With movement towards reduced life cycles and just-in-time operation to reduce costs, the inherent rigidity of cell control systems has become a major roadblock to their implementation. One method of achieving configurability is through a consistent software representation of the manufacturing entities in the cell. It is also desirable to insulate generic control functions from the wide variation of control functions found in low-level devices. System information should be organized in a standard format allowing other entities to understand and use the information effectively.
The concept of Virtual Manufacturing Entities (VME), intended to address problems faced in manufacturing integration particularly the inadequacies of the Manufacturing Message Specification (MMS), is presented in this paper. A VME is defined as an abstraction of a specific set of resources and functions possessed by a physical device. VMEs are a standardized representation which mask the proprietary nature of real manufacturing entities from other software modules in a control environment. VMEs model the control behavior sufficiently to provide an open control interface for constructing integrated control systems. In addition, they support simulation of manufacturing entities, for development and validation of control code.