Wearable Thumb Motion Assistance Device Using Tendon Drive
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Solution Overview
Problem
Conventional motion support apparatuses for hand-finger paralysis are inadequate in assisting thumb movements, limiting grip types and increasing weight, which hinders everyday life activities and significantly degrades Quality of Life (QOL).
Innovation Solution
A wearable hand-finger motion support apparatus that assists thumb movements without restricting its degree of freedom, utilizing a tendon drive system with wires to mimic muscle contractions and provide necessary forces for gripping, while allowing direct contact with objects and preserving sensory input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional motion support apparatuses fix the thumb at the opposite position to assist thumb movements, then thumb flexion and extension are supported, but the degree of freedom of the thumb is restricted and grip types are narrowed
Solution Approach 1:
The apparatus divides thumb movement assistance into separate functional components: a first linear member for flexion/extension assistance and a second linear member for opposition movement assistance. This segmentation allows independent control of different thumb movements, enabling multiple grip types without restricting overall degree of freedom.
Solution Approach 2:
The system dynamically adjusts the assistance provided to thumb movements based on the user's needs. The degree of freedom is maintained by allowing passive movements while providing active assistance only when needed, enabling both supported and unrestricted grip types as required.
2Reliability
If conventional motion support apparatuses use links or frames to assist thumb movements, then structural support is provided, but the weight of the apparatus increases
Solution Approach 1:
The apparatus replaces traditional mechanical link and frame structures with a tendon-driven system using flexible linear members (strings or cables). This substitution maintains the necessary structural support and movement control while significantly reducing the weight and complexity of the apparatus.
Solution Approach 2:
The system uses flexible linear members (strings or cables) instead of rigid mechanical structures. These thin, flexible elements provide sufficient support for thumb movements while minimizing weight, allowing the apparatus to be lightweight yet reliable.
3Ease of operation
If the thumb is covered by the retaining member to assist movements, then motion support is provided, but direct contact with objects and sensory input are impeded
Solution Approach 1:
The fingertip retaining member provides partial coverage of the thumb, offering motion support only where necessary while leaving the pulp and other areas exposed. This partial action maintains sensory contact with objects and preserves tactile feedback while still providing the needed assistance for thumb movements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively assists thumb movements, enabling a wide range of gripping actions, including opposition, adduction, flexion, and extension, thereby improving the ability to perform daily tasks and enhancing QOL for individuals with hand-finger paralysis.
Implementation Method 1
utilizing a tendon drive system with wires to mimic muscle contractions and provide necessary forces for gripping
Data Source
Figure 1
Figure 2(A)~2(C)
Figure 3
AI summary
A wearer is made to judge, based on a detection result by a signal detection unit, either one of an opposition movement, an adduction movement, a flexion movement, and an extension movement of a thumb; and a linear member drive unit is controlled to pull or relax each linear member corresponding to the judged movement in order to cause the thumb's intrinsic muscles and/or extrinsic muscles, which are required for the judged movement, to generate an assist force.