An experimental study on the closed-loop system identification by observer/controller identification (OCID) algorithm

Observer/controller identification (OCID) is one of the identification methods for a state-space model of a system in a closed-loop with an existing feedback controller. A mathematical model of an inverted pendulum system, which is a nonlinear and inherently unstable MIMO system, is usually derived by a linearization method, but it usually includes uncertainties which make it useless depending on the situation. In this paper, the experimental results of the closed-loop system identification for a state-space model of an Inverted Pendulum system using OCID in time domain are presented. With the assumption that existing feedback controller dynamics and open-loop system model are unknown, experiments are carried out to obtain a state-space model. As a result, it is shown that a more accurate state-space model of the system is identified from closed-loop data by using OCID, which leads to improve the performance of controller.