ECCOMAS 2024

Synergistic Design of Compliant Mechanisms by Coupled Topology and Actuator Optimization

  • Nowak, Alexander (Chemnitz University of Technology)
  • Hasse, Alexander (Chemnitz University of Technology)

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Traditionally, topology optimization of compliant mechanisms entails utilizing a predetermined, fixed actuator. However, due to the actuator having constant parameters, and particularly due to its fixed position and orientation, an optimal adjustment between the actuator and the structure cannot be guaranteed. As an alternative, we propose a coupled approach wherein the compliant mechanism is initially designed without consideration of distinct load-cases, allowing a subsequent optimization of the actuators' position and quantitative parameters. This approach ensures that the characteristics of the actuators, such as blocking force and free stroke, are adapted to achieve the optimum performance in interaction with the structure. We first introduce a novel topology optimization method that aims at favorable properties of the structure's static eigenpairs. The presented approach eliminates the need for a computationally expensive condensation of the stiffness matrix, setting it apart from previous modal techniques [1]. Resulting structures are characterized by a single static mode matching a predefined motion pattern and a low eigenvalue compared to other modes. Hence, a structural response is significantly dominated by the designed mode in (almost) all load cases, representing the load-independence inherent in modal approaches. Exploiting this characteristic, we proceed with an actuator optimization with focus on solid-state actuators. As the desired deformation is attainable for arbitrary actuator positions, determining the necessary mechanical properties for each potential actuator in the subsequent optimization becomes straightforward and independent of the other actuators. The primary objective in this work is to minimize the total actuator volume with the least number of actuators required, while ensuring the structural response aligns with the specified motion pattern upon actuation. As a result, an efficient actuator-structure synergy is obtained for the optimized compliant mechanism.