Rolling element eccentric drives promise to be an easy-to-manufacture and performant gear system for robotic actuators. They share characteristics with other eccentric drives, such as strain wave and cycloidal drives, but use rolling elements instead of an eccentric gear. They offer reduced manufacturing complexity and costs by using readily available standard parts. Little research into rolling element eccentric drives is available, and their characteristics are still underexplored. This work uses a contact-based model to investigate the previously unknown stiffness of rolling element eccentric drives. Such calculation methods are well established for structurally similar components, such as cycloidal drives and roller bearings, and provide a high-level and computationally efficient model. Good stiffness models are critical for accurately predicting robotic actuator behavior and enabling better control of robotic systems. Additionally, the proposed model is used to calculate the contact forces under load occurring in rolling element eccentric drives. Contact forces are critical to calculating a drive’s load capacity, lifetime, and efficiency and serve as the foundation for further research. The mathematical description of the proposed model is derived, and the stiffness of a representative rolling element eccentric drive is calculated. Different manufacturing techniques, characterized by tolerance levels and material choices, are compared. Irrespective of manufacturing precision, similar stiffness curves result for drives made of steel, but higher contact forces result from less precise manufacturing. The stiffness of drives made from 3D printed plastic is considerably lower than that of drives made from steel. Additionally, the stiffness of rolling element eccentric drives is compared to similar eccentric drives, and a comparable twist-over-torque curve is shown.

One of the limitations of classical SysML is that it does not provide information on how to model system component's constraints, which can result in individual model solutions for the same elements. To address this issue, we propose utilizing the reference mechanism in SysML to refer to REXS and ECLASS data standards, which can unambiguously define characteristic properties. Environmental factors such as temperature or humidity constraints play a vital role in designing components of mechatronic systems, like transmissions, or electrical and electronic components like sensors and actuators. Mechatronic component's properties may change depending on temperature and humidity and may show degradation. Such information is provided to some extent in the component's classified properties, like ECLASS and/or REXS, the engineering tool to configure gears. Such properties and constraints are further detailed in specification sheets provided by the manufacturer, e.g., by multi-dimensional manufacturer-specific parametric curves which are proposed to be explicitly included in the modeling process as SysML constraints. The proposed approach allows to include additional, not yet standardized environmental effects such as dirt layers in a formalized way. The formalized properties are modeled in parametric diagrams of SysML.

The axes of robots and robot-like systems (RLS) usually include e-motor-gearbox-arrangements for optimal connection of the elements. The characteristics of the drive system and thus also of the robot depend strongly on the gears. Different gearbox designs are available which differ in stiffness, efficiency and further properties. For an application-optimal design of RLS a uniform documentation and a comparability of gearbox concepts is a decisive factor. The application-optimal design is supported by an interdisciplinary approach between mechanical engineering and software design, guided by adequate product development methodology. The quite heterogeneous characterization of gearboxes for RLS which is currently the state of the art is a relevant obstacle in the flexible and optimal design of RLS. The paper shows the analysis of the gear structure with unified symbols for specific machine elements and contact types. The introduced method gives insight into the mechanical structure of the gearboxes. Similarities between gear types can thus be revealed. This also enables the classification of new developments in the state of the art. Moreover, the developed method for analyzing the gear structure can be used to determine the characteristics of gears. Examples for these characteristics are backlash, efficiency or stiffness. Specifically, the stiffness of gears can be synthesized by the force action of individual contacts and the individual phenomena that occur with them. The representation by individual phenomena also makes it possible to extend the calculation to include influencing parameters such as temperature that have not been sufficiently taken into account so far.

Companies producing Robot-Like Systems (RLS) must increase efficiency in design and production in order to stay competitive in the international market. Such RLS range from small SCARA robots to entire production facilities. Very different systems for similar tasks are published in research or offered in the market. A clear path to an optimal configuration for a given task is apparently not available to the engineer. This indicates that the gear drives of such RLS and their integration with automation technology are still insufficiently researched, and their efficient design poses significant challenges for the industry. This paper identifies and provides a concise overview of requirements and challenges in the context of drives for such RLS. Building on this overview, suggestions are made for the future course of action in research.