Prosthetic Knee Swing Assist Actuator
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Solution Overview
Problem
Conventional prosthetic knees face challenges in providing robust stance stability and natural swing-phase motion across various walking cadences and environmental conditions, often resulting in compromised knee movement and increased risk of falls, especially during activities like stair descent and slope walking.
Innovation Solution
A knee prosthesis with a resistive control element and a powered control element, controlled by a sensor and controller system, which applies varying resistance levels and provides powered assistance to correct knee motion errors, ensuring stable stance and natural swing-phase motion, even under perturbations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a modulated dissipater is employed to provide stance knee stability, then knee stability during weight-bearing is improved, but device complexity and weight increase
Solution Approach 1:
The knee mechanism is divided into two independent control elements: a resistive control element for stance phase stability and a powered control element for swing phase motion. This segmentation allows each element to be optimized for its specific function, reducing overall complexity compared to a single integrated control system.
Solution Approach 2:
The swing-phase control function is extracted from the stance-phase control mechanism. The powered control element is added specifically to handle swing-phase motion, while the resistive control element maintains stance stability. This extraction allows the stance mechanism to remain simple while adding swing control capabilities.
2Reliability
If a polycentric knee is used to enhance stance stability, then knee stability is improved, but the knee cannot yield during activities like stair descent
Solution Approach 1:
The knee mechanism transitions from a static polycentric design to a dynamic system with two controllable elements. The resistive control element provides stability during stance, while the powered control element enables controlled yielding during activities like stair descent. This dynamic control allows the knee to adapt its behavior based on operational requirements.
Solution Approach 2:
The control characteristics of the knee mechanism are changed by introducing a powered control element that can modify the resistance level. During stance phase, high resistance is provided for stability. During swing phase or yielding activities, the resistance parameter is changed to allow controlled motion, enabling the knee to adapt to different operational conditions.
3Ease of operation
If conventional resistive mechanisms are used for swing phase, then swing motion is provided, but the knee cannot respond robustly to perturbations
Solution Approach 1:
The purely mechanical resistive swing control mechanism is replaced with a powered control element that can actively respond to perturbations. This substitution allows the knee to detect and correct deviations from desired swing motion, providing robust response to perturbations while maintaining natural swing motion characteristics.
Solution Approach 2:
The powered control element operates with feedback control to monitor actual knee motion during swing phase and compare it with desired trajectory. When perturbations occur, the feedback system detects the deviation and adjusts the control element to correct the motion, ensuring robust response while maintaining ease of operation.
4Weight of moving object
If a lightweight design is pursued, then device weight is reduced, but the ability to provide robust stance stability and swing control is compromised
Solution Approach 1:
The heavy components of a fully-powered knee system are extracted by using a lightweight powered control element only for swing-phase control, while stance stability is provided by a simple resistive control element. This extraction approach maintains reliability for both phases while significantly reducing overall device weight compared to fully-powered designs.
Solution Approach 2:
Different control qualities are applied to different phases of motion: the resistive control element provides high resistance for stance stability, while the powered control element provides controlled assistance for swing phase. This local differentiation of control quality allows each phase to receive appropriate control characteristics without requiring heavy components throughout the entire mechanism.
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 solution enables a lightweight, compact prosthetic knee that maintains consistent and natural knee motion across different walking speeds and conditions, reducing the risk of falls and improving user safety and comfort.
Implementation Method 1
The at least one resistive control element includes a hydraulic actuator cylinder. The hydraulic actuator cylinder is coupled to the knee joint and configured to provide the first, second, and third levels of resistance. The levels of resistance are provided based on hydraulic fluid flow through a hydraulic valve of the hydraulic actuator cylinder.
Data Source
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AI summary
The present disclosure provides for a device and method of control for an artificial prosthetic knee. A prosthetic knee according to the present disclosure relies on strictly passive means of providing support during weight bearing and supplements a resistive swing-phase mechanism with a small powered actuator. This actuator adds power to the knee, exclusively during swing phase, to improve swing-phase behavior. In particular, the knee still relies on the resistive swing-phase mechanism to provide nominal swing-phase knee motion, but supplements that motion as needed with the small powered actuator.