Efficient computation of coordinating controls in hierarchical structures for failure-prone multicell flexible assembly systems

Production allocation in multicell manufacturing systems is considered. A model is developed for a hierarchical control scheme, where each cell consists of several failure-prone machines for which the time scale of the machine state transitions is comparable to the processing times. The production objective is to track a nonstationary demand as closely as possible when the demand is near or exceeds the capacity of the system. A series of approximations is proposed to obtain a model that is realistic while admitting a tractable solution. To solve the resulting stochastic control problem, a general result is derived on the second-order finite-time (transient) statistics of a continuous-time Markov chain. Simulation results are presented to illustrate the proposed model and control methodology. These results are compared with a myopic linear programming approach