Prosthetic Hand Thumb Actuation for Grip Switching
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Solution Overview
Problem
Conventional prosthetic hands require manual effort and time to switch between grip configurations, offering limited grip choices and high force requirements, leading to inefficiency and potential discomfort due to the placement of actuators and increased moment around the socket attachment point.
Innovation Solution
A prosthetic hand design featuring a thumb assembly with a compact, inline actuation system and a controller-driven selector mechanism for easy switching between opposed and non-opposed thumb positions, allowing for a wide range of grip configurations with reduced user effort and improved ergonomics by mounting the actuator close to the wrist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If manual thumb movement is used to switch between opposed and non-opposed positions, then the user can change grip configurations, but it requires significant user effort and time
Solution Approach 1:
The patent replaces the manual mechanical thumb movement system with an electrically-controlled system. A motor (actuator) is integrated into the thumb assembly to automatically rotate the thumb between opposed and non-opposed positions based on controller signals, eliminating the need for manual user effort to switch grip configurations.
Solution Approach 2:
The thumb assembly performs self-adjustment through the integrated motor system. When the controller receives signals from electrodes detecting muscle electrical signals, it automatically actuates the motor to position the thumb appropriately, making the system self-regulating without requiring continuous manual intervention.
2Volume of moving object
If actuators are mounted within the thumb body, then the thumb can be compact, but the grip force is limited due to size constraints
Solution Approach 1:
The patent repositions the motor from within the thumb body to the palm portion of the hand, utilizing available space in a different spatial dimension. This allows the use of a more powerful motor without increasing thumb volume, thereby achieving both compactness and high grip force capability.
3Adaptability or versatility
If the thumb is manually moved to opposed position, then grip choice is limited to two positions, but the force required can cause unwanted rotation or knocking
Solution Approach 1:
The patent incorporates a sensor system that provides feedback to the controller about the thumb's position and the forces applied. This allows the controller to precisely control the motor to achieve the desired thumb position without applying excessive force, thereby preventing unwanted rotation or knocking of the object being gripped while maintaining multiple grip choices.
Data Source
AI summary
The present application describes a mechanical hand comprising a plurality of finger assemblies each selectively moveable by a respective finger drive assembly about a finger pivot axis along a finger flexion/extension plane and between a finger open position and a finger closed position; a thumb assembly selectively rotatable by a first thumb drive assembly about a first thumb axis between an opposed position and a non-opposed position with respect to the finger assemblies, and selectively moveable by a second thumb drive assembly about a second thumb axis along a thumb flexion/extension plane and between a thumb open position and a thumb closed position; a controller operatively coupled to the finger and thumb drive assemblies; and a selector operatively coupled to the controller for selecting a desired thumb rotational position or a desired grip to be defined by the finger assemblies and the thumb assembly.