Research On Application Of Fuzzy And PID Control In Flow Control Of Variable Speed Hydraulic Power Source

With the continuous development of variable frequency motor speed regulation technology,especially the combination with hydraulic transmission,the birth and development of frequency conversion hydraulic technology has been greatly accelerated.The variable speed hydraulic pump-controlled system combines frequency converter with motor,change the motor speed,and then change the pump input speed,in the case of constant displacement,the output flow of the pump increases or decreases following the rotational speed,so that the rotational speed of the hydraulic motor can be controlled.Although the variable speed hydraulic pump-controlled system has the advantages of simple structure,wide speed range,energy saving and reliability,when the load is fast and changeable,there is strong coupling between flow and pressure,and the flow control will be time-varying and unstable,causing slow dynamic response,nonlinear,and the control precision is low of the system,the conventional PID control can not achieve ideal control effect,so it is necessary to seek better control strategy.Combining the principle of fuzzy control and the characteristics of PID control,this paper designs a fuzzy controller and a fuzzy PID controller,research on simulation and experiment,the application of fuzzy and PID control in flow control of variable speed hydraulic power source is researched in detail.In this paper,the simulation analysis and experimental research on the precise control of flow under different typical working conditions are carried out,the dynamic response characteristics,overshoot,control accuracy,stability and robustness are compared and analyzed.The results show that the fuzzy PID control and the fuzzy control can also achieve the precise control of the flow rate of the variable speed hydraulic power source as well as the PID control.The actual control effect of the improved control strategy is good,and the fuzzy PID control is better than the fuzzy control in the response speed,overshoot,control precision,stability and robustness,and the fuzzy control is better than the simple PID control,and the proposed method is more suitable for on-line control of hydraulic system.The main research work of this paper is as follows:(1)According to the structure and principle of the test-bed,mathematical models of each part and global of hydraulic power system is established,as the theoretical basis of the flow control simulation research of the later system;(2)This paper introduces the evaluation index of control performance,the theory and system of fuzzy control,and designs the fuzzy controller and the fuzzy PID controller according to the research object and the characteristics of the system;(3)On the premise of guaranteeing the stability of flow control of power source,the conventional PID control,fuzzy control and fuzzy PID control of flow of variable speed hydraulic power source are simulated by using MATLAB simulation software,and the simulation results are analyzed and evaluated comprehensively,the results show that the effect of fuzzy PID control is better than that of fuzzy control and conventional PID control under different working conditions;(4)The software and hardware parts of the experimental platform for the variable speed hydraulic pump-controlled system are introduced comprehensively and systematically,Complete the design of each controller module and system control program interface under the Lab VIEW software platform;(5)Experiments on conventional PID,fuzzy control and fuzzy PID control of flow rate of hydraulic power source under typical working conditions were carried out on the above-mentioned variable speed hydraulic test bench,the dynamic response characteristics,control accuracy,overshoot,stability and robustness of the three control methods are analyzed and evaluated,the results show that the three control methods can achieve a certain degree of control accuracy,and the fuzzy PID control combines the advantages of both fuzzy and PID control,and achieves a more ideal control effect.