In order to enhance the stability of three-axle vehicle in limited driving conditions, a nonlinear 2 DOF model of three-axle vehicle with all-wheel steering was established by considering the nonlinear characteristics and the vertical load transfer of tires during vehicle steering. Taking zero side-slip angle of mass center as target and using the control method of feed-forward and state feedback, a fuzzy control system of all-wheel steering was designed based on fuzzy control theory. Finally, simulation model of the control system was built by using MATLAB/Simulink software, and the performance of the control system was tested by carrying out various simulations in limited driving conditions. The simulation results show that the fuzzy control method of all-wheel steering can guarantee that the mass-center side-slip angle of three-axle vehicle is basically zero, and the yaw rate and lateral acceleration become stable quickly. In conclusion, the fuzzy control method can effectively avoid the instability of three-axle vehicle in critical steering conditions and improve the initiative security of vehicle significantly.%为了提高三轴车辆在极限工况下的稳定性,充分考虑轮胎的非线性特点以及车辆转向过程中轮胎垂直载荷的转移情况,建立了三轴车辆全轮转向的非线性二自由度整车动力学模型,以车辆的质心侧偏角为零为控制目标,基于模糊控制理论,采用前馈加状态反馈的控制方法设计了零质心侧偏角比例前馈加质心侧偏角反馈的全轮转向模糊控制系统,最后利用MATLAB/Simulink建立了该控制系统的仿真模型,对控制系统在车辆极限转向工况下的控制性能进行了仿真验证.结果表明,全轮转向模糊控制方法可使三轴车辆的质心侧偏角基本为0,横摆角速度和侧向加速度均能很快达到稳态值,因而可有效防止车辆在极限转向工况下发生侧滑失稳,可显著提高车辆的主动安全性.
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