Uncertainty degree and modeling of interval type-2 fuzzy sets: Definition, method and application

Constructing the interval type-2 fuzzy sets (IT2 FSs) models is the essential step to realize computing with words (CWW) using IT2 FSs. This paper presents a novel strategy for the modeling of symmetric IT2 FSs using their uncertainty degrees. First, we provide the definition of uncertainty degree and the properties which show the reasonability of this uncertainty measure. Also, we derive the closed-form equations of the uncertainty degrees for the most widely-used symmetric Gaussian and trapezoidal IT2 FSs. Then, based on this uncertainty measure, we present one method to construct IT2 FS models using the uncertain interval end-points data. Finally, we apply the proposed IT2 FS modeling method to a real-world application—the thermal comfort modeling problem. This application demonstrated the usefulness of the proposed method on modeling words using IT2 FSs.