Remote-Center Joint Guidance for Wearable Hip Motion Alignment
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Solution Overview
Problem
Current exoskeleton technologies have a limited range of motion about the hip and ankle joints due to the internal/external rotation axis being inaccessible for direct alignment, leading to misalignment between the device's movement and the user's motion, and existing solutions are either complex or interfere with the body.
Innovation Solution
A motion guiding device with three rotary joints that intersect at a remote center of rotation, allowing three-degree-of-freedom motion without mechanical interference, using adjustable linkages and actuators to align with the user's joint center, and optionally incorporating a control system for actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the rotary element for internal/external rotation is displaced to a joint that does not intersect the hip joint, then the system can have three DOFs, but the movement of the device does not match the motion of the user
Solution Approach 1:
The patent introduces a fourth degree of freedom (translation along the vertical axis) in addition to the three rotational DOFs. This dimensional extension allows the mechanism to achieve a remote center of rotation that can be positioned at the hip joint center, resolving the conflict between having three DOFs and matching user motion accurately. The spherical parallel mechanism with four DOFs enables the effector to both rotate and translate, creating a virtual spherical joint that matches the hip joint's motion characteristics.
2Measurement precision
If a more complicated joint is employed to create a remote center of rotation within the body, then three purely rotary DOFs are achieved, but the system complexity increases
Solution Approach 1:
The patent segments the complex joint mechanism into multiple simpler spherical parallel mechanisms. Each mechanism consists of three rotational DOFs and one translational DOF, with the rotational axes intersecting at a common point. This segmentation allows the system to achieve accurate remote center of rotation alignment while maintaining relatively simple individual mechanism structures that can be manufactured and assembled more easily.
3Measurement precision
If the rotary joints are aligned with the target joint axes, then the motion matching is accurate, but the mechanical parts interfere with the body
Solution Approach 1:
The patent introduces an intermediary virtual spherical joint that mediates between the mechanical joints and the target hip joint. The effector plate creates this virtual joint through its motion characteristics, allowing the mechanical joints to be positioned away from the body while still achieving accurate motion tracking. The virtual spherical joint acts as an intermediary that translates the mechanical motion into biologically accurate hip joint motion without direct mechanical contact with the body.
Data Source
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AI summary
Examples of a motion guiding device of a target joint of a target body are disclosed. The device allows three degree-of-freedom (DOF) motion about a remote center of rotation that is approximately aligned to a center of rotation of the target joint. The device comprises a base adjustably connected to the target body and three rotary joints interconnected with a network of linkages. One end of the network of linkages is connected to the base and the opposite end to an effector plate. At least one of the three rotary joints is not aligned with an axes of motion of the target joint and any of these rotary joints may be positioned under angle with respect to the others. Each of the rotary joints provides one DOF of rotary motion about the respective axes and each axis of the three rotary joints intersect at the remote center of rotation. The geometry of the network of linkages is adjustable to adjust a position of the remote center of rotation in three dimensions. The three rotary joints and the network of linkages rotate the effector plate about the remote center of rotation that is approximately align with the center of rotation of the target joint. This system may be connected with one or more parallel branches for additional actuation.