Tuning Modules With Elastic Instabilities On-the-Fly for Reconfigurable Shapes and Motions

Multistable structures, known for their ability to rapidly switch between multiple stable states, are increasingly used for various robotic and mechatronic systems (e.g., grippers, swimming, jumping, or crawling robots). However, existing multistable structures generally have a fixed structure after fabrication, leading to a fixed energy profile with respect to deformations, a concept termed as energy landscape (EL) that dictates a structure's stable configurations and dynamic responses. To overcome this limitation, this work investigates how to actively tune the EL of a beam-based mechanism with a linear spring on the fly to enable tunable modules. We consider two tuning strategies to adjust the beam's initial bending angle and the offset of the spring. We establish a forward model to predict the module's EL and conduct experiments to validate this model. We also address the inverse problem to achieve a desired EL by choosing proper values of the initial bending angle and the offset of the spring. Finally, we demonstrate the practical applications of this tunable module with three cases: A kicker, a configurable arm, and a crawling robot. Our research lays the groundwork for advanced robotic and mechatronic systems, enabling them to harness structures with elastic instabilities for tuning their performance on the fly, thereby enhancing their adaptability and functionality.