Closed-loop tuning of process control systems

Abstract

A technique for tuning PID controllers, involving a single dynamic test (such as a step or pulse change in set point) implemented during closed-loop operation, is proposed. The resulting transient data are used to predict the frequency response of the open-loop process which in turn is used to compute the optimum controller settings. Simulation results reveal that this technique provides reliable tuning constants even when such practical problems as process noise and unanticipated load upsets arise during implementation. A comparison with the recently proposed tuning alternative (Yuwana and Seborg, A.I.Ch.E. J. 28, 434, 1982; Jutan and Rodriguez, Can. J. Chem. Engng 62, 802, 1984) confirms that in general the suggested procedure, apart from being more flexible, yields also relatively better results.