Research on a reduced order closed-loop identification algorithms based on AIC for process with time delay

In view of the limitations of traditional closed-loop identification methods, and considering process with time delay, a new closed-loop identification method based on Akaike’s information criterion (AIC) was proposed.it is possible to identify process model using closed-loop data under the reference signal was being excited. Firstly, the time delay term is approximated by first-order Padé and the equivalent closed-loop transfer function of closed-loop system is calculated. Secondly, the high-order discrete model which is determined by proposed method based on AIC can be obtained by the identification of the real closed-loop system. The terminal identification model which is gained from after reduction of the high-order discrete model has the same model structures as the equivalent closed-loop transfer function. Finally, solving methods of process parameters could be deduced by coefficient of same power in the two typical time delay process. Feasibility, universality, high identification accuracy and practicability of the proposed method were verified by a simulation test. It achieves satisfying identification effect in the closed-loop system identification of temperature and liquid level in distillation column reactor.