A Saturation-Based Tuning Method for Fuzzy PID Controller

In this paper, a saturation-based tuning method for fuzzy proportional-integral-derivative (PID) controller is proposed. The key feature is that this tuning method adopts an inherent saturation property resulting from finite rules in practical application. Based on the saturation, fuzzy PID controller can be expressed as a sliding-mode controller that has two nonlinear terms: One plays as an equivalent control, and the other acts as a switching control. A nominal tuning is first presented to design a stable equivalent control using gain margin and phase margin. Then, a robust tuning is presented to design the switching control by using maximum sensitivity function or compensation sensitivity function. The maximum bound of uncertainty is given by the robust analysis. Finally, this proposed tuning method is used to control a clamp rotation of a forging manipulator. The simulations and real-time experiments demonstrate the effectiveness of the proposed tuning method.