Research On The Electro-hydraulic Servo System Used For High-speed Tensile Machine

Nowadays,with the development of expressway network,motor vehicles often drive at a speed of more than 20m/s.Car designers need to know the dynamic properties of materials to design a reliable car structure in case there are major traffic accidents.Under such a background,whole automobile industry is really interested in research on dynamic characteristics of materials used on automobiles.However,common material tensile testing machines are not able to test dynamic characteristics of materials.Thus,it is necessary to design a machine used to test materials' dynamic characteristics.High-speed material tensile machines are used to test dynamic properties of specimens.Taken realities above into consideration,in this paper,a high-speed material tensile testing machine with a electro-hydraulic servo control system based on model predictive control is designed.This tensile machine combines advantages of hydraulic system and electronic system.On one hand,hydraulic system has advantages of high load and relatively high speed,which is widely used in tensile machine systems.On the other hand,electronic system has advantages of high precision and fast response,which could improve control accuracy of pure hydraulic systems.What's more,MPC is used to eliminate delay of response of electro-hydraulic servo valves and improve control accuracy.Python is used to edit a control software,realizing automatic parameter optimization and system control.First of all,analyze the difference between electronic and hydraulic high-speed material testing machines and decide to use a electro-hydraulic servo control system after deliberation.Then,based on design targets,analyze and decide the electro-hydraulic servo system scheme and confirm key points and difficulties in this research.Next,design hydraulic system of the high-speed materail tensile testing machine.Conduct theoretical calculation of system using hydraulic principles and mathematical methods.Design a non-standard clearance cylinder,determine parameters of a hydraulic pump,an electro-hydraulic servo valve and two high-pressure accumulators and confirm safety and effectiveness of the system.Then,discuss a possible compound control method.This method is divided into low-speed part and high-speed part according to target velocity magnitude.In low-speed part,use an optimized PID control and in high-speed part,a open-loop control based on neural network learning is used.This method has a modest control effect and isn't easy to be used in a real system.At last,design and confirm a feasible control method,which is model predictive control method.Model predictive control(MPC)predicts a period of output in the future based on the mathematical model of system,then it could control the output in advance to avoid problems caused by high delay in system.In terms of implementation,Python is used to edit a control software including MPC method,which realizes an effective control of simulation system created in AMESim,with the help of MATALB.Simulation results are very good.Under various conditions,the simulation velocity reaches target velocity and keep constant with a relative error of less than ±3%.