Abstract: In the application of automatic transmission hydraulic control, the hydraulic system of slide valve plate has some defects, such as poor control precision, multi-parameter coupling and difficult to establish system model. This paper presents a pressure control strategy for hydraulic pump driven by brushless direct current (BLDC) motor based on model variable structure proportional integral (PI), which combines the advantages of good dynamic characteristics and high control accuracy with the advantages of simple structure and good reliability of hydraulic pump. The proportional integral control model of motor speed is established according to the characteristic relation of hydraulic pump speed, flow rate and pressure and the parameters of oil temperature, viscosity and elastic modulus, etc. The output pressure of hydraulic pump is adjusted by the motor drive duty ratio signal which is easily controlled. The control system eliminates the pressure deviation and overshoot through the variable structure proportional integral control, and improves the system accuracy. The simulation results show that the variable structure proportional integral control is feasible, and the test results show that the system response of the model control is better than that of the pure proportional integral closed-loop control, and it has a good ability to resist load disturbance.

Key words: Automatic transmission; Hydraulic control; Model control; Variable structure PI control

摘要： 在自动变速箱液压控制的应用中，滑阀板液压系统存在控制精度差、多参数耦合、系 统模型难以建立等缺陷。文章提出基于模型变结构比例积分（PI）的直流无刷（BLDC）电机 驱动液压泵的压力控制策略，将直流无刷电机动态特性好、控制精度高等优点与液压泵结构 简单、可靠性好等特点相结合。根据液压泵的转速、流量、压力特性关系和油液温度、黏度、 弹性模量等参数建立电机转速比例积分控制模型，通过较易控制的电机驱动占空比信号实现 对液压泵输出压力的调节。控制系统通过变结构比例积分控制，消除压力偏差和超调量，提 高系统精度。仿真结果表明，变结构比例积分控制具有可行性，而试验结果证明，模型控制 的系统响应优于纯比例积分闭环控制，并且具有很好的抗负载扰动能力。

关键词: 自动变速箱；液压控制；模型控制；变结构 PI 控制