Online SOPDT Model Identification Method Using a Relay

Abstract

This paper describes a novel method for the online identification of an analog second-order plus dead time (SOPDT) model. It requires the measurement of four physical quantities, for which a relay is used. Based on these measurements, the parameters of the model or the regulator settings can be directly determined and used to autotune PI/PID controllers. The steps required to take the necessary measurements and the computational algorithms used to determine the model parameters are presented. The results of the simulation studies, including the measurements and calculations of the obtained models, are presented to demonstrate the effectiveness of the proposed method. Comparisons were made between the developed SOPDT model and the critically damped SOPDT model that is often used for high-order inertial plants.

Keywords

• relay feedback
• second-order systems
• identification algorithms
• online autotuning
• delay estimation