Variable Stiffness Device Using Granular Jamming
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Solution Overview
Problem
There is a need for devices that provide variable stiffness and shape to assist stroke patients in rehabilitation by minimizing load on weak muscles and bones, while being easy to use and adaptable.
Innovation Solution
Fluid-operated devices with an elastic inner member and an inelastic outer member, utilizing a granular medium to adjust stiffness by compressing it against the outer member, allowing for radial and longitudinal expansion to mimic bone performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a device provides high stiffness for structural support, then it can bear load effectively, but it becomes difficult to adjust and less adaptable for rehabilitation needs
Solution Approach 1:
The device employs a granular medium that can dynamically transition between loose and jammed states, allowing the stiffness to be adjusted in real-time. When the granular medium is loose, the device is flexible; when jammed, it becomes stiff and rigid, providing dynamic adaptability for different rehabilitation stages
Solution Approach 2:
The device changes the physical state of the granular medium from a loose configuration to a jammed configuration through applied force or vibration, thereby changing the stiffness parameter from low to high. This parameter change enables the same device to provide both flexible and rigid support as needed
2Strength
If a device is made rigid to provide structural support, then it can support weight, but it cannot conform to body contours or provide comfortable contact
Solution Approach 1:
The granular medium allows the device to dynamically adapt its shape and stiffness. When loose, the device conforms to body contours for comfort; when jammed, it provides rigid structural support, resolving the contradiction between shape adaptability and structural strength
Solution Approach 2:
The device incorporates a flexible outer layer that can conform to body surfaces, while the granular medium inside provides the structural support when jammed, combining the benefits of flexible contour adaptation with rigid load-bearing capability
3Adaptability or versatility
If granular medium is used to provide variable stiffness, then adaptability improves, but the device complexity increases due to additional components
Solution Approach 1:
The granular medium is self-contained within the device and can be jammed or loosened through simple external forces or vibrations applied to the device itself, without requiring complex external control systems, motors, or actuators, thereby maintaining simplicity while achieving variable stiffness
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 devices offer adjustable stiffness, providing structural support and motion assistance, capable of transitioning from flexible to rigid states based on fluid pressure, effectively supporting rehabilitation efforts and various applications.
Implementation Method 1
an inner member made from an elastic material and defining a compartment for receiving an actuating fluid, the inner members being moveable in a radial, longitudinal direction or both from a relaxed state to an expanded state by introducing an actuating fluid into the inner members
Implementation Method 2
by introducing an actuating fluid into the compartment of the inner member to compress the granular medium against the outer member to increase the stiffness of the device
Implementation Method 3
a granular material disposed between the outer and inner members, which is compressed by the inner members against the outer member to increase the stiffness of the device
Data Source
AI summary
Variable stiffness devices and methods of their use are provided. In some embodiments, a variable stiffness device comprises an inner member defining a compartment for receiving an actuating fluid; an outer member disposed around the inner member; and a granular medium disposed between the inner member and the outer member; wherein the inner member is being moveable in a radial direction from a relaxed state to an expanded state by introducing the actuating fluid into the compartment of the inner member to compress the granular medium against the outer member to increase the stiffness of the device.