Closed-loop identification method for integrating process with delay

For an integral process, disturbances during the identification test of open-loop identification will lead to some uncertain effect. In order to overcome such a problem, a closed-loop frequency domain identification method was presented, which is consisted of two parts. 1. Two-channel Relay Feedback Test (TRFT) can be used to extract the multi-point frequency characteristics of integral process in the closed loop and avoid the uncertainty resulted from the open-loop identification test. 2. A frequency-domain identification algorithm is developed to estimate the time-delay transfer function model of integral process. The simulation shows the effectiveness and verifies the presented method. This method can be combined with the controller design strategies of integral process and improve the control quality.