Research On Electro-hydraulic Servo System Based On Velocity Estimation

Electro-hydraulic load simulator is a kind of equipment which simulates the force that the steering gear of aircraft and ship can bear with the changing environment under laboratory conditions.The electro-hydraulic servo system is the foundation of the electro-hydraulic load simulator,and the quality of its loading force directly determines the loading performance of the electro-hydraulic load simulator.Because the electro-hydraulic servo system is rigidly connected with the position system(i.e.the loaded object),when the position system moves actively in response to the command signal,the electro-hydraulic servo system is dragged by the position system while loading the position system,which brings great interference to the normal loading of the electro-hydraulic servo system.The loading force deviation caused by the electro-hydraulic servo system due to the active movement of the loaded object is called passive loading error.Passive loading error seriously affects the loading accuracy and stability of electro-hydraulic servo system,so it is necessary to take measures to reduce it.In this paper,electro-hydraulic servo system is taken as the research object,and the research goal is to reduce the passive loading error.On the basis of summarizing the methods at home and abroad,we decide to use the method based on velocity estimation and combine with the principle of structural invariance to reduce the passive loading error.Firstly,the mathematical models of the position system and the electro-hydraulic servo system are deduced.According to the parameters of each component in the actual test bed,the open loop characteristics of the position system and the open loop characteristics of the electro-hydraulic servo system are simulated and analyzed respectively.Then the mathematical model of passive loading error is established,and the causes and characteristics of passive loading error,as well as the influence of system parameters on passive loading error are analyzed in detail.In order to reduce the passive loading error,a Kalman filter model was built,which took the acceleration and displacement of the piston of the position hydraulic cylinder as the input information,and estimated the velocity of the piston of the position hydraulic cylinder in real time.The estimated velocity is applied to the principle of structural invariance to reduce the passive loading error.The electro-hydraulic servo system and Kalman filter are modeled and simulated on AMESim software.Finally,the electrohydraulic servo system test bench was designed and built to carry out loading test verification.The simulation and test results show that the velocity estimation method based on Kalman filter can accurately estimate the velocity of the loaded object in real time,and the passive loading error can be reduced well by combining with the principle of structural invariance.This provides a new idea for the theoretical research and engineering practice of reducing passive loading error.