Analysis And Control Of Variable Speed And Variable Displacement Pump Controlled Differential Cylinder System

The pump controlled differential cylinder system has the characteristics of high efficiency,simple structure,easy integration,small volume and so on.It is in line with the development trend of energy saving and modularization of hydraulic system and has more and more extensive application.In this thesis,the closed variable speed and variable displacement pump controlled differential cylinder system is taken as the object,and its related problems are analyzed to promote the research and application of pump controlled differential cylinder system.Based on a large number of literature,this thesis introduces the principle,composition and classification of pump controlled differential cylinder system,and summarizes its development and research status at home and abroad.According to the system composition,this thesis mainly studies the flow balance circuit of auxiliary valve,variable speed and variable displacement hydraulic power source,and the control of variable speed and variable displacement pump controlled differential cylinder system.This thesis enumerates several common auxiliary valve flow balance circuits of pump controlled differential cylinder system,and analyzes the basic principles and performance characteristics of flow balance circuit of hydraulic control check valve and hydraulic control directional valve under the working condition of hydraulic excavator stick hydraulic cylinder,summarizes the causes of oscillation in the circuit and the improvement methods,and verifies the effectiveness of the proposed improvement methods.The hydraulic power source with permanent magnet synchronous motor and axial variable displacement piston pump is controlled and analyzed,including the principle,mathematical model,control and Simulation of servo motor speed control system and servo variable displacement control system.The parameters of the controller are optimized by genetic algorithm,and good control effect is achieved.The characteristics of variable speed and variable displacement hydraulic power source are analyzed.The analysis lays the foundation for its application in the pump controlled differential cylinder system.Aiming at the control problem of variable speed and variable displacement pump controlled differential cylinder system,by describing the principle and composition of the control system and establishing the mathematical model of the system,it is analyzed that the control system has the characteristics of multiplicative nonlinearity.A distributed decoupling controller based on BP neural network is designed to control the position of the system.The system is co-simulated in Simulink and AMESim.The simulation verifies the effectiveness of the proposed position control method,and compares with the result of two kinds of position control methods of fixed speed and variable displacement pump control system.For the situation that both velocity and position are required,the given parabolic velocity curve is used as the input of the speed of the differential cylinder of the servo motor open-loop control,and the integral of the given velocity curve is used as the closed-loop differential cylinder of the variable displacement device.The simulation results show that the control method can maintain good velocity and position composite control effect and position accuracy for different speeds and loads.