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The paper presents a review of a comparative study of two separate techniques for obtaining important frequency and time domain characteristics of a system consisting of a process in series with a PI/PID controller in closed loop. The first technique involves the use of a Pseudo Random Binary Sequence (PRBS) to obtain the closed loop frequency response of the system. This closed loop frequency information may then be manipulated to obtain both open loop frequency response information and process model parameters. A further mathematical simulation using Matlab may then be performed independent of the actual process in order to obtain important time domain characteristics of the system such as rise time, settling time and overshoot. The second technique is a relay-based method described in , which may be used to obtain the open loop frequency response of the system. In this case, it is the open loop frequency response information that is manipulated in order to obtain closed loop frequency response information and process model parameters.
O'Connor, Niall and O'Dwyer, Aidan : Comparative study of two techniques for determining critical frequency response characteristics. Proceedings of the 4th Wismarer Automatisierungssymposium, Wismar, Germany, September 22-23, 2005.