Balancing and Hopping With a Ring Screw Actuation on One Leg

This letter presents the prototype of a human-sized, untethered athletic hopping and balancing underactuated monopedal robot designed to withstand crash landings. Experimental results in 2D of the robot balancing on an unstable contact point, hopping vertically, landing back, and balancing within a narrow point of 2.5 cm are presented and discussed. Furthermore, the first application of a new linear transmission mechanism called the ring screw, an alternative to the ball screw, is presented. The hopping ability of two robots, one equipped with a commercially available ball screw and one with the ring screw, is compared, with the latter achieving a hopping height of 34 cm, three times higher than the former, thanks to its capability to provide extra power derived from its higher speed limit.