Intelligent Control Strategy Based On Constant Pressure Water Supply System With Frequency Conversion

With the rapid development of economy and society, at the same time, the demands forquality and reliability of water supply system are increased continually. So it is inevitabletendency to design one kind of water supply system which is high reliable and saves onenergy well, with the help of advanced technique of automation and control.In order to ensure the quality of urban water supply, the water supply with frequencyconversion and constant pressure is often used. A PID-fuzzy hybrid control strategy, aadaptive PID control based on expert rules and a PID-fuzzy control strategy with Smithpredictor are proposed for the constant pressure water supply system, which has the charactersof nonlinearity, randomicity, large inertia and big delay. This control strategy combines theadvantages of good dynamic response and robustness of fuzzy control and expert control,high regulation accuracy of PID control and pure lag compensation of Smith predictor.If the traditional PID control method is only used, the static and dynamic outputcapability is not very satisfying. The fuzzy control as a branch of intelligence control fieldcould be good at controlling those complicated, nonlinear systems with the characteristic ofthe parameter drift, the inaccurate model and time delay. Fuzzy control makes the systemsmore stable and more robust. This paper mainly studys PID fuzzy control which combine thePID controller with the fuzzy controller to a new type of controller, and design the PID fuzzycontroller. Simulation results have shown that fuzzy control has very good control effect androbustness because it has the sensitivity and flexibility of fuzzy control and high precision ofPID control.Combined expert control with conventional PID, an adaptive PID control strategy basedon expert rules is proposed for the constant pressure water supply system. This kind of controlstrategy based on the practice from expert rules determines the PID controller structure andparameters, and builds the adaptive PID Controller of The Water Supply System withFrequency Conversion and Constant Pressure based on Expert Rules. The simulation resultsshow that this control strategy has evidently improved the speedability of dynamic process,and has well adaptability to variational model parameter in control object on the basis ofretaining good system stationarity of dynamic process and steady state performance, not onlycan well solve the hydraulic pressure unstable problem because of its nonlinearity,randomicity and large inertia in the constant pressure water supply system, but also has broadapplication prospect in the city secondary water supply system.Fuzzy controller is able to overcome the adverse effects of model mismatch, but the control effect is decreased when the delay system model error increases, so a PID-fuzzycontrol strategy with Smith predictor is proposed for the constant pressure water supplysystem. The precision of object model required by control system can be reduced, and systemhas better robust and control performance. Aiming at some kinds of typical control arithmeticand making use of MATLAB, it analyzes and contrasts the influence of various arithmeticthat caused by the change of system parameters. Simulation results show that the proposedmethod has better control performance and reveal good application potential for the largetime-delay processes.