Synthesis of compliant mechanisms in force measurement and weighing technology for precision applications

• Applicants: Professor Dr.-Ing. Thomas Fröhlich; Professorin Dr.-Ing. Lena Zentner
• Subject Area: Measurement Systems
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 461797997

Compliant mechanisms offer advantages such as maintenance-free operation, absence of friction and lubrication, and high reproducibility due to their monolithic structure, making them ideal for precision equipment and metrology. However, metals exhibit time-dependent deformations known as elastic aftereffects. Currently, except for single-crystal materials, no materials are known to be free from these aftereffects. The overarching goal of this project is to minimize or ideally eliminate elastic aftereffects during measurements. Building upon the results of the first project phase, it was found that, in addition to theoretical correction of elastic aftereffects, the use of an innovative structural compensation is promising. Therefore, this project focuses on the model-based investigation of this compensation and the development of methods that enable targeted, rapid, and effective design of creep-compensating systems. Such a system consists of a deformation body and a compensation mechanism with negative stiffness. The underlying hypothesis is that, through the parallel arrangement and tuning of both subsystems, elastic aftereffects can be compensated. This approach is not documented in the current scientific literature. Initially, model-based studies of the deformation bodies and compensation mechanisms will be conducted, scaling dimensionless parameters in analytical models. For the deformation bodies, tilting due to gravity will be modeled, and the volume-to-surface ratio will be experimentally investigated. The insights from these studies will inform the guidelines for design methods. Subsequently, the compensation mechanisms aimed at minimizing elastic aftereffects will be analyzed model-based, and an appropriate design method will be developed and experimentally validated. Specific design methods will be devised for the creep-compensated systems, with the challenge of tuning both subsystems to achieve the most complete compensation of elastic aftereffects. Finally, at least two demonstrators will be designed, manufactured, and experimentally examined to verify functionality and validate the developed models. The developed analysis and design methods are not only applicable in metrology and precision engineering but can also be extended to compliant mechanisms in robotics and medical technology.

• DFG Programme: Research Grants