Modular Prosthetic Hand With Distal Finger Actuators
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Solution Overview
Problem
Existing hand prostheses face challenges in replicating the complex motion of human fingers due to their large number of anatomical parts, leading to issues such as stiffness, high weight, and the inability to replace individual fingers, which results in discomfort and limited biomimetic functionality, especially for smaller users like women and children. Additionally, current sensor systems are costly and require customization, limiting their accessibility and effectiveness.
Innovation Solution
A prosthetic hand structure with finger actuators located within each finger, allowing for independent operation and modularity, combined with a sensor system using force sensors and EMG sensors to detect muscle activity, enabling precise control of finger movements and reducing the need for multiple EMG sensors, thus minimizing weight and cost while maximizing biomimetic functionality and user adaptability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If actuators are arranged in the palm of the hand, then the prosthesis can achieve gripping function, but the fingers cannot be replaced separately and the structure becomes cumbersome
Solution Approach 1:
The prosthesis is divided into modular components where each finger can be independently replaced. The actuators are segmented and distributed along the finger structures rather than centralized in the palm, allowing individual finger modules to be detached and replaced without affecting other fingers.
2Adaptability or versatility
If actuators are located distally in the fingers, then finger replaceability is improved, but the prosthesis becomes heavy and cumbersome
Solution Approach 1:
The actuator distribution follows a local quality principle where smaller, lighter actuators are placed only where needed in each finger segment rather than using large centralized actuators. This allows distal placement for replaceability while minimizing overall weight through localized, optimized actuator selection.
3Weight of moving object
If phalanx joints are simplified to reduce weight, then the prosthesis becomes lighter, but the stiffness increases excessively
Solution Approach 1:
The phalanx joints incorporate dynamic elements such as springs and dampers that allow the joints to be lightweight yet adaptable in stiffness. The joints can adjust their mechanical properties based on operational conditions, providing light weight during normal use while maintaining adequate stiffness when needed for support or impact absorption.
4Measurement precision
If multiple EMG sensors are used for precise muscle activity detection, then detection precision is improved, but the cost and customization requirements increase
Solution Approach 1:
The sensor system is designed with universal, multi-functional sensors that can detect multiple muscle activities simultaneously. Rather than requiring separate specialized sensors for each muscle, the system uses versatile sensors that can identify different muscle patterns, reducing the total number of sensors needed and eliminating customization requirements while maintaining detection precision.
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 provides a lightweight, biomimetically accurate hand prosthesis that can be customized for various users, offering interchangeable fingers and reduced muscle fatigue, along with a cost-effective production method that eliminates the need for individualized fitting, enhancing user experience and accessibility.
Implementation Method 1
a worm screw (116) integral to the proximal stiff link (112) and having a threaded profile... The worm screw (116) is arranged for carrying out a rotation about its longitudinal axis
Implementation Method 2
a rack (117)... adapted to engage with the threaded profile of the worm screw (116)... causing a rotation, of a predetermined amplitude (φ), of the proximal stiff link (112)
Implementation Method 3
The known techniques provide normally an acquisition of ElectroMyoGraphic signals, or myoelectric, by means of EMG sensors arranged in contact with the skin of the stump of the patient. This way, it is possible to measure the muscle activity of the stump of the patient by a measurement of the voltage at the skin level.
Implementation Method 4
The prosthesis may also include at least one force sensor configured to detect a force applied to the prosthesis
Data Source
AI summary
A prosthetic hand structure including at least one mechanical finger having a metacarpal support and a proximal stiff link connected to the metacarpal support by a proximal cylindrical joint. The mechanical finger includes a transmission member connected to the proximal stiff link. The transmission member includes a worm screw integral to the proximal stiff link. The transmission member includes a flexible rack having a first end portion, pivotally connected to the metacarpal support, and a second end portion arranged to engage with the threaded profile of the worm screw at an engagement zone of the flexible rack. The structure also includes an actuator mounted to the mechanical finger and to actuate the worm screw, causing it to rotate about its rotation axis, in such a way that, when the actuator moves the worm screw, the mechanical finger extends or flexes.