基于降维观测器的4WS车辆滑模变结构控制

Sliding Mode Control for 4WS Vehicle Based on Reduced-order Observer

考虑车辆在极限运动工况下转向时的横摆运动、侧向运动以及侧倾运动的影响,建立以质心侧偏角、横摆角速度、侧倾角和侧倾角速度为状态变量的三自由度线性车辆模型。为了实现车辆线传操纵(steer by wire),以车辆实际质心侧偏角和横摆角速度与理想模型的质心侧偏角和横摆角速度之间的误差作为控制器输入,建立滑模跟踪控制器。考虑到状态变量之一的质心侧偏角难以直接测量,设计了降维观测器以重构车辆状态。仿真结果表明,降维观测器跟踪性能良好,准确的重构了车辆状态;与不受控制的前轮转向车辆相比,所设计的控制系统使车辆的动态特性和操纵性能有效提高。

In view of the effects of the vehicle yaw motion,lateral motion and roll motion under ultimate handling maneuver,a 3DOF linear vehicle dynamics model which takes the body side slip angle,yaw rate,roll angle and roll angle velocity as the state variables is presented.By taking the yaw rate and body side slip angle errors between the estimated and the real ones as the input variables of the controller,a model-following sliding mode controller is designed,and the steer by wire system is built.The reduced-order observer is designed to estimate the vehicle states since the body side slip angle is difficult to be measured directly.Simulation results show that the reduced-order observer rebuilds the vehicle states accurately in a considered range of vehicle speed.The control system improves the dynamic characteristic and handling performance of the vehicle by contrast with the one without the controller.