Adjustable Stiffness Prosthetic Foot via Segmented Beams
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Solution Overview
Problem
Current prosthetic feet are primarily passive devices with fixed stiffness, limiting the ability to customize alignment and stiffness for individual patients, as prosthetists lack tools to adjust stiffness during the fitting process due to material constraints and the need for a lightweight, compact design.
Innovation Solution
A prosthetic device with a compliant element featuring stacked beam elements and a transverse shear constraint element that allows adjustable bending stiffness, enabling variation in stiffness without increasing size or weight, by preventing relative sliding of beam elements across specific regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a propped cantilevered beam mechanism is used to vary stiffness, then stiffness can be adjusted, but the device requires substantial material, size, and weight
Solution Approach 1:
The prosthetic foot is divided into multiple independent beam elements (first beam element, second beam element, third beam element) that can be selectively engaged or disengaged. This segmentation allows stiffness adjustment without requiring a heavy propped cantilevered beam mechanism, as each beam element contributes only when needed to the overall structural rigidity.
Solution Approach 2:
The prosthetic foot transitions from a static structure to a dynamic one where the beam elements can be selectively engaged or disengaged based on loading conditions. The system adapts its stiffness characteristics in real-time, being more compliant when beams are disengaged and stiffer when engaged, eliminating the need for heavy continuous structural support.
2Adaptability or versatility
If multiple beam elements are stacked to provide stiffness variation, then stiffness can be adjusted, but relative sliding between beams reduces effectiveness
Solution Approach 1:
A fourth beam element is introduced as an intermediary component that prevents relative sliding between the first, second, and third beam elements. This intermediary element maintains the structural integrity and relative positioning of the stacked beams while allowing them to be selectively engaged or disengaged, ensuring that stiffness adjustment occurs through controlled engagement rather than uncontrolled sliding.
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
Enables precise adjustment of prosthetic foot stiffness, mimicking the mechanical behavior of natural ankles, allowing for personalized fitting and improved patient comfort and performance, while maintaining a compact and lightweight design.
Implementation Method 1
modern composite materials—namely carbon fiber and fiberglass—which are the only known materials capable of storing the requisite elastic energy in a light and anthropometric shape
Implementation Method 2
The transverse shear constraint element prevents relative sliding of at least two beam elements in a region of the beam elements between the first end of the beam elements and the transverse shear constraint element
Data Source
AI summary
Various implementations include a compliant element comprising a spring component, a mounting portion, and a transverse shear constraint element. The spring component comprises two or more stacked beam elements. Each beam element has a first and second end with the first end of each beam is attached to the mounting portion. Furthermore, the transverse shear constraint element is located between the first and second ends of the beam elements and prevents the relative sliding of two or more beam elements in the region of the beams between the first beam ends and the transverse shear constraint element.