Underactuated Prosthetic Hand with Cable Transmission
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Solution Overview
Problem
Existing prosthetic hands are cumbersome, large, and heavy, compromising usability, and they struggle to mimic natural hand movements, especially when gripping small objects, due to complex actuation kinematics and unnatural movement patterns.
Innovation Solution
An underactuated prosthetic hand design with fewer actuators than degrees of freedom, featuring a compact and lightweight structure, natural movement capabilities, and a simple human-machine interface, utilizing a single actuator to control multiple fingers through a system of control cables and elastic mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional actuation kinematics are used in prosthetic hands, then each degree of freedom can be controlled, but the dimensions and weight of the hand become large and cumbersome
Solution Approach 1:
The patent combines multiple actuation functions into a single actuator system. The first cable controls both the first and second fingers, while the second cable controls the third and fourth fingers. This merging of control functions reduces the number of actuators needed, thereby reducing the overall weight and dimensions of the prosthetic hand while maintaining the ability to control all four fingers independently through cable tension variations.
Solution Approach 2:
Each cable in the system serves multiple functions: the first cable actuates both the first and second fingers, and the second cable actuates the third and fourth fingers. This multi-functionality allows a single cable-actuator system to control multiple degrees of freedom, reducing the overall system complexity and weight compared to having separate actuators for each finger.
2Ease of operation
If complex actuation systems are used to control each finger, then precise control is achieved, but the device complexity increases significantly
Solution Approach 1:
The patent merges the actuation of multiple fingers into shared cable systems. The first cable controls both the first and second fingers, and the second cable controls the third and fourth fingers. This reduces the number of independent actuators from four to two, significantly simplifying the device complexity while maintaining control precision through independent cable tension adjustment.
Solution Approach 2:
The system uses dynamic cable tension control to achieve precise finger positioning. By varying the tension in each cable independently, the system can control the position and movement of multiple fingers simultaneously, providing ease of operation without requiring complex mechanical linkages for each individual finger actuation.
3Adaptability or versatility
If multiple actuators are used for each finger, then natural movement patterns can be reproduced, but the prosthetic hand becomes cumbersome and difficult to use
Solution Approach 1:
The patent combines finger actuation into two cable systems that naturally coordinate finger movements. The first cable controls the first and second fingers together, and the second cable controls the third and fourth fingers together, reproducing natural hand movement patterns where adjacent fingers often move in coordination, while maintaining simplicity and ease of use.
Solution Approach 2:
The passive elastic elements in the finger mechanisms automatically return the fingers to their neutral position when cable tension is released, eliminating the need for additional active actuators to reset each finger. This self-service mechanism simplifies the system while maintaining natural movement capabilities.
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 prosthetic hand achieves a high degree of gripping capacity and adaptability, simulating natural hand movements, with improved usability and control, allowing for precise and safe gripping of small objects while maintaining a compact and lightweight design.
Implementation Method 1
The underactuated prosthetic hand comprises at least one actuator suitable to control a rotation of one or more fingers; in detail, the underactuated prosthetic hand is mono-actuated and comprises only one actuator
Data Source
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AI summary
An underactuated prosthetic hand (1) is provided comprising a base body (2); a pair of prosthetic fingers (3) comprising a first prosthetic finger (3) and a second prosthetic finger (3); each finger is hinged to the base body (2); a first control cable (5a); an actuator (4) adapted to move the first control cable (5a); and for each pair of prosthetic fingers (3) a second control cable (5b) having control ends associated with the first prosthetic finger (3) and the second prosthetic finger (3); and a transmission block (6) adapted to allow the first control cable (5a) to control the second control cable (5b); said transmission block (6) comprises a guide (61) integral with the base body (2) and defining a sliding axis (61a); a movable element (62) sliding along the guide (61); a first pulley (64) for the sliding of the first control cable (5a) hinged to the movable element (62) and a second pulley (65) for the sliding of the second control cable (5b) hinged to the movable element (62) so that the actuator (4), when moving the first cable (5a), determines a translational movement of the movable element (62) causing a displacement of the second control cable (5b) and therefore of the prosthetic fingers (3); and elastic means (63) adapted to work in opposition to the translational movement of the movable element (62) so that said translational movement of the movable element (62) is performed in opposition to the elastic means (63) allowing them to facilitate the return to the initial position of the movable element (62).