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tags:

• git
• vcs

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Digital twins

The notion of the DT was first mentioned under the term “mirror world space” by the American researcher Grieves in 2005 (Grieves 2005). He envisioned connecting a physical space to a virtual space through a continuous flow of information and data. However, due to the complexity of the concept and the technological limitations of the time, the idea was not immediately adopted.

The concept was brought back into fashion a few years later, this time by NASA, which renamed it “Digital Twin”. The space agency envisioned using the DT for the maintenance of its space equipment. This concept finds its origin in the early stages of space exploration, where a backup physical model of the shuttles was kept on Earth to help technicians with problem-solving during missions. Unlike the creation of a costly physical copy, the development of a DT represented an economically viable alternative. This concept was then adopted by the United States Air Force for the maintenance of its fighter jets.

identify the DT as being composed of three elements: the physical model, the digital model (DM) and the bidirectional communication link.

Maturity levels

Yong-Woon et al. (2021) proposed a classification of DTs into five maturity levels, based on their characteristics and capabilities. This classification makes it Digital Twins possible to understand the evolution and potential of DTs in different industrial contexts.

• Level 1, Mirroring Digital Twin, represents the most basic form of the DT. It is limited to a 2D or 3D graphical representation of the physical model, without any interconnection or behavior laws. It is essentially a static mock-up comparable to traditional CAD models.
• In continuity, Level 2, Monitoring and Control Digital Twin, establishes a rudimentary connection between the physical model and the DM. This connection is dedicated primarily to the supervision of the physical model. The collected data is used for basic logical analyses, such as process stoppage detection. This level corresponds to what Kritzinger et al. (2018) define as a “digital shadow”.
• Level 3, Modeling and Simulation Digital Twin, fully conforms to the definition of a DM connected in bidirectional mode to the physical model. This connection enables real-time synchronization and advanced simulation based on behavior laws. Although information is communicated instantaneously to the physical system, critical decisions generally remain the responsibility of human operators, for safety reasons.
• Level 4, Federated Digital Twins, evolves beyond individual entities to form complex assemblies. In a future where each component will be accompanied by its own DT, it will be possible to build a global DT by assembling these multiple entities. This would enable a large-scale representation of complex entities such as cities. Level 5, Autonomous Digital Twins, will see DTs become fully autonomous. To this end, perfect synchronization between real and virtual elements is necessary. In this scenario, the DT would be capable of analyzing, making decisions and acting autonomously, reflecting in-depth interpretation and instantaneous responsiveness to events and needs of the physical system.

Design of the digital module

The design of the DM is based on three components: the geometric model, the kinematic model and the MAI, enabling operators to interact with the DT. The geometric and kinematic models will constitute the immersive graphical space. The geometric model provides a precise three-dimensional representation of the system, allowing visualization of its physical configuration in a virtual environment. The kinematic model complements the geometric model by adding movement and dynamism. In the absence of native models, these models must be recreated and assembled to form a faithful digital mock-up of the system. Finally, the MAI optimizes human–DT interaction by displaying various functional indicators. It allows simultaneous visualization and manipulation of the physical system and its DT in coupled mode or only the DT in decoupled mode.