Mobile Magnetometer Calibration Using Gyroscope Data
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Solution Overview
Problem
Mobile device magnetometers face constant bias errors due to magnetic interference from internal components and changing environments, leading to inaccurate readings of the Earth's magnetic field, which existing calibration methods using single quality indicators can ambiguously trigger unnecessary recalibration.
Innovation Solution
A method for calibrating a mobile device magnetometer by obtaining multiple error indicators with different criteria, using gyroscope readings to determine rotation axes and angles, and calculating calibration parameters based on these, to compensate for constant biases and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If single calibration quality indicator is used, then calibration decision is simple, but calibration accuracy is reduced and unnecessary recalibration occurs
Solution Approach 1:
The patent segments the single calibration quality indicator into multiple independent error indicators (e.g., spherical fit error, axis alignment error, magnitude error). Each indicator measures a specific aspect of magnetometer accuracy, allowing for more precise assessment and avoiding unnecessary recalibration while maintaining high reading accuracy.
2Measurement precision
If magnetometer calibration is performed frequently, then measurement accuracy is improved, but device operation efficiency is reduced due to unnecessary recalibration
Solution Approach 1:
The patent implements a feedback mechanism where multiple error indicators are continuously monitored and compared against threshold values. Recalibration is triggered only when the error indicators indicate actual degradation in magnetometer performance, rather than on a fixed schedule. This feedback-driven approach maintains measurement accuracy while avoiding unnecessary recalibration operations that would reduce device productivity.
3Measurement precision
If multiple error indicators are used, then magnetometer accuracy is improved, but system complexity increases
Solution Approach 1:
The patent divides the calibration assessment into multiple independent error indicators, each calculating a specific aspect of magnetometer performance (spherical fit error, axis alignment, field magnitude). This segmentation allows for modular computation where each indicator can be calculated independently using standard mathematical operations, reducing overall system complexity compared to a single complex calibration algorithm.
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 effectively reduces magnetic interference errors, providing more accurate magnetometer readings and reducing unnecessary recalibrations by using multiple error indicators and gyroscope data to determine calibration parameters, enhancing the magnetometer's accuracy and robustness.
Implementation Method 1
A magnetometer is an instrument used to measure the strength and/or direction of the magnetic field in the vicinity of the instrument
Implementation Method 2
using gyroscope readings to determine rotation axes and angles
Data Source
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AI summary
A method and system are provided for operating a mobile device having a magnetometer. The method includes obtaining a plurality of error indicators associated with the magnetometer. At least two of the plurality of error indicators have different criteria for error. The method also includes determining an instruction for operating the mobile device using the plurality of error indicators.