关键词: 自动变速箱；液压控制；模型控制；变结构 PI 控制

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