四轮转向汽车的无模型自适应控制研究

The model-free adaptive control of four-wheel steering vehicle

为提高四轮转向汽车的操纵稳定性,提出一种以质心侧偏角和横摆角速度为反馈量,以后轮转角与横摆力矩为控制器输出的四轮转向汽车无模型自适应控制方法。具体设计方案为:从建立等效车辆的双输入-双输出紧格式线性化模型出发,结合车辆转向动力学的理想模型,引入输入准则函数和参数估计准则函数,采用极值原理分别设计出无模型自适应控制器及其伪雅可比矩阵的估计律,并理论分析了该控制方法的系统稳定性。该方法的控制器设计不依赖精确的整车数学模型,且具有后轮转角与横摆力矩相结合的复合控制特点。控制仿真对比结果表明:在不同车速和转向工况下,该控制方法均能对期望的横摆角速度与质心侧偏角具有良好的跟踪效果,有效提高了四轮转向汽车低速转向的机动灵活性和高速行驶转向的操纵稳定性。

A model-free adaptive control(MFAC)strategy was presented to improve the steering stability of four-wheel steering(4WS)vehicle,which took side slip angle and yaw rate as feedback,and the rear wheel angle and yaw moment as the controller output.The design scheme was as follows:firstly,the double-input-double-output compact linearization model of the equivalent vehicle was established combined with the ideal model of vehicle steering dynamics;secondly,the input criterion function and parameter estimation criterion function were introduced;thirdly,MFAC controller and the estimation law of pseudo Jacobian matrix were designed respectively by the extremum principle;finally,the stability of the 4WS control system was analyzed.The proposed method provides a compound controller with the combination of rear steer angle and direct yaw moment,where the design process is independent of the accurate 4WS model.The control simulation results of 4WS vehicle show that under different vehicle speeds and steering conditions,the control method can track the expected yaw rate and side slip angle,and effectively improves the maneuverability of low-speed steering and the steering stability of high-speed steering of 4WS vehicle.