Designing a No-Wait Cyclic Schedule for a Class of Concurrent Repetitive Production Processes

The concurrent repetitive manufacturing processes sharing resources according to a mutual exclusion protocol are considered. A system of the processes is a composition of subsystems that consist of n cyclic processes sharing one resource. In case of resource conflicts between the processes regarding access to the resources a certain priority is used (e.g. FIFO rule) which guarantees starvation-free access of the processes to the shared resources. A class of systems which are structurally deadlock-free is considered, i.e. resource requests of repetitive processes can’t create closed loop. For this class of systems is searched conflict-free, cyclic schedule for which the processes never wait for the resources, i.e. resource conflicts are avoided and a priority rule is not in the operation. A structure of production processes sharing resources and the operation times are defined. The problem of computing the starting times of the processes for which a no-wait cyclic schedule exists is formulated in a declarative way using constraint programming (CP) method. The necessary and sufficient conditions for existence of a no-wait schedule in the n-process system are given and used to compute the possible schedules of the processes. An illustrative example is presented.