active front wheel steering system (afs) chapter 2
TRANSCRIPT
Active Front Wheel Steering System (AFS)
Chapter 2
Conventional Steering System
• Rack and pinion system
• Constant steering ratio
• Fully mechanical system
AFS
• Wheel steer angle = superposition of steering wheel
angle and AFS actuator
• Variable steering ratio
• Combination of mechanical and electrical systems
Vehicle Handling Model (without side wind force)
Vehicle Handling Model (with side wind force)
Assumptions in modeling and control AFS
Fx = 0 (No braking or throttle inputs)
- Fyf = Cf f
- Fyr = Cr r
Where Cf = cornering stiffness of front tires
Cr = cornering stiffness of rear tires
wheel side slip angle
Controller Structure of AFS
Wind model
Performance Comparison of AFS and non-AFS vehicles
Yaw Rate
AFS
Non-AFS
Lateral acceleration
Simulation Data
• m=3950• Iz=6172• Lf=1.1• Lr=1.36• Cf=71600• Cr=77130• Vx=20• Lw=0.4