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Dynamic Balancing of the Vehicle while Cornering

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Dynamic Balancing of the Vehicle while Cornering is the concept to avoid Roll-Over of the vehicle and provide comfort to the passengers while cornering by tilting the vehicle opposite to the centrifugal force to cancel it, which leads to shift of C.G point of vehicle and provide comfort to the
Passengers.

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Dynamic Balancing of the Vehicle while Cornering

  1. 1. A PROJECT REPORT ON “DYNAMIC BALANCING OF TILTING VEHICLE” SUBMITTED TO THE UNIVERSITY OF PUNE IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF THE DEGREE IN BACHELOR OF ENGINEERING (MECHANICAL ENGINEERING) BY SUHAS S. VYAVAHARE B80100857 SIDDHARTH S. MANIYAR B80100869 SACHIN J. VAKHARE B80100817 VINOD I. VERMA B80100831 Under the guidance of PROF. S.C. FARGADE DEPARTMENT OF MECHANICAL ENGINEERING AMRUTVAHINI COLLEGE OF ENGINEERING, SANGAMNER-422608 YEAR: 2013-2014
  2. 2. AMRUTVAHINI COLLEGE OF ENGINEERING, SANGAMNER – 422 608 DEPARTMENT OF MECHANICAL ENGINEERING 2013-2014 CERTIFICATE This is to certify that the Project report entitled “DYNAMIC BALANCING OF TILTING VEHICLE” Has satisfactorily completed by SUHAS S. VYAVAHARE B80100857 SIDDHARTH S. MANIYAR B80100869 SACHIN J. VAKHARE B80100817 VINOD I. VERMA B80100831 As per the requirement of University of Pune in partial fulfillment of degree in Mechanical Engineering for the academic year 2013-2014. Prof.V. S. Gadakh Prof. P. N. Nagare Prof. A. K. Mishra (Project Guide) (Project Co-ordinator) (HOD) Dr.G.J.Vikhe Patil Principal
  3. 3. UNIVERSITY OF PUNE CERTIFICATE This is to certify that this project entitled “DYNAMIC BALANCING OF TILTING VEHICLE” Has been successfully carried out & submitted by Name Seat No. SUHAS S. VYAVAHARE B80100857 SIDDHARTH S. MANIYAR B80100869 SACHIN J. VAKHARE B80100817 VINOD I. VERMA B80100831 On / /2014 at Amrutvahini College of Engineering, Sangamner - 422 608 Internal Examiner External Examiner
  4. 4. ABSTRACT The high speed of vehicles during cornering due to roll over of the vehicle there may chances of fatal accidents. To minimize this, the concept of tilting of vehicle is come forward. Also, due to tilting of the vehicle in the opposite direction of turning produces discomfort to passengers but, the forced tilting in the direction of turning cancels the displacement of centre of gravity from its original position & also provide dynamic comfort to the passenger at the time of high speed cornering. The use of a tilting car instead of a normal car should dramatically decrease traffic congestion and discomfort while cornering. Now a days most of the automobile industries are focusing on narrow track cars which reduces the traffic. These narrow track cars have an increased rolling tendency. In our project work we have tried to develop a tilting mechanism for a narrow track car to give it the flexibility of a motor cycle. This feature enables the car to tilt in to the curve while negotiating it. Our analysis shows that to increase the maximum curve at speed by more than 25%. The sample calculations are enclosed within. The method we have used is a simple mechanical tilting system controlled by a simple electromechanical actuators or hydraulic actuators which is controlled electronically. This tilting mechanism if successful should dramatically increase the maximum speed in curves. This should also provide the advantages of increased passenger comfort and handling. The idea is to develop a tilting car which tilt either naturally or actively is considered as best way to reduce the accidents while cornering and also reduces the rollover of the vehicles due to less width to height ratio.
  5. 5. CONTENT Abstract I List of Figures II CHAPTER Page no. 1. Introduction 1 2. Literature survey 3 2.1 Narrow Track Cars 3 2.2 Tilting Trains 4 2.3 Three Wheeled Tilting Cars 5 2.4 Tilting Cars 7 3. Objectives & Methodology 8 3.1 Problem Defination 8 3.1 Objectives & Methodology 8 3.1.1 Passive Tilting 9 3.2.1.1 Introduction 9 3.1.2 Active Tilting 10 3.2.2.1 Introduction 10 4 Various Stability Systems 12 4.1 ABS 12 4.1.1 System Components 12 4.1.2 Basic Operation 13 4.2 TCS 14 4.2.1 Components of TCS 15 4.2.2 Working of TCS 15 4.2.3 Use of TCS while cornering 16 4.3 ESP 16 4.3.1 ESP System Operation 18 5 Frame Selection and Selection Of Tilt Mechanism 19 5.1 Frame 19 5.2 Selection of tiliting mechanism 20
  6. 6. 5.3 Design of Actuators 21 5.3.1 Actuator Technology 22 5.3.2 Analytical operations 24 5.4 Hydraulic Circuits 24 5.4.1 Proposed Design 24 5.4.2 Actuators 25 5.4.3 Control Valves 27 5.4.4 Pump 27 5.4.5 Accumulator 28 5.4.6 Unloading Valve 28 5.5 Disturbance Force 29 6 Implementation and Calculations 30 6.1 Prototype 30 6.2 Comparison of threshold velocity 32 7 Advantages 32 8 Conclusion and Future Development 33 8.1 Conclusion 33 8.2 Future Development 33 9 References 34
  7. 7. List of Figures Figure No. Description Page No 2.1 Conceptual Model of Narrow Track Cars 3 2.2 Actual Model of Narrow Track Cars 3 2.3 Tilting Trains 4 2.4 Passive Tilting 5 2.5 Tilting Mechanism (Pendellino) 5 2.6 Carver 6 2.7 Life Jet 6 2.8 Cad Model of Three Wheel Tilting Vehicle 6 2.9 Chassis of Carver 7 2.10 Tilting Car (Conceptual Model of Taxi) 7 3.1 Dynamics of Vehicle 9 3.2 Natural Tilting Mechanism:parson,goodall and saski 10 3.3 Modern Active Tilting Mechanism 11 4.1 Components of ABS 13 4.2 ESP System 17 5.1 Frame Design 19 5.2 Basic actuator Mechanism 21 5.3 Circuit Diagram of Actuator Mechanism 22 5.4 Electromechanical Actuator 23 5.5 Working Diagram 23 5.6 Proposed Hydraulic Circuit for Tilting Vehicle 25 5.7 Actuator lever Arm against Tilt Angle(Graph) 26
  8. 8. 5.8 Actuator Length V/S Tilt Angle (Graph) 26 6.1 Circuit Connection 30 6.2 Prototype 30 6.2 Line Diagram 31 8.1 Application of Heavy Vehicle 32
  9. 9. 1. INTRODUCTION Tilting 4-Wheeler cars are without doubt the future of urban mobility. These cars have a similar wheel track as like our normal cars. Most of the international car companies have production models and prototype of Tilting Three Wheeler cars. Some examples are Nissan Land Glider, Nissan Pivo, Honda 3R-C, etc. Such cars are mostly single seated or double seater with back to back seating configuration. Normal Conventional cars are very susceptible to Skid, Overturn, Underturn, Roll-Over while cornering. As an alternative of conventional car a narrow three wheel tilting cars are developed by the researchers. These Vehicles have following Advantages: 1) Half the width means half the weight, more rigidity, more access to narrow roads, easier parking and much quicker transit times. 2) In an electric vehicle, the lighter weight of this much smaller vehicle will help to enhance torque power characteristics of an electric motor to achieve “linear acceleration”. 3) At highway cruising speeds, such cars will be using half the frontal area and half the drag co efficient, plus reduced running losses make for a very energy efficient vehicle.[3] All these advantages make the Tilting Three Wheel vehicle so appealing as an alternative to the normal car. Such cars combine the comfort of a car with the functionality of a motor bike. But these cars have a very important and dangerous drawback. With a very comparatively narrow track and heights almost equal to normal cars, these cars are very susceptible to rolling which may lead to accidents and as of now all such narrow track cars are electrically driven and have a limited top speed and hence this drawback is comparatively negligible. But sooner or later these cars will have to get highway cruising speeds. Then this drawback will be of grave importance. Our project took shape as an attempt to face this drawback. We thought so if the cars has the functionality of similar to the motor cycle. As we know that while turning or cornering with two wheeler tilting of the C.G takes place hence we make a safe turn at the same time we need good grip on road. This gave use to the idea of an auto-tilting car. There has been many tilting body designs in railway cars at present but not in the 4- Wheelers.We like to travel. Once while travelling we get a question that is it possible to nullify the Pseudo Force effect while cornering of vehicle. Recently there had been some
  10. 10. development in making three- wheeled tilting cars like the carver, but only prototypes or concepts exist in the field of four-wheeled tilters. 2. LITERATURE SURVEY 2.1 NARROW TRACK CARS:
  11. 11. „Narrow track cars‟ is not a new term. Several production models do exist and several prototypes are being tried out by major automobile companies. Some production models are Nissan Pivo, Honda 3R-C etc. Several automobile majors like Toyota, Mercedes, Nissan, Kia, Suzuki etc have prototypes for narrow track cars. Fig.2.1. Conceptual Model of Narrow Track Cars A very successful product is a narrow car of the name NARRO. This car is expensive at $46000, but has managed to find customers which stresses the acceptability of narrow cars for public. Fig.2.2 Narrow cars This car is powered by two motors each driving one rear wheel. It has a maximum speed of 120 kmph. But narrow is a tall car, too tall for its track. It rolls tremendously on curves, the manufacturer have compensated for this by providing it a very stiff suspension. Since the car is only meant for urban road use the compromise made in
  12. 12. suspension does minimum damage, but even with stiff suspension, the threshold velocity of this car in a curve is very low in comparison to a full track width car.[3] 2.2 TILTING TRAIN: Tilting trains are today common in Europe and Japan. These trains are rail- running, they have very high curve velocities. In order to enable trains, to negotiate curves at high speeds, tracks are slightly banked (up to 11 degrees). But these trains are too fast, and it is not possible to tilt track beyond a limit because trains also pass along these curves really slowly at times. Tilting trains are an optimum solution for this problem. These types of train, tilts the body on the curve, this in a sort enables faster curve threshold speed and increased passenger comfort. The figure below shows two tilting mechanisms used in trains.[2] Fig.2.3 Tilting Trains[7]
  13. 13. Fig.2.4 Passive Tilting[7] Fig.2.5 Tilting Mechanism ( pendellino ) 2.3 THREE WHEELED TILTING CARS[8] : These type of cars are a new species, but their number is fast increasing. These cars tilt about their rear wheels. Either there can be two wheels at the rear like the carver. Which has two wheels at the rear and the car body tilts about the rear wheels. Steering is done using front single wheel.
  14. 14. Fig.2.6.Carver[8] Or these can be one wheel at the rear about which the body tilts. Like the GTR (Grand Tilting Racer). Fig.2.7 Life Jet Fig.2.8 Cad Model Of three wheeler Tilting vehicle
  15. 15. Fig.2.9 Chassis of carver 2.4 TILTING CARS: This is a concept of four wheeled tilting car. There is a concept called Naro. But no known mass production model exists. The picture of a concept is shown below. Fig.2.10 Taxi This car is just a concept form and not even a prototype has been made. But expect the research to gain momentum soon.
  16. 16. 3. OBJECTIVES & METHODOLOGY 3.1 PROBLEM DEFINITION: Especially with vehicles of elevated centre of gravity like SUV the loss of control with subsequent skidding may even lead to rollover. The severity of rollover accidents is extremely high. In critical driving situation drivers are overburdened with the stabilizing task as a reason well considered and thought out reaction of driver can not be expected. For the reason Dynamic Balance System has to be designed. From Literature Study we get to know that there are 2 to 3 alternatives are available for these problems but these alternatives also have some disadvantages hence they are still not implemented actually but researchers are trying to eliminate limitations and still the work is going on, we think over it and go through the various research papers and done some work to eliminate these all problems with this project. 3.2 OBJECTIVE AND METHODOLOGY: The objective of this project work is to successfully develop a design of a tilting mechanism for a 4-wheeler auto-tilting car. The mechanism is to be reliable, simple, cost- effective and practically feasible. The aim of this tilting mechanism is to provide banking to the car on unbanked curves, so as to enable added threshold speed on curves in comparison to a non-tilting car. This system is also supposed to enhance passenger comfort as the side force felt by passengers in a car taking a turn is comparatively less in a tilting car. Also in our purpose is the fabrication of a mini-prototype –a remote controlled toy car-to demonstrate the tilting in real world. The methodology adopted to use standard and presently used components in design rather than to design all components from ground up. The advantage of this method is that, we do not have to spend ridiculous amount and time in testing the integrity of each part as they have already proved their worth in real world applications[1] . To fulfil our objective first we have studied various forces affecting vehicle dynamics:
  17. 17. Fig.3.1 Dynamics of Vehicle Actual tilting is done in two ways: 1) Passive tilting(Natural tilting) 2 )Active tilting 3.2.1 PASSIVE TILTING (NATURAL TILTING)[7] : 3.2.1.1 INTRODUCTION: Natural tilt relies on physical laws with a tilt centre located well above the carbody‟s centre of gravity. In a curve, under the influence of lateral acceleration, the lower part of the carbody then swings outwards. If there is no roll stiffness associated with the tilt centre then “perfect” tilting action will arise where no lateral acceleration is experienced within the carbody. In practice, however, there will usually be a non-zero roll stiffness which means that there will be some residual lateral acceleration Figure 3.2.
  18. 18. Fig.3.2 The mechanism of natural tilting; Persson, goodall & Sasaki[7] Today, natural tilting often includes control and actuation to ensure satisfactory dynamic performance, in the present work called active tilt support. Natural tilting is known as passive tilting in some countries. Natural tilt has a negative impact on safety due to the lateral shift of the car body‟s centre of gravity. The merits of natural tilting as follows: 1. The system is simple and reliable. 2. The system has low initial and maintenance costs. 3. The control system is very simple if needed at all 4. Inverse tilting cannot occur. The demerits of Natural tilting are as follows: 1. The carbody‟s moment of inertia will delay the tilt motion. A low-frequency lateral acceleration, caused by imbalance between track plane acceleration and the compression by tilting will thus appear in transition curves. This low-frequency lateral acceleration may be both uncomfortable and motion sickness inducing. 2. The high position of rotation centre gives a lateral movement of the carbody mass centre, which increases the risk of overturning. 3. The lateral movement of carbody lower section reduces the possible carbody width where it is most needed. 3.2.2 ACTIVE TILTING[7] :
  19. 19. 3.2.2.1 INTRODUCTION: Active tilt includes some form of mechanism by which the tilting of the carbody is created, and relies upon control technology involving sensors and electronics and is executed by an actuator, usually hydraulic or electric. Without the actuation there is no significant tilt action. This form of tilt does not normally have an impact on the safety of the train, since the centre of gravity does not essentially change its (lateral) position. Of course the overturning moment is still increased as a consequence of the higher curving forces, but it is not exacerbated by the lateral centre of gravity shift mentioned in the previous section and safety margins with active tilt only become unacceptable in high crosswinds. Fig.3.3Active tilting trains:Alstom Pendolino, Bombardier X2, Persson[7] Active tilting has become the predominant tilting technology, at least for European railways. These systems require the following elements: a suitable mechanical arrangement to provide tilt, powered actuators to operate the system, and sensors and controllers to provide effective operation. Whereas the focus in Japan is upon natural tilting trains, most major European manufacturers offer trains based upon mature and effective active tilt. 4. VARIOUS STABILITY SYSTEMS WHICH ARE TAKEN INTO CONSIDERATION
  20. 20. 4.1 ABS (ANTI-LOCK BRAKING SYSTEM)[9] : Anti Brake System are integrated with the conventional braking system. They use a computer control unit, between the brake master cylinder and wheel cylinders to control Brake system hydraulic pressure. Antilock Brake Systems address two conditions related to brake application; wheel lockup and vehicle directional control. The brakes slow the rotation of the wheels, but it is actually the friction between the tire and road surface that stops the vehicle. Without ABS when brakes are applied with enough force to lock the wheels, the vehicle slides uncontrollably because there is no traction between the tires and the road surface. While the wheels are skidding, steering control is lost as well[1] . An antilock brake system provides a high level of safety to the driver by preventing the wheels from locking which maintains directional stability. A professional driver may be capable of maintaining control during braking by pumping the brake pedal which allows a locked wheel to turn momentarily. Whereas a professional driver may be capable of modulating the brakes approximately once per second, Abs is capable of modulating the brake pressure at a given wheel up to fifteen times per second. An ABS system does something else that no driver can do, it controls each front brake separately and the rear brakes as a pair whenever one of the wheels start to lock. Abs helps stop a car in the shortest possible distance without wheel lockup while maintaining directional control on the most types of road surfaces or conditions. If a ABS system malfunctions, normal braking will not be affected[1] . 4.1.1 SYSTEM COMPONENTS: Each ABS type shares common components which provide information to the ECU. This section will examine each of these components and then describe each of actuator types and their operation. The components are as follows:  Speed Sensors monitor wheel speed.
  21. 21.  G-Sensor monitors rate of deceleration or lateral acceleration.  ABS Actuators control brake system pressure.  Control Relay controls the Actuator Pump Motor and Solenoids.  ABS ECU monitors sensors inputs and controls the Actuator.  ABS Warning Lamp alerts the driver to system conditions. Fig.4.1 Components of ABS 4.1.2 BASIC OPERATION: Four Wheel ABS Systems use a speed sensor at each front wheel and either a single speed sensor for both rear wheels or individual speed sensors at each rear wheel. The speed sensors are monitored by a dedicated ECU. The system controls the front brakes individually and rear brakes as a pair.
  22. 22. In a panic braking situation, the wheel speed sensors detect any sudden changes in wheel speed. The ABS ECU calculates the rotational speed of the wheels and the changes in their speed, then calculates the vehicle speed. The ECU then judges the slip ratio of each wheel and instructs the actuator to provide the optimum braking pressure to each wheel. For example, the pressure to the brakes will be less on slippery pavements to reduce brake lockup. As a result, braking distance may increase but directional control will be maintained. It is also important to understand that ABS is not active during all stops[9] . The hydraulic brake actuators operates on signals from the Abs ECU to hold, reduce or increase the brake fluid pressure an necessary, to maintain the optimum slip ratio of 10% to 30% and avoid wheel lockup. 4.2 TCS (TRACTION CONTROL SYSTEM): A traction control system, in German known As Antriebsschlupfregelung (ASR), is typically (but not necessarily) a secondary function of the anti-lock braking system(ABS) on production motor vehicles, designed to prevent loss of traction of driven road wheels. When invoked it therefore enhances driver control as throttle input applied is mis-matched to road surface conditions (due to varying factors) being unable to manage applied torque. The basic idea behind the need of a traction control system is the difference between traction of different wheels evidencing apparent loss of road grip that compromise steering control and stability of vehicles. Difference in slip may occur due to turning of a vehicle or differently varying road conditions for different wheels. At high speeds, when a car tends to turn, its outer and inner wheels are subjected to different speed of rotation, that is conventionally controlled by using a differential. A further enhancement of the differential is to employ an active differential that can vary the amount of power being delivered to outer and inner wheels according to the need (for example, if, while turning right, outward slip (equivalently saying, “yaw”) is sensed, active differential may deliver more power to the outer wheel, so as to minimize the yaw (that is basically the degree to which the front and rear wheels of a car are out of line.) Active-differential, in turn, is controlled by an assembly of electromechanical sensors collaborating with a traction control unit[5] . The different systems mainly differ in the way of reducing that power output to the wheels:
  23. 23.  Retard or suppress the spark to one or more cylinders  Reduce fuel supply to one or more cylinders  Brake one or more wheels  Close the throttle, if the vehicle is fitted with drive by wire throttle. 4.2.1 COMPONENTS OF TCS: Generally, the main hardware for traction control and ABS are mostly the same. In many vehicles traction control is provided as an additional option to ABS.  Each wheel is equipped with sensors which sense the change in their speed due to loss of traction.  When the traction control is installed as a part of ABS system, an ATC valve will be provided which initiates the ATC function.  The sensed speed from the individual wheels is given to a control unit, called Electronic control Unit.  A cable connects the ECU with the ATC valve. In all vehicles, traction control is automatically started when the sensors detect loss of traction at any of the wheels. 4.2.2 WORKING OF TCS: When the traction control computer (often incorporated into another control unit, like the anti-lock braking system module) detects one or more driven wheels spinning significantly faster than another, it invokes the ABS electronic control unit to apply brake friction to wheels spinning with lessened traction. Braking action on slipping wheel(s) will cause power transfer to wheel axle(s) with traction due to the mechanical action within a differential. All-wheel drive (AWD) vehicles often have an electronically controlled coupling system in the transfer case or transaxle engaged (active part-time AWD), or locked-up tighter (in a true full-time set up driving all wheels with some power all the time) to supply non-slipping wheels with (more) torque. This often occurs in conjunction with the powertrain computer reducing available engine torque by electronically limiting throttle application and/or fuel delivery, retarding ignition spark, completely shutting down engine cylinders, and a number of other
  24. 24. methods, depending on the vehicle and how much technology is used to control the engine and transmission. There are instances when traction control is undesirable, such as trying to get a vehicle unstuck in snow or mud. Allowing one wheel to spin can propel a vehicle forward enough to get it unstuck, whereas both wheels applying a limited amount of power can't get the same effect. Many vehicles have a traction control shut off switch for just such circumstances. 4.2.3 USE OF TCS WHILE CORNERING: Traction control is not just used for improving acceleration under slippery conditions. It can also help a driver to corner more safely. If too much throttle is applied during cornering, the drive wheels will lose traction and slide sideways. This occurs as understeer in front wheel drive vehicles and oversteer in rear wheel drive vehicles. Traction control can prevent this from happening by limiting power to the wheels. It cannot increase the limits of grip available and is used only to decrease the effect of driver error or compensate for a driver's inability to react quickly enough to wheel slip. Automobile manufacturers state in vehicle manuals that traction control systems should not encourage dangerous driving or encourage driving in conditions beyond the drivers' control[1] . 4.3 ESP (ELECTRONIC STABILITY PROGRAMMING)[5] : For a number of years, vehicle manufacturers have been focusing their vehicle design around integral safety systems. With NCAP (New Car Assessment Program) Testing on vehicle become simpler. The Original ABS (Anti-lock Braking System) was a major breakthrough for manufacturers and quickly became widespread throughout automotive design. As with the any of the developing safety features now deployed, it is development in the truck industry which has set the standard for the passenger car producer. The singuarly most alarming event that stimulated a greater need for ESP was the Mercedes A class that was easily flipped over on cornering. With the introduction of multiplexing within vehicle, it was possible to design a braking system which will incorporate a wider operating specification for barking mechanism. The introduction of EBCM‟S (Electronic Braking control modules) which
  25. 25. were able to enhance the ABS system to include system such as ASR (Anti Slip Regulation) and ASD (Adjustable Speed Drive). Mercedes Benz were the first company to incorporate these technologies into the nominal ABS system. Traction control was also incorporated at this time. With the wide spread use of CANbus systems, manufacturers were now able to add new braking system we now call ESP. ESP is available under many different names: many car brands have given it their „own‟ name. A few examples are: ESP (Electronic Stability Program), VSA (Vehicle Stability Assist), DSC (Dynamic Stability Control), VSC (Vehicle Stability Control), DSTC (Dynamic Stability and Traction Control), VDCS (Vehicle Dynamics Control Systems) and PSM (Porsche Stability Management). Fig.4.2 ESP System[5] 4.3.1 HOW THE ESP SYSTEM OPERATES: When the car moves into a position which is determined by the yaw sensors to be outside of the parameter set by the system, the ESP will activate. For the drive, certain
  26. 26. functions in the car will activate which the driver has no control over. Depending on the manufacturer of the system (Bosch, Continental Teves, Delphi), there will functions in the car which are linked together and will operate together to bring the car back under control. If the car begins to skid, the driver will usually attempt to brake and hopefully try to drive into the direction of the skid. In practice, this does not always happen, so the car will do it itself. The vehicle will :  Take over the accelerator and operate this independently.  Apply pressure through the braking system regardless of how much pressure the driver applies.  Alter the steering angle (if the vehicle is equipped with electronic steering wheel control-e.g VW, BMW) During this time, it is usual to see the ESP lamp light and can be accompanied by a continuous “pinging” noise. The duration that ESP operates is variable and dependent on how quickly the car back under control. 5. FRAME AND TILTING MECHANISM SELECTION 5.1 FRAME:
  27. 27. The frame has been designed with parameters taken from an already existing Car i.e HUMMER H2 SUV. In Prototype we use a simple technique for tilting . but for actual tilting of vehicle we need to separate the whole car body in two sub-assembly. The adoption of an already existing frame for our design ruled out the requirement of stress analysis. The frame is sure to hold on, even in case of most hostile conditions, as it is a tried and tested design. Fig.5.1 Frame Design 5.2 SELECTION OF THE TILTING MECHANISM:
  28. 28. The tilting mechanism design was a complex question. After lots of discussion and literature survey we get to know about some various mechanism which we can use for tilting purpose. Initially it was decided to use power screw driven holders for each individual wheel controlled by a stepper motor. The design almost completed. It had several advantages: 1) Each wheel could be moved independent of the other. 2) More precise control was possible with power screw lifters. 3) It could be modified to incorporate other systems like body level control, ground clearance adjustment system etc. But we found some critical disadvantages of screw lifters. They were 1) Their response was slow at very high speed and repeated steering and control steering. 2) The wear and tear in screw parts was more than desirable. This would only aggravate in a real life situation where dust and sand particles can accelerate the wear of the screw and lifters. Hence the design was discarded and we were on the look out for a new and simple tilting mechanism. It was at this point, it was decided to use the present design of a tilting mechanism of Train (pendellino), controlled by Electromechanical Tilt Actuator. The upper sub assembly were linked to this tilting mechanism. After much thought and consultation. 5.3 DESIGN OF ELECTROMECHANICAL AND HYDRAULIC TILT ACTUATOR[2] :
  29. 29. The Electromechanical tilt actuator is to be controlled by a microprocessor based on inputs from the following types of sensors: 1) Speed of sensor 2) Steering position sensor 3) Yaw rate sensor 4) Level sensor Fig.5.2 Basic Actuator Mechanism[2] The signal to the Electromechanical tilt actuator is generated in proportion to the speed of the vehicle. The signal is given to the actuator based on the steering position. The level position sensor senses if the road is already banked, it then adjusts the signal accordingly so that the vehicle does not over tilt at any point.
  30. 30. Fig.5.3 circuit diagram of actuator mechanism 5.3.1 ACTUATOR TECHNOLOGY: Some of the first actively tilting trains relied on active technology based on pneumatic systems where suspension elements were also the active elements, resulting in excessive compressed air consumption as mentioned above. An important technological step forward came with rollers and pendulums, which carry the carbody load and allow movement. The movement may then be controlled by an actuator that does not have to carry the carbody load, resulting in much lower energy consumption. Servo-hydraulic actuator systems became the natural choice for the mechanically-oriented railway engineers. Such hydraulic systems have a hydraulic power supply comprising an electric motor that drives a pump that delivers a fixed pressure and electro-hydraulic valves to regulate the flow that supplies hydraulic cylinders fitted across the tilting arrangement. The electro-mechanical actuators showed advantages and become an alternative in the 1990s. High-efficiency power amplifiers feed electric motors that drive screws fitted with high efficiency ball or roller nuts to convert rotary motion to linear. Below Figure shows a typical electro-mechanical tilt actuator. They are less compact than hydraulic actuators at the point of application, but overall they provide significant integration benefits as they require less space.
  31. 31. Fig.5.4 Electro-Mechanical Actuator[7] A hybrid technology is electro-hydraulic actuation, in which an electric motor driving a fixed displacement pump is used with a sealed hydraulic circuit connected to normal hydraulic cylinders. Control is via the power amplifiers that feed the motors and there is no need for a separate hydraulic power supply. The solution is pointed out as the future activation system in Japan, which has until now tended to use pneumatic actuators; Enomoto, Kamoshita, Kamiyama, Sasaki, Hamada & Kazato[7] Figure.5.5 Working diagram[7]
  32. 32. 5.3.2 ANALYTICAL EXPRESSIONS FOR TILT TORQUE REQUIRED: T h e t o t a l t o r q u e t h e a c t u a t o r s h a v e t o p r o v i d e i s t h e s u m o f t h e t o r q u e d u e t o g r a v i t y o n t h e m a s s , t h e t o r q u e d u e t o t h e c e n t r i p e t a l r e a c t i o n f o r c e o n t h e m a s s , t h e t o r q u e r e q u i r e d t o a c c e l e r a t e t h e m a s s a n d o v e r c o m e a n y d a m p i n g a n d f r i c t i o n i n t h e s y s t e m , a n d t h e t o r q u e d u e t o e x t e r n a l f o r c e s o n t h e m a s s . T h u s , t h e t o r q u e r e q u i r e d t o t i l t t h e v e h i c l e c a n b e e x p r e s s e d a s : Where Fy is the centripetal reaction force, Fg is the force due to gravity, h is the distance from the tilting axis to the centre of mass, J is the inertia of the tilting body, c is the damping of the tilting body, and Tdist is the torque due to external forces on the Mass. The dynamic requirement is to tilt the body from −45° to +45° in 1.5 seconds (Cycle frequency of 0.33 Hz). This is the „worst case‟ duty cycle. The tilt angle, q, as a Function of time is therefore taken to be: For initial evaluation, a simple model of a stationary vehicle will be used, assuming No damping in the tilt action. The torque, T, required to tilt the system is: 5.4 HYDRAULIC CIRCUIT: 5.4.1 PROPOSED DESIGN: The hydraulic circuit has been designed to control the position of the tilting part of the Vehicle with two single acting linear hydraulic actuators. When pressurised, these cylinders control the lean angle of the tilting cabin by rotating it with respect to the
  33. 33. upright rear module. A proportional directional control valve with a closed centre position controls the position of these actuators and locks the cylinders when no Command is given. The system is pressurised by a gear pump driven directly from the engine Crankshaft, providing adequate flow for sinusoidal tilting from maximum to minimum tilt angle at 0.33 Hz. In order to unload the pump, augment the flow and provide flow in the event of pump failure, an accumulator is added to the circuit in conjunction with an unloading valve. When the desired system pressure is reached, the unloading valve opens, allowing flow generated by the pump to return to tank, decreasing the torque demand from the engine. When the accumulator has discharged and the pressure in the system falls below a preset value, the unloading valve closes, directing flow from the pump back to the system to charge the accumulator and pressurise the cylinders until maximum system pressure is reached. Fig.5.6. Proposed hydraulic circuit for tilting vehicle[2] 5.4.2 ACTUATORS: The hydraulic actuators have been positioned in the vehicle between the tilting body
  34. 34. and the upright rear module. They are positioned to optimise the torque generation within the package design constraints. As a consequence, the lever arm varies with respect to tilt angle. Fig.5.7 Actuator lever arm against tilt angle[2] The hydraulic actuators are single acting, being pressurised on the piston side only. When the body tilts to the right to make a right hand turn (q is positive), the left hand cylinder provides the necessary force and vice versa. The relationship between actuator extension and tilt angle is shown in figure 5, for the case of the left actuator. The stroke requirement is 200 mm.
  35. 35. Fig.5.8 Actuator length against tilt angle[2] The actuators need to be sized according to the force requirement. The piston diameter can be determined from the torque equation of a pressurised actuator: Where p is the system pressure, b is the lever arm, A is the piston area, and d is the piston diameter. The highest load on each actuator occurs when fully contracted, so From figure 4, b is 0.122 m. With the maximum torque requirement of 1.25 kNm and a system pressure of 160 bar, the piston diameter needs to be at least 28.5 mm. Commercial cylinders fulfilling this requirement have a piston diameter of 32 mm, and can therefore provide a torque of 1.57 kNm with a system pressure of 160 bar. Approximately 0.16 litres of oil is required for one complete tilt from −45° to +45°. 5.4.3 CONTROL VALVE: The control valve for the system is a 4-port, 3-position proportional directional control valve with a closed centre. A proportional valve is necessary to achieve the system‟s dynamic requirements and continuous regulation during normal driving. The size of the valve can be determined by the maximum flow requirement. Assuming the same 0.33 Hz sinusoidal duty cycle shown in figure 2, the maximum piston speed,
  36. 36. and therefore the peak flow requirement can be determined: this is calculated to be 10.1 l/min. 5.4.4 PUMP: The pump choice is determined by considering the flow requirement and the IC engine used to drive the pump. Analysis of the CVT transmission [3] suggests that when cruising, the engine will spend much of the operating time at around 5500 rpm. Engine idle speed is 1700 rpm, and maximum engine speed is limited to 8500 rpm. The chosen pump would have to operate and function between the two extremes, while providing mean flow at the normal operating point. In order for a gear pump to operate at these engine speeds, the pump will need to be driven through a gear ratio to operate within the limiting speeds of the pump. The 0.33 Hz sinusoidal duty cycle can be used to determine flow requirements. Mean flow required for this duty cycle is 6.434 l/min. Commercial gear pumps operate between 750 rpm and 4000 rpm, so choosing a 3 cc/rev gear pump, matching that to 6.434 l/min, results in a pump speed of 2150 rpm. In order to match this pump speed to an engine speed of 5500 rpm, the necessary gear ratio between the pump and the engine is 2.56:1. 5.4.5 ACCUMULATOR: The accumulator is used within the system for three purposes:  To provide the necessary flow during periods when the pump is unloaded.  To provide additional flow when the pump is loaded and harsh manoeuvres are being undertaken by the vehicle.  To provide emergency flow if the pump or engine fails. Diaphragm accumulators were considered, owing to their lighter weight and reduced size compared to bladder accumulators. The higher pressure and flow capabilities of the latter were not necessary for this application. Sizing the accumulator not only involves examining the simulation results, but also has to take into account design constraints. Larger accumulators would be able to provide flow for more tilt cycles, allowing the pump to be unloaded for longer periods of time. This benefit has to be balanced with the longer charging time required while the pump is loaded, charging the system, and integrating the increased weight and size of a larger accumulator within the vehicle design. A smaller accumulator reduces the number of tilting movements available while
  37. 37. the pump is unloaded and increases the frequency of charging cycles, arguably impairing the drivability. However, smaller accumulators would be quicker to recharge, and integration within the vehicle would be easier owing to their lighter weight and smaller size. 5.4.6 UNLOADING VALVE: As SUV‟s are heavy weight it is beneficial to unload the pump when the system is pressurised, and hence reduce the power consumption from the engine. To accomplish this, an unloading valve needs to be integrated into the circuit. When the system starts, the valve is initially closed, sending flow from the pump through a check valve, charging the system. When the maximum system pressure is reached, the valve opens allowing flow from the pump to return to tank, unloading the pump and reducing the torque load on the engine. As the vehicle tilts, the pressure within the system is reduced until it reaches a threshold pressure, at which point the valve closes again, enabling the pump to recharge the system. One challenge with this situation is the transition between loading and unloading the system and the effect of this on the drivability of the vehicle. With a standard two position valve, the loading can be quite harsh, but by using a proportional or soft-start valve, it would be possible to smooth the transition when loading the pump. When unloading, there is little point in gradually opening the valve, since the throttling that occurs will waste energy. A proportional valve would also require careful control, including pressure measurement to predict when the system will need charging, and hence start to close the valve. 5.5 DISTURBANCE FORCE[1] : The hydraulic tilt system has to take into account disturbances on the tilting body such as wind forces[2] . To test this, a side wind force can be added to the forces applied in the cylinder associated with the tilting force. Side wind force, Fw, can be defined as: Where r is the air density (taken as 1.226 kg/m3), Cd is the drag coefficient, A is the Projected area facing the wind and V is the velocity of the wind. Taking, for example, a wind speed of 100 kph, a Cd value of 1.3, and an area estimation of 2.5 m2 , Fw is 1537 N. The Cd value used in this calculation is particularly pessimistic. The correct
  38. 38. Value for the side of the CLEVER vehicle is unknown, so a value of 1.3 is taken as Worst case. 6. IMPLEMENTATION AND CALCULATION 6.1 PROTOTYPE: The mini-prototype was fabricated on a toy car, which is a 1:12 scale model of a hummer H2 SUV. The entire plastic base of the toy car was modified with sheet metal parts as per our convenience . All modified parts used in the same was designed in mild steel sheet metal. For control of the car, the same PCB as used in the toy car was used. Its connections were re-laid as per requirement . Small d.c motors with no speed or motion control were used for tilting mechanism in prototype. The tilting mechanism was incorporated with steering system of that prototype. Fig.6.1 circuit connection
  39. 39. Fig.6.2 Prototype 6.2 COMPARISON OF THRESHOLD VELOCITY ON CURVES FOR TILTING AND NON-TILTING CARS From equations of vehicle dynamics, for a vehicle in a curve Maximum sliding velocity, Vs2 =gC(sinθ +µcosθ)/(cosθ + µsinθ) Maximum overturning velocity, Vo 2 =gC(a cosθ +2h sinθ)/(2h cosθ – a sinθ) For a non-tilting car under the following parameters Fig.6.3 Line Diagram µ=0.8
  40. 40. θ=130 C=30m g=9.8m/s2 a=1.763m h=1.520m Sliding velocity for non-tilting car =14.34m/s =51.624kmph Overturning velocity for the same =13.06m/s =47.03kmph Whereas for a tilting car that can tilt 13 degrees into the curve, Sliding velocity =16.002m/s =57.62kmph Overturning velocity =16.5m/s = 59.24 kmph Increase in sliding velocity = 11.61475% Increase in overturning velocity =25.94% 7. ADVANTAGES OF 4-WHEELER TILTING CAR 1) This design combines the utility of a car with the flexibility of motor bike. Narrow track cars are definitely future of urban mobility, but our tilting car can also handle highway cruising as well. 2) Improves cornering cruising speed with safety and comfort. 3) We can use this system in heavy duty vehicles also. More technically speaking, it balances the vehicle in any situation which reduces the wear and tear of tire. The concept is very useful in racing vehicles which prevents rollover phenomenon at high speed ensuring high degree of safety.
  41. 41. 8. CONCLUSION AND FUTURE SCOPE 8.1 CONCLUSION: It can be seen from the above result that, our objective to increase the threshold velocity of a narrow car in a curve has been successful. The design of the car and tilting mechanism worked flawlessly. Also we have studied various mechanism which we can implement to tilt the vehicle. But here we found that the actuation by electromechanical tilting actuator is better than the other form of tilting mechanisms. The mini-prototype to demonstrate tilting is also working successfully. We also get to know that we can easily implement this mechanism even in heavy vehicles with trailors and tractors, all these facts point to the completion of our objective in high esteem and this have a wide scope in future transportation system. 8.2 FUTURE SCOPE: 1. The car design in itself is futuristic and can be soon find in some production versions of four-wheeled tilting cars. 2. A feature can be added to the existing suspension using a minor programming change, the system can also act as body leveler in transverse direction using the level sensor, this feature enables added gradability in sideward direction. 3. We can use this in heavy vehicles like trolley and trailors.[4]
  42. 42. Fig.8.1 Heavy Vehicle[4] 4. Tilting of vehicle concept we can use even in our traditional vehicles like taxi, passanger cars, tractors. REFERENCES 1] Thomas D. Gillespie “Fundamentals of Vehicle Dynamics”, Society of Automotive Engineers, Volume No.1. 2] Benjamin Drew, Kevin Edge, Matt Barker, Jos Darling & Geraint Owen “System Development for Hydraulic Tilt Actuation of a Tilting Narrow Vehicle”, The Ninth Scandinavian International Conference on Fluid Power, SICFP ‟05, June 1-3, 2005, Linköping, Sweden. 3] D. Piyabongkarn, T. Keviczky and R. Rajamani “Active Direct Tilt Control For Stability Enhancement Of A Narrow Commuter Vehicle”, International Journal of Automotive Technology, Vol. 5, No. 2, pp. 77−88 (2004). 4] Hans Prem, Luan Mai, Lazslo (Les) Brusza “Tilt Testing Of Two Heavy Vehicles And Related Performance Issues”, M e c h a n i c a l S y s t e m D y n a m i c s P t y L t d . 5 ] E. K. Liebemann, K. Meder, J. Schuh, G. Nenninger “Safety and Performance Enhancement: The Bosch Electronic Stability Control (ESP)”, R o b e r t B o s c h G m b H G e r m a n y , P a p e r N u m b e r 0 5 - 0 4 7 1 . 6 ] A k i h i t o k a z a t o “A Tilt Control System Focused on Preventing Motion Seakness”, R a i l w a y T e c h n o l o g y A v a l a n c h e N o . 3 8 , M a r c h 2 1 , 2 0 1 2 .
  43. 43. 7 ] Rickard Persson “Tilting trains(Description and analysis of the present situation Literature study)” , VTI rapport 595A, Published 2007. 8] Lars Hollmotz, Steffen Sohr “Clever – A Three Wheel Vehicle With A Passive Safety Comparable To Conventional Cars” Germany Heiko Johannsen Technical University Berlin, Paper Number 05-0160. 9] WABCO “Anti-Lock Braking System(ABS) and Anti-Slip Regulation (ASR)” , Version 002/02.11 815 010 194 3. ACKNOWLEDGEMENT “Success is nourished under the kind of combination of perfect guidance, care and blessings” We wish to express our deep sense of gratitude to guide Prof. S.C. FARGADE for this keen interest guidance and all freedom of work. We are also indebted to them for their constructive suggestions, healthy advices and encouragement during the course of this work. Without their help and support this project work would not have been possible. We are also thankful to Prof. A.K. Mishra and all the staff of department of mechanical engineering, AVCOE, Sangamner for their kind support whenever required and their liberal and dynamic outlook towards us. Thanking you,  SUHAS S. VYAVAHARE  SACHIN J. VAKHARE  SIDDHARTH S. MANIYAR  VINOD I. VERMA

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