Optimization-Based Design for Specific Bistable Mechanics of Compliant Mechanisms

Understanding and controlling the nonlinear bistable mechanics is crucial for the development of advanced bistable devices ranging from quantitative mass sensing to functional smart materials and structures. Currently, bistable features including the switching forces, travelling stroke, bistable index parameter ( ratio of the two switching forces) are affected complicatedly by the structure profile, size and loading cases. Due to the complex coupling effects among these bistable features, it is really difficult to design or modify one specific bistable character without affecting other bistable characters. While subjected to different loads (type and position), the phenomenon of mode switching may occur during the snap-through procedure, thus resulting in bistability uncertainty. Aiming to design specific and stable bistable characters for different application requirements, a novel optimization based bistability design method is proposed through simultaneously modifying the geometries of multi-local segments and their arrangements. With the goal of re-adjusting the bistable index parameter as well as minimizing the snapping force, the uniform cosine-shaped bistable beam is reconstructed by adding several reinforced local segments arranged symmetrically and asymmetrically along the length direction. In two numerical examples, the bistable index parameters and switching forces are properly re-designed without changing the profile and overall size of the original structure. The numerical simulation results show that the bistable index parameter can be redesigned to 1.021 and 1.2 from the original value of 0.598, thus validating the effectiveness of the optimization-based bistability design method, which exhibits great application potentials in bistability based products.