基于滑模的线控转向车辆横向稳定性分层控制

Sliding-Mode Based Hierarchical Control of Lateral Stability of Steer-by-Wire Vehicles

为提升线控转向车辆的横向稳定性,针对线控转向系统提出了一种分层控制策略,其中上层控制包括轮胎侧偏刚度估计器和主动转向控制器,下层控制包括转向跟随控制器。当车辆以极小转向角稳定行驶时,上层控制将首先估计出前后轮胎侧偏刚度。而后在车辆转向行驶过程中,主动转向控制器将结合轮胎侧偏刚度估计值并根据二自由度车辆动力学模型,推导出与驾驶员输入前轮转角相对应的车辆稳态转向时的横摆角速度,将其作为期望横摆角速度,并实时对驾驶员输入前轮转角进行补偿以使车辆快速跟踪期望横摆角速度,补偿后的前轮转角将由转向跟随控制器控制电机以使前轮准确地跟踪。

In order to improve the lateral stability of steer-by-wire(SbW)vehicles,a hierarchical control strategy is proposed for SbW systems,in which the high-level control scheme consists of a tire cornering stiffness estimator and an active front steering(AFS)controller,and the low-level contains a steering angle tracking controller(SATC).When the SbW vehicles are driven stably at a very small steering angle,the high-level control scheme will firstly estimate the front and rear tire cornering stiffness coefficients.Then,during the SbW vehicles'steering process,the AFS controller will combine the estimated tire cornering stiffness and the 2-DOF linear single track vehicle dynamics model to derive the yaw rate under steady state,which is considered as the desired yaw rate,corresponding to the front wheel steering angle input by driver.The front wheel steering angle input by driver will be compensated by AFS in real time to make the SbW vehicles quickly track the desired yaw rate,and the compensated front wheel steering angle will be accurately tracked by the motor controlled by the SATC.