Research And Experiment Of High Frequency Electro-hydraulic Servo Actuator Based On Hydrostatic Support Structure

Electro-hydraulic servo actuators have the advantages of high precision,fast response and large output torque,etc.,and have been widely used in various fields such as high-speed railway and aerospace.As the actuating element of servo actuator,the structure of hydraulic cylinder directly affects the response frequency of actuator.Because the hydraulic cylinder adopts the seal combination form,although the sealing of the hydraulic cylinder is ensured,the friction of the hydraulic cylinder is increased,the response speed is reduced,and the side load problem cannot be slowed down.In order to improve the frequency response of the actuator,a new type of hydraulic cylinder with hydrostatic support structure is proposed in this paper.Through simulation and experiment,the main factors affecting the anti-bias load and friction force of the hydraulic cylinder are analyzed.The main research contents are as follows:Firstly,according to the application requirements of high frequency response and high side load,a new type of high frequency response hydraulic cylinder is designed by using the static pressure support structure of constant pressure oil supply.According to the equivalent bridge method,the mathematical model of hydraulic cylinder based on hydrostatic support structure is established.Secondly,the main factors affecting the anti-bias load capacity and friction force of the hydrostatic support structure are analyzed,such as the oil supply pressure,the clearance between the piston rod and the guide sleeve,and the moving speed of the piston rod.Fluent software was used to simulate the elliptical and rectangular hydrostatic cavity structures respectively,and the change rules of anti-bias load capacity and friction force were obtained.The results show that the mechanical properties of the elliptical hydrostatic cavity are better than those of the rectangular hydrostatic cavity under the same conditions.Thirdly,an experimental prototype was made according to the hydraulic cylinder model,and an experimental test platform was built to compare and analyze the two hydrostatic chamber cylinders.The end offset of the piston rod is measured by a three-coordinate tester,and the anti-bias load capacity of the hydraulic cylinder is obtained indirectly.The friction between the piston rod and the guide sleeve is measured indirectly by the coordination of the displacement sensor and the relief valve.The experimental results show that the end offset of the elliptical cylinder is less than that of the rectangular cylinder under the same end load.Finally,the vibration test of the electro-hydraulic servo actuator with the elliptical hydrostatic cavity structure was carried out.Under the input signal of10 Hz,the response signal of the hydraulic cylinder was basically consistent with that of the actuator.When responding to the sweep signal,the amplitude of the prototype was measured to be over 0.1mm at the frequency of 100 Hz,which met the design requirements.It provides theoretical reference for the improvement and research of electro-hydraulic servo actuators in the future.