Precision Robotic Leaping and Landing Using Stance-phase Balance

Prior work has addressed control of continuous jumping using touchdown angle from flight, but greater precision can be obtained by directing individual leaps using liftoff angle from stance. We demonstrate targeted leaping as well as balanced landing on a narrow foot with a small, single leg hopping robot, Salto-1P. Accurate and reliable leaping and landing are achieved by the combination of stance-phase balance control based on angular momentum, a launch trajectory that stabilizes the robot at a desired launch angle, and an approximate expression for selecting touchdown angle before landing. Dynamic transitions between standing, hopping, and standing again are now possible in a robot with a narrow foot. We also present approximate bounds on acceptable velocity estimate and angle errors beyond which balanced landing is infeasible. Compared to a prior Spring Loaded Inverted Pendulum (SLIP)-like gait, the jump distance standard deviation is reduced from 9.2 cm to 1.6 cm for particular jumps, now enabling precise jumps to narrow targets.