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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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This presentation describes a two-phase heuristic method for scheduling and dispatching production in a factory. In the first phase, the production flow is modeled as a multiclass fluid network. This fluid queueing model is a relaxation of the deterministic factory scheduling problem (in addition to being a limit of the stochastic queueing model) so it functions as an approximation of a discrete flexible job-shop with WIP and ongoing inputs. However, buffer levels are allowed to have non-integer values, equipment processing can be simultaneously shared between different products, and a single lot can begin processing at a downstream step before it completely finishes at the previous step. By solving a finite series of quadratic (or linear) programs, an optimal (or nearly optimal) control policy is found for this fluid relaxation problem (with a weighted holding cost objective). In the second phase, production in the discrete factory queueing network is scheduled ahead of time or dispatched in real time by minimizing the deviation of the production from the optimal fluid control policy. Starting assignments are set with a mixed-integer program, and special techniques are used for comprehending batching and for avoiding sequence-dependent set-ups.
