Exoskeleton Link Mechanism for Normal Force Application
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Solution Overview
Problem
Conventional exoskeletons and assistive devices often cause discomfort due to mechanical interactions that result in undesirable force distributions and slippage, constraining motion and flexibility, and are typically heavy and cumbersome.
Innovation Solution
A wearable device with a distal and proximal member connected by a link that applies force normal to the major longitudinal axis, using actuators like ball screw or pneumatic actuators, to mimic natural joint motion and reduce shear forces, allowing for comfortable and flexible movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional mechanical joints are used in parallel with anatomical joints, then device structure is simplified, but flexibility is reduced and discomfort increases
Solution Approach 1:
The patent removes the conventional mechanical joint from the exoskeleton design, extracting the source of flexibility constraint. Instead of using a mechanical joint in parallel with the anatomical joint, the design uses a mechanical interface that allows the limb segments to move relative to each other without constraining the anatomical joint's natural range of motion, thereby eliminating the flexibility trade-off.
Solution Approach 2:
The patent implements a dynamic mechanical interface that adapts to the anatomical joint's motion. The interface includes a link connecting distal and proximal members that can accommodate variable angles and positions, allowing the system to dynamically adjust to the user's joint motion rather than imposing a fixed mechanical constraint.
2Device complexity
If force is applied parallel to the limb axis (shear force), then mechanical interaction is simplified, but user comfort is reduced
Solution Approach 1:
The patent inverts the conventional force application direction. Instead of applying shear force parallel to the limb axis, the mechanical interface applies force perpendicular to the limb axis (normal force). This inversion changes the direction of mechanical interaction from parallel to perpendicular, reducing discomfort while maintaining effective force transmission for joint actuation.
3Device complexity
If mechanical interface motion does not match biological joint motion, then device design is simplified, but slippage and internal mechanical changes occur
Solution Approach 1:
The patent employs a dynamic mechanical interface that tracks and adapts to the anatomical joint's instantaneous center of rotation. The link connecting distal and proximal members is configured to accommodate variable angles and positions, allowing the interface to dynamically match the biological joint's motion trajectory throughout the range of motion, preventing slippage and unwanted internal mechanical changes.
Solution Approach 2:
The patent changes the geometric parameters of the mechanical interface to match biological joint kinematics. The link length, attachment points, and angles are designed to correspond with the anatomical joint's instantaneous center of rotation, ensuring that the mechanical interface follows the same motion path as the biological joint across different positions and angles.
4Power
If powered exoskeletons use heavy mechanical components, then actuation capability is improved, but device weight and cumbersome nature increase
Solution Approach 1:
The patent extracts heavy mechanical transmission components from the exoskeleton design. Instead of using conventional powered exoskeleton mechanisms with heavy gears, belts, and linkages, the design uses a simplified mechanical interface with a single link connecting distal and proximal members, significantly reducing device weight while maintaining actuation capability through direct force application.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances comfort and reduces weight, allowing for more natural joint motion and improved locomotory function, addressing issues of discomfort and constraint in existing devices.
Implementation Method 1
the link includes a ball screw actuator
Implementation Method 2
the link includes a bidirectional actuator, such as a pneumatic actuator
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A link extends between a distal member and a proximal member of a wearable device, such as an exoskeleton, orthosis or prosthesis for a human lower limb. One or other of the distal member and the proximal member includes a crossing member. The link extends from the crossing member of the distal member or the proximal member, to the other of the distal member or the proximal member. Actuation of the link translates to a force at the distal or proximal member that is normal to a major longitudinal axis extending through the distal and proximal members. In one embodiment, a sliding link of a device configured for use with a human joint tracks two degrees of freedom of the joint.