4WS and DYC coordinated control for 4WS-4WID autonomous vehicles considering tire nonlinearity

Area of Science:

• Automotive Engineering
• Control Systems Theory
• Robotics

Background:

• Autonomous vehicles require robust path tracking and stability control, particularly under demanding conditions.
• Four Wheel Steering (4WS) and Four Wheel Independent Drive (4WID) systems offer advanced maneuverability but pose complex control challenges.
• Existing control strategies may struggle with the nonlinear dynamics and extreme scenarios faced by 4WS-4WID vehicles.

Purpose of the Study:

• To develop and validate a coordinated control strategy for 4WS and DYC systems in 4WS-4WID autonomous vehicles.
• To improve both path tracking accuracy and vehicle stability under extreme operating conditions.
• To optimize control parameters for enhanced performance and reduced energy consumption.

Main Methods:

• A sliding mode observer (SMO) was used for lateral force estimation and cornering stiffness correction.
• An adaptive model predictive control (MPC) path tracking controller was designed.
• Sliding mode control (SMC) was applied to design 4WS and DYC stability controllers, accounting for nonlinear tire characteristics.
• An extension method was employed to coordinate 4WS and DYC weights for optimal rear wheel angle and yaw moment control.

Main Results:

• The proposed coordinated control strategy significantly improved path tracking accuracy.
• Vehicle stability, measured by sideslip angle and yaw rate, was substantially enhanced under extreme conditions.
• The method effectively balanced stability control with energy efficiency by optimizing control allocation.

Conclusions:

• The coordinated 4WS and DYC control method provides a robust solution for autonomous vehicle stability and path tracking.
• The integration of SMO, adaptive MPC, and SMC effectively addresses the nonlinear dynamics of 4WS-4WID vehicles.
• Co-simulation and experimental validation confirm the strategy's effectiveness in real-world driving scenarios.