Analysis of Harpy's Constrained Trotting and Jumping Maneuver

TL;DR

This paper analyzes data from Harpy, a hybrid leg-thruster robot, revealing how it achieves stable, symmetric locomotion with controlled joint behavior and effective energy use across trotting and jumping modes.

Contribution

It provides a detailed analysis of hybrid leg-thruster locomotion, highlighting principles for stability, control, and energy management in bipedal robots.

Findings

Harpy achieves stable, bounded trajectories during locomotion.

Legs provide primary propulsion, thrusters assist in aerial control.

Robustness and symmetry confirmed across multiple experiments.

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.