四轮轮毂电机驱动智能电动汽车转向失效容错控制研究

Intelligent four-wheel-independently-actuated electric vehicles can realize front-wheel steering via the driving torque differential of the front-axle wheels. In order to ensure the trajectory tracking performance and vehicle dynamics stability under the circumstances of steer-by-wire system actuator failure, a fault-tolerant control method based on driving torque differential of the front-axle wheels and direct yaw-moment control(DYC) is proposed. It adopts a hierarchical structure and consists of an upper and a lower controller. In the upper controller, the time-varying model prediction control is first proposed to generate the reference steering wheel angle and the additional yaw moment to realize precise trajectory tracking. Then, a sliding mode controller is synthesized to calculate the driving torque differential considering various nonlinear constraints and steering actuator modelling uncertainty. In the lower controller, the optimal torque allocation is realized with the objective of tire load minimization based on the effective set algorithm. The simulation results show that the proposed method can realize accurate trajectory tracking while ensuring vehicle dynamics stability under complete steer-by-wire system failure in the high-speed lane-changing and double lane change maneuvers. The real-time performance indicates that it has the potential to be embedded in a realistic vehicle controller for practical implementation.