Biomimetic Prosthetic Ankle With Variable Stiffness
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Solution Overview
Problem
Current ankle-foot prosthetics fail to effectively mimic the range of motion, energy return, and roll-over shape of a natural ankle, leading to gait asymmetry and increased energy consumption in amputees, as they often sacrifice either range of motion or push-off force.
Innovation Solution
A compliant and articulating prosthetic ankle foot with a phalanges, metatarsals, ankle, and calcaneus portions, featuring biasing members and a rocker design that allows for rotational movement and energy storage, mimicking the kinematics and kinetics of a natural ankle through 3D printing for customization and improved fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the stiffness of the prosthesis is increased to increase propulsion forces, then push-off force is improved, but range of motion of the ankle decreases
Solution Approach 1:
The patent applies a dynamic stiffness mechanism where the prosthesis stiffness varies during the gait cycle. The stiffness is lower during dorsiflexion to allow greater range of motion and higher during plantar flexion to generate sufficient push-off force. This is achieved through a variable stiffness mechanism that adapts to different phases of walking, resolving the contradiction between needing high stiffness for propulsion and low stiffness for range of motion.
Solution Approach 2:
The patent changes the stiffness parameter dynamically during operation. By adjusting the stiffness parameter according to the gait phase (lower during loading, higher during push-off), the prosthesis can simultaneously achieve adequate range of motion and sufficient propulsion force, rather than being constrained by a fixed stiffness value.
2Use of energy by moving object
If a passive mechanical mechanism is used to generate forward motion, then energy efficiency is improved, but capability at speeds faster than normal walking deteriorates
Solution Approach 1:
The patent implements a dynamic stiffness control system that can adapt to different walking speeds. By adjusting the stiffness parameters in real-time based on detected gait phase and speed, the passive mechanism maintains energy efficiency at normal speeds while becoming capable of accommodating faster speeds through parameter adjustment, eliminating the need for active components.
Solution Approach 2:
The patent uses parameter changes to enable the passive mechanism to handle varying speeds. By modifying stiffness and geometric parameters dynamically during the gait cycle and across different speed conditions, the prosthesis achieves both energy efficiency and speed adaptability without requiring active energy input.
3Stability of the object's composition
If the ROM is limited to values experienced during gait on even surface (no more than 30°), then stability is improved, but adaptability to sloped surfaces and gait symmetry deteriorates
Solution Approach 1:
The patent employs dynamic range of motion adjustment where the ankle prosthesis allows greater ROM when needed for sloped surfaces or uneven terrain while maintaining appropriate limits for stability on level ground. The dynamic mechanism adapts the effective ROM based on gait phase and detected conditions, providing both stability and adaptability.
Solution Approach 2:
The patent prepares the prosthesis with a mechanism capable of extended ROM that can be activated in advance when sloped surfaces or uneven terrain are detected. This preliminary capability allows smooth transition between different terrain conditions without compromising stability on level surfaces, as the extended ROM remains available but is only engaged when needed.
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 device enhances gait symmetry and reduces energy consumption by replicating the natural ankle's range of motion and push-off forces, providing a more biomimetic solution that adapts to different walking speeds and surfaces.
Implementation Method 1
The energy storage mechanism of the dynamic response ankle-foot is similar to the role of the Achilles tendon. During gait, the Achilles tendon is stretched and stores potential energy that is released during push-off.
Implementation Method 2
The metatarsals portion is rotatably coupled to the ankle portion by a first biasing member. The calcaneus portion is rotatably coupled to the ankle portion by a second biasing member.
Implementation Method 3
The ankle portion includes a first end with a connector and a second end with a rocker. The metatarsals portion is rotatably coupled to the ankle portion by a first biasing member.
Data Source
AI summary
A prosthetic device includes a phalanges portion, a metatarsals portion that is movably coupled to the phalanges portion, an ankle portion that is movably coupled to the metatarsals portion, and a calcaneus portion that is movably coupled to the ankle portion.