JPS57123403A - Process control method - Google Patents

Abstract

PURPOSE:To decrease the integral quality of an overshoot component, etc. when the load has a sudden fluctuation and to shorten the time of adjustment, by selecting the output of a control part by a specific method and in accordance with the differential quantity, etc. of the deviation between the target value and the process variable signal. CONSTITUTION:The arithmetic processes 2-4 of proportion, integration and differentiation are applied to the deviation TER between the target value TUP and the process variable signal TWO. This result of arithmetic is delivered to control a process 7. In this case, the output TC of a control part is fixed at the limiting value TCmax or TCmin at a time point ts when the differential quantity VTD of the arithmetic result exceeds the 1st set value VS1 and when the value TUP has no change. Then the fixture of the output TC of the control part is released at a time point tE when the quantity VTD crosses the 2nd set value VS2, and the control PID is carried out. Furthermore the selection is carried out through a selecting part 8 to avoid the fixture of the output TC in a period during which a certain period of time lapses after the time point tE, the deviation TER is converged to a level within a certain value or the quantity VTD is converged to a level within a certain value.