Prosthetic Knee Posture Control Using Sensor Fusion Drift Correction
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Solution Overview
Problem
Existing prosthetic leg systems face challenges in accurately controlling posture due to errors in angular velocity sensor detection, particularly when versatility across various motion scenes is required, as current filtering methods are not sufficient to correct these errors effectively.
Innovation Solution
A knee joint system that utilizes a posture calculator based on hypercomplex numbers derived from both angular velocity and angle sensors, allowing for correction of posture calculations using a filter like a Kalman or complementary filter, and includes a calibration unit to estimate and cancel drift in the angular velocity sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an angular velocity sensor is used to calculate posture, then it becomes possible to perform posture control considering rotation and movement, but detection errors occur that prevent highly accurate posture control
Solution Approach 1:
The patent combines data from both angular velocity sensors and angle sensors to calculate posture. By merging the rotational detection capability of angular velocity sensors with the positional accuracy of angle sensors, the system achieves both versatile posture control and high detection accuracy, resolving the contradiction between adaptability and measurement precision.
Solution Approach 2:
The system uses angle sensor data as feedback to correct accumulated errors from angular velocity integration. This feedback mechanism continuously refines the posture calculation, maintaining high accuracy while preserving the dynamic posture control capabilities provided by angular velocity sensing.
2Measurement precision
If a filter is applied to correct angular velocity sensor errors, then detection accuracy improves, but versatility across various motion scenes becomes insufficient
Solution Approach 1:
The patent implements a universal correction approach that works across various motion scenes by combining multiple sensor types rather than using scene-specific filters. The angle sensor provides a reference frame that can correct angular velocity sensor errors regardless of the specific motion context, achieving both high accuracy and broad versatility.
Solution Approach 2:
The system dynamically adjusts the weighting and integration parameters when combining angular velocity and angle sensor data based on the current motion state. This allows the correction mechanism to adapt to different motion scenes while maintaining consistent accuracy, resolving the contradiction between precision and versatility.
3Speed
If angular velocity sensor data is used for posture calculation, then real-time posture control is achieved, but sensor drift accumulates and reduces calculation reliability
Solution Approach 1:
The angle sensor serves as an intermediary reference that periodically corrects the accumulated drift from angular velocity integration. This intermediary measurement provides a reliable reference point that resets error accumulation while maintaining the real-time responsiveness of the angular velocity-based control system.
Solution Approach 2:
The system performs preliminary correction of angular velocity sensor drift using angle sensor data before proceeding with posture control calculations. By proactively eliminating accumulated errors, the system maintains both real-time responsiveness and long-term calculation reliability.
Data Source
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AI summary
A posture calculator that calculates the posture of a moving object based on a first hypercomplex number derived based on a detection result from an angular velocity sensor (108) for detecting an angular velocity of the moving object and a second hypercomplex number that is derived based on a detection result from an angle sensor (110) for detecting an angle of the moving object and that has the same number of terms as that of the first hypercomplex number.