Lower-Extremity Prosthesis Stand-Up Control Using Knee-Ankle Position
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Solution Overview
Problem
Conventional passive prosthetic, orthotic, and exoskeleton apparatus fail to adequately reproduce the biomechanics of a gait cycle, particularly on uneven surfaces like stairs and ramps, due to their inability to actively modulate impedance and apply reflexive torque responses.
Innovation Solution
An active orthotic or prosthetic apparatus with a rotary motor, motor drive transmission, sensors, and a controller that dynamically modulates impedance, position, or torque to mimic the human ankle's biomechanics, including a method to determine the knee joint's position relative to the ankle joint and control the prosthetic to adapt to different terrains and activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If passive or low-power mechanisms are used in conventional prosthetic and orthotic systems, then device complexity is reduced, but the ability to deliver non-conservative positive work on each stride is insufficient
Solution Approach 1:
The patent applies dynamics by making the prosthetic knee joint's impedance, position, and torque dynamically adjustable during the gait cycle. The system transitions from static passive mechanisms to active dynamic control, allowing the knee joint to provide variable resistance and assistance forces that match the biomechanical requirements of different gait phases, thereby enabling non-conservative positive work delivery.
Solution Approach 2:
The patent implements feedback through sensors that detect gait phase and joint position, which are fed to a controller that adjusts motor torque in real-time. This closed-loop control system enables the prosthetic to respond to the user's movement intentions and environmental conditions, optimizing power delivery while maintaining stability and natural gait patterns.
2Adaptability or versatility
If conventional passive prosthetic mechanisms are used, then ease of operation is improved, but adaptability to different terrains and activities is insufficient
Solution Approach 1:
The patent applies self-service by enabling the prosthetic system to automatically detect gait phase, terrain conditions, and activity type through sensors and algorithms, then autonomously adjust impedance, position, and torque without requiring explicit user commands. The system serves itself by making real-time adaptations based on sensed information, reducing the cognitive and physical burden on the user while maintaining high versatility.
Solution Approach 2:
The dynamic adjustment of impedance and torque allows the prosthetic to adapt to varying terrain conditions (level ground, stairs, ramps) and activities (walking, running, sitting-to-standing) by modifying its mechanical characteristics in real-time, providing appropriate assistance or resistance for each condition without requiring manual reconfiguration.
3Reliability
If passive mechanisms are used, then manufacturing precision requirements are reduced, but the ability to reproduce human ankle biomechanics is insufficient
Solution Approach 1:
The patent replaces passive mechanical mechanisms with an active electromechanical system consisting of a motor, transmission assembly, and control system. This substitution enables precise reproduction of human ankle biomechanics through electronic control of torque and impedance, achieving reliability in biomechanics reproduction that cannot be obtained through passive mechanical design alone.
4Productivity
If active impedance modulation is implemented, then productivity of mobility is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the gait cycle into distinct phases (stance and swing) and optimizing the control strategy for each phase independently. The system segments the control functions into impedance modulation, position control, and torque regulation, allowing each subsystem to be optimized for its specific function while contributing to overall mobility efficiency.
Data Source
AI summary
Knee orthoses or prostheses can be used to automatically, when appropriate, initiate a stand-up sequence based on the position of a person's knee with respect to the person's ankle while the person is in a seated position. When the knee is moved to a position that is forward of the ankle, at least one actuator of the orthosis or prosthesis is actuated to help raise the person from the seated position to a standing position.