Kinematic Chain for Spherical Joint Alignment
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Solution Overview
Problem
Existing exoskeletons face challenges in replicating spherical motion of anatomical joints like the thumb's carpo-metacarpal joint without generating parasitic forces and aligning with the joint's center of rotation, especially when adapting to different anthropometric measurements.
Innovation Solution
A kinematic chain with three intersecting rotational joints (x, y, z) that include adjustment means, such as threaded fasteners or orthogonal flat portions, to align the center of rotation with the anatomical joint, allowing for spherical motion without parasitic forces, integrated into a hand exoskeleton that can adapt to various hand sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a kinematic chain with three rotational joints is used to reproduce spherical motion of the carpo-metacarpal joint, then the spherical motion can be replicated without parasitic reactions, but it becomes difficult to align the center of rotation of the kinematic chain with the center of rotation of the anatomic joint
Solution Approach 1:
The patent implements a dynamic adjustment mechanism that allows the center of rotation of the kinematic chain to be moved and repositioned. This enables the system to adapt to different anatomical configurations and achieve proper alignment with the carpo-metacarpal joint center of rotation, resolving the contradiction between maintaining accurate spherical motion reproduction and achieving ease of alignment.
2Adaptability or versatility
If the same kinematic principle is used to assist spherical motion of the thumb articulation, then theoretical spherical motion reproduction is achieved, but the alignment between the two centers of rotation becomes increasingly difficult without adequate regulation systems
Solution Approach 1:
The patent designs a universal kinematic chain that can be applied to different spherical joints (shoulder, thumb carpo-metacarpal joint) while incorporating adjustment mechanisms that simplify the regulation process. The same basic structure serves multiple functions across different anatomical sites, reducing the overall complexity of regulation systems needed while maintaining adaptability.
3Force
If rigid exoskeleton structures are used to apply high forces for spasticity treatment, then high forces or torques can be applied, but the device must simultaneously allow patient autonomy when possible (yielding interface) or apply necessary forces when patient fails (rigid interface)
Solution Approach 1:
The patent incorporates dynamic control capabilities that allow the exoskeleton to transition between rigid and yielding states. When the patient can perform motion autonomously, the system yields and allows natural movement. When the patient fails to complete the motion, the system becomes rigid and applies the necessary forces to complete the movement, thus resolving the contradiction between force application capability and adaptive interaction.
Data Source
Figure 1A~1B
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AI summary
A kinematical chain (100) for assisting a spherical motion of an anatomical joint (200) of a finger of the hand (210) of a user, said anatomical joint (200) having centre of rotation P and being arranged for allowing a relative motion of a finger of the hand (210) with respect to a portion of hand (220) of the user, said finger of the hand (210) defining a longitudinal direction δ. The kinematical chain (100) comprises a first rotational joint (110) engaged to the finger of the hand (210) and to a first connection link (115), said first rotational joint (110) arranged to provide a relative rotation α between the first connection link (115) and the finger of the hand (210) about a rotation axis ϰ coincident with the longitudinal direction δ. The kinematical chain (100) also comprises a third rotational joint (130) engaged to the portion of hand (220) and to a second connection link (125), said third rotational joint (130) arranged to provide a relative rotation γ between the second connection link (125) and the portion of hand (220) about a rotation axis z integral to the portion of hand (220). The kinematical chain (100) comprises then a second rotational joint (120) engaged to the first connection link (115) and to the second connection link (125), said second rotational joint (120) arranged to provide a relative rotation β between the first connection link (115) and the second connection link (125) about a rotation axis y. The rotation axes x, y and z intersect in a centre of rotation O, in such a way that the kinematical chain (100) allows a spherical motion of the longitudinal direction δ with respect to the portion of hand (220) about the centre of rotation P.