Digital twin enables new potential benefits

For more than a decade, comprehensive "Product Lifecycle Management (PLM)" concepts have taken hold, which are based on an integrative platform and support methods and processes for strategic business processes. As an extension to the previously strongly engineering and mechanics-based approaches, PLM offers a cross-disciplinary integration platform for mechanics, electrics/electronics, software and documentation as well as digital manufacturing solutions for merging development and production.

Digital twin - what is it?
The digital twin goes one step further: as a complete digital image, it should not only contain all information aspects, but also the mechatronic behavior in interaction with other objects.

This allows aspects of a real production plant to be checked without affecting ongoing production. For example, in the event of problems with a machine in the real production plant, the interaction of mechatronic components (loading door, sensors, actuators, I/O signals, PLC program, etc.) can be analyzed purely virtually on the digital twin.

Domains of the digital twin
Based on the three basic lifecycle phases of development, production and operation or service, the digital twin can be divided into three different domains (product, production and service twin).

The Product twin is the digital image of a product, which is created at the beginning of a development and is gradually developed before the real product begins to exist. The product representation contains the product structure as well as other defining contents such as geometry in M-CAD, electrical schematic in E-CAD, software, etc.

The production twin is the digital image of a factory and the required manufacturing, assembly and testing processes. The factory can be subdivided into several lines and contain manufacturing equipment, production machines and handling devices. Assembly and testing processes are mapped to a process structure that consumes parts or assemblies across multiple assembly lines until the product is completely assembled.

The Service Twin is the digital image of service contexts (wear and spare parts, service plans) as well as of the operating states of a physical, real object. By recording operating data (temperature, wear indicators, etc.), the current status can be collected in a cloud, regardless of location, in order to specifically specify the necessary service work depending on the actual usage characteristics.

Use for virtual commissioning
With a digital twin, interdisciplinary methods can be used in the development of mechatronic products to create a mechatronic concept at the beginning, which serves as a basis for the individual engineering disciplines so that the teams can work highly parallel and efficiently. In addition, the process for commissioning can also be improved. In the past, the individual components only came together on site and commissioning was a lengthy, risky and costly process because problems were only identified at a late stage. The basis for real commissioning is the real machine, which only becomes available after the development phase.

In contrast, the digital twin is available at an early stage and can already be used during the development phase for virtual commissioning before the first real part is manufactured. The digital twin emulates the mechanics, actuators and sensors of the later real system and offers a realistic 3D representation. New possibilities arise for automation development, since the control code can be tested and optimized against the digital twin at an early stage, whereby there are basically two possibilities:

• Hardware in the loop (HiL),
• Software in the loop (SiL).

In the case of hardware in the loop (HiL), the digital twin interacts with a real controller, i.e. the control hardware is connected to a PC via cabling. Such an intelligent connection of the virtual world with the real world is called a cyber-physical system (CPS). The current state of the PLC code is executed on the controller in interaction with the simulation model in the digital twin. Signals are exchanged between the two systems and the program sequence is displayed in real time via 3D visualization.

In the case of software in the loop (SiL), the digital twin interacts with a virtual controller, and the entire functionality resides on a PC. This can be advantageous in an early phase when the real controller is not yet available.

With virtual commissioning, not only can efficiency increases and shorter development times be achieved, but also a significantly higher development status of the software when entering the real commissioning on site at the construction site. As a result, the real commissioning can be carried out in a shorter time, more cost-effectively and with less risk.

Another important application for virtual commissioning are rebuild scenarios during operation, for which usually only a short period of time is available to rebuild the hardware and commission the new plant with the new control system. Since the permissible downtimes must be strictly adhered to, simulation methods are indispensable for this. In addition, the digital twin can be ideally used for training purposes in order to train operating personnel on the real control system purely virtually via HiL.

Relevance of Industry 4.0
Many consumers now use the Internet to shop online. Sales configurators are becoming more and more flexible, right up to customised products, resulting in mass customisation requirements for factories in order to produce variants that have never before been available in the most automated and cost-optimised way possible. For manufacturers, this means that they have to optimize their internal processes, automate them more and more, and seize new opportunities through digitalization faster than their competitors. Where is this need for action now greatest?

Neither the industry nor the product complexity are decisive for the need and potential with regard to Industry 4.0, but rather the characteristics of the company processes, i.e. how the product is sold on the market (as a standard product or with variability). Efficient Industrie 4.0 processes are primarily required for high product variance and at least medium quantities, which is most likely to be the case for a "Configure To Order" process.

Motivation and need for action
In the past, there were also technology trends with promising benefits. However, the motivation and necessity for digitization with Industrie 4.0 go beyond this because the business environment is changing dramatically. Disruptive innovations are increasingly leading to the demise of business models with which well-known companies have previously enjoyed long-term success. Since 2000, a good half of Fortune 500 companies have disappeared, the main trigger being digitization. By 2020, some 50 billion devices are expected to be on the internet, driving revenue growth in excess of $250 billion. This has been a wake-up call for many CEOs and has led to Industry 4.0 being on their CEO agenda.