Partial Hand Prosthesis Using Wrist-Harness Digit Actuation
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Solution Overview
Problem
Conventional prosthetic limbs for partial hand amputations, particularly those involving the metacarpophalangeal joint, lack functional movement due to the absence of a pivot point for actuation, limiting their ability to mimic natural hand movements.
Innovation Solution
A prosthetic apparatus that utilizes a wrist harness with integrated actuators and sensors to leverage residual motor control from adjacent digits, providing multiple degrees of freedom through tethered and mechanical attachments, and a variable compression system to enhance engagement with the wrist, allowing for functional movements like pinching and gripping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional prosthetic limbs are used for partial hand amputations at the metacarpophalangeal joint, then the prosthetic can be attached to the wrist, but functional movement is lost due to absence of pivot point for actuation
Solution Approach 1:
The prosthetic hand is divided into multiple independent segments (fingers, thumb) that can be individually actuated. Each digit has its own actuation mechanism allowing independent movement control, resolving the complexity issue by breaking down the overall actuation system into manageable modular units.
Solution Approach 2:
A wrist-mounted actuator system serves as an intermediary between the user's residual motor control and the prosthetic digits. The actuators convert electrical signals into mechanical movement through tendons and pulleys, providing the necessary pivot points and actuation forces without requiring complex mechanical linkages at the amputation site.
2Adaptability or versatility
If residual motor control from adjacent digits is leveraged for actuation, then functional movement is restored, but the device requires integrated sensors and actuators increasing complexity
Solution Approach 1:
The wrist harness serves multiple functions: it provides structural support for the prosthetic hand, houses the actuator systems, contains the tendon routing mechanisms, and integrates the sensor arrays. This multi-functionality reduces overall system complexity by consolidating multiple subsystems into a single integrated unit.
Solution Approach 2:
Optical fiber strain sensors are integrated into the tendon routing system to detect finger position and grip force. This feedback is transmitted to the actuator control system, enabling closed-loop control that adapts the prosthetic's movement to the user's intent and the mechanical state of the prosthesis itself.
3Reliability
If variable compression system is added to enhance wrist engagement, then gripping load stability is improved, but the harness structure becomes more complex
Solution Approach 1:
The wrist harness incorporates variable compression capabilities that dynamically adjust the tightness and distribution of pressure across the wrist. This dynamic adjustment allows the harness to adapt to different gripping loads and user comfort requirements, maintaining reliable engagement without requiring an overly complex mechanical structure.
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
Enables functional, voluntary movement of prosthetic digits in response to natural motor functions, restoring dexterous capabilities by mimicking natural hand movements, particularly in cases of partial or complete digit amputations.
Implementation Method 1
an array of optical fiber strain sensors are disposed on the interior of the receptacle
Data Source
AI summary
A prosthetic device and approach for amputee remediation addresses partial or complete replacement of digits, and leverages the use of the remaining functional digits for directing operation of the prosthetic digits. A complete prosthetic digit replaces an amputated digit from actuated movement driven by an adjacent functional digit. A partial amputation leverages residual movement from the remaining digit portion as input to an actuator for amplifying the intent of the input through a motorized actuator to impart movement to the prosthetic digit. A wrist harness supports the apparatus of partial and complete prosthetic digits as a single appliance. A variable compression feature augments tension on the wrist harness to tightly engage the prosthetic appliance to the wrist to offset a gripping load on the prosthetic digits.