Research On Variable Velocity System Using Variable Frequency Based On PLC And FPC

The water supply system of frequency control of constant voltage changes contains position machine,PLC,frequency converter and pressure transmitter etc. This system is formed by 3 pump generators.With general frequency converter realize for three-phase pump generator soft start with frequency control,operation switch adopts the principle of "start first,stop first".The detection signal of pressure sensor of hydraulic pressure,via PLC with set value by carry out PID comparison operation,so control frequency and the export voltage of frequency converter,and then the rotational speed that changes pump generator come to change water supply quantity,eventually,it is nearby to maintain pipe net pressure to stabilize when set value.Fuzzy control is an apery technology which is independent of mathematic model. It uses experts' experience and knowledge to build the fuzzy rules.Traditional fuzzy control is a post pose adjust technology which is similar to PID.The control effect for large delay object is not ideal.Predictive control focuses on the future target as well as past and current target.Predictive control and fuzzy control are two independent control methods.The combination of the two methods is proposed to form a new control method,that is,fuzzy predictive control.Fuzzy Predictive Control theory is applied to the water supply system in this paper.The design of Fuzzy-PID controller of adjusting the factor of revising by oneself is introduced,which can solve the problem existing in the parameter adjustment in the courses of the traditional PID control.The water supply with constant pressure is obtained by speed-frequency variable,and the smith predictor is used to compensate time lag of automation system.We also simulate the system with Matlab,the simulation result shows that compared with the conventional control methods,the proposed one is more robust and simpler for tuning online.By researching the communication agreement between the computer and PLC, this paper has finished setting up the communication between upper and lower computer,and also has described the method to compile computer monitoring program to realize the long-range monitoring and fault reporting for water supply system through communication modular.The system overcomes weakness of traditional regulator,it has advantages (?)ble,programming convenient,adaptable,increases the accuracy of the system.The results show the system has good performance and applicable value.