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
Conclusion Advantageous to 2WS
Complex and expensive
Cost may drop as the system becomes common