四轮轮毂电机驱动智能电动汽车转向失效容错控制研究

四轮轮毂电机驱动电动汽车各轮驱动力矩独立可控，可通过控制前轴左右两轮的力矩差实现前轮转向。以四轮轮毂电机驱动智能电动汽车为研究对象，针对线控转向系统执行机构失效时的轨迹跟踪和横摆稳定性协同控制问题，提出一种基于差动转向与直接横摆力矩协同的容错控制方法。该方法采用分层控制架构，上层控制器首先基于时变线性模型预测控制方法求解期望前轮转角和附加横摆力矩，然后考虑转向执行机构建模不确定性以及路面干扰，设计基于滑模变结构控制的前轮转角跟踪控制策略。下层控制器以轮胎负荷率最小化为目标，利用有效集法实现四轮转矩优化分配。最后，分别在高速换道和双移线工况下仿真验证了该控制方法的有效性和实时性。

Fault-tolerant Control for Intelligent Four-wheel-independently-actuated Electric Vehicles under Complete Steer-by-wire System Failure

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.