Simulation of an electro-hydraulic servo valve driven by an ultrasonic motor

Abstract. The conventional electro-hydraulic servo valve is driven by an electromagnet, which is easily disturbed and has poor dynamic performance, seriously restricting the flow control accuracy. In view of this situation and based on the high-precision, fast-response, and self-locking characteristics of ultrasonic motors, a structural scheme involving a hollow ultrasonic motor driving a servo valve through a ball screw is designed in this work. The structure and the principle of the whole system are analyzed, and a mathematical model is established; moreover the dynamic characteristics of the system under adaptive fuzzy proportional–integral–derivative (PID) control are analyzed using MATLAB/Simulink and Simcenter Amesim simulation software. The results show that, compared with electromagnetic drive and conventional PID control, under adaptive fuzzy PID control, the overshoot of the servo valve driven by an ultrasonic motor is eliminated and the adjustment time is reduced by 33 %. Furthermore, after being disturbed, the recovery time is reduced by 25 %. After the system is stable, the influence of a hydraulic pressure change can be eliminated. Therefore, the system has a better robustness and anti-interference ability, can realize the accurate control of spool displacement, and is more suitable for the high-precision control of flow.