Currently, the digital twin is an emerging technology which is being discussed in several domains. The concept is based on modeling assets with all their geometrical data, kinematic functionality and logical behavior using digital tools. The digital twin refers directly to the physical asset and allows it to be simulated, controlled and improved. According to Gartner, “less than 1 percent of the physical machines and components in use today are modeled such that the models capture and mimic behavior”.
At the moment, digital twins are being discussed in Industry 4.0 working groups in the context of asset administration shells or Industry 4.0 components. From our point of view, digital twins will become a major topic for research over the coming years because they are not single objects or monolithic data models, but include different aspects of digital representations, functionalities, models, interfaces etc. From a manufacturing and engineering perspective, it is evident that digital twins require and cover a number of different aspects, such as
- Self-description using unique attributes and parameters describing configuration data, e.g. for auto-identification, to connect machines and components easily to MES and other Industrial IoT-solutions
- Description of skills, including parts of the control code with the result that an assembly of components and their respective control logic elements fit into a running control program. This creates a PLUGandWORK environment where new components can be plugged in at runtime and integrated automatically on a functional level.
- Models of the correct runtime behavior of a machine, a line or an entire manufacturing shop, based on learned data from machine learning.
- An extremely wide range of offline- and online-simulations, such as finite element simulations, virtual commissioning or physics simulations in which the manufactured goods interact with the machine kinematics. Ideally, the various simulation models should be able to interact in order to generate an integrated simulation model. Up until now, the digital twin has been used primarily in the context of simulation; as we point out here, this definition is much too narrow.
- A digital factory describing machines and other manufacturing resources, buildings and utilities. A building information model (BIM) might also be part of a digital twin as long as it contains relevant information, e.g. topology. The concept of digital factories already has a long history and is described by well-known standards, such as VDI 4499.
- Services that a cyber-physical component offers to its users.
- IT security, access rights, handling of certificates, version management and compatibility checks of different versions of digital twins.
Digital twins are essential for Industry 4.0 and the digitization of manufacturing. Their content is key during all stages of the life cycle and within different types of platforms and tools, from engineering to after sales services.