Study On Electro-Hydraulic Conversion Characteristics And Nonlinear Control Method Of Piezoelectrically-Actuated Fuel Nozzle Flapper Valve

Electro-hydraulic servovalve is a control component widely used in fuel and actuation system of aeroengines.Because of fast response and convenient processing,nozzle-flapper typed servovalves are more popular in application.Generally,traditional nozzle flapper servovalves use a torque motor as electro-mechanical convertor.Based on electromagnetic principle,it realizes the electro-hydraulic conversion process by generating electromagnetic torque to deflect the flapper,thereby changing the pressure inside the nozzle chambers to move the main spool.However,too many elements,high processing and assembly requirements and vulnerability to electromagnetic interference,as well as reliability defects including low resolution,large zero drift and poor high temperature resistance,seriously restrict the development of high-performance servovalves.Therefore,there exists urgent demand for developing new driving schemes to substitute torque motors.In this paper,an electro-hydraulic conversion device actuated by piezoelectric stack for nozzle flapper valve is proposed,and its electro-hydraulic conversion characteristics and nonlinear control method are studied in simulation and experiment.Firstly,the working principle of the system is introduced,and the MATLAB/Simulink model of the piezoelectric actuator and the nozzle flapper valve is established.Bouc-Wen hysteresis model is used to describe the hysteresis characteristics of piezoelectric stack actuator.Based on the global inertial coordinate system dynamics method,a mathematical model of elastic deformation of the flapper is established.The electro-hydraulic conversion characteristics of the two actuation scheme are compared through the simulation results.Secondly,aiming at two nonlinear factors,piezoelectricity hysteresis and elasticity of flapper,a compensation control method is proposed.The Bouc-Wen model for piezoelectric hysteresis is built to compensate the hysteresis.The results show that the average hysteresis of the piezoelectric actuator is reduced by 61.7%.PI control is utilized to compensate the elasticity of the flapper.The load pressure and load flow rate of the valve are increased by 14.5% and 12.2% respectively.Finally,development of the experimental system,such as component selection and valve block design,is introduced,and reconstruction of the test system is implemented.The experiment of electrohydraulic conversion characteristics of piezoelectrically-actuated fuel nozzle flapper valve is conducted and compared with that of conventional torque motor scheme.The results show that the experimental data are basically consistent with the simulation.The piezoelectrically-actuated nozzle flapper valve is superior to the torque motor actuated valve in response,load pressure and load flow.The test results of nonlinear compensation show that,the average hysteresis of the piezoelectric actuator is reduced by52.7%,and the flow rate of the load excitation of the valve is increased by 11.6%.