A novel principle for relay-based autotuning

Abstract

This paper presents a new simple principle for aperiodic tuning of SISO controllers used in autotuning schemes. Autotuners represent a combination of relay feedback identification and some control design method. In this contribution, models with up to three parameters are estimated by means of a single asymmetrical relay experiment. Then a stable low order transfer function is identified. Subsequently, the controller is analytically derived from general solutions of Diophantine equations in the ring of proper and stable rational functions RPS. This approach enables to define a scalar positive parameter through a pole-placement root of the characteristic closed loop equation. A first order identification yields a PI-like controllers while a second order identification generates PID ones. The analytical simple rule is derived for aperiodic control response and the scalar tuning parameter m>0 is then tuned according to identified time constant of an approximated transfer function.