Research On The Control Strategy Of The Parallel Driven Electro-hydraulic Servo System Of Pump-valve Circuits

Hydraulic control technology is widely used in hydraulic ship lifts,multi-degree-of-freedom test platforms and other heavy-duty long-stroke single-rod hydraulic cylinder control systems.These control systems not only require high control performance,but also have great energy-saving significance.However,the current pump control loop has low energy consumption and high working efficiency,but its dynamic characteristics are poor;although the traditional valve control loop has high control accuracy,its energy utilization rate is low.Therefore,the research group combined the high performance of the pump control circuit and the high performance of the valve control circuit,and proposed a control circuit for asymmetric hydraulic cylinders driven by pump valves in parallel.In a pump-valve parallel drive asymmetric cylinder system,the two circuits of the pump-valve not only coordinate with each other,but also influence each other,forming a complex system.This paper presents the control scheme of the system,and studies the coordinated control strategy of pumps and valves,the smooth switching of pumps and valves in parallel with double loops,and the loop control algorithm.Aiming at the coordinated work of valve control and pump control loops,a coordinated control strategy is studied.The strategy is based on the principle that the pump control loop works during dynamic operation and the valve control loop works during steady state operation;the displacement error and speed of the hydraulic rod are taken as Condition,judge the switching of the pump valve circuit.The purpose is to realize the high-efficiency and high-performance operation of the system,and the effectiveness of the designed coordinated control strategy is verified through simulation.Aiming at the impact of pump control loop and valve control loop in the switching process,a fuzzy switching controller based on fuzzy inference is adopted.The controller takes the displacement error and speed of the hydraulic rod as input and the switching coefficient as output,and smoothly switches the pump-valve parallel circuit according to the switching coefficient.Simulation research shows that the fuzzy switching controller can reduce the impact on the system when the two loops are switched,and at the same time can improve the performance and efficiency of the system.Aiming at the system's characteristics such as nonlinearity,model parameter uncertainty,and the asymmetry of the bidirectional operation of the single rod cylinder,this paper adopts a model reference adaptive controller.Through the joint analysis of AMESim-MATLAB,the linear models of the pump-controlled cylinder subsystem and the valve-controlled cylinder subsystem were obtained,and the validity of the model was verified.On this basis,a suitable reference model was selected.With the displacement,velocity and acceleration of the hydraulic rod as state variables,the control law of the controller is designed according to the reference model,the linear model of the system and the Lyapunov stability principle.Compared with the PID controller,this controller improves the dynamic performance of the pump valve parallel drive asymmetric cylinder system.