Linguistic hedges on trapezoidal fuzzy sets: a revisit

Trapezoidal fuzzy sets (including triangular ones) are most commonly used in fuzzy modelling for computational simplicity. Applications of conventional linguistic hedges over such sets, however, often fail to result in significant changes of the sets definition. The paper presents an improved version of more effective hedges specifically devised for trapezoidal fuzzy sets, to be applied to dilate or concentrate a given set by expanding or shrinking its constituent parts. It also introduces three new hedges, named UPPER, LOWER and MID. Simulation results are provided to demonstrate the advantages of utilising the revised and newly introduced hedges for assisting fuzzy modelling, in comparison to the use of conventional ones