Abstract: In order to solve the problems of unsymmetrical area of pump controlled single rod hydraulic cylinder and low power density of electric cylinder, a new hydraulic motor-mechanical linear actuator system using closed pump controlled hydraulic motor instead of servo motor to drive ball screw is proposed. At the same time, in view of the defect that the new system is difficult to achieve accurate positioning due to the leakage dead zone, a variable universe fuzzy PID with load feedforward is designed to compensate the dead zone. The compensation method fully considers the nonlinearity of the dead zone and the uncertainty of load disturbance. In principle, it does not strictly depend on the mathematical model of the system, and can adaptively adjust the control system when the dead zone changes. Then, in Simulink and SimulationX, the joint simulation model of the system is established. The research results show that, compared with the traditional PID controller, the proposed variable universe fuzzy PID with load feedforward not only effectively solves the problem of dead time compensation, significantly improves the positioning accuracy of the system, but also improves the dynamic response characteristics of the system, and makes the system have good robustness and anti load interference ability.

Key words: pump-control-motor, ball screw, dead-zone compensation, load feed-forward, variable universe fuzzy PID