Body Position Detection Using Accelerometer Axis Comparison
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Solution Overview
Problem
Existing body position detection methods using accelerometers require high processing power due to trigonometry calculations and complex matrix operations, and can lead to position detection issues when the accelerometer coordinate system is tilted.
Innovation Solution
A computer-implemented method that detects body positions by comparing the absolute values of acceleration components without requiring trigonometry functions, using a gravity vector projection on a plane formed by the accelerometer's axes, and employing threshold adjustments based on the tangent of desired angles to account for tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If trigonometry calculations and matrix operations are used to calculate tilt angle from accelerometer data, then body position detection accuracy is improved, but processing power requirements increase
Solution Approach 1:
The patent extracts only the essential comparison operation from the complex trigonometry calculations. Instead of computing full tilt angles using sinus, cosine, and tangent functions, the invention directly compares the absolute values of acceleration components to determine body position, removing unnecessary computational complexity while preserving detection accuracy
Solution Approach 2:
The patent inverts the conventional approach by not calculating the tilt angle first and then determining position. Instead, it directly compares acceleration component values to classify body positions, reversing the computational sequence to eliminate trigonometric operations entirely
2Device complexity
If gravity vector projection is used for position detection, then calculation complexity is reduced, but position detection accuracy deteriorates when accelerometer is tilted
Solution Approach 1:
The patent changes the parameter being compared from projected gravity vector magnitude to the ratio of absolute acceleration component values. By comparing |ax|/|ay|, |ay|/|az|, or |az|/|ax| ratios against threshold values, the system maintains accuracy across tilted orientations without complex calculations
Solution Approach 2:
The patent introduces threshold values as a filtering mechanism that allows valid position detections while rejecting false detections caused by tilting. The thresholds act as a permissive filter that accommodates orientation variations while maintaining detection precision
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 approach reduces calculation power, prevents false position detection, and accurately determines body positions such as sleeping, non-sleeping, standing, and side positions without trigonometric calculations, even when the accelerometer is tilted.
Implementation Method 1
They can only do this reliably when they are static and not moving
Data Source
AI summary
The present invention relates to body position detection. In order to improve body position detection, a computer-implemented method is provided that comprises the steps of:a) receiving (210) accelerometer data from an accelerometer mounted on a user,wherein the received accelerometer data comprises three acceleration components including a first acceleration component in a first axis direction, a second acceleration component in a second axis direction substantially perpendicular to the first axis direction, and a third acceleration component in a third axis direction substantially perpendicular to a plane formed by the first and second axes; andwherein the first axis direction is parallel to a frontal axis of the user, the second axis direction is parallel to a longitudinal axis of the user, and the third axis direction is parallel to a sagittal axis of the user;b) determining (220), based on the received accelerometer data, at least one body position based on a comparison between an absolute value of a projection of a gravity vector on a plane formed by two of the first, second, and third axes and an absolute value of an acceleration component in a remaining axis direction.