Dynamic legged locomotion for palm-size robots

Minimally-actuated palm-size robots are capable of running at speeds greater than 2 meters per second (20 body lengths per second), with leg stride rates of greater than 20 Hz. In this dynamic regime, passive stabilization is needed for roll-and-pitch instability. However, we have found that certain roll-oscillation modes can be used for continuous high speed turning. Other continuous turning modes have also been identified, such as modulating foot contact location through foot compliance, and controlling differential leg velocity. For the small minimally actuated robots examined, the dynamically enhanced roll-steer mode showed the best turning rate, of over 8 degrees per step, but only appears at certain running frequencies. Interstride phase and velocity control appears promising as a mode for in-plane maneuverability for under-actuated robots.