A new type reduction method for type-2 fuzzy logic controller

In interval type-2 fuzzy logic systems (IT2-FLSs), the inference engine outputs are type-2 fuzzy sets, and type reduction (TR) is needed to convert them into a type reduced set. Recently, researchers have proposed many efficient TR algorithms to find the boundary of the type reduced set, but they don´t have an effective scheme to obtain the defuzzified crisp output. In this paper, we propose an optimal TR method, which searches the optimal point from the type reduced set as a defuzzified output. In order to demonstrate the effectiveness and superiority of the proposed method, simulations and comparisons are given. Simulation results show that the designed interval type-2 fuzzy logic controller (IT2-FLC) can smoothly achieve backing up control of the mobile robot from all initial positions.