Fuzzy Simulation in Uncertain Circumstances

This article proposes composition of fuzzy sets theory with discrete-event simulation and puts it into application in order to model uncertain activity duration in simulating a real-world system. The purpose of this paper is to assess the usefulness of fuzzy simulation for modeling uncertain activity duration، especially when insufficient or no sample data is available. In this research، fuzzy numbers are used to describe uncertain activity durations which is reflecting vagueness، imprecision and subjectivity in the estimation of them. Initially، a simulation model is designed on the basis of classic (probability distribution-based) approach and then by using activity durations estimated by experts، this model is changed to a fuzzy one. Based on a number of common probability distributions، Some simulation models are designed and their results are compared with those of fuzzy simulation model. The results indicates that، firstly، fuzzy simulation outputs are achieved through only one cycle of fuzzy discrete-event simulation and secondly، the range of fuzzy simulation outputs entails the results of multiple cycles of probability distribution-based simulation experiments. Therefore، the fuzzy simulation is an acceptable approach to present the real system; especially in uncertain circumstances that no sample data is available or there is some insufficient or unreliable data.