Object-Oriented Encapsulation-Based Virtual Equipment Modeling for Digital-Twin Production Systems

As digital-twin technology becomes integral to smart manufacturing, the creation of high-fidelity yet maintainable virtual equipment models is critical for effective production-unit debugging and system-level coordination. This paper presents an object-oriented encapsulation approach that leverages information-hiding and interface-uniformity mechanisms to modularize device states, interfaces, and behavior logic. By encapsulating each physical device within a self-contained class exposing only standardized input/output methods, the proposed method reduces coupling and enhances model reusability. We further introduce a hierarchical composition strategy, enabling seamless aggregation from single devices to work-unit, production-line, and workshop-level models. On top of this, we develop a semantic-signal aggregation framework and event-triggering mechanism that automatically translate low-level physical signals into discrete events for control and scheduling. A case study of a riveting workstation demonstrates improvements in interface consistency, modeling accuracy, and extensibility. The results confirm that our encapsulation-based modeling method offers a portable, scalable, and easily maintainable solution for digital-twin production systems, laying a solid foundation for advanced debugging workflows and intelligent decision support.