FOUR WHEEL STEERING SYSTEM

This paperwork deals with the details of four wheels steering (4ws) system. According to this mechanism in a four wheels steering system, all the four wheels are steered, thus can turn the vehicle easily to either lift or right using the steering wheel. This system serves more effective and stability in controlling the vehicle at cornering and at parking .The operation of this system take change as the speed of vehicle increase or decrease.

At low speed motion of the vehicle, the front wheels turn to the direction of the steering wheel, at the same time the rear wheels turn   in the opposite direction .Four wheel mechanism is active only in position when the vehicle moves at low speed and below 35 km .There after the rear wheels follow in the same direction of the print wheels.

There are three types of 4 wheels steering system

Mechanical 4ws

Hydraulic 4ws

Electro-hydraulic 4ws

The concept of four wheel steering is hardly and relatively new as four wheel drive .Admittedly those systems were custom, typically controlled and separately controlled from the front wheels.

The first production four wheels steering for the average, American automobile consumer was offered 20 years ago. On the 1988, this system was entirely self contained, automatic and mechanical: no electronic, no speed sensors, no computers, no hydraulic, just two racks and a rod between them.

Four wheel steering (4ws) is also called the rear wheels steering or all wheel steering .The (4ws) four wheel steering should not be confused with four wheel drive. 4ws system improves handling and helps the vehicle at lighter turns. The front wheels do the actual steering work. The rear wheel turning is generally limited a 50 to 20 0 during an opposite duration turn. During the same direction turn rear wheel steering is limited the about 10 to 1.5 0. In a (4ws) system, the front and rear wheels steer towards same direction which is said to be in-phase at high speed, where as the front and rear wheels turn in an opposite direction at slow speed which is called anti- phase or opposite phase and it is produced at a sharper turn and tighter turn.

Steering system allows the driver to control the direction of the vehicle travel. This is made possible by linkage that connects the steering wheel to the steerable wheels and tires. The steering system may be either manual or power .When the energy source for the steering system is the force, the drives applies to the steering wheel, then the vehicle has manual steering .Power steering used a hydraulic pump or in motor to assist the driver effects. In the modern age most of the vehicles are manufacture with a power steering mechanism.

The operation is same for both manual and power steering .As the drive turns the steering where the movement is carried to the steering gear. It chains the rotary matron of the steering wheel, in to straight line or linear motion. The linear motion acts through steering linkage /tie rod attached to the steering knuckle .arms or steering arms. The steering knuckle then turns the wheels in to left or right side.