Throwing a Tight Spiral American Football by a Humanoid Robot
2026-08-17 • Robotics
Robotics
AI summaryⓘ
The authors developed a humanoid robot that can throw an American football in a stable, spinning spiral like a skilled human player. To do this, the robot controls both the speed and spin of the ball by carefully coordinating its whole body during the throw and the split-second release. They created special control methods to handle fast, complex finger movements and wrist actions while the ball leaves the hand. Their tests showed the robot achieved nearly perfect spin and good alignment of the ball's nose during flight at realistic throw speeds.
American footballspin stabilizationhumanoid robottrajectory optimizationmodel predictive controldegrees of freedomrelease dynamicsangular momentumlinear velocityaerodynamic stability
Authors
Zaid Mahboob, Bowen Weng
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.