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CHAPTER 1 INTRODUCTION TO AUTOMOBILE An Automobile is a self–propelled vehicle which is used for the transportation of passengers and goods upon the ground .A vehicle is a machine which is used for the transportation of passengers and goods. A self propelled vehicle is that in which power required for the propulsion is produced from within. Aeroplane, ship motor boat ,locomotive ,car bus ,truck, jeep ,tractor ,scooter ,motor cycle are the example of self propelled vehicles. Motor vehicle is another name for the self propelled and used for the transportation purposes upon the ground, so it differs from other types of self –propelled vehicles. Like aeroplane, helicopter, rocket, ship, motor boat, locomotive. Automobile engineering is a branch of engineering in which we study all about the automobile and have practice to propel them. The words “Automotive Engineering” is also used having the same meaning. M obile or motive means one which can move. Automobile or automotive means one which itself can move. A railway wagon cannot move itself on the rails if it is not pushed or pulled by external force. A trolley cannot move itself on the road if it is not pulled by external force. The railway wagon is pulled on the rails by a locomotive. The trolley is pulled on the road by an automobile which may be a jeep or tractor. In automobile engineering we study about the self –propelled vehicles like car, bus, jeep, truck, tractor, scooter, motorcycle. Aeronautical engineering deals with aeroplane, helicopter, rocket, etc., which fly in air. Marine engineering deals with ship, motor, etc which sail in water.

1.1TYPES OF AUTOMOBILES The automobiles are classified on the following basis: 1. PURPOSE

i. Passenger vehicles – car, jeep, bus. ii. Goods vehicles – Truck 2. CAPACITY

i. Light motor vehicles – car, jeep, motor cycle, and scooter. ii. Heavy motor vehicles – Bus, coach, tractor. 3. FUEL USED i. Petrol vehicles – car, jeep, motor cycle, scooter.

ii. Diesel vehicles – Truck, bus, tractor, bulldozer. iii. Electric cab – Battery truck, fork lift. iv. Steam carriages – Steam road roller. 4. No. Of wheels

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i. Two wheelers. ii. Three wheelers. iii. Four wheelers. iv. Six wheelers. 1.2 INTRODUCTION TO STEERING SYSTEM

The steering of a four wheel vehicle is, as far as possible, arranged so that the front wheels will roll truly without any lateral slip. The front wheels are supported on front axle so that they can swing to the left or right for steering. This movement is produced by gearing and linkage between the steering wheel in front of the driver and the steering knuckle or wheel. The complete arrangement is called the steering system. The steering system essentially consists of two elements- a steering gear at the lower end of the steering knuckles and steering linkage .shows a simplified diagram of a steering system.

Fig 1.1 Steering System.

The function of the steering system is to convert the rotary movement of the steering wheel into angular turn of the front wheels. The steering systems also absorb a large part of the road shocks, thus preventing them from being transmitted to the driver. Fig 1.1 shows a late model of steering system. It has worm and roller type steering gear and relay type steering linkage. When the driver turns the steering wheel, the resulting motion is transmitted down a steering tube to a steering gear set at the end of the steering tube. The gear set changes the direction of motion, and multiplies the twisting force according to the gear steering knuckles through the relay road , idler arm , two tie rods , two steering arm and the ratio. Its output shaft rotates to move the pinion arm which transmits the motion of the two front wheels. Thus as soon as the driver puts his hands on the steering wheel the motion of the front wheels is in his hands. If he wants to turns the vehicle to the left, he turns the steering

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wheel to the left, and if he wants to turn the vehicle to the right, he turns steering wheel to the right, otherwise the steering wheel is in its middle position and the vehicle is going in a straight line. 1.3 REQUREMENTS OF STEERING SYSTEM

For the smooth performance of the system, the steering system of any vehicle should fulfill the following requirements: 1. It should multiply the turning effort applied on the steering wheel by the driver. 2. It should be to a certain degree irreversible so that the shocks of the road surface encountered by the wheels are not transmitted to the driver’s hand. 3. The mechanism should have self –rightening effect so that when the driver release the steering wheel after negotiating the turn , the wheel should try to achieve straight ahead position . The readers may bear in mind that the requirements of any system may vary but they should have some kind of average compromise. 1.4 FUNCTIONS OF THE STEERING SYSTEM The various functions of the steering wheel are 1. To control the angular motion the wheels and thus the direction of motion of the vehicle. 2. To provide directional stability of the vehicle while going straight ahead. 3. To facilitate straight ahead condition of the vehicle after completing a turn. 4. The road irregularities must be damped to the maximum possible extent. This should co-exist with the road feel for the driver so that he can feel the road condition without experiencing the effects of moving over it. 5. To minimize tyre wear and increase the life of the tyres. 1.5 TYPES OF STEERING

Depending on the number and position of the wheels being steered, steering systems can be classified as follows: 1.5.1 Front wheel steering The most commonly used type of steering, only the two front wheels of the vehicle are used to steer the vehicle. This type of steering suffers from the comparatively larger turning circle and the extra effort required by the driver to negotiate the turn. 1.5.2 Rear wheel steering Some types of industry battery trucks and backhoe loaders use this type, where only the two rear wheels control the steering. It can produced smaller turning circles, but is unsuitable for high speed purposes and for ease of use.

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FIG:1.2 Conventional front wheel steering system. With advances in technology, modern four wheel steering systems boast of fully electronic steer-by-wire systems, equal steer angles for front and rear wheels, and sensors to monitor the vehicle dynamics and adjust the steer angles in real time. Although such a complex 4WS model has not been created for production purposes, a number of experimental concepts with some of these technologies have been built and tested successfully. Compared with a conventional two wheel steering system, the advantages offered by a 4WS system include: 1. Superior cornering stability. 2. Improved steering responsiveness and precision. High speed straight line stability. 3. Notable improvement in rapid lane-changing maneuvers. 4. Smaller turning radius and tight-space maneuverability at low speed. 5. Relative Wheel Angles and their Control. The direction of steering the rear wheels relative to the front wheels depends on the operating conditions. At low-speed wheel movement is pronounced, so that rear wheels are steered in the opposite direction to that of front wheels. This also simplifies the positioning of the car in situations such as parking in a confined space. Since the rear wheels are made to follow the path on the road taken by the front wheels, the rear of a 4WS car does not turn in the normal way. Therefore the risk of hitting an obstacle is greatly reduced. At high speed, when steering adjustments are subtle, the front wheels and rear wheels turn in the same direction. As a result, the car moves in a crab-like manner rather than in a curved path. This action is advantageous to the car while changing lanes on a high-speed road. The elimination of the centrifugal effect and, in consequence the reduction of body roll and cornering force on the tyre, improves the stability of the car so that control becomes easier and safer. In a 4WS system, the control of drive angle at ‘front and rear wheels is most essential.

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Fig.1.3 Four wheel steering system. 1.6 TWO MODES ARE GENERALLY USED IN THESE 4WS MODELS: 1.6.1 Slow Speeds - Rear Steer Mode:

At slow speeds, the rear wheels turn in the direction opposite to the front wheels. This mode comes in particularly useful in case of pickup trucks and buses, more so when navigating hilly regions. It can reduce the turning circle radius by 25%, and can be equally effective in congested city conditions, where U-turns and tight streets are made easier to navigate. 1.6.2 High Speeds: In high speeds, turning the rear wheels through an angle opposite to front wheels might lead to vehicle instability and is thus unsuitable. Hence, at speeds above 80 kmph, the rear wheels are turned in the same direction of front wheels in four-wheel steering systems. This is shown in fig no1.6

Crab Mode The front-to-rear steering ratio variation with respect to vehicle speed is defined by the following Front-Rear Steering Ratio with respect to speed For a typical vehicle, the vehicle speed determining the change of phase has been found to be 80 km/hr. The steering ratio, however, can be changed depending on the effectiveness of the rear steering mechanism, and can be as high as 1:1. 1.6.3 ZERO TURNING CIRCLE RADIUS - 360 MODE

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In addition to the aforementioned steering types, a new type of fourcould significantly affect the way our vehicles are parked in the future. Its shown in the following FIG 1.5

FIG 1.5 - The Jeep Hurricane concept with Zero Turning Circle Radius This vehicle has all the three modes of steering described above, though it sports a truly complex drive-train and steering layout with two transfer cases to drive the left and right wheels separately. The four wheels have fully independent steering and need to turn in an unconventional direction to ensure that the vehicle turns around on its own axis. Such a system requires precise calculation from a servo motor with real-time feedback to make certain that all three steering modes function perfectly. The concept didn’t make it to production, possibly due to the high costs involved in the power train layout. But the idea presented by the concept continues to find importance. The only major problem posed by this layout is that a conventional rack-and-pinion steering with pitman arms would not be suitable for this mode, since the two front wheels are steered in opposite directions. Steer-by-wire systems would work fine, however, since independent control can be achieved.

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CHAPTER 2 REVIEW OF LITEREATURE 2.1 HONDA 4WS SYSTEM This system is dependent on the steer angle so that the movement of the rear wheels is controlled by the angular movement of the front wheels. For steering of the front wheels up to about 130 degrees, the rear wheels are so arranged that they turn through a small angle in the same direction as the front wheels. Beyond this angle, the rear wheels gradually straighten up and then turn through a comparatively large angle in the opposite direction (Fig. 2.2). An Epicyclic gear mechanism incorporated in the rear steering gearbox controls the rear wheels angles. A fixed annulus is meshed with a large planet gear, which is driven by an eccentric on the input shaft. SThis shaft transmits a drive through a slider and guide to a stroke rod, connected to the rear wheel track rods (Fig. 2.1 A). Slight movement of the input shaft rotates the planet which in turn moves the offset output shaft slightly in the same direction as the input (Fig.2.1 B). the input shaft moves the offset shaft towards the TDC position (Fig. 2.1 C), the stroke rod rotates back to the central position so that the rear wheels are set in a straight ahead position. As the input shaft and planet are rotated towards the full-lock position (Fig. 2.1D), the stroke rod attains maximum displacement and consequently a corresponding movement of the rear wheels takes place. The rear gearbox is maintenance free and is greased for its entire life. The centre shaft couplings have splines to both steering gearboxes. A master spline at each connected point ensures correct assembly of the units.

Fig. 2.1. Epicyclic Gear Action (Honda).

2.2 MAZDA 4WS SYSTEM

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The rear wheels in this system are steered by a hydraulically operated power unit, which is electronically controlled in accordance with the steering wheel angle and vehicle speed. The Mazda 4WS layout is more complicated than the Honda arrangement and hence incorporates suitable fail-safe for trouble free operation. The fail-safe device includes a centering lock spring and special safety solenoid. If hydraulic or electronic failure takes place, these devices set the rear wheels to the straight-ahead position. Two electronic sensors, installed at transmission output and speedometer drive, measure the vehicle speed. The signals are passed to the built-in memory of an electronic control unit (ECU), which commands the hydraulic system for setting the direction and angle for the rear wheels. For speeds less than 35 kmph, the rear wheels are steered in the opposite direction to that of the front wheels. As 35 kmph is approached, the rear wheels are turned to the straightahead position. Above this speed the rear wheels are steered in the same direction as the front wheels with an angle limited to 5 degrees. 13

of

Fig. 2.2. Schematic Layout Wheel Steer Unit (Mazda).

Rear-

schematic of the main system. The components are as follows: 1. Sensors to measure vehicle speed.

Figure 2.3 represents the the system and indicates components used in this functions of these in steering the rear wheels

2. Steering phase control unit conveys to the hydraulic control valve the required stroke direction of movement. (Hi) Electric stepper motor alters the yoke angle and bevel gear phasing in accordance with the signals received from the ECU . 3. Rear steering shaft provides the position of the front wheels to the bevel gear in the steering phase control unit. 4. Control valve controls the hydraulic pressure supplied to the ram cylinder.5. Hydraulic ram cylinder steers the rear wheels depending upon the requirements.

Fig. 2.3. Steering Phase Control Unit.

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The steering phase control unit (Fig. 2.4) alters the direction and angle of the rear wheels. The electrical pulses from the ECU to the stepper motor, and the movement from the steering shaft to the bevel gear, alter the position of the hydraulic control valve to suit the conditions.

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CHAPTER 3 WORKING PRINCIPLE When the steering is steered the power is transferred to the front rack and pinion steering gear box, and a bevel gear arrangement is made to transfer the power to the rear rack and pinion steering gear box. Bevel gear is used to transmit the rotary motion perpendicularly, so the one bevel gear is introduced in the front steering rod. Other bevel gear is connected to the transfer rod. Two supports are used to support the transfer rod. Transfer rod is connected to the rear rack and pinion steering gear box. Rear rack and pinion steering gear box is fixed to the car body by bolts and nuts and the ends of the steering box are connected to the rear wheel hub where the tyres are mounted. As the steering is steered the rear wheels also turn by the arrangements made and the rear wheel turn in the opposite direction by the arrangements in the bevel gear. 3.1 ACKERMAN STEERING MECHANISM

Shown in FIG 3.1, Ackermann steering geometry is a geometric arrangement of linkages in the steering of a car or other vehicle designed to solve the problem of wheels on the inside and outside of a turn needing to trace out circles of different radii. The steering pivot points are joined by a rigid bar called the tie rod which is also a part of the steering mecby all wheels will lie at a common point. But this may be difficult to arrange in practice with simple linkages, and designers draw or analyze their steering systems over the full range of steering angles. Hence, modern cars do not use pure Ackermann steering, partly because it ignores important dynamic and compliant effects, but the principle is sound for low speed maneuvers, and the right and left wheels do not turn by the same angle, be it any cornering speed. This presents a difficult problem for vehicles with independent steering, as the wheels cannot be easily given the correct Ackerman turning angles. This would directly affect the dynamic handling of the car, making it impossible to control properly. With all the four wheels steered, the problem gets compounded, since the appropriate steering angles for all four wheels need to be calculated. It is to be noted that the variation in steering angles as a result of Ackerman geometry is progressive and not fixed, hence they have to be pre calculated and stored by the controller. This dictates that the control of fourwheel steering systems be very precise, and consequently, complex. This is another reason why manufacturers have not preferred the use of such systems in their vehicles, even with recent advances in technology. The cost of such systems can be high, and a good amount of research & development is required.

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Fig3.1 - Ackerman Steering Geometry

Nevertheless, the benefits that engineers can reap out of this technology are significant enough to work around these obstacles. We chose to use a simple control circuit to demonstrate the effectiveness of a four wheel steering system, and at the same time, simulated the suspension steering assembly of a typical car to predict the Ackerman angles for corresponding steer angles 3.1.2 STEERING RATIOS

Every vehicle has a steering ratio inherent in the design. If it didn't you'd never be able to turn the wheels. Steering ratio gives mechanical advantage to the driver, allowing you to turn the tyres with the weight of the whole car sitting on them, but more importantly, it means you don't have to turn the steering wheel a ridiculous number of times to get the wheels to move. Steering ratio is the ratio of the number of degrees turned at the steering wheel vs. the number of degrees the front wheels are deflected. So for example, if you turn the steering wheel 20° and the front wheels only turn 1° that gives a steering ratio of 20:1. For most modern cars, the steering ratio is between 12:1 and 20:1. This coupled with the maximum angle of deflection of the wheels gives the lock-to-lock turns for the steering wheel. For example, if a car has a steering ratio of 18:1 and the front wheels have a maximum deflection of 25°, then at 25°, the steering wheel has turned 25°x18, which is 450°. That's only to one side, so the entire steering goes from -25° to plus 25° giving a lock-to-lock angle at the steering wheel of 900°, or 2.5 turns (900° / 360). This works the other way around too of course. If you know the lock-tolock turns and the steering ratio, you can figure out the wheel deflection. For example if a car is advertised as having a 16:1 steering ratio and 3 turns lock-tolock, then the steering wheel can turn 1.5x360° (540°) each way. At a ratio of 16:1 that means the front wheels deflect by 33.75° each way. For racing cars, the steering ratio is normally much smaller than for passenger cars - ie. Closer to 1:1 - as the racing drivers need to get fuller deflection into the steering as quickly as possible.

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3.1.3 TURNING CIRCLES The turning circle of a car is the diameter of the circle described by the outside wheels when turning on full lock. There is no hard and fast formula to calculate the turning circle but you can get close by using this: Turning circle radius = (track/2) + (wheelbase/sin (average steer angle)) The numbers required to calculate the turning circle explain why a classic black London taxi has a tiny 8m turning circle to allow it to do U-turns in the narrow London streets. In this case, the wheelbase and track aren't radically different to any other car, but the average steering angle is huge. For comparison, a typical passenger car turning circle is normally between 11m and 13m with SUV turning circles going out as much as 15m to 17m. 3.1.4 KING PIN AND KING PIN AXIS: The imaginary axis about which the steered wheels are swivelled. In older models a solid structural component is used a s a king pin and its center line is the king pin axis. In present day models the solid component is absent. Instead ball joints are used. The imaginary line joining upper and lower ball joint acts as king pin axis.

Fig 3.2 King Pin Axis King-pin inclination or steering axle inclination The angle between the vertical line and centre of the king pin or steering axle, when viewed from the front of the vehicle is known as king pin inclination or steering axle inclination. The king pin inclination, in combination with caster, is used to provide directional stability in modern cars, by tending to return the wheels to the straight – ahead position after any turn. It also reduces steering effort particularly when the vehicle is stationary. It reduces tyre wear also. The king pin inclination in modern vehicle range from 4 to 8 degree .It must be equal on both the sides. If it is greater on one side than the other, the vehicle will tend to pull to the side having the greater angle. Also, if the angle is too large, the steering will become exceedingly difficult. The king-pin inclination is made adjustable only by bending. 3.1.5 CENTER POINT STEERING:

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When center line of the wheel meets the center line of the king pin axis at the road surface it is called center point steering. 3.6.1 Disadvantages of not having center point steering: 1. Unnecessary couple formed due to forces of vertical weight and road resistance separated by a distance . 2. Steering becomes heavy as the wheel movement is along an arc of radius equal to the distance Between king pin 3. Large bending stresses in steering components. 3.1.6 SCRUB RADIUS: The distance between the center line of the wheel and the king pin axis at the road surface. 3.7.1 Positive scrub radius: When king pin axis meets the road inside the tyre tread line. 3.7.2 Negative scrub radius: When king pin axis meets the road outside the tyre tread line.

Fig.3.3 scrub radius

3.2 VEHICLE DYNAMICS AND STEERING 3.2.1Understeer: Understeer is so called because when the slip angle of front wheels is greater than slip angle of rear wheels. Understeer can be brought on by all manner of chassis, suspension and speed issues but essentially it means that the car is losing grip on the front wheels. Typically it happens as you brake and the weight is transferred to the front of the car. At this point the mechanical grip of the front tyres can simply be overpowered and they start to lose grip (for example on a wet or greasy road surface). The end result is that the car will start to take the corner very wide. In racing, that normally involves going off the outside of the corner into a catch area or on to the grass. In normal you-and-me driving, it means crashing at the outside of the corner. Getting out of understeer can involve letting off the throttle in front-wheel-drive vehicles (to try to give the tyres chance to grip) or getting on the throttle in rear-wheel-drive vehicles (to try to bring the back end around). Fig 3.4

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Fig 3.4.under steer

3.2.2 Oversteer: Over steer is defined when the slip angle of front wheels lesser than the slip angle of rear wheels. With oversteer, the car goes where it's pointed far too efficiently and you end up diving into the corner much more quickly than you had expected. Oversteer is brought on by the car losing grip on the rear wheels as the weight is transferred off them under braking, resulting in the rear kicking out in the corner. Without counter-steering (see Fig ) the end result in racing is that the car will spin and end up going off the inside of the corner backwards. In normal you-and-me driving, it means spinning the car and ending up pointing back the way you came.

Fig3.5over steer 3.2.3 Neutral steer or counter steering: Counter-steering can defined as when the slip angle of front wheels is equal to slip angle of rear wheels is what you need to do when you start to experience oversteer. If you get into a situation where the back end of the car loses grip and starts to swing out, steering opposite to the direction of the corner can often 'catch' the oversteer by directing the nose of the car out of the corner. In drift racing and demonstration driving, it's how the drivers are able to smoke the rear tyres and power-slide around a corner. They will use a combination of throttle, weight transfer

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and handbrake to induce oversteer into a corner, then flick the steering the opposite direction, honk on the accelerator and try to hold a slide all the way around the corner. It's also a widely-used technique in rally racing.

Fig3.6. Neutral steer

3.3 DESIGN OF FOUR WHEEL STEERING SYSTEM : It is to be remembered that both the steered wheels do not turn in the same direction, since the inner wheels travel by a longer distance than the outer wheels, as described in FIG 3(a)

Fig3.7 - Variation in steer angles for left and right wheels 3.4 FUNDAMENTAL EQUATION FOR CORRECT STEERING When the vehicle takes a turn, the outer wheels moves faster than the inner wheels. The four wheels must roll on the road so that there is a line contact between road surface and tyres .This is essential to prevent tyre wear. The rolling motion of the wheels on the road surface is possible only if these describe concentric circles on the road at an instantaneous centre, when the vehicle is taking a turn. In order for turning the vehicle to the left or right ,its two front wheels are mounted on short axles, known as stub axles, pivoted to the chassis of the vehicle. The axes of these axles, when produced meet at an instantaneous centre which lies on the common axis of the rear wheels. The axis of the inner wheel makes a larger turning angle θ than angle ф made by the axis of outer wheel.

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Let

a =CD wheel track b =AB = distance between the points of front axles L = AE wheel base

I =common instantaneous centre of all four wheels. Draw IP perpendicular from I to AB produced meeting at p. Then,

b= AP – BP =lcotф –lcotθ = l (cotф – cotθ)

Or

cotф- cotθ= b/L. 53

Fig 3.8 Steering Angles

This is the fundamental equation for correct steering. If this equation is satisfied, there will not be any lateral slip of the wheels when the vehicle is taking a turn. The mechanism is used for automatically adjusting the values of θ and ф for correct steering are known as steering gear mechanism. 3.4.1 STEERING TORQUE REQUIRED As the name implies, steering torque is the torque required to steer the wheels. The following calculations belong to steering torque required to steer single wheel when the vehicle is stationary. The steering torque required will be maximum when the vehicle is stationary, and is given by the equation 54 T = 3 X √P μW(3/2) Where T = Steering Torque (N) μ = Coefficient of friction between the road and the tyre W = Load (N)

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P = Tire Pressure (N/m2 ) 3.4.2 WHEEL ALIGNMENT CONSTRAINTS FOR FOURWHEEL STEERING

Proper alignment of the wheels is maintained to avoid undesirable scrubbing of the wheels as the vehicle turns. To maintain alignment, the steering angle on each wheel must be tangent to concentric circles. In the case of the four-wheel steered vehicle, the inside wheels (i.e., the wheels on the right during a right turn and those on the left during a left turn) will be traveling along the path described by a circle with radius r1 (circle 1 in Fig 3.4(a) )while the outside wheels travel along a circle with the longer radius r2 (circle 2 in Fig 3.4(a). The turning rate of the vehicle increases as those radii shorten and the center point of the circles moves toward the center of the vehicle along its midline. Maximum turning rate is achieved when the centers of the circles coincide with the center of the vehicle. For the vehicle to have full turning range, that is, have the ability to rotate about its center in either direction, each wheel must be free to rotate through 180° . 3.5 BENEFITS OF THE 4WS MODEL • With the 360 mode, the vehicle can quickly turn around at the press of a button and a blip of the throttle. Complicated three-point steering manoeuvres and huge space requirements to park the vehicle are entirely done away with • Crab mode helps simplify the lane changing procedure • In conjunction with rear steer mode, four-wheel steering can significantly improve the vehicle handling at both high and low speeds. • Due to the better handling and easier steering capability, driver fatigue can be reduced even over long drives • The only major restriction for a vehicle to sport four-wheel steering is that it should have four or more wheels. public transport vehicle, be it cars, vans, buses, can benefit from this technology • Military reconnaissance and combat vehicles can benefit to a great extent from 360 mode, since the steering system can be purpose built for their application and are of immense help in navigating difficult terrain 3.6 APPLICATIONS OF 4WS WITH 360 MODE 3.6.1 PARALLEL PARKING As has been discussed previously, zero steer can significantly ease the parking process, due to its extremely short turning footprint. This is exemplified by the parallel parking scenario, which is common in foreign countries and is pretty relevant to our cities. Here, a car has to park itself between two other cars parked on the service lane. This

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manoeuvre requires a three-way movement of the vehicle and consequently heavy steering inputs. Moreover, to successfully park the vehicle without incurring any damage, at least 1.75 times the length of the car must be available for parking for a two-wheel steered car. As can be seen clearly, the car requires just about the same length as itself to park in the spot. Also, since the 360 mode does not require steering inputs, the driver can virtually park the vehicle without even touching the steering wheel. All he has to do give throttle and brake inputs, and even they can be automated in modern cars. Hence, such a system can even lead to vehicles that can drive and park by themselves.

CHAPTER 4 CONCLUSION AND SCOPE OF FUTURE WORK

An innovative feature of this steering linkage design is its ability to drive all four (or two) wheels using a single steering actuator. Its successful implementation will allow for the

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development of a four-wheel, steered power base with maximum maneuverability, uncompromised static stability, front- and rear-wheel tracking, and optimum obstacle climbing capability. Thus the four-wheel steering system has got cornering capability, steering response, straight-line stability, lane changing and low-speed manoeuvrability. Even though it is advantageous over the conventional two-wheel steering system, 4WS is complex and expensive. Currently the cost of a vehicle with four wheel steering is more than that for a vehicle with the conventional two wheel steering. Four wheel steering is growing in popularity and it is likely to come in more and more new vehicles. As the systems become more commonplace the cost of four wheel steering will drop.

REFERENCE

1. Dr. N. K. Giri, “Automotive Mechanics”, Khanna Publishers, 2-B, Nath Market, Nai Sarak, New Delhi – 111006. (1996) , 7th Edition. 2. Thomas. D. Gillespie, “Fundamentals of Vehicle Dynamics”, Society of Automotive Engineers, Warrendale. (2000) Online Edition.

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3. Akihiko Miyoshi. (1988) ‘four-wheel steering system, Mazda Corporation, JAPAN. U.S patent No. 4,719,981. 4. Hiroshi Ohmura (1990) ‘Rear wheel steering apparatus’, Mazda Motor Corporation, U.S patent No. 4,953,648. 5. Yuichi Ushiroda, okazaki, kaoru sawase. (2008) ‘Power Transmission System For fourwheel steering system, Mitsubishi jidosha kogyo kabushiki kaisha Tokyo, Japan, U.S patent No. 7,325,640. 6. Dr.K.R.Govindan “Automobile Engineering” Anuradha Publication, Chennai-600017 3 rd Edition. Websites: 7. http://www.jeep.com/en/autoshow/concept_vehicles/hurricane/ - The Jeep Hurricane Concept. 8. auto.howstuffworks.com/jeep-hurricane.htm – Working of the Hurricane 4WS System. 9. www.carbible.com – Basics of 4-wheel Steering 10.http://forums.mscsoftware.com/adams/ubbthreads.php - ADAMS / Car Software VPD Discussion Forum. 11. www.rctek.com – Ackerman Steering Principles and control of steering arms.

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