Closed-loop identification is essentially needed in control of an unstable plant stabilized by a feedback controller. A new direct closed-loop identification approach is proposed based on an output inter-sampling scheme, in which by taking faster sampling of the output than the input of the system the restrictive identifiability condition is removed. In a case of unstable system, since the noise model becomes non-minimum phase system, the prediction error method is not available. In order to solve these problems we clarify that the output inter-sampling yields the SIMO structure of the plant model and give a new identification method in which the denominator polynomial can be identified in an open-loop manner and the numerator polynomial can also be obtained by a modified instrumental variable method. The proposed algorithm is validated in an experimental study using a magnetic suspension system.
CITATION STYLE
SUN, L., MIYAKE, Y., OHMORI, H., & SANO, A. (2000). New Direct Closed-loop Identification Method for Unstable Systems and Its Applications to Magnetic Suspension System. Transactions of the Society of Instrument and Control Engineers, 36(4), 348–355. https://doi.org/10.9746/sicetr1965.36.348
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