A distinguishing feature of a flexible manufacturing system (FMS) is the ability to perform multiple tasks in one machine or workstation (alternative machining) and the ability to process parts according to more than one sequence of operations (alternative sequencing). In this paper, we address the issue of deadlock avoidance in systems having these characteristics. A deadlock-free and maximally permissive control policy that incorporates this flexibility is developed based on finite automata models of part process plans and the FMS. The resulting supervisory controller is used for dynamic evaluation of deadlock avoidance based on the remaining processing requirements of the parts.

One of the characteristics of flexible manufacturing systems (FMSs) is that they can consider multiple part routing due to alternate machining and alternate sequencing in the processing of parts. This paper presents a new architecture based on colored Petri nets (CPNs) that allows the supervisory controller of a flexible manufacturing cell to consider alternate machining and alternate sequencing in real time control of the cell. This capability for real time alternate routing is an extension of prior research on the application of CPN to modeling FMSs.