Experiment Study On Control Performance Of Variable Speed Hydraulic System Based On Zero Phase Filter

Hydraulic equipment is widely used in space navigation,ocean development,engineering machinery and many other fields because of its advantages of stable transmission,large capacity,convenient speed adjustment and strong adaptability to complex working conditions.Due to the low energy utilization of hydraulic transmission,the efficiency of the machine is low too.With the development of the variable frequency speed regulation technology,variable speed hydraulic system with remarkable energy saving effect has been widely used in many engineering practices.However,the high efficiency and energy saving brought by variable speed hydraulic system,the problem of low control precision,slow response speed and low speed stability also limits its application in more industrial fields.Therefore,the study of how to improve the control performance of hydraulic system has important practical significance.From the point of view of practical engineering application,the conventional PID feedback control is widely used in industrial process control,aerospace control and other fields due to the advantages of mature algorithm,good stability and easy implementation.In the actual measurement and control system,because of the environment and other external interference,the measurement signal will always be mixed with a variety of interference components,such as electromagnetic interference,high-frequency noise,which affects the control performance of the system.In view of this problem,this article uses the method of theoretical analysis,simulation analysis and experimental verification,based on the measurement and control platform of the hydraulic system of the variable speed pump-control motor,a new method of filtering the feedback signal and filtering the signal into the feedback input of the PID controller is put forward,which can be used to improve the control performance of the system.The main research contents of the thesis are as follows:(1)According to the design principle and method of digital filter,taking Butterworth Lowpass digital filter and zero phase digital filter as example,the design and realization of the two are accomplished by programming in MATLAB,and the filtering characteristics are obtained by simple filtering simulation,The simulation results show that the Butterworth Low-pass digital filter is a non-zero phase distortion digital filtering,which can filter out the high frequency interference component,but has phase lag,while the zero phase digital filter can realize zero phase distortion digital filtering.(2)With variable speed pump-controlled motor hydraulic system physical model,the mathematical model of each subsystem is established,and the global mathematical model is deduced,and then the system simulation model is built on the basis of Simulink.Through the simulation experiment of flow closed loop control,the dynamic response,control precision and robustness of the system flow are compared and analyzed in three cases,such as the filter processing of flow feedback signal,non-zero phase distortion digital filtering processing and zero phase distortion digital filtering processing.The simulation results show that: the feedback signal zero phase distortion digital filtering has better control precision and robustness.(3)Based on the experimental basis of variable speed pump-control motor hydraulic system,a closed-loop control feedback signal filtering experiment program and contrast experiment are designed.By using LabVIEW and MATLAB,the design of the feedback signal zero phase distortion digital filtering program is completed.The contrast experiments of pressure,flow closed loop control feedback signal don't filter,non-zero phase distortion digital filtering and zero phase distortion digital filtering were designed,and the result shows that,although the filtering process can achieve steady state,there is a great fluctuation,and the feedback signal is not zero phase distortion digital filtering processing has steady state error and low control precision.The feedback signal zero phase distortion digital filtering can not only achieve steady state,but also has a little fluctuation,and has better control precision and robustness.