A robust fuzzy PI controller for a flexible-joint robot arm with uncertainties

The improved fuzzy controller designed is based on an existing fuzzy PI controller, which can control an uncertain flexible-joint robot arm to produce satisfactory tracking results. The improved fuzzy PI controller not only can control (stable and unstable) conventional linear systems, performing as well as the conventional PI controller, but also is capable of controlling many nonlinear systems such as the flexible-joint robot arm under investigation which contains uncertainties within ten percent tolerance of all the nominal system-parameter values. In this improved fuzzy PI controller, we used only three simple membership functions plus six simple fuzzy logic control rules. In this paper, we briefly describe the design principle of this improved fuzzy PI controller and its tracking performance in handling the nonlinearity, flexibilities and uncertainties of the flexible-joint robot arm system