Robust topology optimization of a flexural structure considering multi-stress performance for force sensing and structural safety

This paper demonstrates a new robust topology design formulation for a compliant sensor structure considering multi-stress performance. Compliant mechanism design is one of the main applications of topology optimization that can be used to achieve displacement or force requirements based on its elastic deformation. Most compliant mechanisms have hinge joints where high stress is observed and this should be carefully considered in the design formulation. In this paper, we investigate a new design formulation that considers multiple stress components for force measurement and structural safety in a compliant mechanism—a wind tunnel balance. An internal wind tunnel balance is a multi-axis force sensor that measures aerodynamic forces and moments during wind tunnel testing. For the axial section of the balance, it is required to have substantial stress reading (sensor performance) by the axial load. In this paper, two stress measures are used in the design formation: (1) local directional stress to meet the sensor performance by a small axial force, and (2) normalized P-norm stress with a relaxation approach to ensure the safety of the balance by a large normal force. The high force ratio between axial and normal forces (1:10 +) is investigated in this paper. In addition, a robust approach is applied to reflect the manufacturing uncertainties from three different projected design variables. The manufacturable blueprint designs using this approach show satisfactory performance with respect to sensing and structural safety.