Research On High Performance Force Control Strategy Of Direct Drive Volume Control Electro-hydraulic Servo System

Direct Drive Volume Control(DDVC,Direct Drive Volume Control)electro-hydraulic servo system is a highly integrated and compact closed pump control drive unit,which is composed of servo motors,quantitative pumps,servo hydraulic cylinders,etc.,and is compatible with traditional valves.Compared with the control system,it has the technical advantages of high power-to-weight ratio,high integration,environmental friendliness,high efficiency and energy saving.However,as industrial equipment has higher and higher requirements for motion output accuracy,it is very important to study the pressure pulsation caused by low-speed instability in the pressure control of the DDVC electro-hydraulic servo system.Pressure and flow nonlinearity,hydraulic cylinder friction nonlinearity and many other nonlinear characteristics have more and more obvious influences on the control performance of DDVC system,and gradually become a bottleneck restricting its performance improvement.Therefore,the in-depth study of the low-speed characteristics and nonlinear control strategies of the DDVC electro-hydraulic servo system in the pressure control process has high academic significance and wide application value.This paper will study the high-performance force control strategy of DDVC electro-hydraulic servo system through the combination of "hardware" and "software".First,according to the basic composition and working principle of the DDVC electro-hydraulic servo system,the mathematical model of the system is established.Based on the mathematical model,MATLAB/Simulink is used for simulation modeling to build a complete DDVC electro-hydraulic servo system simulation model,to study the action law of the servo motor and pump control system,and to lay a theoretical foundation for the research of high-performance force control strategies.Secondly,in view of the low-speed instability problem in the pressure control system,considering both the speed pulsation of the servo motor and the output pulsation of the axial piston pump,a parameter optimization method based on and ζ is proposed to eliminate the pulsation of the accumulator.The accumulator absorbs pressure pulsation,optimizes its parameters,and solves the pressure pulsation problem caused by low-speed instability in the pressure control system.Take this as the "hardware" part of the high-performance force control strategy;aiming at the non-linear factors such as flow non-linearity and friction non-linearity in the system,a model-based feedback linearization control strategy is proposed to solve the non-linear control problem in the pressure control system.Use this as the "software" part of a high-performance force control strategy.Finally,the simulation model and experiment platform of the DDVC electro-hydraulic servo pressure control system are built and related simulation and experimental research are carried out.The results show that the high-performance force control strategy that combines "hardware" and "software" proposed in this paper is compared with traditional PID Control can significantly improve the accuracy of pressure output,and it also has good dynamic and static characteristics under low-speed conditions.