REAL-TIME DISTRIBUTED SCHEDULING OF HETERARCHICAL MANUFACTURING SYSTEMS

Lack of master-slave relationships and absence of a centralized superv isor in heterarchical manufacturing systems prohibits the use of centr alized scheduling. A fully distributed scheduling method for these sys tems is described in this paper. Entities in the system continually ge nerate tentative local schedules in real time using a cooperative sche duling heuristic and select the best schedule for execution. Tentative schedules are evaluated in time-scaled, distributed simulations using software that is a replica of the real system software. The state of the real system is copied into this virtual system at the beginning of each simulation, eliminating cumulative uncertainties and immediately incorporating equipment failures and other unexpected events into sch edule evaluation. Experimental results illustrate the real-time distri buted scheduling method and its response to faults.