Benjamin Kraus

Digital Twins are being used more and more frequently and provide information from the Real Twin for different applications. Measurements on the Real Twin are required to obtain information, which in many cases requires the installation of supplementary sensors. For their conception and design, it is particularly important that the measuring principles are selected purposefully and the appropriate sensors are integrated at the goal-oriented measuring positions without impairing the functions and other properties of the Real Twin by the integration of these sensors. In this article, a “Design for Digital Twin” approach is discussed for the systematic procedure and demonstrated using a multi-staged gearbox as a concrete example. The approach focuses on the mechanical and hardware side of the Real Twin. For the systematic conception and design of the Digital Twin solution, an understanding of the stakeholder demands and the expected use cases is necessary. Based on the stakeholder demands and use cases, the relevant product properties can be determined. Using the relevant properties, an iterative process of conception, design, and analysis takes place. The conception is carried out by means of target-oriented cause–effect analyses, taking into account systemic interrelations of the Real Twin components and systematics for the selection of measurement principles. Systemic considerations, combined with an effect graph, allow for the analysis and evaluation of disturbing factors.

In the context of condition monitoring and predictive maintenance, collecting accurate data from technical systems is an important corner stone of the advancing digitalization. For gathering precise data of the current state of a system, measurements from within the process can be utilised. To measure in process without disrupting the system is a challenge that can be tackled by using the physical properties of the components of the system. In this paper a method to systematically find such possible sensory utilizable components (SuC), based on their inherent physical effects is presented.

The sensory acquisition of in situ data in technical systems is one of the key requirements set by ongoing digitalization. The sensory utilization of mechanical design elements is a step towards the accomplishment of this requirement. To set a common ground for further research in the context of sensory utilizable design elements, this paper reviews the current state of research in this topic. First, the aim, potentials and classification of sensory utilizable design elements are introduced. Next, examples of sensory utilizable design elements are presented. These examples are used to demonstrate the technical and methodical challenges that have to be addressed in order to establish sensory utilizable design elements as a solution for the requirements of digitalization.

Gaining accurate data from technical systems has become of interest, particularly in the context of condition monitoring and predictive maintenance. Hereby it is important to gather precise and reliable data. To accomplish this task, various sensors with different physical effects are used. Depending on the sensor’s position and measurand, different models are necessary to describe the path from the desired variable of interest to the actual measured one. To support designers, a physical effect catalog was digitalized using a graph data structure, which uses the inherent properties of a graph to represent physical variables, physical effects and their relationships. This graph structure together with its applicability in a sensor selection process will be shown in this paper.

Several machine elements, for example roller bearings, embody physical effects that can be exploited to evoke a sensorial effect. The utilization of these effects results in so-called sensing machine elements, which might turn out to be an enabler for the digitalization of mechanical systems. Sensor-integration offers a starting point to connect these basic elements of engineering design to embedded systems, so that a point of contact for cyber physical systems arises. This novel research topic is gaining momentum with a potential impact on production machinery since the goal is to provide high quality measurement data out of positions from inside the process of interest (called in-situ measuring), enabling new functionality on a system level. The coverage of this area comes along with development difficulties so that there are only few concepts mature enough for the mass market. The challenges are ranging from energy supply in rotating systems, over data transfer across system borders up to robustness of the sensorial concept of the machine element in the application environment. The presentation and the corresponding paper cover a systematic classification of machine elements and explains sample concepts. Research challenges as well as opportunities in future applications are described with emphasis on applications in production technology for electric drive.