PURPOSE: To effectively control a system which increases in overshoot since its process delay time and dead time are long.
CONSTITUTION: A fuzzy arithmetic part 21 once inputting a set value SV and a process value PV of the controlled system finds their deviation and the quantity of variation in the deviation and also calculates the speed type manipulated variable of PI type control by fuzzy inference while referring to variation in PV, and outputs it to a manipulated variable conversion part 22. The manipulated variable conversion part 22 converts the manipulated variable into a position type. Further, a differential operation part 23 similarly finds the deviation and the quantity of variation in the deviation from the SV and PV and calculates a D manipulated variable by position type differential operation while referring to even variation in the PV. The calculated PI manipulated variable and D manipulated variable are added and the sum is sent to a process. Further, the quantity of variation in the process value is also used for control. Thus, the manipulated variables are determined on the basis of variation in process variation to improve the control characteristics.
ITO MASAMITSU
KAWAURA MASATO
FUJI ELECTRIC CO LTD