Decentralized relay-based multivariable process identification in the frequency domain

In this paper, a modified decentralized relay test is designed for multivariable processes, and then, a new method is proposed to identify the frequency response matrix at multiple points based on the test. In the modified decentralized relay test, only very first periods of oscillating inputs are implemented, so that the unsymmetrical two-sided pulse signals are produced automatically. The two-sided pulse waveform contains enough continuous spectrum over the important frequency range so that the frequency response matrix of interest can be obtained by using Fourier analysis without prior knowledge of the processes. Simulation examples are given to show both effectiveness and practicality of the identification method for a wide range of multivariable processes.