Predicate/transition nets in FMS control

The author presents a design methodology for high-level control of flexible manufacturing systems (FMSs). The design procedures are addressed for the control model specification, the process execution software and the monitoring functions. A functional classification hierarchy of the system resources is introduced which is used for the representation of object class types in generic predicate/transition subnets (Pr/T). The subnets can be parameterized to the instances of the object class types. They can be related through internal and external topology relations. The relations describe the interaction and the synchronization between the resources. The complete Pr/T-net is called the functional model of the FMS. It describes the concurrency and synchronization of the FMS. It is used for the discrete event driven control of the process. The indeterminacy problem in the Pr/T-net was solved with the help of a task scheduler and a task-to-primitive-operation structure. The Pr/T-net was implemented in Prolog