Active Front Wheel Steering System (AFS)

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Active Front Wheel Steering System (AFS)

• Chapter 2

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Conventional Steering System

• Rack and pinion system
• Constant steering ratio
• Fully mechanical system

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AFS

• Wheel steer angle superposition of steering
  wheel
• angle and AFS actuator
• Variable steering ratio
• Combination of mechanical and electrical systems

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Vehicle Handling Model (without side wind force)
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Vehicle Handling Model (with side wind force)
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Assumptions in modeling and control AFS

• S Fx 0 (No braking or throttle inputs)
• Fyf Cf af
• Fyr Cr ar
• Where Cf cornering stiffness of front tires
• Cr cornering stiffness of rear tires
• a wheel side slip angle

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Controller Structure of AFS
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Wind model
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Performance Comparison of AFS and non-AFS vehicles
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Yaw Rate
AFS
Non-AFS
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Lateral acceleration
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Simulation Data

• m3950
• Iz6172
• Lf1.1
• Lr1.36
• Cf71600
• Cr77130
• Vx20
• Lw0.4