Identification of inverse response process with time delay using relay feedback test

Abstract

Inverse Response plus Time Delay (IRPTD) processes are frequently encountered in process industry and are difficult to identify and control. In this paper, a systematic approach for identification of IRPTD process using relay feedback test at the stable oscillation condition is proposed. The model structure is identified using the shape information and the model parameters are estimated by solving the analytical expressions using boundary conditions. A single run of relay feedback test is carried out to estimate all the process parameters without any prior information. Since the identification is done using the information obtained at the stable oscillating condition, the difficulty faced to capture the initial data from the relay test can be alleviated. A procedure to identify the IRPTD process in the presence of measurement noise is also presented. The proposed method uses hysteresis relay feedback test in the presence of measurement noise for estimating the parameters of IRPTD process. The results thus obtained can be used subsequently for autotuning.