Analysis of Harpy's Constrained Trotting and Jumping Maneuver

Abstract: This study presents an analysis of experimental data from Harpy, a thruster-assisted bipedal robot developed at Northeastern University. The study examines data sets from trotting and jumping experiments to understand the fundamental principles governing hybrid leg-thruster locomotion. Through data analysis across multiple locomotion modes, this research reveals that Harpy achieves stable locomotion with bounded trajectories and consistent foot placement through strategic leg-thruster synergy. The results demonstrate controlled joint behavior with low torques and symmetric tracking, accurate foot placement within kinematic constraints despite phase-transition perturbations, and underactuated degree-of-freedom stability without divergence. Energy level analysis reveals that legs provide primary propulsion, while the thrusters enable additional aerial phase control. The analysis identifies critical body-leg coupling dynamics during aerial phases that require phase-specific control strategies. Consistent repeatability and symmetry across experiments validate the robustness of the hybrid actuation approach.