In order to realize closed loop automatic control during whole process of the coal mill

on the basis of the least squares method

the coal mill operation data were fitted and the dynamic model of the coal mill start-up and normal operation was established.Moreover

according to this model

this paper proposes a compound control strategy that combing the fuzzy control with fuzzy PI control.In startup phase

the cold and hot air damper is controlled by the fuzzy controller.In normal operation stage

the outlet air temperature is controlled by the fuzzy PI controller while the inlet air flow is still controlled by the conventional PI controller.The simulation results show that

after this control strategy is adopted

the air volume of the coal mill during start-up process reaches stable and the mill outlet temperature rises according to the predetermined heating rate.During normal operation of the coal mill and under disturbance conditions for coal

dynamic deviations of both the air flow and mill outlet temperature are smaller than that under the conventional PI control.Therefore

this compound control strategy has good control effect.