Identification of non-minimum phase processes with time delay in the presence of measurement noise

Time domain based generalized analytical expressions are derived to estimate the exact model parameters of a class of stable non-minimum phase (NMP) processes with time delay. The novelty of the proposed method lies in generalizing a second order plus time delay (SOPDT) NMP process model in terms of a class of models like first order plus time delay (FOPDT), SOPDT underdamped, critically damped and integrating processes. The mathematical expressions are employed to estimate four accurate parameters at a time. Relay with hysteresis reduces the effect of noise and further mitigation of noise is achieved through a denoising block yielding a clean process output. Processes modeled in the form of transfer functions are considered to validate the technique. (C) 2015 ISA. Published by Elsevier Ltd. All rights reserved.