智能电动车辆横纵向协同运动控制

Lateral and longitudinal motion cooperative control of intelligent electric vehicle

针对车速变化下的车辆轨迹跟随稳定性问题,提出一种基于模型预测控制(MPC)与滑模控制结合的横纵向协同控制策略。建立描述车辆纵向、横向及横摆运动状态的三自由度动力学模型;然后,设计模型预测控制器对车辆期望轨迹进行跟踪,考虑车辆行驶运动过程中横纵向耦合问题,将纵向车速作为横向控制系统的状态量,并利用反馈矫正机制不断更新预测模型;在此基础上,采用滑模控制算法对期望车速及加速度进行跟踪,并采用饱和函数作为指数趋近率以减小抖振;采用基于规则的制动转矩分配方式得到行驶过程中各个车轮的需求转矩。该控制策略考虑了车辆动力学中的横纵向耦合问题,可在线处理车辆动力学约束,将车辆稳定跟踪期望轨迹的问题转化为求解带约束的最优控制问题。仿真结果表明所提出控制策略的有效性。

In order to solve the problem of vehicle path following stability under the change of vehicle speed,a lateral and longitudinal cooperative control strategy based on model predictive control(MPC)and sliding mode control was proposed.Firstly,a three-degree-of-freedom dynamic model describing the longitudinal,lateral and yaw motion of the vehicle was established,and then a model predictive controllerwas designed to track the desired trajectory of the vehicle,taking into account the problem of horizontal and vertical coupling in the process of vehicle movement.The longitudinal speed was taken as the state of the lateral control system,and the prediction model was constantly updated by feedback correction mechanism.On this basis,the sliding mode control algorithmwasused to track the expected speed and acceleration,and the saturation functionwasused as the exponential approach rate to reduce buffeting.Finally,the rule-based braking torque distribution method wasused to obtain the demand torque of each wheel.The control strategy takes into account the horizontal and vertical coupling problem in vehicle dynamics,can deal with vehicle dynamics constraints on-line,and transforms the problem of vehicle stable tracking the desired path into solving the optimal control problem with constraints.Simulation results show the effectiveness of the proposed control strategy.