A methodology for creating a virtual model for a flexible manufacturing system

Proposed in the paper is an object-oriented methodology to create a virtual flexible manufacturing system (FMS) model. The proposed virtual FMS model consists of four types of objects: the virtual device model (object model), the transfer handler model (functional model), the state manager model, and the flow controller model (dynamic model). A virtual device model consists of two parts: shell and core. To improve the reusability of a virtual device model, the shell part is designed to adapt to different FMS configurations. For the fidelity of the virtual FMS model, a transfer handler model has a set of device-level commands imitating the physical mechanism of a transfer. As a result, we can expect more accurate simulation results. The flow controller model makes decisions on firable transfers based on decision variables, which are maintained by the state manager model. For the implementation of the proposed virtual FMS model, this paper employs Discrete Event Systems Specifications (DEVS) formalism, which supports the specification of discrete event models in a hierarchical, modular manner. The proposed virtual FMS model has been implemented and tested with many examples.