Method for determining displacement and characterizing spatial kinematic misalignment in a rigid exoskeleton

Ott, Oliver; Ersoysal, Samet; Kraus, Niklas; Weidner, Robert

doi:10.3390/machines13040284

Method for determining displacement and characterizing spatial kinematic misalignment in a rigid exoskeleton

Publication date

2025-03-30

Document type

Forschungsartikel

Author

Ott, Oliver

Ersoysal, Samet

Kraus, Niklas

Weidner, Robert

Organisational unit

Fertigungstechnik

DOI

10.3390/machines13040284

URI

https://openhsu.ub.hsu-hh.de/handle/10.24405/23027

Publisher

MDPI

Series or journal

Machines

ISSN

2075-1702

Periodical volume

13

Periodical issue

4

Article ID

284

Peer-reviewed

✅

Part of the university bibliography

✅

Language

English

Abstract

With the increasing use of exoskeletons to reduce physical strain in industrial applications, precise adaptation to the user’s anthropometry is crucial for effective force transmission and user acceptance. This paper presents a method that compensates for axial misalignment between the human joint and the exoskeleton’s axes of rotation to optimize the anthropometric alignment. It further quantifies the resulting displacement, providing instructional recommendations for manual refinement of the exoskeleton’s initial kinematic configuration. The method thereby represents a first step toward a comprehensive investigation of the initial offset’s influence on an anthropometric fit. The mathematical derivation was described using the rigid shoulder exoskeleton “Lucy”. The validation on increasingly complex mock-ups showed an average calculated error of 0.84mm (SD 0.24mm) in 2D and 7.97mm (SD 1.30mm) in 3D, where the errors decreased with smaller initial offsets. A preliminary field study with three participants revealed improved anthropometric alignment but indicated limitations in the exoskeleton’s structural adjustment possibilities, highlighting the need for further modifications. Building on these findings, subsequent studies will involve further investigation of factors such as the migration of the instantaneous center of rotation during motion, soft tissue deformations, and greater population diversity.

Description

This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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