ECHPS旁通流量比例电磁阀开度模糊PID控制

为了使车辆电控液压转向系统（ECHPS）具有良好的随车速可变的助力特性，研究了用于控制ECHPS旁通流量的比例电磁阀的开度控制策略。分析了旁通流量控制式ECHPS的基本原理和比例电磁阀的结构组成，建立了比例电磁阀的动力学模型和控制模型。针对动态多工况ECHPS旁通流量的精确稳定控制要求，提出了模糊PID控制策略，把模糊推理运用于PID参数的整定，以补偿控制系统因非线性和时变性所导致的误差。仿真结果表明：在低、中、高3种车速工况下ECHPS的旁通流量和比例电磁阀开度的响应符合随车速可变助力特性的要求；与常规PID控制相比，所设计的模糊PID控制具有响应速度快、稳态精度好、超调量小的优点，可实现比例电磁阀开度的精确稳定控制。

Opening Fuzzy PID Control for Bypass Flow Proportional Valve of ECHPS

In order to have good alterable assist characteristics with speed on vehicle electrical controlled hydraulic power steering system (ECHPS), the opening control strategy for bypass flow proportional valve of ECHPS was studied. The basic principle and structural form of bypass flow controlled ECHPS were analyzed, and the dynamics and control models of proportional valve were established. Aimed at the requirements of control the bypass flow of ECHPS on dynamic multi-mode conditions accurately and stably, a fuzzy PID control strategy was proposed. The fuzzy reasoning was applied to self-tuning of the PID parameters to compensate the error caused by the nonlinearity and time-variation of the control system. The results of simulation show that, the bypass flow of ECHPS and the opening response of proportional valve at low, medium and high speed conditions were comply with the request for alterable assist characteristics with speed. As compared with the conventional PID control, the designed fuzzy PID control has advantages of less overshoot, higher steady-state accuracy and rapid response, which can realize the opening control of proportional valve accurately and stably.