MODELING FOR FLEXIBLE MANUFACTURING SYSTEMS AND STRUCTURAL-PROPERTIESOF OPTIMAL WORK ROUTING POLICY

We consider flexible manufacturing systems (FMSs) which are composed o f a set of workstations linked together with a material handling syste m (MHS). Each workstation consists of an input buffer, a single machin e and an output buffer. The MHS consisting of a single cart routes wor k among the workstations according to the process paths required by th e work. We deal with an optimal control problem in this FMS. We model the FMS as a closed queueing network. In the model, the cart routes th e work to the workstations in accordance with a Markov routing with ex ponentially distributed routing time, and the machines process work wi th exponentially distributed processing time. An objective is to rnd a work routing policy that maximizes the total expected reward earned b y operating machines. This optimal control problem is formulated as an undiscounted semi-Markov decision process. Structural properties of a n optimal policy are analysed. Moreover, a sufficient condition is der ived for the optimal policy to be of control limit type. An example is given to illustrate the result.