JPS6429902A - Pid controller - Google Patents

Abstract

PURPOSE:To eliminate overshoot, by performing no integral arithmetic operation if a prescribed condition is satisfied, and setting a dead band transiently if the prescribed condition is not satisfied, when a preset value is decreased. CONSTITUTION:At a positive direction control arithmetic part 6a or a negative direction control arithmetic part 6b, the arithmetic operations of a proportional, an integral term, and a differential term are executed at arithmetic parts 8a-8c, respectively according to a prescribed PID computing equation, and the arithmetic operation of an output ratio in a positive or a negative direction is performed by multiplying the sum of them by a prescribed gain at a proportional gain arithmetic part 8d via an output judging block 9. A processing selection judging block 10 adds a prescribed dead band DB on the input side of the proportional arithmetic part 8a, and also, controls the integral arithmetic operation of the integral term arithmetic part 8b. In such a way, since the dead band is set based on the prescribed condition or the integral arithmetic operation is limited when the preset value is decreased, negative overshoot can be suppressed.