Adaptive Steering Actuator Delay Compensation for a Vehicle Lateral Control System

Abstract

This thesis presents an adaptive control algorithm for steering actuator delay compensation in a ground vehicle lateral control system. Unknown and time-varying actuator delay values are considered. Many active safety systems and all autonomous vehicles rely on a lateral control system in order to follow a desired path. Lateral control systems designed without considering actuator delay may not achieve desired path following performance or may exhibit an undesirable system response such as steering oscillation, resulting in an uncomfortable ride or even instability or collisions. The delay compensating controller presented in this thesis is implemented at a low level within the lateral control system. It attempts to mitigate the effects of the time delay without using a vehicle model or altering the high level path following controller. The estimation algorithm used in this thesis utilizes knowledge of the control input and measured steer angle to estimate both the communication delay and the actuator dynamics present in the control system. This allows the compensating controller to adapt to changing or unknown actuator delay. The performance of the inner-loop compensation algorithm is evaluated with multiple path following controllers. The controller is then tested in a lane-keeping simulation, and finally applied to a real-world path following experiment. The proposed compensation algorithm is shown in both simulation and real-time tests to improve steering response and overall path following performance.