Models for simulation and discrete control of manufacturing systems

A methodology is presented for constructing models of manufacturing processes for simulation and design of the discrete control logic. The models represent the discrete event evolution of the system as well as features of the underlying continuous processes. For applications such as discrete parts manufacture and assembly, the process is decomposed into operations with specified precedence relations. For each operation the required resources and associated discrete resource states are identified. Also associated with each resource is a set of resource attributes which are modified by the processes underlying each operation. The structure of the discrete-level control is modeled by modified Petri nets which are synthesized from single resource activity cycles. Construction of the net provides discrete control logic for error recovery loops and other real-time decision structures with guaranteed properties based on extensions of previous results in Petri net theory. The modeling methodology is applied to a two-arm robotic assembly cell example.