A new method of self-tuning digital PID controllers

Abstract This paper presents a new method of self-tuning digital PID controllers. This method uses a technique of pattern recognition; it supposes a first-order model for the process and uses the quarter decay ratio on the error signal as tuning criterion for the PID parameters. The theoretical foundation of the method is the study of the root-locus for the closed-loop system.The PID parameters are set, according to the characteristics of the process model, so that the root-locus have a prescribed form. As the simulations shows, the method is suitable to a wide class of typical processes, p.e. those which transfer functions can be characterized by a steady-state gain, one time constant and a dead time.