兼顾操纵性与节能性的ECHPS可变助力特性与控制策略

转向系统的助力特性设计与控制对重型车辆的操纵稳定性和节能性具有重要影响。以重型商用车旁通比例阀式电控液压转向系统(Electronically controlled hydraulic power steering system，ECHPS)为研究对象，在Matlab/Simulink中建立包含比例电磁阀子模型、机械系统子模型、液压系统子模型和3自由度整车转向动力学模型的ECHPS系统仿真模型，基于能量流原理分析转向助力特性对转向系统节能性的影响，设计了兼顾操纵性与节能性的ECHPS可变助力特性曲线。采用模糊比例积分微分(Proportional integral derivative, PID)控制策略对比例电磁阀的阀芯位移进行控制，使旁通流量随车速可变。搭建ECHPS性能试验台，对ECHPS在不同车速下的助力特性进行测试，试验结果与仿真设计的理想可变助力特性基本一致，可以实现重型车辆低速时转向轻便性和高速时的良好路感，同时改善了转向系统的节能性。

Variable Assist Characteristics and Control Strategies for ECHPS in Terms of Maneuverability and Energy Efficiency

The design and control of assist characteristics have a significant impact on handling stability and energy efficiency for Heavy-duty vehicles. The establishment of electronically controlled hydraulic power steering system(ECHPS) is built in Matlab/Simulink, which contains proportional valve sub-models, child models of mechanical systems, hydraulic systems and three degrees of freedom steering dynamics system. Based on the principle of energy flow, the impact on the energy saving of the assist characteristics is analysed. A design method of variable assist characteristics aiming at maneuverability and energy saving is developed. The bypass flow is variable with speed by using fuzzy proportional integral derivative(PID) control strategy for proportional valve spool displacement control. ECHPS performance platform is built, and characteristics at different speeds are tested. The test results are consistent with the designed variable assist characteristics, which can not only meet the requirements of steering handiness but also assure proper road feeling, while improving energy efficiency.