Propeller-Assisted Robust 3D Hopping Robot with Hierarchical Force Allocation

2026-06-06

AI Summary

This work addresses the challenge of achieving robust three-dimensional hopping in legged robots, which typically lack control authority during flight and struggle with stability under disturbances. To overcome this limitation, the authors propose a novel hopping robot that integrates an actively actuated 3-RSR parallel leg mechanism with an onboard tricopter system. Leveraging a single rigid-body dynamics model, they develop a hierarchical force allocation framework that, for the first time, enables coordinated control of leg-ground contact forces and rotor thrusts throughout the entire hopping cycle—spanning both stance and flight phases—to ensure consistent attitude stabilization and motion control. Experimental results demonstrate that the robot can sustain hopping locomotion in complex indoor and outdoor environments, effectively handling abrupt terrain changes and external perturbations, thereby significantly enhancing hopping robustness and terrain adaptability.

Abstract

Monopedal hopping robots are conceptually simple but highly dynamic and inherently unstable. Achieving robust 3D hopping is still difficult because ground reaction forces are available only during the short stance phase, while the robot is underactuated in flight. A key unresolved issue is how to improve flight-phase control authority. Propeller assistance provides a promising solution, but it requires careful coordination of leg-generated contact forces and propeller thrusts across stance and flight. This paper presents Pro-OMEGA2, a propeller-assisted 3D monopedal hopping robot with an active 3-RSR parallel leg and a trunk-mounted tri-rotor for auxiliary attitude regulation. To address the force coordination challenge, we propose a Hierarchical Force Allocation (HFA) framework based on a single rigid body (SRB) model. The leg generates the main stance contact wrench, while the tri-rotor provides auxiliary attitude regulation, compensating the residual attitude moment in stance and maintaining attitude during flight. Real-robot experiments in indoor and outdoor scenarios demonstrate sustained 3D hopping, including terrain transitions and impulsive push recovery, validating robustness under unmodeled contact and external disturbances.

Problem

• monopedal hopping
• flight-phase control
• underactuated
• 3D hopping
• attitude regulation

Innovation

• propeller-assisted hopping
• hierarchical force allocation
• 3D monopedal robot
• attitude regulation
• underactuated locomotion