Research On The Key Technology Of 50KN Elelctro-hydraulic Servo Fatigue Testing Machine

Lightweight is an important way to reduce energy consumption of automobile.The key parts of automobile are threaded fasteners.Thread connection system is an important means to ensure safety and lightweight.Axial fatigue strength is an important parameter for fasteners.Axial fatigue strength is a key index to ensure connection strength and service life,and its measuring device is fatigue tester.Electro Hydraulic servo tester is one important component part for testers,and its control performance does an important influence on the reliability and efficiency of the testers.Aimed at the poor adaptability and low intelligence of the traditional electro hydraulic tester and with the method of math modeling and Electro-hydraulic joint simulation,this paper develop a research of new Electro Hydraulic servo tester.The Main research work is shown below.(1)Aimed at the fastener type,this paper designs the metal structure part,lifting platform part,clamping device and the servo actuator part of the fatigue testers and through the software,the paper builds the 3Dmodel of the structure of the tester.The Hydraulic principle of the fatigue tester is carried out and according to the system requirements of the electro hydraulic servo system,the type and parameter of the main hydraulic component of the servo system are confirmed,which lays a foundation for the follow-up modeling and simulation analysis of the servo system.(2)The math models of the servo valve,servo actuator,accumulator and the amplifier are built up and the transfer function of the servo system is deduced.According to the transfer function,the time-domain response of the servo system is carried out and the result shows that the model is correct.(3)The control strategies of the servo control are researched in order to further improve the performance of the servo system.Firstly the structure and the merit and demerit of the traditional PID control method is introduced.Secondly based on the demerit of the traditional PID,the servo control strategy based on fuzzy PID is introduced and the structure and realization process of the fuzzy PID is alsointroduced.Finally in order to the improve stability of the system and avoid the influence of the sensor interference to the system,this paper proposes a filtering and curve fitting method based on least square and the principle and realization process is also give out.(4)In order to verify the effectiveness of the fuzzy PID control strategy,the electro hydraulic joint simulation of AMESim and MATLAB of the servo system is carried out.And the simulation curves under different load and different control strategies is analyzed.