Prosthetic Knee Joint Transmission for Powered Step Ascent
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Solution Overview
Problem
Prosthetic legs, such as those described in Patent Literature 1, lack the ability to generate power for bending and stretching, particularly when ascending steps, which requires load application to the knee joint.
Innovation Solution
A joint device with a power source and power transmission mechanism that includes multiple gear ratios and connection/disconnection mechanisms, allowing controlled power transmission to change the angle between members, enabling stretching and bending via a motor-controlled system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a hydraulic cylinder with a variable valve is used to adjust resistance, then resistance of bending and stretching can be generated, but power of bending and stretching cannot be generated
Solution Approach 1:
The patent replaces the passive hydraulic resistance system with an active motor-driven system. A motor (power source) is coupled to the knee joint mechanism through a transmission mechanism, enabling the system to generate active power for both bending and stretching motions, transforming it from a passive resistance-only system to an active power-generating system.
Solution Approach 2:
The motor-driven transmission system serves multiple functions: it generates power for knee joint stretching, provides power for bending motion, and can control the degree of assistance. This single power source system replaces the need for separate hydraulic resistance mechanisms, achieving multi-functionality in power generation and control.
2Device complexity
If a single transmission gear ratio is used, then the structure is simple, but it cannot provide optimal power transmission for different motion conditions (stretching and bending)
Solution Approach 1:
The transmission mechanism is designed with switchable gear ratios that can be dynamically changed based on the required motion. The system includes a first transmission gear ratio optimized for stretching power transmission and a second transmission gear ratio optimized for bending power transmission, allowing the system to adapt its mechanical characteristics to different operational requirements.
Solution Approach 2:
The transmission system incorporates variable gear ratios as a key parameter change mechanism. By switching between different gear ratios, the system optimizes the torque and speed characteristics for different phases of motion (stretching vs. bending), enabling optimal power transmission under varying motion conditions without requiring completely separate transmission systems.
3Productivity
If power transmission is continuously engaged, then power can be transmitted efficiently, but the system cannot switch between different transmission gear ratios for different motions
Solution Approach 1:
The power transmission system is segmented into distinct transmission paths, each with its own gear ratio optimization. A transmission switching mechanism divides the power flow into separate channels (first transmission path and second transmission path), allowing independent optimization of each path for specific motions while maintaining efficient power transmission through dedicated pathways.
Solution Approach 2:
A transmission switching mechanism acts as an intermediary between the motor and the knee joint mechanism. This switching mechanism selectively engages different transmission paths based on the required motion, enabling the system to achieve both continuous efficient power transmission and adaptability to different motion conditions through controlled engagement of appropriate transmission paths.
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
Enables smooth ascending of steps by generating the necessary power for stretching and bending of the knee joint, improving the functionality of prosthetic legs by using a motor-controlled power transmission system with adjustable gear ratios.
Implementation Method 1
a power source; and a power transmission portion configured to transmit power of the power source
Implementation Method 2
a first power transmission path configured to transmit the power at a first transmission gear ratio; and a second power transmission path configured to transmit the power at a second transmission gear ratio
Data Source
AI summary
A joint device includes a control unit configured to control the power source, the first connection and disconnection mechanism, and the second connection and disconnection mechanism, and an applied weight acquisition unit which acquires an applied weight applied to the joint device. The control unit controls at least one of the first connection and disconnection mechanism and the second connection and disconnection mechanism based on the applied weight acquired by the applied weight acquisition unit.