Compact Modular Multi-Part Torsion Springs: Broadening the Design Space with Series Configurations
Published in IEEE/ASME Transactions on Mechatronics (T-MECH), 2025
Abstract: Springs are a vital component in many mechanical systems, where compactness and low mass are key. In a prior study, we demonstrated best-in-class energy density with a novel torsion spring, but it was fundamentally limited by its maximum allowable deflection. In this work, we present a novel series-connected torsion spring architecture that overcomes this constraint, enabling the realization of arbitrarily large deflection ranges in a highly compact and lightweight form factor. We introduce two modular series-connection designs and provide a nonlinear analytical model to account for backlash effects inherent in series connections. Experimental validation demonstrates the scalability and tunability of the proposed architecture, with measured stiffness closely matching designed values and a consistently low energy loss (∼5%). This approach broadens the design space for torsion springs, enabling new opportunities for lightweight, compact actuation across a wide range of robotic, automotive, and consumer applications.