Sundaresan-Krishnaswamy Technique for Estimation of Process Parameters

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Consider a first-order plus delay model defined by the transfer function , where , , and are the gain, time constant, and time delay, respectively. In order to find and , Sundaresan and Krishnaswamy [1, 2] use the normalized response of the model to a step-forcing function: at two different times, and . These times are selected such that the normalized response reaches 35.3% at and 85.3% at . The recipe gives the estimated values of the time constant and delay time by and .


The Demonstration plots the normalized response for user-set values of and . Perfect agreement is observed between the estimated values and and actual values ( and ).


Contributed by: Housam Binous, Mohammad Mozahar Hossain, and Ahmed Bellagi (November 2015)
Open content licensed under CC BY-NC-SA




[1] K. R. Sundaresan and P. R. Krishnaswamy, "Estimation of Time Delay Time Constant Parameters in Time, Frequency, and Laplace Domains," The Canadian Journal of Chemical Engineering, 56(2), 1978 pp. 257–262. doi:10.1002/cjce.5450560215.

[2] D. E. Seborg, T. F. Edgar, D. A. Mellichamp, and F. J. Doyle III, Process Dynamics and Control, 3rd ed., New York: Wiley, 2011.

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