Plant model analysis based on closed-loop step response data

In this paper, a simple scheme to estimate frequency responses of linear time-invariant single-input single-output (SISO) systems based on closed-loop step response data is investigated. The method uses only a single set of step response data of plants under closed-loop operating conditions. The input and output of a plant are filtered by a simple bandpass filter, and the frequency response of the plant is obtained with the Discrete Fourier Transforms (DFTs) of the filtered input and output signals. The validity of the proposed method is illustrated through simulations and experiments.