Stable, distributed, real-time scheduling of flexible manufacturing/assembly/disassembly systems

The authors consider general flexible manufacturing/assembly/disassembly systems with the following features: (i) there are several-types each with given processing time requirements at a specified sequence of machines; (ii) each part-type needs to be produced at a prespecified rate; (iii) parts may incur variable transportation delays when moving from one machine to another; (iv) set-up times are required whenever a machine changes from a production run of parts of one type to another; (v) some part-types may also need assembly or disassembly; and (vi) a proportion of parts of a part-type may upon exiting from a machine require separate routing (due to say poor quality). The authors exhibit a class of scheduling policies implementable in real time in a distributed way at the various machines, which ensure that the cumulative production of each part type trails the desired production by no more than a constant. The buffers of all the machines are guaranteed to be bounded, and the system can thus operate with finite buffer capacities. The authors exhibit finite upper bounds on these buffer levels for the given distributed real-time scheduling policies. They also exhibit a lower bound on the average buffer levels for any scheduling policy.