Supervisory control of reconfigurable flexible-manufacturing workcells - temporary addition of resources

Traditionally, the function of a supervisory controller has been to coordinate the various resources comprising the 'physical' workcell for the production of an a priori set family of parts. That is, the supervisor-synthesis methodologies have assumed that the set of resources comprising the workcell remains constant. In recent practice, however, workcells are assumed to be (temporarily) reconfigurable to form virtual workcells by the introduction of new machines. Virtual workcells may be used, for example, in order to increase throughput. The workcell supervisory-control approach proposed in this paper advocates the use of a pair of independent supervisors, working in concert, to achieve effective control of the expanded workcell including the (a priori unknown) new machines that are temporarily added into the workcell. The nominal supervisor is responsible for controlling the flow of parts when the parts follow any one of their nominal routes, while the complementary supervisor is responsible for controlling the flow of parts when they follow any one of the new processing routes that were added to the parts' processing routes due to the introduction of new machines. Each supervisor is synthesized individually.