An approach to automatic tuning of a fuzzy controller for manipulators

This paper presents an approach to automatic tuning of fuzzy logic controller for manipulators, which modifies the shape of membership functions automatically according to previous responses to achieve a desired control performance. On the basis of defining a set of cubic splines as membership functions regarding change-in-error e˙_j (t), the optimum membership functions are found by the Nelder and Mead´s simplex algorithm. The proposed control scheme consists of a traditional fuzzy logic controller and a conventional derivative controller. In order to demonstrate the effectiveness and the robustness of the control scheme, we report a number of simulation results involving both step and tracking control of a two-link manipulator in the presence of load and friction changes