Objectives of human-centered VMS (virtual manufacturing system) are to expand the capabilities of humans and to support their creativity and collaboration among people in a manufacturing system. Presented in this paper is architecture of virtual factory emulator as a component of the human-centered VMS. The virtual factory emulator is used to construct a factory model consisting of a variety of virtual manufacturing devices (VMD) and then to emulate its operations according to human-defined scenarios (or commands) that are manually defined by users or automatically generated from schedules.
When developing the virtual factory emulator, the following requirements were taken into account: 1) rapid layout design, 2) ease of command modeling, 3) realistic emulation using 3D animation, and 4) integration with other components of the VMS. To support these functional requirements, a hierarchical command structure together with the concept of hierarchical VMD model are employed while the Zeigler's DEVS formalism is adapted in the execution engine of the virtual factory emulator.
As a software system, the proposed virtual factory emulator consists of four modules: 1) a device modeling module for constructing VMD models of real devices, 2) a command modeling module for modeling user scenarios, 3) an emulation module for building and executing the virtual factory model, and 4) DB interface module for integrating with other components in the VMS. When fully implemented, the virtual factory emulator may be used as a virtual protolyping tool for the design of a new factory and/or as an operational tool for validating schedules.