Throwing a Tight Spiral American Football by a Humanoid Robot

2026-08-17

AI Summary

This study addresses the challenges of insufficient spin control and complex release dynamics in humanoid robotic American football throwing by proposing a coupled whole-body control framework. The approach synergizes trajectory optimization with model predictive control to coordinate upper and lower limb motions, integrated with a phased upper-limb control strategy to achieve the first spin-stabilized tight spiral throw. Experimental validation on the Unitree G1 robot demonstrates a release velocity of 5.35 m/s, a spin efficiency of 93.6%, and a nose angle error of only 0.286 radians. These results confirm the framework’s effectiveness in overcoming the difficulties associated with high-dynamic dexterous manipulation, marking a significant advancement in humanoid athletic performance.

Abstract

Accurate throwing of the American football requires precise regulation of release conditions, where coupled linear and angular momentum determine flight stability and targeting accuracy. While prior work on robotic object throwing has largely focused on generating dynamically feasible release velocities using open-gripper paradigms, explicit control of spin injection at detachment remains underexplored, particularly for aerodynamically anisotropic objects like the American football. In this paper, we present the spin-stabilized controlled tight spiral throw of an American football by a humanoid robot. Achieving this requires (i) accurately reaching the desired coupled momentum, which often involves high degrees-of-freedom (DoF) movements completed within approximately half a second, and (ii) managing the complex transient contact dynamics that arise during the sub-100-millisecond release phase, when the football is effectively underactuated as it moves partially across the fingers. To this end, we develop a coupled whole-body control strategy where the lower body is performing informed stabilization while the upper body is further divided into two phases with (i) a throw phase accelerating the football to a target state through trajectory optimization and tracking, and (ii) a follow-through phase utilizing model predictive control to actively control the wrist and remaining in-contact fingers. The proposed framework is empirically validated on a 29-DoF Unitree G1 humanoid equipped with a 7-DoF Dex3-1 three-fingered gripper. The thrown American football reaches up to 93.6% spin efficiency and a 0.286 radians linear-velocity-to-nose-alignment (nose-angle) error (where an ``ideal'' tight spiral corresponds to 100 % spin efficiency and 0 radians nose-angle error) at up to a 5.35 m/s linear velocity and an angular velocity of 14.5 rad/s.

Problem

• Humanoid Robot
• American Football Throwing
• Spin Stabilization
• Contact Dynamics
• Tight Spiral

Innovation

• Spin-stabilized throwing
• Coupled whole-body control
• Model Predictive Control
• Transient contact dynamics
• Humanoid robot