Chest-Mounted Sensor Calibration for Posture Detection
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Solution Overview
Problem
Chest-mounted wireless sensor devices face challenges in accurate posture detection and activity monitoring due to improper calibration, as the patch can be worn in various positions, leading to non-calibrated accelerometer data that is difficult to interpret.
Innovation Solution
A method and system for calibrating wireless sensor devices by determining a vertical calibration vector and rotation matrix to align native axes with body axes, using automatic, manual, and sleep study calibration techniques, ensuring accurate posture and activity detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the patch is worn in different positions without calibration, then the device can be used flexibly in various positions, but the posture detection accuracy deteriorates
Solution Approach 1:
The patent implements a calibration process that must be performed before normal operation to establish the relationship between sensor axes and body axes. This preliminary action (calibration) enables the device to accurately detect posture regardless of wearing position, resolving the contradiction between flexibility and accuracy.
Solution Approach 2:
The calibration process changes the reference frame parameters by determining a rotation matrix that transforms sensor coordinates to body coordinates. This parameter transformation allows the device to maintain accurate posture detection across different wearing orientations.
2Measurement precision
If calibration is performed to improve posture detection accuracy, then measurement precision improves, but device complexity increases
Solution Approach 1:
The calibration process is designed to be automatically performed by the device itself using its own sensors and processing capabilities. The device determines the calibration vector and rotation matrix using internal resources, eliminating the need for external calibration equipment and reducing overall system complexity.
Solution Approach 2:
The patent replaces complex mechanical calibration procedures with computational methods. Instead of requiring physical alignment tools or manual adjustment mechanisms, the system uses mathematical calculations (rotation matrices and calibration vectors) to achieve accurate posture detection.
3Ease of operation
If non-calibrated accelerometer data is used, then the device can operate immediately without calibration steps, but the data interpretation becomes difficult
Solution Approach 1:
The calibration process is performed as a preliminary step before data collection begins. This one-time preliminary action establishes the coordinate transformation needed for accurate data interpretation, allowing subsequent operation to be both fast and informative without repeating calibration.
Solution Approach 2:
The calibration vector and rotation matrix act as intermediary elements that bridge the gap between raw sensor data and meaningful posture information. These intermediaries transform the accelerometer data from sensor coordinates to body coordinates, making the data interpretable without losing operational efficiency.
Data Source
AI summary
A method and system for calibrating a wireless sensor device are disclosed. In a first aspect, the method comprises determining a vertical calibration vector and determining a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes. In a second aspect, a wireless sensor device comprises a processor and a memory device coupled to the processor, wherein the memory device includes an application that, when executed by the processor, causes the processor to determine a vertical calibration vector and to determine a rotation matrix using the vertical calibration vector to line up native axes of the wireless sensor device with body axes.