PID Auto-Tuning Based On Frequency Response

This paper summarizes a new method for the auto-tuning of PID controllers. Firstly two characteristic points of the open-loop frequency are identified based on relay feedback experiments: the ultimate point and the bandwidth point. Used the identification of bandwidth point ,a first-order-plus-dead-time model can be available .Meanwhile a 4-parameter model can be obtained with the two points . With the model available,the two-degree-of-freedom PID controller is designed based on the IAE specification and a robustness specification . It is a quasi-optimization of both the response to setpoint and the response to load disturbance changes simultaneously. The simulation shows that this method is effective to most of the process models: the resulting PID settings have good performance of disturbance attenuation and robustness ,and the use of setpoint weighting make good improve to setpoint response.