Tendon?Driven Auxetic Tubular Springs for Resilient Hopping Robots

Compliance in jumping robots improves gait stability and enables energy-efficient locomotion. Here, 3D printable auxetic tubular springs from thermoplastic polyurethane (TPU) for rapid sustainable hopping are developed. Because the have negative Poisson's ratios, they become stiffer as compression proceeds theoretically stores 35.2% more energy than a linear spring with same stiffness. As stress concentrates on hinges, it is revealed through experimental, numerical, analytical investigations that hinge geometries, example, lattice angle radius, governs global stiffness robustness of springs. The robot leg composed three parallel sustains 1,000 cycles repeated, one-degree-of-freedom (1-DOF) vertical two-degree-of-freedom (2-DOF) forward hopping. 2.5 kg-robot system requires minimum 420 mJ elastic repeated pre-compressed by tendon-driven actuators 1.08 J during release when touching ground. power stroke calculated 15–18 W. average velocity reaches 0.06 m s?1 increase touchdown to 0.125 rad. cost transport 6.7, similar those living organisms.