SCHEDULING FLEXIBLE FLOW SHOPS WITH NO SETUP EFFECTS

This paper presents an efficient, optimization model-based approach for scheduling the production of discrete-part, make-to-order type of flexible flow shops, where setup effects are negligible. A nominal scheduling algorithm based on Lagrangian relaxation and minimum cost linear network flow is first developed for scheduling under nominal conditions. Fast rescheduling algorithms that exploit the economic interpretation of the Lagrange multipliers and the network structure of production flows are then proposed for timely adjusting the nominal schedule to cope with disturbances. Numerical results on realistic examples demonstrate that our methodology is quite effective; it generates near-optimal schedules, provides relatively smooth adjustment (i.e., no drastic change from the nominal schedule) for small disturbances, and is computationally efficient.