four wheel steering system1

8/19/2019 Four Wheel Steering System1

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INTRODUCTION Cont..,1

To improve stability, most cars nowadays aredesigned to exhibit under-steer characteristicwhen driven at high speeds.Although under-steer condition improves stabilityof the vehicle, it increases the driver's steeringeffort. Also since a vehicle handling changes with

road speed, the response to a steering movement, both in time and direction, is difficult to predict.These disadvantages can be overcome to a greatextent by using four wheel steering (4 !".



TYPES OF STEERING SYSYEM2

#ront wheel steering.$ear wheel steering.#our wheel steering.



MODES IN FOUR WHEELSTEERING SYSTEM

3

T % &% ! A$ ) * $A++! * T/ ! 4 ! &% +

!low !peeds - $ear !teer &ode0

/igh speeds 1 2rab &ode.



TURNING CIRCLES4

The turning circle of a car is the diameter of thecircle described by the outside wheels when turningon full loc3.

Turning circle radius = (track/2) +(wheelbase/

sin(average steer angle))



VEHICLE DYNAMICS ANDSTEERING

5

Understeer: ndersteer is so called because when the slip angle

of front wheels is greater than slip angle of rearwheels.

O ersteer: %ver steer is defined when the slip angle of front

wheels lesser than the slip angle of rear wheels.Ne!tr"# steer or $o!nter steer%n&:

2ounter-steering can defined as when the slip angle

of front wheels is e ual to slip angle of rear wheels



6

Understeer O ersteer

Ne!tr"# steer or

$o!nter steer%n&



'ENEFITS OF THE (WS MODEL7

n con5unction with rear steer mode, four-wheelsteering can significantly improve the vehiclehandling at both high and low speeds.

ue to the better handling and easier steeringcapability, driver fatigue can be reduced even overlong drives.

!tability of the vehicle increases.Turning radius of the vehicle can be decreased to agreater extent by rear steer mode.

four wheel steering system1

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