Concept, Information model and
Development of an implementation concept for the use of the "Shared Digital Twin".
Mister Rodriguez is project leader Digital Marketplaces
Concepts, information model and product description
Development of an information model
Subproject 1 (SP 1) ‘Concept, information models and product description’ establishes important basics. It creates the prerequisites for developing a shared digital twin. This makes it possible to share data across all stakeholders. For this purpose, information must be processed as semantic models that make up a Asset Administration Shell for the wire harness. To get there, data that turns out to be relevant must be defined as precisely as possible. The project team is moving forward piece by piece with questions like: What data is there? What does that mean? How are they connected? Which data types can be grouped and how? Parallel to this base project, SP 2–4 were initiated. They address the individual value-added areas of the wire harness: Development, production and assembly. These steps require painstaking attention to details. Thousands of plugs, cables and grommets have to be disclosed and designations must be aligned to turn the vast amount of tiny details into something really big by the end of 2024.
Objective of the Subproject
The goal is to describe all components of the wire harness and their information or data with corresponding information models. An information model describes real objects by precisely defining names, properties or relationships, etc. In the context of the wire harness, the name of a certain component (for example, a plug) is thus described unambiguously with the associated properties ‘heat-resistant, splash-proof’ and other product data. But even with a simple composite component consisting of a plug plus cable, a lot of data comes together. This is where the Asset Administration Shell comes into play: it is the central instrument where information and data can be stored. Moreover, it can be accessed in the form of component, resource and process data over the entire product life cycle.
Another challenge of project 1 is to link the data models from the established data standards in the industry via the value creation process. Apart from that, concepts are being developed on how to combine the individual standards and submodels, which can be highly detailed.
The wire harness production is characterised by change processes. Numerous changes to the wire harness are made during engineering (i.e. during technical development) or can even take place when production has already started.
Over the years, companies have built their own data interfaces with a large amount of data to be processed. So far, there has been a lack of suitable standardisation that would have made it possible to manage the variety of data related to the wire harness along the entire value chain. Thus, there are company-specific information silos that are created, stored and retrieved in the most diverse information systems. This is a disadvantage because there is always the risk that data derived from earlier process steps is lost and not available for later process steps. Another issue is if changed data is only recorded in Excel lists instead of being entered in an understandable way at a fixed location and made traceable. This common practice is supposed to be vanquished with SP 1.
The Asset Administration Shell is supposed to become the data hub where everything is aggregated, from product data to construction data and usage data. The advantage is: In a continuous, digital process chain, there is no loss of information. The principle of the Asset Administration Shell provides that data can be continuously added or changed throughout the entire product life cycle. It also stipulates that all necessary information about machines, products and processes is stored and can be retrieved. None of this would be possible without standardisation that works across companies. The transfer of information is consciously and reversibly controlled. At any point in time, the totality of information can be made visible, for example, about on-board electrical systems, a total parts list or production data. It is also possible to hide information or to make only certain data visible via controlled access.
Figure 1: Triad of product – process – resource (source: DRÄXLMAIER)
The results of the SP are developed along the essential process steps of development, production and assembly of the wire harness. The participants maintain close professional exchange with the SP ‘Integration of the Asset Administration Shell ’, ‘Automated Negotiation Processes’, ‘Data Business Policy, Data Governance and Monetisation’, as well as ‘Data Storage Policy, Security, Connection to Catena-X’ and therefore counts as a cross-sectional project.
The concepts, models and descriptions to be developed here form the basis for all other SP and are an outstanding foundation for implementation of the Asset Administration Shell .
It will include all preliminary work, for example by the Industry 4.0 platform, the ZVEI, the VDMA and other stakeholders for applicability to the wire harness. Furthermore, a collaboration on the standards, for example, for the various manifestations of the OPC UA Comp. Spec. (full name: Open Platform Communications Unified Architecture Companion Specification) in the respective committees is essential and offers the opportunity to help shape one of these standards.
At the beginning of the project, the editors initially collected many requirements for the Asset Administration Shell . Likewise, it quickly became clear at the beginning that it would be better to work with existing specifications for the part ‘product’ from the triad product/process/resource (PPR for short, see figure above). The cable harness list (KBL) and the Vehicle Electric Container (VEC) were particularly suitable for the product specification. Compared to the KBL, the VEC is a much more wide-reaching variant. It represents much more than just a wire harness. The VEC can even be used to map entire on-board electrical systems including the control units.
The OPC UA standard is used to describe the process and the resource. OPC UA is considered a standard interface in the context of Industry 4.0 and a universal interface – not only for the cable industry, but for a range of industry sectors. It can be used to pass on machine data and describe it semantically so that a machine can interpret it. In the VWS4LS project, this serves as the basic model for the wire harness. The OPC UA Comp. SPec. for Machinery is particularly suitable to build upon, as it already defines applications as well as modules. Other standards are currently under discussion: the OPC UA Result Transfer and OPC UA Job Management. There are still deliberations in this area as to whether parts can be applied to the wire harness. Nevertheless, everyone seems to agree that it is useful to work with both. For everything else that is not covered by the KBL, the VEC or the OPC UA Comp. Spec, the concept of a Manufacturing Execution System (MES) would be another viable option that could be used in wire harness production.
The processes for cable cutting and crimping were described in the first step. All other process steps are still being worked on. Furthermore, there are open questions that are Asset Administration Shell -specific and cannot be traced back to the triad of product, process, resource alone. For example, a mechanism is being sought to integrate the data blocks in the Asset Administration Shell .