Research On Valve Spool Dynamics Of Direct Acting Solenoid On-off Valve Based On Electromechanical Hydraulic Model

Solenoid on-off valve is an important basic flow control component in valve-controlled hydraulic system,and the dynamic performance of the spool determines the overall performance of the system.The conventional driving mode causes the valve spool response to lag behind the excitation current,which hinders the improvement of the frequency response.One of the solutions is to add a control loop,by active controlling and compensation of the displacement and speed of the valve spool,it's hysteresis during operation will be reduced.The precise measurement of spool displacement is the key previous work of spool closed-loop control.At present,the main measurement method of spool displacement is to use a contact sensor,which inevitably changes the dynamic characteristics of spool.Therefore,starts from the non-contact measurement method of valve spool,a coil current-inductance based spool displacement measurement method is proposed in this paper,which has been verified by experiment.In this paper,a dynamic,circuit and magnetic circuit model of the valve spool are established based on the spring vibrator system.The models are developed from the coupled electromagnetic model of the solenoid valve,resulting the inductance-spool displacement model,and based on the opening electromagnetic characteristics of the valve spool,an inductance displacement fitting algorithm is designed,which establishes an empirical model of the valve spool dynamics.The numerical method and finite element method are devoted to the simulation research of the solenoid on-off valve,analyzing the key factors affecting the dynamic performance of the valve spool.The simulation models of dynamics,electromagnetics and flow field are built according to the actual size of the valve spool,and the simulation parameters are corrected by the test results.In order to verify the simulation results and establish the empirical model of valve spool dynamics based on inductance recognition,three kinds of valve spool test systems are built,they respectively have the function which is to synchronously measure the displacement and electromagnetic force,measure the valve spool displacement in air and oil,and load pressure to the valve spool,each test device is equipped with optical imaging element and non-contact displacement sensor,which can accurately measure the spool displacement in air and oil.According to the error source of the measurement process,the system error is eliminated by data processing.In the analysis of test results,the dynamics empirical model and simulation model of valve spool are verified.The analysis of the dynamics empirical model shows that the measurement errors of the model are 7%and 9.2%respectively in the air and oil,it can reflect the displacement trend of the valve spool,but the spool speed fluctuation affected by the damp-driving force in oil will reduce the accuracy of the empirical model.The analysis of the simulation model shows that damping and static pressure of the flow field are the main factors of the spool speed,and the structure of the valve spool has a great influence on the pressure distribution of the internal flow field.Based on the above analysis,by changing the valve spool material,structure and adding a control loop to it,the valve spool performance will be improved.Finally,this paper summarizes and prospects the non-contact and sensorless measurement technology of valve spool displacement,and expounds the specific scheme to further improve the accuracy of the dynamics empirical model.