Prosthetic Digit Actuation With Flexible Link and Load Support
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Solution Overview
Problem
Existing prosthetic digits do not sufficiently mimic natural fingers, leading to inadequate functionality and potential damage under high loads.
Innovation Solution
Prosthetic digits with a rigid link having a flexible portion, single-sided drive transmission, and a compact actuator with a gearbox positioned parallel to the knuckle joint, featuring a support side that provides rotational resistance and absorbs loads, along with a gearbox that adjusts speed and torque output based on mechanical and electronic feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a rigid link structure is used in prosthetic digits, then structural strength is improved, but the ability to absorb high loads and reduce damage risk deteriorates
Solution Approach 1:
The link transitions from a completely rigid structure to one with controlled flexibility through the inclusion of a flexible portion. This flexible portion allows the link to bend and absorb excessive loads beyond a threshold amount, preventing damage to the digit and actuator while maintaining sufficient rigidity for normal operation and structural strength.
2Device complexity
If actuation forces are transmitted from a single side of the digit, then device complexity is reduced, but the ability to handle lateral loads deteriorates
Solution Approach 1:
The transmission system is designed with asymmetric functionality: one side of the digit (drive side) transmits actuation forces through a drive transmission, while the opposite side (support side) provides lateral support through opposing surfaces that contact under lateral loads. This asymmetric design achieves both single-sided actuation simplicity and lateral load resistance.
3Volume of moving object
If a compact actuator with parallel motor and gearbox is used, then volume is reduced, but manufacturing complexity increases
Solution Approach 1:
The motor and gearbox are arranged in a parallel configuration rather than a series arrangement, and transfer gears are positioned perpendicular to both components. This three-dimensional spatial arrangement achieves compact actuator volume while maintaining manufacturability through standardized gear configurations.
4Strength
If the opposing surfaces are positioned close together, then lateral load resistance is improved, but friction under normal operation increases
Solution Approach 1:
The opposing surfaces on the support side are pre-positioned with a gap between them that prevents contact during normal operation, eliminating unnecessary friction. When lateral loads exceed a threshold amount, the gap closes and the surfaces contact to provide rotational resistance and prevent damage, applying support action only when needed.
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 the mimicry of natural finger movement, provides enhanced gripping functionality, and reduces the risk of damage by absorbing high loads and adjusting actuation forces, resulting in improved prosthetic digit performance.
Implementation Method 1
The link's flexibility may absorb loads beyond a threshold amount to absorb force and reduce the risk of damage to the digit and actuator
Implementation Method 2
under high lateral loads the gap is closed and the surfaces contact each other to introduce rotational resistive friction into the digit and prevent damage
Data Source
AI summary
Features for prosthetic digits and actuation systems including transmission features for a worm wheel rotation by a lead screw. A keyed member such as a central axle is spring-biased and transmits rotation from the worm wheel to the digit while allowing for manual rotation of the digit without damaging the worm wheel or other components. In some embodiments, the digit may include a link having flexibility to cause rotation of the digit segments while absorbing shock or otherwise high rotational loads. The digit may include a single-sided drive mechanism, where the opposite side provides support in case of high lateral loads. The digit may include a motor and gearbox in parallel and connected mechanically via a transfer gearbox. The digit may include a variable speed and variable torque gearbox.