V. Chalvet and D.J. Braun, Criterion for the Design of Low Power Variable Stiffness Mechanisms, IEEE Transactions on Robotics, vol. 33, no. 4, 1002-1010, 2017.
This paper introduces a physical measure for identifying mechanical designs that achieve stiffness modulation with low power cost. Using this measure, the authors present an ideal variable stiffness mechanism unaffected by external loads and analyze existing designs against this standard. The study highlights a practical realization that not only holds stiffness settings with zero input force under no load but also enables infinite-range stiffness modulation using finite control forces.
Why it matters: Designing actuators that adapt stiffness efficiently is critical for reducing energy use in robotics. This work provides a clear design criterion and identifies mechanisms capable of low-power, wide-range stiffness modulation, paving the way for energy-efficient robotic systems and assistive devices.