Exoskeleton Joint with Circular Arc Rails for Wrist Alignment
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Solution Overview
Problem
Existing exoskeletons and rehabilitation devices lack a joint with two degrees of freedom that accurately mimics the human wrist joint, leading to instability and limited movement, with most solutions either restricting rotation or causing potential injury due to misalignment of rotation axes.
Innovation Solution
A compact hollow joint with two degrees of freedom, featuring circular arc rails and sliders, where the rails are either interconnected or the sliders are, allowing for wide-range movement while ensuring the joint rotation axes align with the user's joint axes, providing stability and protection against excessive bending.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If two ordinary rotation joints are used to provide two degrees of freedom, then the joint can move in two axes, but the maximum joint rotation is limited in one of the axes (palmar and ulnar duction or palmar and dorsal flexion)
Solution Approach 1:
The patent employs circular arc rails instead of straight rails, creating curved guide paths that enable the joint to achieve wider rotation ranges in both axes. The circular geometry allows the connection element to follow an arc-shaped trajectory, eliminating the rotation limitations inherent in straight-rail designs and accurately replicating the spherical motion characteristics of the human wrist joint.
2Reliability
If member / draw bar mechanisms are used to provide stable rotation axis, then the rotation axis is stable and identical to user's joint rotation axis, but the structural complexity and large dimensions increase
Solution Approach 1:
The patent extracts the essential function of providing a stable rotation axis from the complex member/draw bar mechanism and implements it through a simplified circular arc rail system. By removing unnecessary structural elements and retaining only the critical circular guide rails with connection elements, the design achieves rotation axis stability identical to the user's joint axis while dramatically reducing structural complexity.
Solution Approach 2:
The circular arc rails inherently provide a stable rotation axis through their curved geometry, eliminating the need for complex mechanical structures. The circular shape ensures that the connection element rotates along a precise arc path, naturally maintaining alignment with the user's joint rotation axis without requiring additional stabilization mechanisms.
3Volume of moving object
If hollow cardan joints are used, then the joint structure is compact, but the inner space for the user's hand is too small
Solution Approach 1:
The patent transitions from a traditional hollow cardan joint configuration to a circular arc rail system where the rails and connection elements are arranged in a spatial configuration that optimizes both compactness and inner space. By utilizing circular arc geometries and strategically positioning the rails, the design creates sufficient internal volume for the user's hand while maintaining an overall compact joint structure suitable for wearable exoskeletons.
4Reliability
If rail mechanism is used to provide stable rotation axis, then the rotation axis is stable, but the solution only provides rotation in a single axis and never for application for the wrist joint
Solution Approach 1:
The patent merges two circular arc rail systems into a single integrated joint structure, where the rails work together to provide stable rotation axes in two perpendicular directions. This combination enables the joint to achieve two degrees of freedom while maintaining the stability benefits of the rail mechanism, making it suitable for wrist joint applications that require multi-axis movement.
Data Source
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AI summary
A joint with two degrees of freedom for use in exoskeletons and rehabilitation devices for connection of a first and a second relatively moving parts of the exoskeleton, the joint comprises at least a first and a second rail in shape of circular arcs, which are located in two planes parallel to each other, wherein the centers of circles of the circular arcs differ and the straight lines intersecting centers of circles of circular arcs and perpendicular to the respective planes defined by the circular arcs intersect each other in a single point, and further a movably arranged slider on each rail, with either rails (3, 31, 32) firmly interconnected and sliders (6, 7) each suitable for connection to another relatively moving part of the exoskeleton, or with sliders (6, 7) firmly interconnected and rails (3, 31, 32) each suitable for connection to another relatively moving part of the exoskeleton.