重型车辆旁通流量式电控液压转向附加力矩控制研究

Control Strategy for Bypass Flow Type ECHPS Extra Torque of Heavy-duty Vehicle

重型车辆旁通流量式电控液压转向系统(ECHPS)通过改变旁通流量的大小调节液压助力,实现低速转向轻便性和高速转向稳定性。汽车高速转向时由于旁通流量大而导致转向响应性变差,提出在紧急转向时施加附加力矩来提高转向跟随性。研究了基于车速和转向角速度的附加力矩控制策略,在相同的转角速度下,车速越大比例阀电压越大,助力越小;在同一车速下,随着角速度的增大,比例阀的电压减小,助力增大。建立了附加力矩的控制模型并进行了仿真,结果验证了控制策略的正确性,说明附加力矩能增强ECHPS紧急转向下的快速响应性。

Heavy-duty vehicle bypass flow type electronically controlled hydraulic power steering system （ECHPS） regulates hydraulic assist force by varying the volume of by-pass oil, and thus realizes low-speed steering portability and high-speed stability. Due to the massive by-pass flow, the steering responsiveness descends when steering at high speed. The idea of applying an extra torque is proposed to improve the steering sensitivity when steering urgently. The extra torque control strategy based on speed and steering angle rate was studied. At the same angle rate, the higher the proportion valve controlled voltage is the faster the vehicle speed is, while the assist force is smaller. At the same vehicle speed, with the increasing of angle rate, the voltage of proportional valve is reduced, and the assist force is increased. The extra torque control model is established and simulated, the results verify the validity of control strategy and indicate that the extra torque can enhance ECHPS quick responsiveness at urgent turning.