Fuzzy flexible flow shops at two machine centers for continuous fuzzy domains

Flexible flow shops can be thought of as generalizations of simple flow sho ps. In the past, the processing time for each job was usually assumed to be known exactly, but in many real-world applications, processing times may v ary dynamically due to human factors or operating faults. In T.P. Hong, W.C . Chen [Journal of Advanced Computing Intelligence 2 (4) (1998) 142-149], w e have demonstrated how discrete fuzzy concepts could easily be used in the Sriskandarajah and Sethi's algorithm for managing uncertain flexible-flow- shop scheduling. In this paper, we generalize it to continuous fuzzy domain s. We use triangular membership functions for flexible flow shops with two machine centers to examine processing-time uncertainties and to make schedu ling more suitable for real applications. We first use triangular fuzzy LPT algorithm to allocate jobs, and then use triangular fuzzy Johnson algorith m to deal with sequencing the tasks. The proposed method thus provides a mo re flexible way of scheduling jobs than conventional scheduling methods. (C ) 2000 Elsevier Science Inc. All rights reserved.