SUBMITTED BY: -

ROHAN KUMAR SHARMADHEERAJ BARNWAL

CONTENT:-

INTRODUCTION TO STEERING

TYPES OF STEERING SYSTEM

FOUR WHEEL STEERING

TURNING RADIUS

INTODUCTION TO STEERING:-Steering is the collection of components, linkages, etc. which allow

a vehicle (car, motorcycle, bicycle) to follow the desired course. An

exception is the case of rail transport by which rail tracks combined

together with railroad switches (and also known as 'points' in British

English) provide the steering function.

Requirement of steering-

•It should multiply the turning effort applied on the steering wheel by

the driver.

•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.

•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.

TYPES OF STEERING SYSYEM

Front wheel steering.

Rear wheel steering.

Four wheel steering.

FOUR WHEEL STEERING:-

• Four-wheel steering (or all wheel steering) is a system employed by some vehicles to improve steering response, increase vehicle stability while maneuvering at high speed, or to decrease turning radius at low speed. A 4-wheel steering system is superior to a 2- wheel steering system. It reduces the turning radius as well as the space required for turning. It also enables to change road lane while driving even at high speed.

• At lower speeds, turning the rear wheels in the opposite direction to the front wheels results in a smaller turning radius and faster cornering responses. At high speeds, turning all four wheels in concert improves high-speed stability.

The Four Wheel steering system offers a 21% reduction in turning

radius. So if a vehicle is capable of making a U-turn in a 25-foot

space. It allows the driver to do it in about 20 feet. . A front wheel

active steering function was added to Rear Active Steer adopted

on the Fuga. By controlling the steering angle of all four wheels,

this active steering system helps improve stability and response at

high speed and helps reduce driver’s steering workload at low

speed. To achieve precise vehicle

• Vehicles move smoothly and are easy to drive both in the city

and on winding roads.

• Added stability means vehicles can be driven safely on

expressways and when changing lanes.

• Quick and responsive control system will allow gentle steering

operation.

TURNING RADIUS:-

The turning radius of a vehicle is the radius of the smallest circular turn

(i.e. U-turn) that the vehicle is capable of making. it refers to the tightest

turn a vehicle can make and is dependent on several factors. One obvious

one is the width of the wheel base — that is, how far apart the front tires

are. All other things being equal, a smaller wheel base can offer a tighter

radius, while a large wheel base, such as those on large trucks, will have a

larger radius, regardless of other factors.

4-WS SYSTEM PARTS: -

• Rack and pinion front steering, • hydraulically controlled• Rear-steering shaft• Vehicle speed sensors• Steering-phase control unit• Centering lock spring• Solenoid valve

At higher speeds, the rear wheels turn in the same direction of the

front wheels to increase stability by preventing oversteer and fish

tailing. And reduces the turning radius.

AT HIGH SPEED:-

4-WS DRIVE AT DIFFERENT SPEED

At lower speeds, the rear wheel turn in the opposite direction

from the front wheels. This will help in easy maneuverability

of the vehicle during parking and taking a tight curve. The

turning radius of a vehicle can be reduced by a minimum of

20% by having this mechanism, which is a significant benefit

for bigger cars and trucks.

AT LOW SPEED

ADVANTAGES OF 4WS

• Speed can be varied

Slow Medium Fast

• Improved maneuverability

Better handling

in tight corners

Better parking

Stability is

increased

4WS 2WS

MODERN CARS WITH ACTIVE FOUR WHEEL STEERING: -

•Acura RLX (P-AWS)

•BMW 850CSi (only Euro spec models)

•BMW 7-Series (2009 onward, part of sport package)

•BMW 5-series (2011 onwards, Integral Active Steering option)

•Toyota Camry / Vista JDM 1988–1999 (Optional)

•Toyota Carina ED / Toyota Corona EXiV (world's first dual-mode switchable

2WS to 4WS)

•Toyota Celica (option on 5th and 6th generation, 1990–1993 ST183 and

1994–1997 ST203) (Dual-mode, high and low speed)

•Toyota Soarer (UZZ32)

CONCLUSION: -

An innovative feature of this steering linkage

design and its ability to drive all four (or two)

wheels using a single steering actuator makes it

more efficient than 2WS. Though it is expensive

now but by producing it at big level cost may be

decreased. Its successful implementation will

allow for the development of a four-wheel, steered

power base with maximum maneuverability,

uncompromised static stability, front- and rear-

wheel tracking, and optimum obstacle climbing

capability.