Variable Speed Ratio Artificial Hand via Friction Hinges
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Solution Overview
Problem
Sub-actuated artificial hands with fewer actuators than degrees of freedom are limited in the number of poses and grips they can achieve, as they have an invariable speed ratio between phalanges/fingers connected to a single actuator, making it difficult to change finger closure order or assume different poses/grips effectively, particularly in prosthetic applications where command variability is restricted.
Innovation Solution
The design incorporates a sub-actuated robotic hand with a mechanism of hinges and elastic means allowing variable rotation speeds between phalanges and the palm, utilizing a distribution mechanism with pulleys and cables of different friction coefficients to control reciprocal rotation speeds, and an EMG sensor for muscle contraction-based control, enabling a greater variety of poses and grips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single actuator controls multiple phalanges/fingers, then the number of actuators is reduced, but the speed ratio between connected phalanges becomes invariable
Solution Approach 1:
The patent applies the dynamics principle by making the transmission ratio variable rather than fixed. The mechanism allows the speed ratio between connected phalanges to change dynamically during movement, enabling different phases of finger closure to occur at different relative speeds. This resolves the contradiction by maintaining the reduced actuator count while gaining speed ratio variability through a dynamically adjustable transmission mechanism.
Solution Approach 2:
The patent changes the transmission ratio parameter from a fixed value to a variable parameter that can be adjusted during operation. By implementing a mechanism where the transmission ratio between the actuator and connected phalanges can be modified, the system achieves variable speed control without increasing the number of actuators, thus resolving the technical contradiction.
2Device complexity
If sub-actuated artificial hands are used, then the number of actuators is smaller than degrees of freedom, but the number of definable poses is limited
Solution Approach 1:
By implementing variable transmission ratios in the mechanism, the patent enables the hand to achieve a greater number of distinct poses with fewer actuators. The dynamic adjustment capability allows the system to access multiple configuration states that would otherwise require more actuators, thus resolving the contradiction between reduced actuator count and limited pose variability.
3Device complexity
If sub-actuated artificial hands are used, then the structure is simpler, but the ability to change finger closure order is reduced
Solution Approach 1:
The patent resolves this contradiction by incorporating a dynamic transmission mechanism that allows the operator to control the closure order of fingers independently. The variable transmission ratio enables different phalanges to move at different relative speeds, allowing the operator to achieve desired closure sequences without requiring a complex multi-actuator system, thus maintaining structural simplicity while improving operational flexibility.
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
This approach allows the artificial hand to define a larger number of poses and grips, better meeting user expectations by varying the relative speeds of degrees of freedom, enhancing usability and simplicity of control, and improving the satisfaction of prosthetic hand users.
Implementation Method 1
utilizing a distribution mechanism with pulleys and cables of different friction coefficients to control reciprocal rotation speeds
Implementation Method 2
an EMG sensor for muscle contraction-based control
Implementation Method 3
a mechanism of hinges and elastic means allowing variable rotation speeds between phalanges and the palm
Data Source
AI summary
An artificial hand is provided. The artificial includes phalanges suitable to reproduce at least one finger, hinges hinging a first element identifying a phalanx to a second element identifying a second phalanx, and an implementation mechanism suitable to command a reciprocal rotation between the hinges defining a mutual rotation speed between the first and second element. The hinges define different damping coefficients so that, during a mutual rotation of the first and second element, they are subject to distinct damping forces opposing mutual rotation and proportional to the mutual rotation speed so as to vary the movement of the artificial hand as a function of the mutual rotation speed.