This paper presents a closed-loop Laguerre-based subspace identification method for continuous-time systems via orthogonal projection approach. A bank of Laguerre filters operating in the all-pass domain, which is capable of handling the non-equidistant data, is used to get the input–output matrix equation of the systems. We put the emphasis on the parity space opposed to the observable subspace. The instrumental variable method and principal component analysis estimate the system consistently, solving the issue of biased estimate for the closed-loop operation of the system caused by the feedback controller. The simulation results demonstrate the effectiveness of the proposed approach.
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