Identification of transfer function models from the relay feedback test

A MIMO process is considered to be composed of several single-input-multi-o utput (SIMO) processes. In this article, a method for identifying such SIMO process is devised. To identify each SIMO process, a single run of relay f eedback experiment on a particular input is required. For each of such expe riments, models of FOPDT (First-Order-Plus-Dead-Time) or of SOPDT (Second-O rder-Plus-Dead-Time) are identified. Estimation of the parameters is carrie d out one-by-one and does not involve least square minimization. Direct app lication of these SIMO identification to MIMO processes is thus illustrated . The accuracy of each estimated gain can be controlled within one single r un of experiment. A sufficient condition for the experiments to ensure robu stness of the resulting model is presented. Thus, this proposed method can be applied to some MIMO processes even they are ill-conditioned.