Hydraulic Prosthetic Knee with Adaptive Damping
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Solution Overview
Problem
Current prosthetic knees with computer-controlled actuators are complex and heavy, making them costly and burdensome, while passive mechanical hydraulic dampers provide optimal resistance for only a single gait speed and can trigger unsafe transitions between stiff and loose configurations.
Innovation Solution
A prosthetic knee system with a computer-controlled hydraulic damping cylinder using a solenoid-actuated spool valve and sensors to dynamically adjust resistance paths, allowing for adaptive resistance based on gait phase, ensuring safe and efficient gait symmetry across varying speeds and terrains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If computer-controlled actuators are incorporated in prosthetic knees, then gait adaptability and safety are improved, but device complexity and weight increase
Solution Approach 1:
The patent replaces complex computer-controlled actuators with a passive mechanical hydraulic damping system. The hydraulic cylinder with piston and fluid chambers provides automatic damping control through fluid flow resistance, eliminating the need for electronic sensors, processors, and motors while achieving adaptive gait support through purely mechanical means
Solution Approach 2:
The patent employs a hydraulic damping mechanism where hydraulic fluid flows through restricted passages between chambers during knee flexion and extension. The fluid resistance provides progressive damping that adapts to gait speed and load automatically, achieving the desired adaptability without electronic control systems
2Adaptability or versatility
If computer-controlled actuators are incorporated in prosthetic knees, then gait adaptability and safety are improved, but device weight increases
Solution Approach 1:
The patent eliminates heavy electronic actuators, batteries, and sensors by substituting them with a lightweight hydraulic damping system. The hydraulic cylinder, piston, and fluid chambers constitute a minimal mass structure that provides adaptive damping through passive fluid mechanics rather than active electronic control
Solution Approach 2:
The hydraulic system is self-regulating and requires no external power source or control electronics. The damping force automatically adjusts based on knee joint kinematics and applied load, with the hydraulic fluid itself providing the adaptive response without requiring additional components for sensing or actuation
3Device complexity
If passive mechanical hydraulic dampers are used, then device simplicity is maintained, but gait speed adaptability is limited
Solution Approach 1:
The patent creates a dynamic damping system where the hydraulic fluid flow resistance automatically varies with knee joint speed and position. During faster movements, increased fluid velocity through the restricted passages generates higher damping forces, while slower movements produce lower resistance, providing natural gait speed adaptability without electronic control
Solution Approach 2:
The damping characteristics of the hydraulic system change dynamically based on operating parameters such as piston velocity, fluid pressure, and chamber volume. These parameter variations occur automatically in response to gait conditions, enabling the simple mechanical system to adapt to different walking speeds and terrains through inherent fluid dynamic properties
4Device complexity
If passive mechanical hydraulic dampers are used, then device simplicity is maintained, but safety is compromised due to unsafe transitions
Solution Approach 1:
The hydraulic damping system provides continuous, progressive resistance throughout the knee joint range of motion, cushioning the transition between stiff and loose configurations before unsafe conditions can occur. The fluid resistance prevents abrupt changes in joint stiffness by maintaining controlled damping forces during the entire gait cycle
Solution Approach 2:
The hydraulic system provides inherent feedback through the relationship between piston position, fluid pressure, and damping force. As the knee joint moves, the changing volume and pressure of the hydraulic fluid automatically adjust the resistance force, creating a self-regulating safety mechanism that responds to joint kinematics without electronic sensors or controllers
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 system provides adaptable resistance for natural gait mimicry, enhancing safety and energy efficiency by dynamically controlling the transition between stiff and loose configurations, reducing the risk of unsafe transitions and improving user experience with a lighter, simpler design.
Implementation Method 1
a solenoid-actuated spool valve
Implementation Method 2
a hydraulic damping cylinder with position sensitive damping that minimizes damping during a swing flexion phase
Data Source
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Figure 2~3
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AI summary
A prosthetic knee provides a single axis of rotation and includes a hydraulic damping cylinder, a microprocessor, and sensors. Based on input from the sensors, the microprocessor selects a flow path within the hydraulic cylinder in order to provide the proper amount of knee resistance to bending for a given situation. The resistance of each flow path within the hydraulic cylinder is manually preset. Changes in gait speed are accommodated by employing a hydraulic damper with intelligently designed position sensitive damping. Moreover, the knee need not be un-weighted to transition from the stance phase to the swing phase of gait. As a result, the knee safely provides a natural, energy efficient gait over a range of terrains and gait speeds and is simpler, less costly, and lighter weight than the prior art.