基于变传动比的全轮线控转向车辆可拓H_(∞)控制方法研究

Extension H_(∞)Control Method for All-wheel Steer-by-wire Vehicles Based on Variable Transmission Ratio

为了解决传统固定转向传动比以及鲁棒H_(∞)控制方法无法很好地改善车辆稳定性的问题,提出全轮线控转向车辆的变传动比和可拓H_(∞)控制策略。首先,建立八自由度车辆动力学模型和轮胎模型。其次,以车辆方向盘转角和车速为输入信息,基于模糊控制方法设计全轮线控转向车辆的转向传动比,并计算出全轮线控转向车辆的前轮转角。然后,以横摆角速度偏差和偏差微分为特征值,基于可拓控制理论将车辆状态划分为3个区域:经典域、可拓域和非域;在经典域中,采用基于横摆角速度反馈的鲁棒H_(∞)控制方法,实时获取全轮线控转向车辆的后轮转角;在可拓域和非域中,结合可拓控制和H_(∞)控制策略,动态调整H_(∞)控制器的输出信号,在保证控制系统鲁棒性的前提下改善车辆的操纵稳定性。最后,基于MATLAB/Simulink仿真平台和自主研制的全轮线控转向特种消防救援车辆,通过正弦转向、单移线、阶跃转向、双移线等典型工况对所提控制方法进行验证,并以平均绝对误差和均方根误差为评价指标,与无控制和H_(∞)控制方法进行对比分析。仿真和试验测试结果表明:(1)变传动比控制方法不仅可以提高车辆低速时的转向灵敏度,也能改善车辆高速时的稳定性;(2)相比传统鲁棒H_(∞)控制,可拓H_(∞)控制策略提高了全轮线控转向车辆的操纵稳定性,改善了车辆全轮线控转向控制系统的鲁棒性。

Existing fixed steering ratio and robust H_(∞)control methods cannot improve vehicle stability well.Accordingly,variable transmission ratio and extension H_(∞)control strategies were proposed for all-wheel steer-by-wire vehicles.First,an eight-degree-of-freedom vehicle dynamics model and a tire model were established.Second,by using the steering wheel angle and vehicle speed as input,the steering transmission ratio of an all-wheel steer-by-wire vehicle was determined using a fuzzy control method,and then the front-wheel angle of the vehicle was calculated.Third,based on extension control theory,vehicle states were divided into three regions:classical domain,extension domain,and non-domain.In the classical domain,a robust H_(∞)control method based on yaw rate feedback was adopted to obtain the rear-wheel angle in real time.In the extension domain and the non-domain,the extension control and H_(∞)control strategies were combined to dynamically adjust the output signal of the H_(∞)controller,thus improving vehicle handling stability on the premise of ensuring the robustness of the control system.Finally,based on the MATLAB/Simulink simulation platform and the self-developed all-wheel steer-by-wire special fire rescue vehicle,the proposed control methods were verified under sinusoidal steering,single-lane change,step steering,and double-lane change conditions.Furthermore,by using the mean absolute error and root mean square error as evaluation indexes,the proposed extension H_(∞)control method was compared with H_(∞)control and non-control methods.The results indicate that the variable transmission ratio control method can not only improve vehicle steering sensitivity at low speed,but also vehicle stability at high speed;furthermore,compared with the traditional robust H_(∞)control,the extension H_(∞)control strategy improves the handling stability of all-wheel steer-by-wire vehicles and the robustness of all-wheel steer-by-wire control systems.