Characteristic Analysis And Research Of Servo Direct Drive Dual Pump Differential Pressure Control System

The servo direct drive pump-controlled hydraulic system adopts the servo motor to directly drive the quantitative pump as the power source,which has many advantages,such as energy saving,high efficiency,simple structure,high reliability,easy integration and low noise,etc.It is more and more widely used in the industrial field.When the servo direct drive pump-controlled hydraulic system is used for pressure control,it is mainly used in the occasions with large flow,such as electrohydraulic servo loading system,industrial injection molding machine,hydraulic molding machine,precision forging press and variable frequency driven hydraulic elevator,etc.Limited by the minimum speed of the fixed displacement pump,the lowspeed stability of the servo direct drive pump-control hydraulic system with a single fixed displacement pump is poor,which,to a certain extent,limits the range of pressure regulation that can be achieved when the servo direct drive pump-control hydraulic system is used for pressure control.In this paper,the characteristics of servo direct drive dual pump differential pressure control system are analyzed and studied.The composition of the system is analyzed in detail,including the detailed analysis of the hydraulic circuit and the control system;According to the working principle of the system components,the corresponding mathematical models are established;According to the mathematical model of the components,the corresponding component simulation model is established in Matlab / Simulink,and the corresponding system simulation model is established according to the working principle of the system,and the system pressure characteristics are simulated and analyzed in detail by using the system simulation model;The step input response of single pump and the pressure response of closed cavity are studied experimentally.The main research contents are as follows:(1)The composition of servo direct drive dual pump differential pressure control system is analyzed in detail,including two parts of hydraulic circuit and control system.The working principle of these two parts and the function and performance parameters of the components are analyzed in detail.(2)The significance of establishing the mathematical model of system components is analyzed,and the corresponding mathematical model is established according to the working principle of each component of the system.It includes the mathematical model of theoretical output flow and internal leakage flow of external gear pump,the mathematical model of throttle valve,the mathematical model of accumulator,the mathematical model of pilot relief valve,the mathematical model of pressure loss,the mathematical model of servo motor and the pressure formula of sealing cavity.(3)According to the mathematical model of each component,the corresponding component simulation model is built in Matlab/Simulink,and the corresponding system simulation model is built combined with the working principle of the system.According to the system simulation model,a comparative simulation analysis was made on the pulsation of a single pump when the system pressure was stable at different rotating speeds;Through the simulation analysis,the improvement of the accumulator to the pressure pulsation of the single pump system is explored;Aiming at the pressure pulsation of single pump system,a fuzzy controller is designed to dynamically adjust the input speed according to the system pressure error and error change rate.The simulation results show that the method can effectively improve the system pressure pulsation;The pressure response of pilot relief valve under different flow input characteristics is simulated and analyzed;Through simulation analysis,the influence of pressure and speed on internal leakage flow of external gear pump is explored;The pressure response of closed cavity under single pump and double pump differential operation is simulated and analyzed;In order to realize the closed-loop control of the pressure of the closed cavity when the two pumps are differential,a fuzzy controller is designed.The input speed difference is adjusted dynamically according to the system pressure error.The simulation results show that the method can effectively achieve the stability and continuous change of the system pressure value.(4)The controller(PLC)is used to control the operation of the hydraulic test bench,and the sensor data acquisition system is built based on OPC technology Through the experimental study,the response curves of the system flow and pressure under different step speed input are obtained.Through the experimental study,the variation of the system flow rate with the system pressure is obtained.Through the experimental study,the pressure response curves of the closed cavity at different speeds of a single pump are obtained.