Research On Friction Compensation And Application Of High Frequency Responsive Direct Drive Valve

The high-precision micro-displacement compensation system is the key device for special shape interpolation in the special-shaped hole processing equipment.The core control element of the micro-displacement compensation device is a servo valve.The servo valve plays the role of power amplification and electro-hydraulic conversion.Its frequency response determines the dynamic performance of the micro-displacement system.The output pressure of the valve directly affects the position accuracy of the micro-displacement system.The traditional proportional magnet direct drive valve has a slow response,and the pressure output accuracy is difficult to guarantee.Taking this valve as the research object and using the micro-displacement compensation system as an application,this thesis analyzes a new type of high frequency direct drive servo valve,and focuses on the dynamic and static characteristics of direct drive valve,friction modeling and model modification,parameter identification and friction compensation,etc.The thesis is committed to improving the response characteristics of the servo valve and the accuracy of output pressure.New direct drive servo valve is analyzed,using voice coil motor as new actuator has improved the response speed of the direct drive valve.Firstly,the load pressure model of the deformed body under the condition of active cover slide valve,the direct drive valve hydrodynamic model,the voice coil motor model and the double closed-loop control loop model are obtained,and finally the linearized model with pressure as output of direct drive valve is obtained.Then the influence of valve opening on the hydrodynamic force and the influence of structural parameters on the dynamic characteristics are analyzed,and the control method for improving the step characteristics of the direct drive valve is explored.Finally,the dynamic high frequency response characteristics and static pressure characteristics of the direct drive valve are verified with the help of Simulink and AMESim.Aiming at the special contour of the special-shaped hole,explore the spool movement rule of the servo valve and its mapping relationship.The spool movement law is variable acceleration movement.The traditional LuGre model cannot describe the effect of acceleration.In addition,the LuGre model has instability when switching between high and low speeds.At the same time,combined with the friction problems encountered in actual work,the traditional LuGre model is modified.To improve the accuracy of output pressure of direct drive valve,double closed loop feedback control is adopted,and a friction feedforward compensation scheme is designed.The spool displacement is used as the inner ring,and the output pressure of the valve is used as the outer ring to design a double closed loop feedback control scheme,and the stability of the double closed loop feedback control is analyzed.For friction compensation,firstly build an electro-hydraulic servo experimental platform,and design identification experiment of modified LuGre model’s dynamic and static parameters,and obtain multiple sets of experimental data.Then use the improved AFSA to process the obtained data to obtain the optimized parameters.Finally,the principle of structural invariance is used to design the friction feedforward compensation controller,and the obtained parameters are substituted to compare the tracking accuracy of the direct drive valve spool with and without friction compensation,and verify static pressure characteristics of direct drive valve with friction compensation.