Praktyczne aspekty metody strojenia algorytmów PID i PID-podobnych opartej na eksperymencie przekaźnikowym

W artykule omówiono praktyczne modyfikacje metody strojenia regulatorów PID, opartej na metodzie przekaźnikowej, wynikające z syntezy algorytmu w sterowniku PLC oraz przeprowadzonych eksperymentów w rzeczywistym układzie stabilizacji czynnika redox. Zaletą metody przekaźnikowej, z uwagi na jej prostotę, jest zdolność układu sterującego do dostrajania parametrów nastawnych algorytmu sterującego w trybie on-line, np. przy zmianie wartości zadanej.

A fundamental problem of the control systems dedicated to continuous processes is an optimal tuning in a sense of the specific quality criterion. From a practical point of view a perfect solution in that case would be an opportunity of tuning with a help of the „one push button” application, which releases operators from necessity of manual or semi-manual tuning. In this paper practical modifications of the relay tuning method, dedicated to PID and PID-like algorithms, are described. The most important reasons for using it in a practice are: simplicity of calculations and opportunity of applying without stopping a process. The idea of using an On-Off algorithm in a tuning process is not new, but still there are some practical problems (determination of amplitudes of control signals in ON and OFF states, calculation of the controlled signal amplitude, which generally is disturbed and finally switching a control signal from On-Off state to the continuous control, based on the PID control algorithm) in case of applying it in a real time control system. At the beginning, some additional reasons for using the relay method as a tuning method are described. In the next part a conception of the tuning procedure (Fig. 1) is given. Next, a methodology of applying an On-Off algorithm (Figs. 2, 3) and remarks related to modifications of the original procedure (dynamic determination of On and Off amplitudes in the On-Off control algorithm (Fig. 4), etc.), are presented. In the final part of this paper selected results of the experimental research (Figs. 6, 7), related to the redox stabilization system (Fig. 5), according to the presented procedure are given and described.