KaRMA: A Kinematic Metric for Fine Manipulation Ability in Robotic Hands

2026-05-14

AI Summary

Existing robotic hand evaluation metrics predominantly focus on static attributes and fail to capture the ability to dexterously adjust object poses under sustained contact. This work proposes KaRMA, a purely kinematic metric that, for the first time, defines fine manipulation capability as the reachable pose space under rolling contact, explicitly incorporating joint limits, self-collision avoidance, rolling constraints, and antipodal force feasibility. By employing breadth-first search over elementary translation and rotation primitives, KaRMA quantifies two-finger precision pinch performance along three dimensions: translational coverage, rotational coverage, and sensitivity to initial grasp configuration. Validation across 16 representative robotic hands demonstrates that KaRMA effectively discriminates performance differences indistinguishable by static metrics, yields results qualitatively consistent with task-based benchmarks, and avoids the misleading tendencies inherent in Jacobian-based measures.

Abstract

Traditional robotic hand metrics focus on static properties such as workspace, manipulability, and grasp stability. However, these metrics do not directly measure dexterity under the standard definition in robotic manipulation: the ability to continuously change an object's pose within the hand while maintaining contact from an initial grasp. We introduce Kinematic Rolling Manipulation Ability (KaRMA), a kinematic-only metric for fine manipulation that quantifies reachable in-hand translation and reorientation of a spherical test object within a two-finger precision pinch through feasible rolling motions. KaRMA enforces joint limits, collision constraints, rolling contact, and antipodal force feasibility, then investigates reachable in-hand object poses via breadth-first search over translation and rotation primitives. KaRMA reports three scores: translational coverage (KaRMA-T), rotational coverage (KaRMA-R), and sensitivity to the initial grasp (KaRMA-S). We evaluate KaRMA on 16 widely used robotic hands and compare against static baselines, showing that KaRMA separates hands that rank identically under static proxies, reveals translation-rotation tradeoffs invisible to existing baselines, and is qualitatively consistent with selected published task benchmarks where Jacobian-based metrics can be misleading.

Problem

• dexterity
• in-hand manipulation
• kinematic metric
• robotic hands
• fine manipulation

Innovation

• KaRMA
• in-hand manipulation
• kinematic metric
• rolling contact
• dexterity evaluation