of the aerospace components are developed through simulation driven product development and in this case it is established for axial compressor.
Dynamic Stability of Zaghloul Drainage Pumping Station, Kafr El Shiekh, EgyptIJERA Editor
Zaghloul Pumping Station located at El-Moheet drainage in Kafr El Sheikh Governorate. The station consists of four axial pumping units. The operating system depends on running not more than three pumping units. The old station is replaced by new one and the old sump is reused with some modifications. Each pump takes 20 second to start and takes 300 second to reach steady state. Activation more than two units lead to decrease the suction water level, disturbance of velocity distribution in suction intake and increase vibration and noise levels. The disturbance in velocity distribution generates dynamic instability of pumping units which leads to failure, damage and other operation and maintenance difficulties. Field measurements and numerical simulation were done to investigate dynamic stability of the station. The Solid Works flow simulation software, Computational Fluid Dynamics (CFD) is used to simulate the flow conditions at different water levels to predict the hydraulic problem at the suction side. The field measurements are used to investigate the dynamic problem. Measurements are used to measure pump flow rate, pump head and vibration levels. The (MVP2C OneproD/ ACOEM) two channel vibration analyzer and data collector was used to prepare dynamic balancing for each unit with different weights. In general, the results indicated that with the decrease of water level; approach velocity increases, swirl and vortices induce vibrations and excessive bearing loads. From simulation results the geometry of suction intake is proper for running three parallel axial flow pumps with the designed flow rate. The input data to simulation model were taken from the filed measurements and this data is validating to simulation model. The dynamic balancing as a solution leads to reduce vibration level and save bearing life. It is very important to investigate the dynamic stability and check the dynamic balancing for pumping units at the primary operation of the new stations as mentioned in the bidding
This paper describes the operating principle and the constructive solution for a rotating volumetric pump with two profiled rotors. Calculation relations are established for the flow rate and the driving power of the rotating pump. An example of a calculation for determining the pump driving power according to the conveyed flow rate is presented; the flow rates were chosen for the case when the pump would be used in an irrigation pumping station. The pump can carry different categories of fluids such as: (1) Fluids with suspended particles (water + ash, water + sand), (2) Viscous fluids (oil, diesel, oil), (3) Multi-phase fluids (water + air, water + steam).
Nonlinear integral control for dc motor speed controlSaif al-din ali
This document discusses nonlinear integral control for DC motor speed control with unknown and variable external torque. It begins with an introduction to DC motors and common speed control techniques. It then provides the basic model of a DC motor and derives the transfer function. It discusses nonlinear control systems and elements like saturation, deadband, and friction. It describes methods for solving nonlinear transient responses, nonlinear system stability, and provides a Simulink model example comparing PI and P controller performance for speed and error. References for DC motor speed control and optimization of PI controllers are also provided.
Variable speed operation of hydraulic turbines has been researched for over two decades. It provides advantages such as improved performance at off-design heads and discharges. Variable speed allows turbines to operate at higher efficiencies over a wider range of flows and heads. This increases energy production and reduces operational issues like cavitation. Commercially available variable speed turbine systems include Turbinova, the DIVE turbine, VLH turbine, and systems from Kawasaki Plant Systems which use permanent magnet generators and water lubrication for high efficiency without oil requirements.
This document reports on a numerical investigation of a jet pump with twisted tapes. Water and air were used as the primary and secondary fluids, respectively. Computational fluid dynamics software was used to simulate flow through nozzles with diameters of 4mm and 6mm, both with and without single or double twisted tapes. Results found that double twisted tapes increased efficiency the most by enhancing momentum exchange and pressure drop after the nozzle through increased vorticity. Velocity, turbulent kinetic energy, and vorticity profiles along the length supported these findings. The maximum 10% efficiency increase was with a double twisted tape compared to no tape.
Slavery In America by Rachel CooperriderRachelCoop3
Slavery was established in America between 1700-1770 to meet labor needs as indentured servants became unreliable. Slaves were captured in Africa through bartering, kidnapping, and warfare. They endured a brutal months-long journey to America where they were auctioned off and forced into plantation labor. Though some African traditions were preserved, slave life was unpredictable and families could be separated. The slave population grew rapidly despite rebellions and resistance. By 1750, African Americans comprised 4/5 of the population in some colonies. Slavery resulted in increasing legal restrictions and racism against slaves.
As a follow up to the May webinar on IT Planning & Budgeting, we organized a joint webinar with Nonprofit Roundtable to share case studies and best practices. While everyone agrees that technology is an essential resource, organizations often underestimate technology costs and overlook critical conversations with their IT team/partners.
In this webinar Johan Hammerstrom, COO at Community IT Innovators, talked about the essential elements of an annual IT budget, IT considerations in a project budget, and key personnel in building the budget and managing it.
We also had a guest speaker, Norwin Herrera, IS Manager at La Clinica del Pueblo who shared his organization’s experience around IT Planning & Budgeting.
The document discusses instructional analysis, which is the second step in the Dick and Carey instructional design model. It explains that instructional analysis identifies the subordinate skills needed to achieve a learning goal. There are different types of analysis diagrams used depending on whether the goal is psychomotor, intellectual, verbal, or an attitude. The most common is a hierarchical analysis approach diagram. Students will practice setting a goal, identifying subordinate skills, and creating a hierarchical analysis diagram using an online tool.
AMERICA'S BLACK WALL STREET - How The Ku Klux Klan Went About TERRORIZING & D...VogelDenise
The document summarizes the history of "Black Wall Street", a once thriving African American community in Tulsa, Oklahoma that was destroyed in the 1921 Tulsa race riot. It describes how Black Wall Street had over 600 black-owned businesses and was a model of black prosperity, before being burned to the ground by white mobs in a period of less than 12 hours. Over 800 people were injured, 10,000 left homeless, and 35 city blocks containing over 1,000 residences and businesses were destroyed by fire and bombing from airplanes. The riot left 3,000 African Americans dead and destroyed one of the most affluent black communities in America at the time.
02/14/07 COMPLAINT (Newsome vs Spring Lake Apartments)VogelDenise
02/14/07 COMPLAINT (Newsome vs Spring Lake Apartments)
This appears to be a Lawsuit in which Baker Donelson Bearman Caldwell & Berkowitz used a FRONTING Law Firm (DunbarMonroe) and a TAINTED/CORRUPT Judge (Tom S. Lee) and Magistrate (Linda Anderson) to throw Lawsuit. Filed an EMERGENCY Complaint with the United States Congress.
The document appears to be a legal case filing from August 2006 consisting of 16 pages. It describes a criminal case with a case number of 2:06-cr-20304-JPM filed on August 8, 2006. No other essential information could be gleaned from the document as it only contains page numbers and no other textual content.
Este documento explica brevemente qué es un PLE (Personal Learning Environment), o entorno personal de aprendizaje, el cual consiste en las herramientas, fuentes de información, conexiones y actividades que una persona usa para aprender. Luego, presenta el PLE de una persona llamada Ana Luisa Padrón, indicando que aunque tiene nociones básicas, le falta dirección. Finalmente, ofrece algunas sugerencias para mejorar un PLE como ordenar, clasificar, elaborar, compartir y cooperar la información.
UNITED STATES CODE ANNOTATED - Chapter 1VogelDenise
This summary provides the key information from the document in 3 sentences:
The document outlines several sections of the US Copyright Act, including definitions of terms like "audiovisual works", "collective works", and "derivative works". It also describes what can be copyrighted under sections 101-102 such as original works of authorship fixed in a tangible medium of expression. The sections summarized relate to subject matter, ownership duration, rights of authors, fair use, and international standards.
GEORGE ZIMMERMAN & EBOLA CRISIS (Estonian)VogelDenise
Seost AMEERIKA ÜHENDRIIGID rassismi ja Ebola!
Mis seos on George Zimmerman ja Ebola puhang / Crisis Aafrikas? Tundub, et rassistlikud rünnakud Ameerika Ühendriikide poolt despotismi süsteemi, mis kontrollib, juutide ja valge paremmuuteen!
Mis on nii kurb on see, et pettuse kohta Ameerika Ühendriikidest, Iisraelist ja nende liitlased põhjustavad genotsiidi tavad Ebola haigustest!
Huvitav on see, kuidas Ebola haigus ei levinud Ameerika Ühendriikides, kuigi neid väidetavalt NAKATUNUD puutus palju ja YES, kehavedelike olid kohal. MIS häbi ja häbi!
See on häbi ja häbi, et Aafrika liidrid näivad olevat asjatundmatu FAKTID, et Ameerika Ühendriigid, Iisrael ja nende WHITE ALLY kolleegiga soovivad juurdepääsu oma maad ja ressursse - st otsin tappa ära ja / või paigutada neid PLANTATIONS!
TaxCycle Software and Tax Update Seminar Tour October 2013 for Canadian Tax P...Trilogy Software
This document provides an agenda and information for a training and tax update tour occurring in October/November 2013. The agenda includes sessions on TaxCycle training, a tax update and year-end planning, Excel tips for tax preparers, and closing remarks. Biographies of the presenters Marc Labrecque and Cameron Peters are provided, along with background on their experience in the tax software industry. Information is given on TaxCycle software capabilities for personal T1 returns, T4 slips, corporation T2 returns, and support. Pricing and purchase details are outlined.
Barry Jennings was a New York City Housing Authority official who experienced an explosion inside World Trade Center 7 before the collapse of the Twin Towers on September 11, 2001. According to Jennings' testimony, he and Michael Hess felt and heard explosions while trapped inside WTC 7 for several hours as both towers collapsed. Jennings' account contradicts the official explanation that WTC 7 collapsed due to fires and has led some to believe explosives were used to bring down the building. Jennings' death in 2008 at age 53 fueled alternative theories about his involvement in 9/11 investigations.
This document is a court docket listing case information and filings for USA v. Deborah Palfrey, case number 1:07-cr-00046-JR. It shows that Deborah Palfrey was indicted on racketeering and other charges. The docket lists motions, orders, hearing dates, attorney entries of appearance, and other procedural matters for the case up to April 2007. Palfrey entered a not guilty plea and the docket includes filings related to requests for travel, appointment of counsel, and other matters as the case was proceeding.
A Methodology for Modeling the Influence of Construction Machinery Operators ...Reno Filla
This paper is concerned with modeling the actions of a human operator of construction machinery and integrating this operator model into a large, complex simulation model of the complete machine and its environment. Because human operators to a large degree affect how the machine is run, adaptive operator models are a necessity when the simulation goal is quantification and optimization of productivity and energy efficiency. Interview studies and test series have been performed to determine how professionals operate wheel loaders. Two models using different approaches were realized and integrated into a multi-domain model for dynamic simulation. The results are satisfactory and the methodology is easily usable for other, similar situations.
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51998
http://dx.doi.org/10.1007/978-3-642-02809-0_65
Towards Finding the Optimal Bucket Filling Strategy through SimulationReno Filla
The purpose of earth-moving equipment like wheel loaders is to engage with the ground or other material. It is therefore obvious that the bucket filling phase must be included when studying optimal machine control over a complete working cycle because total productivity and efficiency of the machine are to a large extent determined by it. This paper reports and discusses the results of research into how to utilize Discrete Element Method simulations in combination with Optimal Control to find the optimal bucket filling strategy and what has been learned regarding preparing and conducting both simulations of bucket filling and physical testing for verification. This paper also discloses which bucket filling strategy appears to be optimal, based on the results so far – and why we cannot be completely certain.
Evaluating the efficiency of wheel loader bucket designs and bucket filling s...Reno Filla
In this paper we outline how optimising bucket design and bucket filling is connected to improving the total energy efficiency of a wheel loader. Results from our work with particle simulations are shown and it is discussed that, while ideally such simulations should be coupled to models of the machine, operator and the work environment, it is nonetheless possible to simulate stand-alone and utilise simple performance indicators to compare different bucket designs and different bucket filling strategies in a reasonably fair manner. Suitable and less suitable performance indicators are derived and discussed in detail.
An Event-driven Operator Model for Dynamic Simulation of Construction MachineryReno Filla
Prediction and optimisation of a wheel loader's dynamic behaviour is a challenge due to tightly coupled, non-linear subsystems of different technical domains. Furthermore, a simulation regarding performance, efficiency, and operability cannot be limited to the machine itself, but has to include operator, environment, and work task. This paper presents some results of our approach to an event-driven simulation model of a human operator. Describing the task and the operator model independently of the machine's technical parameters, gives the possibility to change whole sub-system characteristics without compromising the relevance and validity of the simulation.
http://arxiv.org/abs/cs/0506033
Simulating Operability of Wheel Loaders: Operator Models and Quantification o...Reno Filla
In this paper make the case that operability needs to be considered early on in the development of wheel loaders, alongside such established design targets as productivity and energy efficiency. We summarise research that shows how proper operator models can introduce a “human element” into dynamic simulations, providing more relevant answers with respect to operator-influenced complete-machine properties such as productivity and energy efficiency. We then show two ways of also drawing conclusions on the operability of wheel loaders by analysing either measurement data from physical tests or simulation results.
Fuel efficiency in construction equipment – optimize the machine as one systemReno Filla
In order to further optimize the fuel efficiency and productivity of construction equipment, 3 main potentials have been identified:
• job site optimization
• machine use optimization
• machine optimization
The focus of this paper is the machine optimization on the example of a wheel loader.
Optimizing losses in individual components must be done, but it will not be a game changer for fuel efficiency improvement. Three areas for promising improvement potentials:
• Optimizing the systems interactions
• Decoupling of systems
• Reduction of losses
One example is shown for a total machine optimization approach: the “Reverse by Braking” function is using the machine operating brakes to slow down the machine during power shuttle instead of using the engine power.
Decoupling of systems requires continuously variable transmission (CVT) functionality for the driveline. This can be achieved with hydraulic or electric CVTs. Two examples for decoupling systems are shown: the Volvo hydrostatic powersplit CVT prototype and a series hybrid wheel loader.
Further future potentials are explored, while the driveline and hydraulic technology are the enablers for drastic improvements: electrified site, plug in hybrid, alternative fuels, and new machine concepts.
Optimizing the trajectory of a wheel loader working in short loading cyclesReno Filla
This document summarizes a study examining alternative trajectories for wheel loaders working in short loading cycles. It describes analyzing trajectories beyond the traditional V- or Y-cycle patterns. Different cycle variants were examined, including maintaining the classic cycle shape but varying parameters. The document outlines limitations in simplifying curves to circular arcs for analysis versus using clothoid curves. It also describes optimizing cycle parameters like reversing point angle and turning radii to minimize transport distance or time for given load receiver positions. The goal is to identify more efficient trajectories for applications like simulations, operator assistance, autonomous machines and hybrid energy management.
On Increasing Fuel Efficiency by Operator Assistance Systems in a Wheel LoaderReno Filla
This document discusses the potential for increasing fuel efficiency and productivity in wheel loaders through an operator assistant system. An empirical study found large variations between operators, with some achieving fuel efficiencies up to 200% higher and productivities up to 700% higher than others. The document argues that an operator assistant system could help all operators achieve the levels of the most efficient operators. It suggests a system that recommends optimal operations to the operator, with some automated functions, as a good starting point. Fuel efficiency improvements of 20-40% and productivity increases of 40-80% are estimated to be possible.
Selecting representative working cycles from large measurement data setsReno Filla
1. The document describes three methods for selecting representative work cycles from large datasets of machine usage data: the Mean Cycle Method, Synthetic Mean Method, and Least Error Method.
2. The Mean Cycle Method constructs an average cycle and selects the measured cycle closest to it. The Synthetic Mean Method constructs a cycle based on peak frequencies and amplitudes and selects the closest measured cycle. The Least Error Method compares all cycles and selects the one with the smallest deviations.
3. When tested on 100 wheel loader work cycles, the three methods produced similar but not identical results for the most representative cycle depending on the signals considered. Considering multiple important signals led to more agreement between the methods.
Using Dynamic Simulation in the Development of Construction MachineryReno Filla
As in the car industry for quite some time, dynamic simulation of complete vehicles is being practiced more and more in the development of off-road machinery. However, specific questions arise due not only to company structure and size, but especially to the type of product. Tightly coupled, non-linear subsystems of different domains make prediction and optimisation of the complete system's dynamic behaviour a challenge. Furthermore, the demand for versatile machines leads to sometimes contradictory target requirements and can turn the design process into a hunt for the least painful compromise. This can be avoided by profound system knowledge, assisted by simulation-driven product development. This paper gives an overview of joint research into this issue by Volvo Wheel Loaders and Linköping University on that matter, lists the results of a related literature review and introduces the term "operability". Rather than giving detailed answers, the problem space for ongoing and future research is examined and possible solutions are sketched.
http://arxiv.org/abs/cs/0305036
Dynamic Simulation of Construction Machinery: Towards an Operator ModelReno Filla
In dynamic simulation of complete wheel loaders, one interesting aspect, specific for the working task, is the momentary power distribution between drive train and hydraulics, which is balanced by the operator.
This paper presents the initial results to a simulation model of a human operator. Rather than letting the operator model follow a predefined path with control inputs at given points, it follows a collection of general rules that together describe the machine's working cycle in a generic way. The advantage of this is that the working task description and the operator model itself are independent of the machine's technical parameters. Complete sub-system characteristics can thus be changed without compromising the relevance and validity of the simulation. Ultimately, this can be used to assess a machine's total performance, fuel efficiency and operability already in the concept phase of the product development process.
http://arxiv.org/abs/cs/0503087
Alternative system solutions for wheel loaders and other construction equipmentReno Filla
- The document discusses alternative system solutions for wheel loaders and other construction equipment to reduce fuel consumption by 50% through hybrid technology.
- It analyzes wheel loaders as complex energy conversion systems and describes the key balances of force, motion, and power that must be maintained for high productivity, energy efficiency, and operability.
- Hybridization is proposed to maintain these balances through additional electric drive components that can assist both the hydraulic and drivetrain systems in parallel or series configurations.
This document describes a project on pressure control of an electro-hydraulic brake system using sliding mode control. It establishes a 4-order nonlinear mathematical model of an actuator with a four-way sliding valve and hydraulic cylinder. It then designs a sliding mode controller based on this model to control the hydraulic pressure. Simulations are performed in MATLAB/Simulink to test the controller on sine waves, square waves, and disturbances, showing that it can track the target pressure within 0.25 seconds with less than 1.2 bar of error. The goal is to enhance stability and robustness of electro-hydraulic brake systems.
This document summarizes energy efficient hydraulic system solutions that can minimize losses and reduce energy consumption. It discusses valve-controlled mobile systems and compares conventional designs to more advanced concepts using techniques like flow matching to reduce pressure differences. It also examines pump-controlled industrial systems using variable speed pumps for improved efficiency. Specific solutions presented include counterbalancing, hydraulic transmissions, and hybrid systems to recover braking energy. Analysis shows energy savings of 10-50% are possible in many applications through optimized system design.
This document provides an overview of fundamentals of hydraulic systems. It begins by listing the chapter learning objectives for skills and knowledge related to hydraulic systems. It then defines key terms like flow, pressure, pumps, actuators, and others. It describes Pascal's law of hydraulic pressure transmission and gives examples. It explains how hydraulic systems provide force multiplication and gives advantages like precise control, flexibility, and disadvantages like potential leaks and cleanliness requirements. Bernoulli's principle of fluid dynamics is also mentioned. Safety organizations and concerns unique to hydraulic systems are covered at the end.
An approach to evaluate the heat exchanger retrofit for installed industrial ...eSAT Journals
This document summarizes an economic evaluation of retrofitting heat exchangers to existing industrial gas turbines to improve their efficiency. It describes using the net present value method to compare the economics of simple cycle and recuperative cycle configurations for two gas turbine models. The analysis found that retrofitting heat exchangers can increase the net present value over the simple cycle, with differences ranging from $11 million to over $46 million depending on the turbine model and assumptions. However, the payback period for the retrofit may be longer, and the analysis also examined the effects of utilization rate and other factors on the economic viability.
Cfd study of a Pelton turbine runner by M.Minozzo R.Bergamin M.Merelli M.Galb...TUM
This document compares two computational fluid dynamics (CFD) approaches - traditional Eulerian and novel Lagrangian Moving Particle Simulation (MPS) - for simulating Pelton turbine runners. The traditional Eulerian approach requires significant geometry simplification and simulation time. The novel MPS approach can simulate the entire turbine geometry without simplification in less time. It also provides new insights not previously discovered, such as jet-jet interactions, opening possibilities for further optimization. Both approaches produce results within 1% of theoretical values, but MPS saves considerable time and resources.
Hybrid Power Systems for Construction Machinery: Aspects of System Design and...Reno Filla
This paper will examine the wheel loader as a system with two parallel energy conversion systems that show a complex interaction with each other and with the power source. Using a systematic design approach, several principle design solutions for hybridization can be found.
Furthermore, the human operator with his/her control actions needs to be considered as part of the total system. This paper will therefore also connect to results from ongoing and previous research into operator workload and operability.
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51999
http://dx.doi.org/10.1115/IMECE2009-10458
Energy and exergy analysis of a 250 mw coal fired thermal power plant at diff...eSAT Journals
Abstract In this present investigation exergy and energy efficiencies of a coal fired 250 MW thermal power plant operating in eastern part of India are determined both for 100% and 90% load based on actual operating data. The efficiencies are evaluated for the overall plant as well as for different equipments like boiler, turbine, all feed water heaters and condenser. Similarly effectiveness of the feed water heaters is evaluated for both the loads. Exergy destruction % for each of the equipment are also given for clear understandingof the loss of available energy due to irreversibilities involved in the processes for each equipment and the whole plant. It is observed that a major irreversibility or, exergy destruction takes place at boiler though 1st law energy efficiency is quite high. This signifies that there might have further scope of improvement in this equipment. Similar analyses are carried out for other equipments. The results obtained in present analysis are compared with those of other investigators. Keywords: Energy, Exergy, Efficiency, Effectiveness, Exergy destruction, Power plant
The document discusses the thermo-mechanical analysis of a crankcase for a six cylinder truck diesel engine. It outlines the process of identifying loads from combustion, inertia, thermal effects and assembly and applying them in a finite element analysis of the crankcase. The analysis seeks to determine the durability and fatigue life of the crankcase under the varying operating loads of the engine.
Similar to A Case Study on Quantifying the Workload of Working Machine Operators by Means of Psychophysiological Measurements (20)
In support of removal of periodic calibration of Flight RecordersReno Filla
This is not a Position Paper on Periodic Pressure Altitude Calibration of FR.
This is a paper on why the above is not needed.
This document will not contain a technical discussion of if, how, why and when the accuracy of pressure sensors in Flight Recorders possibly deviates and whether it then varies with absolute altitude, calendar age, frequency of use or some other variable.
We will not present statistical evidence for either occurrence or non-occurrence of "drifting" of pressure readings. Nobody has these data anyway.
What we will do in this document is to deliberate why we in our sport measure altitude to begin with and what the “good enough” level of accuracy is. From there we will examine how this can be achieved in FAI's legal framework and address possible needs for adjustment of the Sporting Code, if necessary at all.
Spoiler alert: the conclusion will be that unlike regularly visiting a dentist, periodically having to calibrate the pressure sensor in your Flight Recorder is not actually good for you. It is at best an expensive nuisance and if we can get by without this recurring hassle then we all are off for the better.
Brave new electric world: will hydraulics survive and who needs hydraulics anyway? A provocation delivered by an unsentimental system integrator. A real engineer doesn't "love" or "hate" but makes balanced and well-considered technology decisions based on performance, efficiency, application, quality, robustness, cost, etc.
Reflections on Research (and a Fractal Perspective on Systems Engineering)Reno Filla
This round-kick presentation for the 2022 LINK-SIC workshop (https://liu.se/en/article/link-sic-workshop-2022) spans the arc from research and predevelopment to knowledge in general (vs belief and opinion), systems engineering and the ongoing specialization/fragmentation of engineering , uncertainty, the climate-change related challenges ahead - and more.
This document summarizes Reno Filla's presentation on electric roads (e-roads) and the experience from pilot projects in Germany and Sweden. It discusses the power requirements for electric trucks, including 250-300 kW for constant speed driving and additional 120 kW per 1% grade. It also notes challenges like adaptive driver assistance systems in certain weather conditions and catenary interruptions. The presentation evaluates having enough power capacity for varying operating conditions and argues that 250 kW per truck is not over-dimensioned given power needs for acceleration, battery charging, and only partial road electrification.
SEC lecture "Electrification of Future Transports"Reno Filla
The document discusses the electrification of future transports. It notes the four main drivers of sustainable transport as congestion, pollution, energy security, and climate change. Scania is a leading provider of transport solutions and is working with partners and customers to drive the shift towards a more sustainable transport system. The presentation outlines Scania's goals to cut emissions from its operations and products by 2025 to help fuel the transition to more sustainable options.
Presentation for graduate students: Zoom in to learn the basics and refine your knowledge, then zoom out for perspective and to make connections. Then repeat until convergence. Which you might attain until the next disruption. ;-)
Der Diplom-Ingenieur Reno Filla ist verheiratet und hat ein Kind. Nach seinem Abschluss 1998 an unserer Hochschule ging er zu Volvo nach Schweden, wo er bis heute mit seiner Familie lebt. Seine Freizeit verbringt er gerne mit Segelfliegen. Über seine Zeit des Studiums und sein Werdegang nach dem Studium berichtet er uns in diesem Interview.
https://www.hs-magdeburg.de/hochschule/einrichtungen/alumni-management/interviews.html
Keynote presentation held at the 15th Scandinavian International Conference on Fluid Power 2017 in Linköping, Sweden
It covers the topics energy efficiency, electromobility, operator assistance, automation, connectivity and site solutions.
Towards Finding the Optimal Bucket Filling Strategy through SimulationReno Filla
The document discusses using simulation to find the optimal bucket filling strategy for a construction vehicle. It analyzed 5781 trajectories with 5 different filling strategies (labeled A through E) through discrete element method simulation. Various problems were encountered in the simulations, such as particles jumping unpredictably and large upward forces on the bucket, and solutions were developed to address them, such as adjusting the time step or adding more particle layers. Overall strategy A seemed most efficient while B was very inefficient. The analysis noted several important factors that were not captured in the simulations, such as the full loading cycle and stability of the vehicle, and suggested coupled large-scale simulation and optimization of the machine, environment, and operator may be needed to fully address finding the optimal strategy
Electromobility and Construction MachineryReno Filla
The search for energy efficient solutions goes on also for construction machinery, and hybrids are a given topic. This seminar looks at related research and pre-development at Volvo Construction Equipment and focuses on wheel loaders. In these machines, drive train and hydraulics are both equally powerful and compete for the limited engine torque. There is a large theoretic potential for the increase of energy efficiency, but to leverage this, a holistic approach is needed. The wheel loader is examined as a system with drive train and hydraulics as two parallel energy conversion systems that show a complex interaction with each other and the power source. Using a systematic design approach, several principle design solutions for hybridization can be found and are discussed.
Gliding Contest Scoring: current and proposal 8.1.4 for the 2016 IGC plenaryReno Filla
This is a supporting presentation to explain how scoring currently works (visualizing the official equations in a rearranged way) and what the effect of Dutch proposal 8.1.4 will be
For the joint IQPC Conferences "Automation & Connectivity for Mobile Machinery" and "HMI for Mobile Machinery", for which I also had the honor to serve as the conference chairman.
Classification of physiological signals for wheel loader operators using Mult...Reno Filla
This summarizes a research paper that presents a classification approach called MMSE-CBR to classify physiological parameters of wheel loader operators. It combines case-based reasoning (CBR) with multivariate multiscale entropy analysis (MMSE) to fuse data from multiple physiological sensors. The MMSE algorithm is used to extract features from signals measured by sensors like ECG, finger temperature, skin conductance, and respiration rate. These features are used to form cases in a case library. The CBR approach then classifies new cases by retrieving similar past cases. The approach was evaluated on data from 18 professional drivers and achieved 83.33% accuracy in classifying subjects as "stressed" or "healthy", comparable to an expert's
Mental State Monitoring System for the Professional Drivers Based on Heart Ra...Reno Filla
The consequences of tiredness, drowsiness, stress and lack of concentration caused by a variety of different factors such as illness, sleep depletion, drugs and alcohol is a serious problem in traffic and when operating industrial equipment. This is especially important for professional drivers since both expensive equipment and lives may be at stake, e.g. in mining, construction and personal transportation, reduced concentration, stress or tiredness are known to be the cause of many accidents. A system which recognizes the state of the driver and e.g. suggests breaks when stress level is too high or driver is too tired would enable large savings and reduces accident. Today different sensors enable clinician to determine a driver’s status with high accuracy. The aim of the paper is to develop an intelligent system that can monitor drivers’ stress depending on psychological and behavioral conditions/status using heart rate variability. An experienced clinician is able to diagnose a person’s stress level based on sensor readings. Here, we propose a solution using case-based reasoning to diagnose individual driver’s stress. During calibration a number of individual parameters are established. The system also considers the feedback from the driver’s on how well the test was performed The validation of the approach is based on close collaboration with experts and measurements from 18 driver’s from Volvo Construction Equipment are used as reference.
http://www.mrtc.mdh.se/index.php?choice=publications&id=3046
Representative Testing of Emissions and Fuel Consumption of Working Machines ...Reno Filla
Out of necessity, emission and fuel consumption test cycles are a simplified representation of the real-life use of a vehicle or component that is assumed to be most common. In reality, variations are introduced by both the driver and the environment – and to a lesser degree also by the vehicle itself through performance deviations because of tolerances in the components’ characteristics. However, since such simplified test cycles exist and are accepted (or even required by law), OEMs tend to use them also in product development to benchmark their products against the competition, and to make decisions on how to optimize design.
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A Case Study on Quantifying the Workload of Working Machine Operators by Means of Psychophysiological Measurements
1. The 13th Scandinavian International Conference on Fluid Power, SICFP2013, June 3-5, 2013, Linköping, Sweden
A Case Study on Quantifying the Workload of Working Machine Operators
by Means of Psychophysiological Measurements
R. Filla1
, E. M. G. Olsson2
, B. H. C. von Schéele3
, and K. Ohlsson4
1
Emerging Technologies, Volvo Construction Equipment, Eskilstuna, Sweden
E-mail: reno.filla@volvo.com
2
Department of Public Health and Caring Sciences, Uppsala University, Uppsala, Sweden
E-mail: erik.olsson@pubcare.uu.se
3
Stress Medicine AB, Bergvik, Sweden
E-mail: bo.vonscheele@stressmedicin.se
4
Department of Management and Engineering, Linköping University, Linköping, Sweden
E-mail: kjell.ohlsson@liu.se
Abstract
In this study of eighteen wheel loader operators, test-driving a machine in three different
traction force settings, we examine if a workload index derived from psychophysiological
measurements of heart rate, finger temperature, skin conductance, respiration rate and end-tidal
CO2-concentration in exhaled air can be easily used to assess operator workload in sufficient
detail to use it as a complement to traditional subjective evaluations in machine testing, either of
real machines or in a human-in-the-loop simulator. In a longer perspective, such measurements
are expected to play a role in a workload-adaptive operator assistance system.
However, the findings do not give support for this vision. Instead they indicate that other types
of measurements than what have been used in our study should be employed if ease of use for
practitioners such as test engineers is in focus, but also that other factors than just machine
operability must be considered to have a great influence on the operator workload.
Keywords: operator, working machines, wheel loaders, operator workload, stress, operability,
human-machine interaction
1 Introduction
Working machines in construction, mining, agriculture, and
forestry are not only becoming ever more sophisticated in
terms of digital control, but are also complex in architecture.
Many of these machines consist of at least two working
systems that are used simultaneously and the human
operators are essential to the performance of the machines in
their working place.
With their productivity and energy efficiency being linked
to the operators’ workload, it is essential to make working
machines easier to use. The immediate goal of our research
is to support product development by complementing the
traditional subjective evaluation of a prototype machine’s
operability (involving asking the operator to rate the
machine according to a specific scale) with a less subjective
measure based on the operator’s workload. In order to be
usable in product development projects, such a measure
needs to be easy to derive for a test engineer who is not a
trained researcher in the field of psychophysiology. Ideally,
this measure would be calculated automatically and online
in order to be available during or immediately after testing.
This article will report on the setup and results of a larger
study conducted to investigate if common psychophysio-
logical measurements of finger temperature, heart rate,
respiratory rate, CO2 concentration in exhaled air, and
galvanic skin response can be used to quantify the workload
of wheel loader operators during operation of the machine.
In a longer perspective, such measurements might be
employed for giving workload-adaptive assistance to the
machine operator.
2 Wheel loader application and challenges
In our on-going research, a wheel loader was chosen as the
object of study, although working machines of similar
complexity and with similar challenges can be found in
construction, agriculture, forestry and mining.
2. The short loading cycle shown in Figure 1 is highly repre-
sentative of the majority of a wheel loader’s application.
Typical of this cycle is bucket loading of granular material
(for instance gravel) on an adjacent dump truck (or other
load receiver, mobile or stationary) within a time frame of
25-35 seconds, depending on working place setup and how
aggressively the operator uses the machine, but also
depending on the operator skill. A detailed description with
identification of wheel loader working cycles, together with
the challenges they present for machine design and
operability, can be found in [1].
Figure 1: Short loading cycle.
In Figure 1 the short loading cycle has been divided into ten
phases, beginning with bucket filling. Visualising test results
obtained in earlier studies, Figure 2 shows that the fuel
consumption rate (expressed in volume or mass per time
unit) is approximately 60% higher during bucket filling than
the cycle average. Expressed in absolute values, bucket
filling accounts for 35-40% of the mean total fuel
consumption per cycle, yet the time spent on filling the
bucket is only 25% of the average cycle time.
Figure 2: Fuel consumption during short loading cycle.
After bucket filling, the operator drives backwards towards
the reversing point and steers the wheel loader to
accomplish the characteristic V-pattern of a short loading
cycle. The lifting function is engaged the whole time. The
operator chooses the reversing point such that having
arrived at the load receiver and starting to empty the bucket
(phase 6 in Figure 1), the lifting height will be sufficient to
do so without delay. Figure 2 shows that the fuel
consumption rate for phases 2 to 6 is approximately constant
and close to the average fuel consumption rate of the
complete short loading cycle.
In the remaining phases, the bucket needs to be lowered and
the operator steers the wheel loader back to the initial
position in order to fill the bucket again in the next cycle.
Phases 7-10 are less energy-demanding and the fuel
consumption rate is therefore lower than the average for the
complete short loading cycle.
The higher fuel consumption rate during bucket filling (as
shown in Figure 2) warrants a closer look at this phase. The
inner loop in Figure 3 shows how the human operator
interacts with the wheel loader. In order to fill the bucket,
the operator needs to control three motions simultaneously:
a forward motion that also exerts a force (traction), an
upward motion (lift) and a rotating motion of the bucket to
load as much material as possible (tilt). This is similar to
how a simple manual shovel is used. However, in contrast to
a manual shovel, the operator of a wheel loader can only
observe, and cannot directly control these three motions.
Instead, he or she has to use different subsystems of the
machine to accomplish the task. The gas pedal controls
engine speed, while the lift and tilt levers control valves in
the hydraulics system that ultimately control movement of
the linkage’s lift and tilt cylinder, respectively.
Figure 3: Simplified power transfer and control scheme of a
wheel loader.
The difficulty lies in that no operator control directly affects
only one single motion. The gas pedal controls engine
speed, which affects both the machine’s longitudinal motion
and via the hydraulic pumps also affects the speeds of the
lift and tilt cylinders. The linkage between the hydraulic
cylinders and the bucket acts as a non-linear planar
transmission and due to its design a lift movement will also
change the bucket’s tilt angle and a tilt movement affects the
bucket edge’s height above the ground.
Furthermore, Figure 3 also shows how in the outer loop the
primary power from the diesel engine is split up between
Auxiliaries
Bucket
Wheels
Lifting +
Breaking/Tilting
Travelling/
Penetration
Drivetrain
Hydraulics
Σ Engine
Linkage
External (+/-)
Gravel
pile
OperatorECU
ECU
ECU
ECU
3. hydraulics and drive train in order to create lift/tilt
movements of the bucket and traction of the wheels, but is
connected again when filling the bucket from for example a
gravel pile. Figure 4 shows that in this situation, the traction
force from the drive train, acting between wheels and
ground, creates a reaction force between gravel pile and
bucket edge, which in turn creates a moment of forces
around the loading arm’s centre of rotation that counteracts
the moment of forces created by the push of the lift cylinder.
Figure 4: Force balance during bucket filling.
In effect, the traction force, indirectly controlled by the
operator through the engine speed, reduces the available
lifting force. Depending on lifting height and applied
traction force, the lifting force can be completely cancelled
out, and the bucket cannot be moved upwards any further.
The operator then has to either apply the tilt function or
reduce the traction force by reducing the engine speed –
which is rather counter-intuitive as a common mental model
of vehicle drivers is that an increase in gas pedal deflection
leads to more torque from the engine until any external
resistance can be overcome.
In our study, the different machine setups (as described in
section 4.1) are using this phenomenon to create machines
with three different levels of maximum engine speed during
bucket filling, translating to different levels of perceived
ease of use, depending on the operators’ individual skills.
Another general challenge for wheel loader operators exists
in that the hydraulic levers control the speed of the hydraulic
cylinders, not the force exerted by them. In an old-fashioned
less energy-efficient hydraulic system of the Open Centre
type a higher external load would result in a lower cylinder
speed for the same amount of lever actuation. This would
give the operator an indication of the external load acting on
the cylinder. This is no longer the case in a modern load-
sensing hydraulic system.
In summary, there are many interdependencies and it thus
takes a certain amount of training to be able to use a wheel
loader efficiently and with high productivity. It is therefore
of great interest to investigate machine operability closer
and to develop operator-assisting functions.
3 Quantifying human workload with
psychophysiological measurements
Operating a wheel loader involves both physical and mental
workload. Even though the operator sits still and the
controls do not demand a large amount of physical strength
he/she has to keep balance and be prepared. Mentally the
operator has to maintain attention and respond appropriately
all the time. Measuring this workload therefore calls for a
measure that handles several physiological signals.
As mentioned in the introduction, the short-term goal is to
enable test engineers to derive a less subjective measure of
how easy a machine is to operate. With the personnel
involved in machine testing usually not being trained in
performing and analysing measurements of psycho-
physiological parameters, the scope needs to be limited to
signals that are easy to measure and handle.
There are many aspects of how our physiological systems
interact with physical and mental workload. Heart rate (HR)
and respiration rate (RR) are classical measures of physical
workload where a higher HR and RR result in a better
supply of oxygen to the working body. Both HR and RR
also interact with mental workload.
Other physiological measures involved mainly in mental
workload are skin conductance level (SCL) derived from
palm sweat gland release and peripheral temperature
(typically measured in fingers), derived from smooth
muscles constricting the peripheral blood vessels. A higher
workload is associated with higher SCL and lower finger
temperature. However, the magnitude of changes is
dependent on individual vasoconstriction and sweat gland
activities.
All physiological parameters are highly influenced by
autonomic nervous system (ANS) activity and mainly by the
sympathetic branch but heart rate variability (HRV) and
respiratory sinus arrhythmia (the portion of HRV that is
related to breathing) are associated with both sympathetic
and parasympathetic nervous system activity.
Respiration is regulated in a more complex way which
includes cognitive, chemical, and metabolic systems as well
as the ANS. When subjected to mental or physical
challenges, ventilation increases, which in turn results in a
drop in plasma pCO2. The pCO2 level can therefore be used
to assess whether breathing is in excess of metabolic
demands resulting in a low pCO2, which is the definition of
hyperventilation [2]. A change in pCO2 level is the result of
changes in RR and/or tidal volume. Some researchers have
pointed out that CO2 level can be an advantageous measure
of psychosocial stress, since it can differentiate between
metabolic and psychosocial demands, which in most other
measures generate the same response [3]. The pCO2-level is
often, as in our study, measured as end-tidal CO2 (EtCO2)
which is satisfactorily correlated to pCO2 and permits
assessment of breath by breath variation. The physiological
systems mentioned interact with each other in a complex
way, cooperating with and compensating for each other [4].
In case of immense stressful events people tend to stop
4. breathing, with a direct impact on several regulatory systems
as a consequence.
4 Method
4.1 Machine setup
The wheel loader used was a Volvo L70F equipped with a
general purpose bucket with a load capacity of 2.3m3
. The
total operating weight of the machine is approximately
13.4t.
In order to study the effect of the previously mentioned
interdependencies during bucket filling, the wheel loader
software used in this study was modified to limit engine
speed, and thus traction force, whenever the transmission’s
1st
gear was automatically engaged, which occurs only
during bucket filling (all machines normally start in 2nd
gear).
The first limitation of engine speed was chosen so that
maximum traction force was reduced to 62% in 1st
gear,
which resulted in a maximum engine speed that was
comparable to what expert operators on average used the
wheel loader at. This setting also prevented wheel spin.
There was a slight impact on the speed of the hydraulic
functions (due to the rotational speeds of the engine, torque
converter and hydraulic pump being connected, see Figure 3
and the explanation in an earlier section).
In the other condition, engine speed was limited such that
maximum traction force was reduced to 47% in 1st
gear. We
deliberately used an engine speed limit below what was
needed for the working task planned, which also affected the
speed of the hydraulic functions more noticeably.
Furthermore, the maximum obtainable traction force in 1st
gear was even lower than what was available in 2nd
gear, all
of which an operator would experience as clearly negative.
In both conditions the counteracting effect of the traction
force is clearly less pronounced so that even at maximum
use of the traction force available the lifting force is never
cancelled out completely. This should be experienced
positively, especially by less experienced operators (but the
question is whether this positive aspect outweighs the
artificial limitation of maximum available traction force).
The test machine’s automatic functions were set to gear-
dependent BSS (Boom Sus-pension System is deactivated
when in 1st
gear), Automatic Power Shift (automatic gear
shifting of the transmission) and Auto Kick-down enabled
(automatically changing base gear from 2nd
to 1st
when
needed). We also disabled the function for automatic bucket
tilt-in stop at level position.
A more detailed description of the technical setup of our
study can be found in [5].
The radio and most of the external displays were turned off
in order to not distract the operator from the working task.
However, the display for the load weighing system had to
stay turned-on and since there were other people and
machines present at the proving ground, we also decided to
turn on the rear camera monitor for increased safety.
4.2 Apparatus and sensor placements
Our study also included another part, reported in [5] and
therefore not further presented here, in which the hypothesis
was tested that the operator’s use of the controls available
(gas pedal, lift lever and tilt lever) is indicative of a working
machine’s operability and that a measure for comparative
operability can thus be derived based on the operator’s
control commands. That study required essentially the same
type of data and equipment (and operators) as the one
presented in this article, which led to the decision to run
both studies concurrently.
During all sessions various data were recorded off the wheel
loader’s CAN bus, onto which data from externally mounted
sensors were also merged (thus providing signals of interest
that were not readily available in a standard machine).
Vector Informatik’s CANcaseXL equipment and CANalyzer
software were used for the recording of all traffic on the
machine’s CAN bus to a laptop placed inside the cab. The
need for particular signals required in some cases
modification of the software for engine and transmission
control, while in other cases an external ECU (Parker IQAN
MDL) was used to place calculated signals on the CAN bus.
The latter was also used to acquire additional data from
externally mounted sensors for lift and tilt cylinder stroke
and lever position for lift and tilt. A modified LoadTronic
load weighing system from AADI was used to measure the
net weight of the bucket. The data were transmitted to the
machine controller via SAE J1587 protocol and then merged
into the data stream on the CAN bus.
The psychophysiological measurements were conducted
using the cStress software from PBM Stressmedicine
Systems, running on a second laptop installed in the cab of
the wheel loader. Finger temperature, heart rate (via
Electrocardiogram, ECG) and skin conductance were
acquired using a C2 physiological monitoring system from
J&J Engineering and a LifeSense AirPas oxycapnograph
handled data acquisition and pre-analysis of the operator’s
respiration (Figure 5).
Figure 5: Apparatus for measuring and recording of the
psychophysiological data.
The ECG sensors were placed on both wrists (see Figure 6
and Figure 7) using isotonic gel. We knew from earlier
5. measurements that these sensors need to be secured against
relative movement in order to avoid misreadings. Since the
operator in a wheel loader cab is exposed to vibrations and
accelerations of various frequencies and magnitudes,
potentially rendering ECG measurements impossible to
perform in this environment, we were pleased to find that
good data could be acquired when using the suspended
chair’s integrated arm rests to support the operator’s lower
arms and asking the operator to control the machine’s
articulation angle (for steering) and forward/reverse gear not
through the steering wheel and main gear shift lever but by
using the controls on the left side of the chair instead (see
Figure 7).
Figure 6: Right hand controls and sensor placement on
right wrist.
Figure 7: Left hand controls and sensor placement on left
wrist and fingers.
Figure 7 also shows the placement of the other sensors. The
operator’s finger temperature was acquired by a thermistor
taped to the top of the left little finger (the tape did not
restrict the blood flow). The sensors for measuring galvanic
skin response were attached to the inner phalanges of the
ring and middle fingers of the left hand, again using isotonic
gel. The operator’s respiration was sampled by a nasal
sample line, inserted some millimetres into the left nostril;
in connection with this the operator was asked to exclusively
breathe through the nose.
All tests were also recorded on video using an externally
placed digital video camera and later synchronised with all
other acquired data. Synchronising video to CAN data was
possible by using stationary points in the recorded data for
bucket height and wheel speed. Synchronisation of machine
data (recorded in CANalyzer) and psychophysiological data
(recorded in cStress) proved a little more challenging. In the
end we chose an offline semi-manual approach: at the
beginning and end of each test recording we would press
two buttons simultaneously, where activation of the first
button was logged on the CAN bus and the other logged as
an event in cStress. These synchronisation markers were
later used to automatically merge both data streams.
A simple kitchen timer counted backwards and sounded an
alarm when the required operating time was reached. Both
the timer and all measuring equipment were placed so that
the operator was unable to look at the displays.
4.3 Working cycle
With the intriguing facts visualised in Figure 2 (fuel
consumption in a loading cycle), Figure 3 (hydraulics and
drivetrain as parallel power systems), and Figure 4
(interaction of traction force and hydraulics) in mind, we
specifically wanted to study the wheel loader operator
during the bucket filling phase. We therefore chose to
modify the short loading cycle such that the operator was
instructed to still go through most of the motions, but not to
use steering (as mentioned previously) and thus empty the
bucket at the same spot where it was filled. Since the
material used was sorted gravel which does not stick
together like for example clay, and is thus fairly easy to
handle, this procedure did not introduce any skewing of the
test results as far as the bucket filling phase is concerned.
Not using steering also solved another problem that would
have had an impact on the results: inexperienced operators
are unused to using the joystick rather than the steering
wheel, and forcing them to do so would have introduced
additional workload, thus potentially skewing the test
results. The decision not to use the steering function at all
solved this dilemma.
4.4 Psychophysiological Stress Profile
Every human being has an individual response to workload,
which means that some sort of reference or calibration is
needed in order to be able to correctly evaluate the results of
psychophysiological measurements. While not common
procedure in the research community, establishing a PSP
(Psychophysiological Stress Profile) has proven to be
valuable in our (Olsson and von Schéele) clinical work with
patients with stress-related dysfunctions.
The PSP shown in Table 1 is essentially taken from [6] and
has been implemented in the cStress software. It contains 15
minutes of data recording, guiding the patient (or in our case
the wheel loader operator) through six steps.
In step 1 we provided the operator with a neutral text to
read, informing him that this was not an exam and while we
asked him to read carefully and try to understand the text, he
was not required to read all of it or even remember anything.
This put some workload on the operator, but far from
enough to induce stress. (In our case the text handed out was
a newspaper article about the Nobel Prize for Literature and
6. whether receiving it means the end of an author’s career – it
is fair to state that this text was neutral as none of the
operators got overly excited by reading it).
Table 1: Psychophysiological Stress Profile (PSP)
# Designation Time Description
1 Base line 3 min Relaxed silent reading of a neutral
text
2 Deep breathing 2 min Deep breathing under guidance,
approx. 6 bpm
3 Nonverbal
stress
2+2 min Two periods of thinking about a
stressful situation, feedback and
guidance in-between
4 Relaxing 2 min Relaxing with closed eyes, normal
breathing
5 Math stress 2 min Counting aloud backwards from
2500 in steps of 7
6 Relaxing 2 min Relaxing with closed eyes, normal
breathing
During step 2 the person was guided to breathe slowly and
deeply (using the stomach) with about 6 breaths per minute
(with small individual deviations), and by this means
attained a very relaxed state.
Step 3 is called “Verbal stress” in [6] and according to that
paper in the first half of this step the person is to be
instructed to relate some stressful event that they have
experienced. During the second half, the person shall then,
instead of talking, just think about the same negative and
stressful event. However, in our case the test leader (Filla) is
a close colleague and personal friend of all of the operators,
who in turn were not patients with psychological problems
in need of treatment. Therefore, modifying this step into a
phase of non-verbal stress seemed more appropriate. At the
beginning of this step we therefore asked the operator to
think of a negative and stressful event, real or imaginary,
and keep thinking of it for two minutes. After this time the
test leader approached the person again, gave feedback and
asked him to continue for two more minutes, but this time to
also breathe irregularly as if was stressed.
In the following phase, step 4, the operator was asked to
close his eyes and just relax thoroughly, using individual
techniques without any other requirement e.g. on breathing.
The results show how quickly the person recovers from
stress.
In step 5 the person was tested for reaction to directly
induced stress, coming from the requirement to count aloud
backwards from 2500 in steps of 7. To increase the pressure
the operator was told that it would be noted how many
subtractions he would manage to perform during the two
minutes of testing and that each mistake would be noted,
required to correct before being allowed to continue. (It was
interesting to see that this indeed induced an enormous
amount of stress in some individuals, but not all.)
Step 6, the last step within the PSP, is a repetition of step 4,
i.e. relaxing without any other requirement.
Figure 8: Questionnaire during PSP.
After each step the operator was asked to fill in a
questionnaire (Figure 8).
4.5 Participating operators
In all, eighteen people, all male, agreed to participate in this
study; all of them close colleagues of the author. Their data
have been recorded and handled securely in a way that
prevents drawing conclusions as to their identities.
The people asked to participate as test operators in this study
are all male, mostly in order to exclude possible skewing
due to gender differences in the way the human body reacts
to mental workload. The potential operators were not
randomly chosen, but pre-selected according to the author’s
preliminary judgement of their wheel loader operating skills.
However before starting the test each operator was asked to
make a self-report with respect to their skill, using a visual
analogue scale without values, but with some helpful
guidance, see Figure 9 left.
Figure 9: Sorting of the participating operators into skill
groups.
Self-evaluation
How do you evaluate your own performance, did you cope?
(Put an X somewhere on the line.)
It did not OK, It went
go well at all as required very well
I felt OK, I felt
very stressed no major problems no stress at all
Do your hands feel warmer or colder than before – or the same?
(Circle the answer)
Estimate your finger temperature: ________°C
7. To the right, Figure 9 shows the division of the scale into
four skill groups and how the individual operators are placed
in these groups, using their self-reported skill ranks. These
turned out to be similar to the author’s preliminary
judgement, resulting in nine operators in skill group 1
(inexperienced), six in skill group 2 (experienced) and three
in skill group 3 (expert). This also gives the possibility to
combine groups 2 and 3 at a later stage into an aggregated
“experienced and above” group that matches the
“inexperienced” group in size, which would benefit the
statistical strength of direct comparisons.
In our pre-selection of potential test operators for this study
we chose not to focus on expert operators alone, but to
include operators of all skill groups in order to test whether
there is any difference in how operators in these groups
handle and evaluate the different machine variants.
However, we deliberately avoided newcomers in order to
guarantee at least a theoretical knowledge of how to operate
a wheel loader, and in order to exclude learning effects as
much as possible. The ten minutes of self-training before
each live testing session would not have sufficed for
newcomers, but were deemed sufficient for operators in skill
group 1 and above.
4.6 Design of the study and procedure
Each operator was given an exclusive 2.5 hours session after
lunch, starting with the Psychophysiological Stress Profile
(PSP) described earlier. For this, we took the operator of the
day to a secluded place. The PSP was conducted with the
operator sitting in working position in the cab of the wheel
loader and the person administering the test standing on the
ladder, instructing through the open door, and monitoring
through the closed door when recording was in progress.
After the PSP, the operator took the machine to the proving
ground, where a smaller area was reserved for this study.
The testing of all three machine variants was then per-
formed, with the traction force setting as the independent
variable. The study design is in essence a three-condition
within-subjects setup, with the two limited settings of 47%
and 62% tested against the unmodified software version
with 100% maximum traction force, in random order,
unknown to the operator. The operators were not told what
had been modified and how, but most of them, especially
the more experienced ones, were able to deduce this fairly
quickly.
In order to minimise the skewing influence of learning
effects, before testing a machine version each operator was
given ten minutes’ self-training just to familiarise himself
with the specific characteristics of the current machine
version. After the training followed five minutes’ live test-
driving, where the operator was asked to make sure to fill
the bucket completely and use the machine at a normal
production tempo, resulting in a cycle duration of approx. 25
seconds (both of which most of the inexperienced operators
did not manage to achieve completely, but at least this
demand created a certain pressure). The session ended with
a subjective evaluation where, among other things, the
operator was asked to judge the tested machine version’s
ease of bucket filling and perceived power on a visual
analogue scale (without printed values). The operator was
also asked to rank his overall impression of the machine in
comparison to all previously tested variants on a nominal
scale (“better”, “worse” or “same”). See Figure 10 for the
questionnaire used after testing of the third machine variant.
Since the study was performed during the autumn,
comparable conditions for the operators were ensured by
performing tests only on days with good weather (no rain)
and at the time of the highest ambient temperature, at 13:00
local time. The latter also guaranteed that the operators were
rested and had eaten recently.
Figure 10: Questionnaire, to be filled in after testing of each
machine variant.
5 Analysis
5.1 General setup
The measurements conducted during this study resulted in
several gigabytes of data, making at least semi-automated
analysis necessary.
The main parts of the calculations were executed in
MathCad worksheets that merged data originating from
machine and operator by using synchronisation markers
Evaluation of machine variant #3
How do you rank the machine in this setup,
especially during bucket filling? (Put an X somewhere on the line.)
Very hard OK, Very easy
to fill the bucket about normal to fill the bucket
The machine feels OK, The machine feels
powerless, slow about normal powerful, quick
Does the machine feel better or worse than the first one – or the same?
(Circle the answer)
Does the machine feel better or worse than the second one – or the same?
(Circle the answer)
How do you evaluate your own performance, did you cope?
(Put an X somewhere on the line.)
It did not OK, It went
go well at all as required very well
I felt OK, I felt
very stressed no major problems no stress at all
Do your hands feel warmer or colder than before – or the same?
(Circle the answer)
Estimate your finger temperature: ________°C
8. embedded in both data streams. A function then
automatically tagged each bucket filling phase within each
loading cycle and exported part of the data stream back to
cStress for expert review (see next section). This result of
this review was a consensus figure for each operator’s
absolute workload level in each condition. These data and
the results from the various questionnaires each operator had
to fill in were then imported into MathCad and merged with
all other recorded data for further analysis.
5.2 Expert review of psychophysiological data
As mentioned in the introduction, our immediate goal is to
support product development, in which the operability of
prototype machines is traditionally evaluated subjectively by
asking the operator to compare the tested machine with a
base line and rate it according to a specific scale. Thus, a
measure of operator workload is required, ideally calculated
automatically either during or immediately after testing.
However, we are aware of the magnitude of this. There
exists a relationship between finger temperature and mental
workload in that increased workload leads to decreased
finger temperature and vice versa [7]. Such relationships can
also be found other signals, e.g. heart rate, heart rate
variability, respiratory rate etc [8][9][10][11]. However,
these data have to be evaluated in context and in relation to
the PSP and each other, which today requires expert
knowledge. Furthermore, a reliable algorithm to
automatically remove measurement artefacts in data for
ECG and respiration has yet to be developed.
It is precisely this problem of analysing the output of
interacting and compensating systems in context that drives
the development of Artificially Intelligence systems for such
tasks. The on-going research reported in [12] is promising,
but the results cannot yet easily be implemented into a
system as described above. Instead, we simulated the output
of such an automatic system: three of us (Olsson, von
Schéele, and Ohlsson) used their expertise in this field to
manually review and analyse the measurement data and
derive an absolute workload index for each operator in each
of the conditions (PSP and three machine variants), without
knowledge of the operator’s skill level, his subjective
evaluation, and which machine variant (setting of traction
force limitation) corresponded to which condition for this
particular operator. After each of us analysed the data
individually, we compared our results and agreed on a
consensus workload index for each operator in each
condition.
Our manual analysis uses all of the recorded data (not just
from the bucket filling sequences) with the following
criteria applied. The ratings ranged between 1 and 5 in eve-
ry time period. The highest ratings (5) should be applied if
all the criteria listed below showed a very functional pattern
well within known reference values for each physiological
signal. The lowest rating (1) should be applied when the
workload seem very high in all signals. If a physiological
signal contained many measurement errors, this signal was
not used in the rating of that period.
The physiological signals were rated as described below and
in the priority order listed:
1. Level of HR, RR, EtCO2 and peripheral
temperature. A HR below 80, RR be-low 20,
EtCO2 above 4.5% and peripheral temperature
above 25ºC indicates low workload.
2. Noticeable recovery mainly in HR, RR and
SCL between bucket fillings and during
relaxation in the PSP indicates a more effort-
economic behaviour and therefore low
workload.
3. A clear connection between breathing and
heart rate variations, RSA (Respiratory Sinus
Arrhythmia), indicates low workload.
4. Extreme reactivity or extreme rigidity in
mainly HR and SCL indicates high workload
Signs of habituation in any system, with priority to HR by
bucket fillings, indicate a more effort-economic behaviour
and therefore low workload.
6 Results
Table 2 shows the expert’s consensus on the operators’
workload during the PSP and the three test conditions. To
the right this table, sorted by operator skill level, also shows
in which individual order the machine variants with their
respective traction force setting were tested by the operators.
Table 2: Results, workload index and test order of variants
It is peculiar that the four operators with the highest skill
levels consistently have a high workload for all machines,
not affected by traction force limitation. This is presumably
a ceiling effect. It is interesting to note that none of the
operators were aware of their high workload. In their
opinion, the work performed was little demanding,
especially in comparison to other possible tasks such as
loading of shot rock.
With the exception of one, all operators show a higher
workload during the Psychophysiological Stress Profile than
during the first machine test. Comparing the different
conditions, it shows that the workload does not vary much
within each subject, despite the operators clearly
9. commenting on experiencing the machine variants
differently, as shown in Table 3.
Table 3: Results, questionnaire responses on personal
satisfaction and stress-free operation
No clear overall trend emerges when comparing the
operators’ answers in the questionnaire on how well they
felt they had managed (“personal satisfaction”) and how
stress-free they felt during the operation with the experts’
consensus on the operators’ workload.
The operators’ responses related to the tested machines,
evaluated for their ease of bucket filling, overall impression
of power and comparative rank are shown in Table 4. Here
again, no clear trend is immediately obvious.
Table 4: Results, questionnaire responses on subjective
machine evaluations
In conclusion, the workload index, derived from the
psychophysiological measurements, mostly shows no
obvious variation with any of the independent or other
dependent variables. Naturally, the next step to take as a
researcher interested in discovering any correlation would
be to employ sophisticated statistical methods, such as
principal component analysis or structural equation
modelling.
However, the purpose of our study was not to show whether
a correlation between self-assessed ease of bucket filling
and measured workload index could be established at all,
using such sophisticated statistical methods. Rather, the goal
was to study whether such possible correlation was strong
enough for application-oriented test engineers without
research background to employ simple statistical methods
for converting measured workload indices back to degrees
of machine operability, without having the operators
performing any self-assessment. In other words, if the
possible correlation is that weak and fragile, that in order for
it to be discovered sophisticated statistics is required, then
no engineer in the field will be able to make any use of it.
Despite this, we do not plan to abandon the data generated
by the measurements performed during this study. Further
statistical analysis is still planned, but its results will have to
be reported in a later paper. As for now, the findings do not
give support for our vision of using psychophysiological
measurements as a complement to traditional subjective
evaluations of a machine’s operability and even less for
using such measurements for workload-adaptive operator
assistance; instead they indicate that also other factors have
a great influence on the operator workload.
7 Discussion of possible sources of error
While performing the measurements, as well as during
analysis and reporting, we significantly improved our
knowledge with regard to appropriateness of equipment and
procedures. This will be discussed in the following.
7.1 Procedure
We were able to secure a specific machine and a dedicated
test area for our study, thus ensuring that all operators were
operating under the same conditions.
During the testing phase we tried to keep the environmental
conditions as similar as possible. We only tested on days
with good weather (no rain) and at the time of the highest
ambient temperature, i.e. immediately after lunch (which
also ensured that the operators were rested). But since this
study was performed in mid-autumn, temperatures were
generally lower; during the testing around 5-10°C. The
machine was parked outside overnight and had therefore
cooled quite substantially by the morning. Together with 20-
30 minutes’ engine warm-up each day (about two hours
before testing) and a 1.5km drive to the testing site, the first
ten minutes of self-training should provide enough waste
heat to warm up the machine (engine, transmission, axles,
and hydraulics), so that testing conditions were similar for
all cycles, independent of order.
At the proving ground we had a dedicated area, but were at
times surrounded by other machines using the same
facilities. This may have distracted the operator and
generated higher workload.
During testing, the wheel loader’s automatic functions were
fixed at gear-dependent BSS (Boom Suspension System),
automatic APS (Automatic Power Shift), and with Auto
Kick-down enabled. Of course, the BSS is only deactivated
when in 1st gear, which means it is activated during the first
seconds of the bucket filling phase, until the transmission
automatically shifts from 2nd
to 1st
gear. This is done via an
adaptive algorithm, which might differ between operators.
10. Perhaps one of the pre-defined fixed APS settings L (low
power), M (medium power) or H (high power) should have
been used instead. Or perhaps the automatic kick-down
function might have better been disabled altogether, in order
to give the operator the freedom to choose when to shift
gear.
The operators were asked to use the machine for three times
10 + 5 minutes, in total 45 minutes. There is a risk of
fatigue, especially for the less experienced operators, but we
can at best only find weak support for this in the workload
index data.
Furthermore, in spite of the ten minutes of self-training
before each live testing session, a learning effect might still
be present, especially for the less experienced operators.
The significance of a Psychophysiological Stress Profile is
to see the individual dynamic variation, as well as record the
base line and review the subject’s ability to relax. Before
testing at the proving ground, we took the operator of the
day to a secluded place to establish the PSP. While this
location was isolated visually, it was not so audibly, since it
was still within hearing distance of the proving ground, a
nearby motorway and the R&D workshop’s busy prototype
parking area (with the backing alarm of a machine driving in
reverse being a particularly disruptive sound). This may
have influenced the PSP measurement data. A possible
improvement may also be to establish a PSP in a non-work
place environment for comparison.
7.2 Measuring equipment and data acquisition
The measuring equipment used to acquire the
psychophysiological data was originally developed for
clinical applications, i.e. use in a stationary, stable and clean
environment. Using it, as we have done, in a mobile
environment, exposed to large and frequent accelerations
might have introduced measurement errors other than what
is discussed below.
As explained earlier, the operators were instructed to lay
their lower arms on the arm rests attached to the suspended
chair. This dramatically lowered the amount of
measurement artefacts in the ECG signal, yet some still
occurred and had to be accounted for manually in the
analysis phase.
Many measurement artefacts were found in the respiratory
signal, which was acquired with a nasal sample line, inserted
some millimetres into the left nostril and secured by a piece
of tape. However, in a few cases the operator’s facial hair
prevented good adhesion, leading to a temporary
detachment of the cannula and thus giving erroneous
readings. For some operators we therefore used a nasal
cannula that could be secured via the operator’s ears. With
only three such nasal cannulas available, we had to decide in
which cases to employ this alternative method.
During both the PSP session and machine operation the
operator was asked to exclusively breathe through the nose.
However, we suspect that some of the artefacts in the
respiratory data are due to the operator unintentionally
breathing through the mouth (which itself is a sign of high
workload and stress, but hard to clearly identify in
retrospect).
The PSP was conducted with the operator sitting in working
position in the cab of the wheel loader and the person
administering the test standing on the ladder, instructing him
through the open door, and monitoring through the closed
door when recording was in progress. With the colder
ambient temperatures, yet still strong sunshine, this led to a
cooling of the cab’s interior while instructing the operator,
yet gradual warm-up during execution of the PSP steps –
both of which had an impact on at least the finger
temperature measurements. In some cases operators
complained about low temperature and wanted to turn on the
heating and air conditioning system. But since this would
have required a running engine, which might have distracted
the operator from the required task, the decision was taken
to only do so during the instruction phases before each PSP
step.
Furthermore, we discovered that the finger temperature
readings were affected by heat influx from the sun and by
the flow of cold/warm air from the cabin’s heating and air
conditioning system, both during the PSP sessions and at the
proving ground. Some operators even deliberately directed
air flow to their hands to cool/warm them during operation
of the machine. This discovery discredited the finger
temperature readings enough for us to decide to completely
disregard them when determining the workload index.
With regard to the above discussed we were still able to
obtain satisfactory data from all subjects to estimate their
psychophysiological functioning based on ocular analysis.
7.3 General considerations
There are several general considerations to make with
regard to this study. To begin with, the workload index we
derived is a compound measure that does not only reflect the
necessary mental effort of the operator to handle different
traction force settings of a wheel loader. With the lack of
distinct results at hand, it is thus probable that other effects
had a larger influence on the psychophysiological data we
acquired.
Operators themselves commented on distracting elements,
such as poor gear shifting quality of the automatic kick-
down function, other machines nearby which required one to
look out when driving in reverse, or looking straight into the
sun when turning the head in order to check that nobody was
standing behind the machine (even though we specifically
instructed him to check the rear-view camera monitor).
These are normal for a working place, but it might be that
the impact of the different traction force settings was too
small to be registered in measurements with durations of a
mere five to six minutes. Next time we should consider
aiming for 30 minutes or more.
Related to this the question arises of when to consider a
workload to be different, e.g. whether or not a difference of
0.1 in value is to be considered significant, and how this
relates to testing time.
11. In the future we need to consider measuring other data
known to be indicative of workload. The quality of our
measurements of finger temperature was too poor to use the
data acquired. But as finger temperature is normally an
important measure of activity in the sympathetic nervous
system, SNS, we should try to vary the sensor placement for
increased reliability and validity. Although heart rate and
heart rate variability can change within seconds, reliable
measurements are obtained for periods with a minimum of
30-40 seconds (i.e. four times longer than a typical bucket
filling sequence), and a maximum of 5 minutes. It is warned
that sensitivity decreases for shorter or longer periods [9].
Respiratory Sinus Arrhythmia, RSA [13] can be analysed
dynamically and is the most sophisticated way to analyse
activity in the autonomous nervous system, ANS. This is
very complex and at the moment there are no automatic
analysis methods available, but we included RSA in our
manual estimation of the subjects’ workload index, based on
our understanding of the problem.
Finally, we need to reassess the working cycle. It could be
that the workload index was impacted so little by even the
severe traction force limitation in the “47%” machine
because there were no immediate consequences of falling
behind in pace or bucket load. In reality, for instance at a
saw mill or an asphalt processing plant, trucks would be
arriving continuously to be filled by the wheel loader. A
decrease in productivity is clearly visible in a constantly
lengthening line of trucks waiting their turn. Furthermore,
when truck and wheel loader are properly matched it takes
four buckets to fill a truck. Again, the productivity decrease
is clearly visible if an operator needs a fifth run. In our study
the operators would have to face none of these stress-
increasing consequences. We need to consider either more
closely representing the situation at real working places or
introducing consequences by artificially adding some
productivity-related feedback by visual or acoustic means.
There was also the ambivalence of our instructions to keep
“a normal cycle time of 20-25 seconds” (again, without
consequences for not doing so) and the conflicting
requirements of both keeping pace and completely filling
the bucket each time, especially for the “47%” machine
variant with severely limited traction force which simply
does not permit a bucket to be filled as fast and as much in
comparison with the unmodified “100%” machine. Each
operator handled this trade-off individually. Some operators
chose to keep the bucket fill factor constant, which led them
to spend more time at the gravel pile. Others chose to keep
the pace with the consequence of less material in the bucket.
8 Conclusion and outlook
At the beginning of this article we described our vision of
using psychophysiological measurements to assess operator
workload in sufficiently detail to use it as a complement to
traditional subjective evaluations, but also use such
measurements in a workload-adaptive operator assistance
system in a longer perspective. Even though the data allow
for some interesting observations at both individual and skill
group level, the results of this study indicate that measures
other than ones based on heart rate, finger temperature, skin
conductance and respiratory air flow should be considered.
All of these parameters seem hard to measure reliably in the
tough environment of a mobile working machine, but will
be less prone to artefacts in the controlled environment of a
human-in-the-loop simulator. This of course requires the use
of a simulator that has both the fidelity required to produce
correct results on the machine side and the immersiveness
required to produce correct results on the side of the
operator. The research summarised in [14] shows that this is
possible in principle.
In a simulator as well as in reality it is important to provide
relevant test scenarios. We suspect that the operators in our
study did not experience enough pressure, because there
were no immediate consequences for not keeping the set
cycle pace or not filling the bucket completely. In the future
we will try to add this pressure by either more closely
representing a real working place or by adding productivity-
related feedback artificially, for example by tactile, acoustic
or visual means.
We also found that the sensitivity of the psychophysio-
logical measurements conducted appears to be too low for
our requirements. On the other hand, promising research is
been done on the use of Artificial Intelligence techniques
(such as Case-Based Reasoning) to evaluate data from
psychophysiological measurements [12][16]. With proper
input, perhaps such systems can provide the sensitivity we
require and might then also be able to recognise
measurement artefacts. The need to automatically analyse
all acquired data in context is the major driver for such AI-
based analyses, since a manual review of multiple channels
with data from interacting and compensating systems can
today only be performed by experts, relying on clinical data
which cannot very easily be transformed into complex work
situations.
We and others, for example [15], also work with the
development of new wireless sensors that can be deployed
without distracting the operator from the working task,
while at the same time being able to acquire data without the
amount of measuring artefacts we have to cope with today.
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