A Method to Estimate the Oblique Arch Folding Axis for Thumb Assistive Devices

Visakha K. Nanayakkara, Nantachai Sornkaran, Hasitha Wegiriya, Nikolaos Vitzilaios, Demetrios Venetsanos, Nicolas Rojas, M. Necip Sahinkaya, Thrishantha Nanayakkara

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


People who use the thumb in repetitive manipulation tasks are likely to develop thumb related impairments from excessive loading at the base joints of the thumb. Biologically informed wearable robotic assistive mechanisms can provide viable solutions to prevent occurring such injuries. This paper tests the hypothesis that an external assistive force at the metacarpophalangeal joint will be most effective when applied perpendicular to the palm folding axis in terms of maximizing the contribution at the thumb-tip as well as minimizing the projections on the vulnerable base joints of the thumb. Experiments conducted using human subjects validated the predictions made by a simplified kinematic model of the thumb that includes a foldable palm, showing that: (1) the palm folding angle varies from 71. 5 to 75. 3 (from the radial axis in the coronal plane) for the four thumb-finger pairs and (2) the most effective assistive force direction (from the ulnar axis in the coronal plane) at the MCP joint is in the range 0 < ψ< 30 for the four thumb-finger pairs. These findings provide design guidelines for hand assistive mechanisms to maximize the efficacy of thumb external assistance.

Original languageEnglish
Title of host publicationTowards Autonomous Robotic Systems
Subtitle of host publication20th Annual Conference, TAROS 2019, Proceedings, Part 1
EditorsKaspar Althoefer, Jelizaveta Konstantinova, Ketao Zhang
PublisherSpringer, Cham
Number of pages13
ISBN (Electronic)9783030238070
ISBN (Print)9783030238063
Publication statusPublished - 29 Jun 2019
Externally publishedYes
Event20th Annual Conference on Towards Autonomous Robotic Systems - London, United Kingdom
Duration: 3 Jul 20195 Jul 2019
Conference number: 20

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume11649 LNAI
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference20th Annual Conference on Towards Autonomous Robotic Systems
Abbreviated titleTAROS 2019
Country/TerritoryUnited Kingdom


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