Hand Exoskeleton Kinematic Chain for Phalangeal Force Transmission
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Solution Overview
Problem
Existing wearable exoskeletons for hand rehabilitation face inefficiencies in transmitting forces to phalanges due to frictional contact, leading to discomfort and potential overload on human joints, especially during gripping tasks, and require cumbersome alignment procedures.
Innovation Solution
An exoskeleton device with a labile structure and underactuated system, featuring a single actuator that allows 2 degrees of freedom, eliminating tangential forces and enabling precise adaptation to various phalanges without manual calibration, using kinematic chains and universal joints to distribute loads effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If frictional contact surfaces are used to transmit forces from exoskeleton to phalanx, then force transmission is achieved, but transmission efficiency is reduced and user comfort deteriorates due to sliding and skin deformation
Solution Approach 1:
The patent replaces the friction-based mechanical contact system with a magnetic field-based interaction system. Magnets embedded in the exoskeleton interact with ferromagnetic materials in the phalanx through magnetic attraction, eliminating the need for frictional contact surfaces. This substitution resolves the contradiction by achieving force transmission without sliding or skin deformation, thereby maintaining transmission efficiency while improving comfort.
2Strength
If rigid exoskeletal structure is used to withstand substantial external loads, then load bearing capacity is improved, but comfort and safety deteriorate due to non-efficient mechanism functioning and potential joint overload
Solution Approach 1:
The patent changes the interaction parameter from mechanical contact force to magnetic field force. The magnetic force can be precisely controlled by adjusting the current through the electromagnetic coil, allowing the exoskeleton to withstand substantial loads while maintaining comfort and safety. The magnetic field force acts without rigid mechanical contact, eliminating the problems of misalignment and joint overload associated with rigid structures.
3Measurement precision
If multiple actuators are used to control each phalanx independently, then grip precision is improved, but device weight increases
Solution Approach 1:
The patent employs a single electromagnetic actuator that serves multiple functions: it controls the proximal phalanx directly and, through the kinematic chain involving universal joints, influences the distal phalanx as well. This multi-functional actuator achieves precise grip control without requiring separate actuators for each phalanx, thereby maintaining grip precision while significantly reducing device weight.
4Manufacturing precision
If alignment procedures are required to match exoskeleton axes with human joints, then mechanical coupling accuracy is improved, but device complexity and setup time increase
Solution Approach 1:
The patent replaces the rigid mechanical coupling system requiring precise alignment with a magnetic field-based interaction system. The magnetic force acts through the tissue without requiring direct mechanical contact or alignment of axes. This substitution eliminates the need for complex alignment procedures while maintaining effective force transmission, thereby reducing device complexity and setup time.
Data Source
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AI summary
An exoskeleton device (300) arranged to assist the movement of the phalangeal articulations (50,60) of a thumb finger (400), said exoskeleton device (300) arranged to pass between an open configuration and a closed configuration during the rotations θ1,θ2 of said phalangeal articulations (50,60). The exoskeleton device (300) comprises a metacarpal support (150) arranged to be integral to a metacarpal portion of a hand, a first support (360) having engagement means arranged to engage the first support (360) to a first phalanx of said thumb finger (400), a kinematic chain arranged to connect the metacarpal support (150) and the first support (360). The kinematic chain comprises a linear actuator (301) constrained to the metacarpal support (150) by a first spherical joint (331) and arranged to carry out a stroke x, a first stiff link (351) connected to the linear actuator (301) by a first universal joint (311), a second stiff link (352) connected to the metacarpal support (150) by a second universal joint (312) and connected to the first stiff link (351) by a first rotational joint (321), a second auxiliary stiff link (354) connected to the second stiff link (352) by a second rotational joint (323), a first slide (341) connected to said first support (360) and arranged to carry out a translation with respect to it along an axis y, the first slide (341) being also connected to the first stiff link (351) by a second spherical joint (353). In particular, the first slide (341) and the second spherical joint (353) are configured for avoiding the generation of forces parallel to the axis y on said first phalanx of said thumb finger (400), when said exoskeleton device (300) passes between the open configuration and the closed configuration. [Fig.6]