A fuzzy-PID control strategy for water supply system with variable frequency and constant pressure is proposed,according to characters of system such as nonlinearity,randomicity,large inertia and pure lag.The control strategy combines the advantages of good dynamic response of fuzzy control and high regulation precision of PID control.If the error is small,control output will be determined by PID control algorithm.And if the error is large,control output will be determined by fuzzy control algorithm.The simulation experimental results show that this control strategy can solve the problem of un...