Optimal routing and scheduling by maximum gap policies in manufacturing systems

In this paper, the formalization of performance optimization problems for flexible manufacturing systems is considered. In the adopted model, production resources are multipurpose, in the sense that they are able to perform more than one kind of operation; on the other hand, an operation can in general be carried out by more than one resource. This flexibility leads to the problem of optimally managing the part routing (i.e., the assignment of an operation to a resource) and the local scheduling (i.e., the choice of the next operation in a resource operation sequence). Thus, the performance optimization of such systems requires the solution of combinatorial optimization-problems. In this connection, the introduction of maximum gap policies makes it possible to reduce the number of combinatorial degrees of freedom, by writing constraints,. deriving from the structure of such policies, on the dynamic behaviour of the system. The formalization of the optimization problem is carried out by using a system representation built via the use of deterministically transition-timed Petri net.