Parameter estimation of integrating and time delay processes using single relay feedback test

Abstract

Autotuning using relay feedback is widely used to identify low order integrating plus dead time (IPDT) systems as the method is simple and is operated in closed-loop without interrupting the production process. Oscillatory responses from the process due to ideal relay input are collected to calculate ultimate properties of the system that in turn are used to model the responses as functions of system model parameters. These theoretical models of relay response are validated. After adjusting the phase shift, input and output responses are used to find land mark points that are used to formulate algorithms for parameter estimation of the process model. The method is even applicable to distorted relay responses due to load disturbance or measurement noise. Closed-loop simulations are carried out using model based control strategy and performances are calculated. Highlights: Relay responses of integrating processes have been mathematically modeled. From relay responses of unknown systems, algorithms are provided to identify/estimate process model parameters. IMC-PID tuning rules for integrating processes with numerator zeros are provided. Real time results are also provided.