ONLINE PROCESS IDENTIFICATION AND AUTOMATIC TUNING METHOD FOR PID CONTROLLERS

We propose a new and simple on-line process identification method for the automatic tuning of the PID controller. A least-squares method is used to obtain the model from measured process outputs and inputs with out any structural information. Thus, any kind of test signal generato rs such as a relay, a P controller, the controller itself, pulse and s tep signal generators, etc can be utilized only if they contain suffic ient information because it requires only the measured process output and the controller output. General time-invariant linear systems inclu ding open-loop stable, nonminimum phase, unstable and integrating proc esses can be identified effectively by the proposed identification met hod. We then use a model reduction method to tune the PID controller u sing usual tuning rules based on the first- or second-order plus time- delay model. (C) 1998 Elsevier Science Ltd. All rights reserved.