Ankle-foot prosthesis for automatic adaptation to sloped walking surfaces
Inventors
Hansen, Andrew H. • Nickel, Eric A.
Assignees
University of Minnesota Twin Cities • US Department of Veterans Affairs • University of Minnesota System
Publication Number
US-9549827-B2
Publication Date
2017-01-24
Expiration Date
2033-09-10
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Abstract
An ankle-foot prosthesis includes a foot plate, an ankle frame attached to the foot plate, a yoke pivotally connected to the ankle frame and including a member for attaching to a leg, a damper having a first end connected to the yoke and a second end connected to the ankle frame, and a control mechanism for switching the damper between low and high settings.
Core Innovation
The invention is an ankle-foot prosthesis designed to automatically adapt to different sloped walking surfaces on each and every step of walking. It comprises a foot plate, an ankle frame attached to the foot plate, a yoke pivotally connected to the ankle frame with a member for attaching to a prosthetic leg, a damper connected between the yoke and ankle frame, and a control mechanism to switch the damper between low and high settings. The prosthesis includes a spring disposed in parallel to the damper and a microprocessor-operated fluid control circuit controlling the extension and compression of the damper.
The problem addressed is that most available prosthetic ankle devices operate about a single equilibrium point, which works only on level terrain but causes instabilities on sloped surfaces. Existing systems with hydraulic dampers and microprocessor control face issues such as energy loss, requirement of multiple steps to adapt to new terrain, or heavy power needs due to motors and batteries. Current powered ankle-foot prostheses are expensive, heavy, and require frequent charging, limiting practicality.
This invention provides a more natural, comfortable, and energy-efficient gait by automatically adapting ankle function to level and sloped surfaces every step. It uses variable damping properties controlled by a microprocessor that switches damping levels during different phases of the gait cycle, allowing the foot to find the walking surface securely. Furthermore, it offers a stable mode for standing and swaying by setting high damping in both compression and extension, thereby improving stability. The design is compact, simple, durable, quieter, and user-friendly, resisting undesirable backward swing and requiring low maintenance.
Claims Coverage
The patent includes two main independent claims that describe the structure and control of the ankle-foot prosthesis, detailing its components and the fluid control circuit operation.
An ankle-foot prosthesis with a foot plate, ankle frame, yoke, hydraulic damper, spring, and microprocessor-controlled fluid circuit
The prosthesis includes a foot plate with rear and forward deflectable portions, an ankle frame with anterior, posterior, and apex portions, and a yoke pivotally connected to the apex. A hydraulic damper is pivotally connected between the yoke and posterior ankle frame portion, with a spring in parallel. The fluid control circuit controls extension and compression, including check valves permitting compression only and a cutoff valve allowing damper extension during specific gait cycle intervals (between toe off and up to 0.13 seconds or the next foot flat).
The microprocessor-operated fluid control circuit managing damper operation during gait cycles and standing mode
The fluid control circuit includes a cutoff valve that prevents compression and extension of the damper between foot flat and toe off during walking mode, and allows compression and extension between toe off and foot flat. It also prevents compression and extension during standing mode, providing a stable base. Check valves further control damper operation, with optional variable fluid-flow restrictors adjusting hydraulic resistance in dorsiflexion and plantarflexion.
The independent claims collectively describe an ankle-foot prosthesis equipped with a hydraulic damper and spring arrangement controlled by a microprocessor-operated fluid circuit. This circuit selectively manages damping states during walking and standing modes to deliver automatic adaptation to sloped walking surfaces and enhanced stability.
Stated Advantages
Provides a more natural and comfortable gait for the user.
Increases energy efficiency during walking.
Features a simple design with fewer parts and low or no maintenance requirements.
Offers a compact and durable structure reducing failure rates compared to complex mechanical systems.
Prevents undesirable backward swing to avoid imbalance or injury.
Operates quietly, is lightweight, less clumsy, and more user-friendly.
Automatically adapts on every step to different sloped walking surfaces.
Includes a stable mode for standing and swaying tasks for improved user stability.
Documented Applications
Use by lower limb amputees to walk more easily and safely over a variety of sloped terrains.
Provides stability during standing and swaying tasks such as washing dishes.
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