Modelling and investigations of piezobender used in control of electrohydraulic servovalve

Electrohydraulic servo drives can be found in many industrial applications. A typical design of a servo valve uses the known torque motor. The main concept of the design modification in the presented servovalve was concerned in the application of a piezoelectric bender actuator in the first valve stage, working between nozzles as a flapper. Reason for that is very complex machining and assembling processes of torque motor, where tight tolerances significantly increase cost of such transducer. The biggest advantage of piezo bender is simplification of this stage, moreover piezo bender provides better dynamic properties. Piezo bender belongs to group of so-called smart materials. In this case it can bend under external stimulus in the form of electric field. Displacement of free end of piezo bender vs. applied voltage is distinguished by hysteresis which hinder control process, but it can be effectively compensated by proper mathematical model. Authors present in the paper piezo control stage concept and experimental results. Authors prepared for tested sevovalve Matlab Simulink model which is described in this paper. Results of model simulation and servovalve experimental researches were compared and discussed.