Relay based identification of process dynamics under noisy environment

Using an asymmetrical relay based approach, a set of generalized expressions for the identification of integrating first order plus dead time (IFOPDT) and second order plus dead time (ISOPDT) processes are derived. From derived expressions, calculation for unknown process model parameters with small and large dead time is performed. When the process output is subjected to measurement noise, a well known method is attempted in order to extract the important information from the limit cycle output. Examples are illustrated to show the effectiveness of method which successfully recovers the limit cycle under noisy environment. Subsequently, from denoised limit cycle, identified parameters are used for estimation of process model dynamics. Finally, a comparison between identified and actual process is demonstrated through simulation by Nyquist plot.