Analysis of dynamic control strategies of an FMS under different scenarios

This paper presents a simulation study aimed at evaluating the performances of a flexible manufacturing system (EMS) in terms of makespan, average flow time, average delay time at local buffers and average machine utilization, subject to different control strategies which include routing flexibilities and dispatching rules. The routing strategies under evaluation are 'no alternative routings'; 'alternative routings dynamic'; and 'alternative routings planned'. Above routing strategies are combined with seven dispatching rules, and studied in different production volume which varies from 50 to 500 parts. In addition, impacts of both infinite and finite local buffer capacities arc analyzed. Since an FMS usually deals with a variety of products, effects of changing the part mix ratio are also discussed. Finally, machine failure is also introduced in this research to study the effects of machine reliability on the system. Simulation results indicate that the 'alternative routings planned' strategy outperforms other routing strategies if the local buffer size is infinity. However, there is no particular dispatching rule that performs well in all buffer size settings but infinity buffer size is not the best choice with respect to the four performance measures. In addition, the four performance measures, except machine utilization, under different control strategies seem quite insensitive to the variation in part mix ratios. (C) 2004 Elsevier Ltd. All rights reserved.