Research On Predictive Control Method Of Dual Valve Parallel Electro-hydraulic Servo System

With the continuous deepening of the application of electro-hydraulic servo technology,the industry has put forward higher requirements on the instantaneous flow rate,control accuracy,and dynamic response performance of electro-hydraulic servo systems.In order to improve the overall performance of electro-hydraulic servo system,the traditional solutions mostly choose high-performance electro-hydraulic servo valves with higher frequency and higher frequency.However,the large-flow electro-hydraulic servo valve not only has poor low-speed characteristics and high price,moreover,the control accuracy and dynamic response performance gradually decrease with the increase of the rated flow of servo valve.To solve these problems,in this paper,a method of parallel connection between large flow proportional valve and small flow servo valve is put forward,and the optimal configuration and control method of double valves paralleling of paralleled valves electro-hydraulic servo system is studied.The main work of this paper is as follows:(1)According to the valve-controlled cylinder modeling theory,the state-space expression of the proportional valve and the servo valve is established in a linear superposition method.The parameters of the main components of the system are calculated according to the actual use and simulation requirements,and finally the unit step response simulation of the system is carried out by using the established model and the calculated parameters.The results showed that compared with single valve control,the increase time of the double valve parallel control is reduced by 80% and the overshoot is reduced by 18.8%,which can effectively compensate the effect of the dead zone of the proportional valve on the tracking precision.(2)In view of the optimal configuration and control method of double valves paralleled,a multivariable dynamic matrix control algorithm is proposed.A compound control algorithm with PID control as inner loop control and a multivariable dynamic matrix control as outer loop control is studied and designed.The algorithm is derived in detail,and the physical characteristics of the valve and servo valve are considered.The adjustment direction of the main parameters of the algorithm is also defined.(3)In order to better simulate the dead zone and other nonlinear factors existing in the double valve parallel electro-hydraulic servo system,using CO simulation method,a system co-simulation model is established under the environment of AMESim and Matlab.The slope signal and the sinusoidal signal is simulated.The tracking accuracy of the double valve PIDMPC control slope signal is 78.6% higher than that of the single valve PID control,and the tracking accuracy of the sinusoidal signal is increased by 70%.(4)A dual valve parallel electro-hydraulic servo testing machine control system is set up.Combined programming with VB.Net and Matlab,the control software of dual valve parallel electro-hydraulic system testing machine is developed.The experiment of slope and sine curve tracking is carried out.The slope tracking accuracy controlled by PID-MPC is improved by 66.4% and 59.1% of the sinusoidal tracking precision compared with the dual valve PID control,and the effectiveness of the PID-MPC complex control algorithm is verified.