Cascade Backstepping Control with Augmented Observer for Lateral Control of Vehicle

This paper proposes a cascaded backstepping control method with an augmented observer for the lateral control of an autonomous vehicle. The proposed cascaded backstepping control structure consists of an inner-loop electric power steering (EPS) system and an outer-loop lane-keeping system (LKS). The outer-loop controller for LKS calculates and provides the desired steering angle to the inner-loop EPS system for maintaining the vehicle at the center of the lane. Subsequently, the inner-loop controller for the EPS system generates steering torque to track the desired steering angle from the outer loop. The proposed method can guarantee the stability of the vehicle considering both inner-loop and outer-loop dynamics. In addition, an augmented observer affords robustness against unknown model parameters and external disturbances. The stability of the closed loop of the overall system, including the lateral dynamics and the EPS system, is proven using the input-to-state stable property. Controller design with consideration of the overall system can improve the lateral control performance.