A new practical method for closed-loop identification with PI control
一种新的实用PI控制闭环辨识方法

For a closed-loop system with a PI controller, we propose a method to identify the transfer function of the controlled object. From the under-damped-response of the closed-loop system, we approximate the closed-loop system by a second-order-plus-dead-time(SOPDT) transfer function. The transfer function of the PI controller is then removed from the approximate closed-loop transfer function. From the remaining transfer function, the open-loop transfer function of the controlled object is determined through a coefficient-comparison process. Both the simulations and the control experiments on a pilot-equipment show advantages of the proposed method, such as the high identification-accuracy, the low computational complexity and the easy online implementation, thus demonstrating its application potential.