Comparison of PI Controller Tuning Methods

The development of model-based methods for tuning proportional-integral (PI) and proportional-integral-derivative (PID) controllers is a topic of renewed research interest. A number of techniques have appeared in the last five years aimed at improving upon the standard "(gamma)-tuning" or direct synthesis (DS) approaches. This paper compares the Skogestad internal model control (SIMC), direct synthesis for disturbance rejection (DS-d), and Wang-Shao (WS) tuning algorithms with the IMC improved PI technique as implemented on first-order-plus-deadtime systems. The main objective was to assess the relative control effort and robustness of these proportional-integral controllers when tuned for the same level of performance. Recommendations were provided for selecting the most appropriate tuning method for a given application based upon the primary function of the feedback loop (servo versus regulatory, etc.) and the plant deadtime-totime constant ratio.