Stable In-hand Manipulation for a Lightweight Four-motor Prosthetic Hand

Fuente: arXiv
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Main Authors: Kuroda, Yuki, Takahashi, Tomoya, Beltran-Hernandez, Cristian C., Tanaka, Kazutoshi, Hamaya, Masashi
Format: Preprint
Published: 2026
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author Kuroda, Yuki
Takahashi, Tomoya
Beltran-Hernandez, Cristian C.
Tanaka, Kazutoshi
Hamaya, Masashi
author_facet Kuroda, Yuki
Takahashi, Tomoya
Beltran-Hernandez, Cristian C.
Tanaka, Kazutoshi
Hamaya, Masashi
contents Electric prosthetic hands should be lightweight to decrease the burden on the user, shaped like human hands for cosmetic purposes, and designed with motors enclosed inside to protect them from damage and dirt. Additionally, in-hand manipulation is necessary to perform daily activities such as transitioning between different postures, particularly through rotational movements, such as reorienting a pen into a writing posture after picking it up from a desk. We previously developed PLEXUS hand (Precision-Lateral dEXteroUS manipulation hand), a lightweight (311 g) prosthetic hand driven by four motors. This prosthetic performed reorientation between precision and lateral grasps with various objects. However, its controller required predefined object widths and was limited to handling lightweight objects (of weight up to 34 g). This study addresses these limitations by employing motor current feedback. Combined with the hand's previously optimized single-axis thumb, this approach achieves more stable manipulation by estimating the object's width and adjusting the index finger position to maintain stable object holding during the reorientation. Experimental validation using primitive objects of various widths (5-30 mm) and shapes (cylinders and prisms) resulted in a 100% success rate with lightweight objects and maintained a high success rate (>=80) even with heavy aluminum prisms (of weight up to 289 g). By contrast, the performance without index finger coordination dropped to just 40% on the heaviest 289 g prism. The hand also successfully executed several daily tasks, including closing bottle caps and orienting a pen for writing.
format Preprint
id arxiv_https___arxiv_org_abs_2601_07559
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Stable In-hand Manipulation for a Lightweight Four-motor Prosthetic Hand
Kuroda, Yuki
Takahashi, Tomoya
Beltran-Hernandez, Cristian C.
Tanaka, Kazutoshi
Hamaya, Masashi
Robotics
Electric prosthetic hands should be lightweight to decrease the burden on the user, shaped like human hands for cosmetic purposes, and designed with motors enclosed inside to protect them from damage and dirt. Additionally, in-hand manipulation is necessary to perform daily activities such as transitioning between different postures, particularly through rotational movements, such as reorienting a pen into a writing posture after picking it up from a desk. We previously developed PLEXUS hand (Precision-Lateral dEXteroUS manipulation hand), a lightweight (311 g) prosthetic hand driven by four motors. This prosthetic performed reorientation between precision and lateral grasps with various objects. However, its controller required predefined object widths and was limited to handling lightweight objects (of weight up to 34 g). This study addresses these limitations by employing motor current feedback. Combined with the hand's previously optimized single-axis thumb, this approach achieves more stable manipulation by estimating the object's width and adjusting the index finger position to maintain stable object holding during the reorientation. Experimental validation using primitive objects of various widths (5-30 mm) and shapes (cylinders and prisms) resulted in a 100% success rate with lightweight objects and maintained a high success rate (>=80) even with heavy aluminum prisms (of weight up to 289 g). By contrast, the performance without index finger coordination dropped to just 40% on the heaviest 289 g prism. The hand also successfully executed several daily tasks, including closing bottle caps and orienting a pen for writing.
title Stable In-hand Manipulation for a Lightweight Four-motor Prosthetic Hand
topic Robotics
url https://arxiv.org/abs/2601.07559