Microprocessor-Controlled Hydraulic Knee-Ankle Prosthesis for Stair Descent
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Solution Overview
Problem
Current knee-ankle prostheses for lower-limb amputees face challenges in efficiently managing movements, particularly when descending stairs, due to inadequate torque control and energy consumption, leading to increased effort and limited mobility, especially in varying situations like stairs and slopes.
Innovation Solution
A knee-ankle prosthesis with a hydraulic system controlled by a microprocessor, featuring dual hydraulic dampers connected through a conduit with on-off and proportional valves, allowing synchronized flexion and dorsiflexion movements based on the walking phase and situation, mimicking the natural bi-articular muscle movements of the gastrocnemius.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional passive knees with hydraulic dampers are used, then the braking torque is strong in stance phase to avoid falling, but the braking torque remains lower than needed when descending stairs, causing the prosthetic foot to fall on the contralateral limb
Solution Approach 1:
The patent implements dynamic adjustment of braking torque based on walking phase and detected situations. The microprocessor controls solenoid valves to modify hydraulic damper resistance in real-time, transitioning from strong braking in stance phase to reduced braking during swing phase, and specifically lowering braking torque when descending stairs is detected, enabling smooth stair descent without foot dropping
Solution Approach 2:
The system uses sensors to detect walking phase and situation (including stair descent) and feeds this information back to the microprocessor, which adjusts the hydraulic damper braking torque accordingly. This closed-loop control enables the knee to adapt braking force to match actual walking conditions, resolving the contradiction between needing strong braking for stability and reduced braking for smooth stair descent
2Ease of operation
If precise foot placement on the nose of the step is required to allow foot roll and tibia advance, then stair descent is possible, but extra attention is required from the user, causing persons to avoid descending stairs
Solution Approach 1:
The hydraulic damper system with microprocessor control automatically adjusts braking torque and coordinates knee flexion/extension movements to enable smooth stair descent without requiring user intervention for precise foot placement. The system self-regulates the braking force and movement coordination, eliminating the need for user attention and skill, thereby making stair descent accessible to all users
3Adaptability or versatility
If situation recognition algorithms are made more elaborate to recognize complex situations like climbing stairs, slopes, and seated position, then adaptability improves, but the number of sensors and algorithm complexity increase
Solution Approach 1:
The patent employs a multi-functional sensor system where a relatively small number of sensors serve multiple purposes: detecting walking phase, determining walking speed, identifying stair descent, recognizing slopes, and detecting seated position. The microprocessor integrates signals from these universal sensors to recognize various situations and appropriately adjusts hydraulic damper parameters, achieving high adaptability without proportionally increasing sensor count or algorithm complexity
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
This solution enables more natural and efficient triple flexion movements, reduces energy consumption, and improves stability and mobility by automatically adjusting resistance and angle coordination between the knee and ankle, allowing for smoother transitions and reduced effort during activities like stair descent.
Implementation Method 1
They contain a hydraulic or magnetorheological damper that controls the flexion and extension movements of the knee
Implementation Method 2
The upper chamber of the first hydraulic damper is connected to the lower chamber of the second hydraulic damper
Implementation Method 3
They contain a hydraulic or magnetorheological damper that controls the flexion and extension movements of the knee
Data Source
AI summary
A prosthesis can include a femoral segment suitable for a femoral connection to a user and a tibial segment connected to the femoral segment based on an articulation which reproduces movements of the knee, the tibial segment being articulated on a foot segment based on an articulation reproducing movements of the ankle, a first hydraulic damper the ends of which are joined respectively with the femoral and tibial segments, and a second hydraulic damper of which the ends are joined respectively with the tibial and foot segments.