Table 1.

The definition of DT

No.	Reference	Year	DT definition
1	[9]	2012	DT is a multi-scale integrated simulation of a physical equipment or system that makes full use of virtual models, real-time sensor data, and historical data on the equipment or system to map the entire life cycle of the process
2	[8]	2012	DT models need to meet the requirements of the system and subsystems throughout their life cycle, enabling the assessment of the vehicle’s mission accomplishment capabilities
3	[10]	2013	DT is an approach that uses data-driven analytical algorithms and other physical models to simulate the operational state of an entity, which can be described as a 5S system consisting of sensing, storing, synchronizing, synthesizing, and serving
4	[11]	2015	DT comprises a large collection of digital products, requiring a good architecture to link all components
5	[7]	2017	DT requires not only virtual mapping of products at the macro-geometric level, but also all the information about the actual manufactured products at the micro-atomic level
6	[12]	2017	DT of a product needs to realize the full-factor digital mapping of physical entities in virtual space, to simulate, predict, and control the feedback of physical entities
7	[13]	2018	DT is a real time mapping of physical, virtual, and interaction data in the entire life cycle of a physical entity
8	[14]	2018	DT is an all-encompassing digital representation of a product that simulates the properties, conditions, and behavior of an actual physical object through data and models
9	[15]	2019	DT is a dynamic virtual model that digitally builds multi-dimensional, multi-physical entities of multi-temporal scale to reflect the properties and behaviors of the real environment
10	[16]	2019	DT is a simulation process that integrates multiple physical quantities and scales in the entire life cycle of physical equipment, using physical models, real-time sensor data, operational history data, etc., to build models in virtual space to complete the mapping
11	[17]	2022	The twin is a refined digital description of the product entity. Simulation experiments based on digital models can more realistically reflect the characteristics, behavior, formation process, and performance of physical products. The real-time collected data are associated and mapped onto the DT to identify, track, and monitor the product. The DT can predict and analyze the behavior of simulated objects, diagnose faults and issue warnings, locate and record problems, and achieve optimal control