Modular Kinematic Chain for Joint Alignment
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Solution Overview
Problem
Existing robotic exoskeletons for orthopedic rehabilitation face challenges in size, weight, and kinematic alignment, leading to unnatural movement experiences and parasitic forces on anatomical joints, particularly in the hand, due to high stiffness and lack of adaptability to user dimensions.
Innovation Solution
A modular kinematic chain with rotating elements and roto-translation constraints that can be adjusted to align with anatomical joints, allowing for flexible adaptation to different anthropometric measurements and joint types, minimizing parasitic forces by using a system of cables and pulleys or toothed profiles for actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid kinematic chain is used to assist joint movement, then structural stability is improved, but adaptability to different anthropometric dimensions deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the kinematic chain adjustable and adaptable through modular design. The chain can be reconfigured with different link lengths and configurations to match various user anthropometric dimensions, allowing the rigid structure to adapt dynamically to different users while maintaining structural stability during operation.
Solution Approach 2:
The patent segments the kinematic chain into modular components that can be independently adjusted or reconfigured. This segmentation allows different parts of the chain to be optimized for specific joint types and user dimensions, resolving the contradiction between maintaining overall structural stability and achieving local adaptability.
2Device complexity
If the kinematic chain is disposed above or sideways of the joint, then actuation is simplified, but parasitic forces on bone segments increase
Solution Approach 1:
The patent introduces an intermediary mechanism that transfers the actuation force from a convenient location to the joint axis. This intermediary transmission system allows the actuator to be positioned away from the joint while still applying force directly along the joint's rotation axis, eliminating parasitic forces while maintaining actuation simplicity.
Solution Approach 2:
The patent employs asymmetric positioning of the kinematic chain elements relative to the joint, where the chain is deliberately offset and uses mechanical advantage through linkages to produce symmetric rotational effect about the joint axis. This asymmetric design simplifies actuation while maintaining proper force alignment.
3Strength
If the kinematic chain has high stiffness, then load-bearing capacity is improved, but comfort of use and effectiveness deteriorate
Solution Approach 1:
The patent applies parameter changes by making the stiffness characteristics of the kinematic chain variable rather than fixed. The system can adjust its mechanical impedance and stiffness parameters in real-time to match the user's needs, providing high load-bearing capacity when required while maintaining comfort during normal operation through softer, more compliant settings.
Data Source
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Figure 3A~3B
AI summary
A kinematic chain (10) for assisting the movement of an anatomical articulation comprising at least one kinematic module (100,100a,100b,100c) comprising a frame (105) having a first end (106) and a second end (106') comprising a profile P' 0 and a centre of rotation O' 0, said frame (105) having a reference plane π 0 passing through the centre of rotation O' 0. The kinematic module then comprises a number n of rotating elements (110, 120, 130), defined with index i= 1,...,n, each i-th rotating element having a first end (111, 121, 131), comprising a profile P i and a centre of rotation O i , and a second end (111', 121', 131'), comprising a profile P' i and a centre of rotation O' i , each i-th rotating element having a reference plane π i passing through the centres of rotation O i and O' i . The kinematic module also comprises an elongated element (140) having a first end (141) comprising a profile P n+1 and a centre of rotation O n+1 . The kinematic chain (10) is configured in such a way that the reference plane π 0 is parallel to the reference plane π 1 and coplanar to the reference plane π 2; for i = 1,...,n each reference plane π i is parallel to a reference plane π i +1 and coplanar to a reference plane π i + 2; the rotating element i = 1 is constrained to make a relative rotation ϑ 1 with respect to the frame (105) about an axis passing through the centres of rotation O 1 and O' 0; for i = 1,...,n each rotating element i + 1 is constrained to make a relative rotation ϑ i +1 with respect to a rotating element i about an axis passing through the centres of rotation O i +1 and O' i ; the profile P' 0 contacts the profile P 2 at a point C 1 in such a way that O' 0 O 2 = O 1 O' 1 = r' 0 + r 2; for i = 1,...,n-1 each profile P' i contacts a profile P i +2 at a point C i +1 in such a way that O' i O i +2 = O i +1 O' i +1 = r' i + ri+2 = r i +1 + r' i +1· Furthermore, the contact between profiles P' 0, P i , P' i and P n +1 allows a transmission of a rotational movement without slipping between the frame (105), the rotating elements (110, 120, 130) and the elongated element (140), verifying the equation ϑ i +1 = ϑ i *(r' i -1/r i +1).