Abstract:  A kind of fault-tolerant controller with two-level structure is proposed in order to improve the handling stability and fault tolerance performance of wire controlled four wheels steering vehicles. It takes the front-wheel reference angle of the ideal vehicle model as the reference input. The basic control law of the top-level is designed based on the optimal control theory, to obtain the pseudo-control command. The control alloter of the bottom-level is then designed to distribute the front and rear wheel angles and drive the vehicle movement. The possible gain-type steering actuator faults are converted into the time-varying parameter perturbations for the control alloter design. A robust fault-tolerant control allocation algorithm is thus yielded, which can suppress the time-varying parameter perturbations and possible faults. The vehicle handling stability and fault tolerance are guaranteed. Finally, comparative simulation is executed for a four wheel steering vehicle time-varying 2-DOF model. The results indicate that the yielded controller based on the proposed fault-tolerant control allocation can effectively improve the vehicle handling stability and fault tolerance performance in the fault case.

Key words:  Steer-by-wire system, control allocation, fault-tolerant control, optimal control

摘要： 为了提高线控四轮转向汽车的车辆操纵稳定性及故障容错性能，提出了一种具有分层结构的容错控制器。该控制器以理想车辆模型前轮的参考转角信号为参考输入，根据最优控制理论设计上层基本控制律以获得伪控指令，再设计下层控制分配器驱动车辆前后轮的实际转角。针对车辆转向机构可能存在的增益型异常故障，在设计下层控制分配器时，将其转化为系统时变参量的摄动，给出了一种能够抑制系统时变参量摄动的鲁棒容错控制分配方法，从而保证了故障下车辆操控的稳定性和较好的容错性能。对某型四轮转向汽车时变2-DOF模型的仿真对比结果表明，所提出的基于容错控制分配的分层控制器有效改善了车辆故障下的操纵稳定性，提高了车辆的容错性能。

关键词: 线控转向系统, 控制分配, 容错控制, 最优控制