FOUR-WHEEL STEERING SYSTEM

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Topics Covered

IntroductionWhy Four-wheel Steering (4WS) System?Types

Mechanical Hydraulic Electro-hydraulic

Actual 4WS Fail-safe measures Advantages Application Conclusion

INTRODUCTION

What is 4WS? How does it work?

Why Four-wheel Steering (4WS) System?

Types

MechanicalHydraulicElectro-Hydraulic

Mechanical 4WS System

Inside a rear-steering gear box is a simple planetary gear setup

Hydraulic 4WS System

Simple Hydraulic 4WS System

Electro-hydraulic 4WS System

An Electronically & Hydraulically controlled 4WS System using a Stepper motor & Control yoke

Actual 4WS

Rack and pinion front steering, hydraulically controlled

Rear-steering shaft Vehicle speed sensors Steering-phase control unit Centering lock spring Solenoid valve

Fail-safe measures

Hydraulic failure

Electrical failure

Positioning of the wheels

Advantages of 4WS Speed can be varied

Improved maneuverability

Slow Medium Fast

• Better handling in tight corners

• Better parking• Stability is

increased

4WS 2WS

Application

Conclusion Advantageous to 2WS

Complex and expensive

Cost may drop as the system becomes common

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