Precision Jumping Limits from Flight-phase Control in Salto-1P

We developed a deadbeat foot placement hopping controller for an untethered monopedal robot, Salto-1P. The controller uses a third order Taylor series approximation to an offline dynamic model and performs well on the physical platform. The robot demonstrated precise foot placement even on trajectories with aggressive changes in speed, direction, and height: in a random walk, its error standard deviation was 0.10 m. We establish how foot placement precision is tightly limited by attitude control accuracy, requiring attitude error less than 0.7 degrees for some tasks. We also show how foot placement precision degrades linearly as hopping height increases. These precision results apply to the large class of controllers that prescribe touchdown angle to control running velocity.