Prosthetic Arm Hand Assembly Segmentation and Variable Stiffness
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Solution Overview
Problem
Existing prosthetic arms have limited movement and capability, particularly for individuals who have lost their entire arm from shoulder to hand, offering restricted degrees of freedom and realistic movement, which hinders finer tasks and user comfort.
Innovation Solution
A prosthetic device incorporating a compliant structure with multiple joints (shoulder flexion, abduction, humeral rotation, elbow flexion, wrist rotation, and wrist flexion) equipped with motors, gear trains, harmonic drives, potentiometers, non-backdriving clutches, and compliance sensors, along with a hand assembly featuring parallel actuators and indeterminate linkages for enhanced dexterity and tactile feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing prosthetic arms use simple mechanical structures, then device complexity is reduced, but range of motion and degrees of freedom are limited
Solution Approach 1:
The prosthetic arm is divided into multiple independent joint segments (shoulder flexion, shoulder abduction, humeral rotation, elbow flexion, wrist rotation, wrist flexion), each capable of independent movement. This segmentation allows each joint to contribute to the overall range of motion while maintaining modular complexity management.
Solution Approach 2:
The prosthetic arm employs dynamic compliance mechanisms that allow the structure to adapt its stiffness and movement characteristics in real-time. This enables the device to achieve human-like realistic movement patterns while managing the complexity through adaptive control rather than fixed mechanical constraints.
2Adaptability or versatility
If prosthetic hands provide only one degree of movement, then device complexity is minimized, but capability for finer tasks is limited
Solution Approach 1:
The hand assembly is segmented into multiple movable components including fingers and thumb, each with independent degrees of freedom. This segmentation enables complex grasping and manipulation tasks while managing overall system complexity through modular actuation mechanisms.
Solution Approach 2:
The hand assembly utilizes variable stiffness mechanisms that allow the structure to change its mechanical parameters dynamically. This enables the hand to transition between rigid and compliant states, providing fine motor control capability while managing the complexity through adaptive parameter adjustment rather than fixed complex mechanisms.
3Ease of operation
If prosthetic arms lack compliant structures, then device complexity is reduced, but user comfort and tactile capabilities decrease
Solution Approach 1:
Compliant structures with variable stiffness parameters are integrated into the prosthetic arm, allowing the device to adapt its mechanical properties to user needs. This provides enhanced user comfort and tactile feedback while managing complexity through controlled parameter variation rather than fixed complex compliance mechanisms.
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 arm provides improved range of motion, increased comfort, and decreased reliance on manual positioning, enabling users to perform finer tasks with increased degrees of freedom and realistic movement, similar to a human arm.
Implementation Method 1
The harmonic drive has an interior wave generator that corresponds with the flexible spline. The spline in turn engages the exterior circular spline, resulting in drastic reduction rates and driving the shoulder output flange
Implementation Method 2
The circular spline, series elastic elements and reactor elements are circumferentially disposed around the interior of a clamp. Upon application of force, the position of the circular spline alters causing the series elastic elements to compress against the reactor elements. The movement of the reactor elements transmits the rotational displacement of the circular spline
Implementation Method 3
The clutch has an input cage, an output hex, and a clutch race, or ground. When the shoulder flexion joint is acted upon by an output force, the output hex is engaged in a friction lock with the clutch race and bearings lining the exterior of the output hex, preventing backward transfer of power through the clutch
Data Source
AI summary
A prosthetic arm apparatus comprising a plurality of segments that provide a user of the prosthetic arm apparatus with substantially the same movement capability and function as a human arm. The segments are connectable to one another and connectable to a harness mount that may be adorned by the user. Each segment of the plurality of segments provides a portion of the movement capability, enabling the plurality of connected segments connected to the harness mount to provide substantially the same movement capability as that lacking in the user.