Analysis, optimization and synthesis of compliant linkage mechanisms for ultra-precision applications

• Applicants: Professor Dr.-Ing. René Theska; Professorin Dr.-Ing. Lena Zentner
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: from 2014 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 258176829

Flexure hinges are used as material coherent revolute joints in compliant linkage mechanisms for ultra-precision applications. In this case, the requirements for the precision are in the range of nanometers or angular subseconds. Compliant mechanisms are often synthetized by the substitution of rigid-body mechanisms. There is a need for research, because the influence of the concrete constructional design on the kinematic behavior has not been investigated in literature so far with the required resolution. Mostly flexure hinges with basic cut-out geometries are used. Therefore, compliant mechanisms based on these flexure hinges show a limited motion range and path accuracy. To overcome these limitations, in existing approaches the number of joints is increased in the kinematic chain of the mechanism, while there are no studies on the optimization of the flexure hinge contour with respect to the design of monolithic mechanisms. Thus, the inadequate knowledge of the kinematic properties limits advances in modern ultra-precise applications claiming for both highest precision and significantly increased motion ranges.The goal of this project is the development of fundamentals for the synthesis of compliant mechanisms with optimized flexure hinges. As the focal point of the first project phase, specifically the influence of the hinge contour on the mechanism properties has been investigated in comparison to the rigid-body counterpart. The investigations have shown that polynomial flexure hinges, which are directly optimized in the mechanism, are advantageous. Compared to conventional hinge contours polynomial flexure hinges allow a simultaneous increase of the range of motion and the precision. An additional improvement can be achieved by the application of different flexure hinges in one mechanism and by an appropriate design of the hinge orientation and of the coupler geometry as well. Based on the results of the first project phase, additional research is needed regarding the geometric design of monolithic micro and nanopositioning systems with macro dimensions. Here, the focus is on the further development of a novel synthesis method based on the rotation angles of each hinge, which is more precise compared to rigid-body model. It allows the goal-oriented design of the compliant mechanism with consideration of the influence of the scaling of spatial positioning systems.Compared to the current state of research, particularly the aim to increase both, the precision and the stroke of compliant mechanisms is a new approach. Thus, the project contributes to the development of a multi-scale synthesis method for spatial compliant linkage mechanisms, which considers the degree of freedom of the mechanism and the integration of the drive into the position system. The results will be verified at two prototypes with different scaling. Finally, design guidelines for the further use in the ultra-precision technology will be formulated.

• DFG Programme: Research Grants