Closed-Form Mathematical Representations of Interval Type-2 Fuzzy Logic Systems

Interval type-2 fuzzy logic systems (IT2 FLSs) have a wide range of applications due to their abilities to handle uncertainties compared to their type-1 counterparts. This paper discusses the representation of IT2 FLSs in closed mathematical form. Two novel inference mechanisms are introduced, each of them represents a whole IT2 FLS. The two forms are based on approximating Coupland and John's geometric method and the Nie-Tan method. Having closed-form representations is preferred in the design of control systems, especially when stability analysis is studied. Additionally, the simplicity of the proposed mechanisms, offers an easy way for implementation. Simulation results show that the proposed method perform very closely to other methods. Simulation results are provided.