Study On The Piezoelectric Drive Electro-hydraulic Servo Valves

The most important element in a hydraulic actuation system is the servo valve,whose dynamic characteristics greatly affect the performances of the whole hydraulicactuation system. The piezoelectric actuator is a new type of electrical-mechanicalconverter, which has features of fast response, large output force and high precisiondeformation. Thus it can replace of electromagnetic torque motor or electromagneticforce motor to actuate servo valve in order to solve the problem of its poor frequencyresponse and control accuracy.In this article, two types of novel piezoelectric drive electrohydraulic servovalve-piezoelectric direct-drive servo valve (PDDSV) and piezoelectric drive nozzleflapper servo valve have been studied.The structures of the proposed servo valves are designed firstly in reference to thebasic structure of electrohydraulic servo valve. And the working principles of them areintroduced. In addition, the key performance parameters of the proposed servo valves aredesigned and calculated.Moreover, the dynamic characteristics of the piezoelectric stack actuator forPDDSV are analyzed according to the piezoelectric theory. Firstly, based on the structureof PDDSV, the dynamic system model of piezoelectric stack actuator is established. Then,according to the transfer function of this model, the piezoelectric stack actuator isanalyzed both in the time domain and frequency domain. Moreover, the influences ofmain parameters on the dynamic characteristics and output displacement of piezoelectricstack actuator are investigated through simulation.The mathematical model of thepiezoelectric actuator in piezoelectric drive nozzle flapper servo valve is also established.The displacement and output force characteristics of the piezoelectric actuator with alever amplifier are analyzed. According to the analysis above, the nonlinear dynamic model of the PDDSV isestablished. And then the dynamic characteristics of the PDDSV are simulated based onthe mathematical model. What’s more, the influences of key parameters of this valve onthe dynamic characteristics are analyzed. The dynamic performances of the PDDSV arecompared with other piezoelectric servo valves, which show that the PDDSV hassatisfactory dynamic characteristics for high frequency applications.The mathematicalmodel of the piezoelectric drive nozzle flapper servo valve is established. Thecharacteristics of the proposed servo valve, such as flow rate, time response andfrequency response, have been simulated. The simulation results show that the proposedservo valve could ensure both a high bandwidth and good flow rate characteristic.