DIGITAL PID PROCESS CONTROL APPARATUS

A digital PID process control apparatus is proposed wherein dynamic characteristics of the process are identified by supplying a persistently exciting signal to a closed-loop control system, and the persistently exciting signal is not supplied to the system after identification is completed, thereby tuning PID control parameters in accordance with the identified pulse transfer function. The control apparatus has a detector for detecting model error of the process in operation, a pulse generator for superposing a pulse signal on a set-point signal to the process when the model error is detected, a calculator for detecting a transient change in the model error when the input signal to the process changes in a pulse form, and a restart circuit for restarting generation of the persistently exciting signal when a change in the model error is detected, and for restarting an identification/tuning function.