Elliptical Calibration Model for Magnetometer Soft Magnetic Distortion
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Solution Overview
Problem
Electronic devices with magnetometers, such as smartphones and smartwatches, face inaccuracies in determining the Earth's magnetic field due to distortions from both hard and soft magnetic materials, which can change with removable components like securement bands, leading to erroneous directional data.
Innovation Solution
A method involving detecting changes in magnetism, collecting magnetic field data at a high sampling frequency, and generating an elliptical calibration model to compensate for distortions, allowing the magnetometer to accurately determine the Earth's magnetic field by fitting collected data to a sphere or ellipsoid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If soft magnetic components are used in the electronic device, then the device structure and functionality are enhanced, but the magnetometer measurements become distorted and inaccurate
Solution Approach 1:
The system performs preliminary calibration by detecting the Earth's magnetic field in multiple orientations before normal operation, storing this calibration data to compensate for soft magnetic distortions during subsequent measurements
Solution Approach 2:
The system changes the operational parameters of the magnetometer by adjusting sampling frequency (at least 1 Hz) and collecting data over extended periods (at least 2 minutes) to gather sufficient calibration information for distortion compensation
2Ease of operation
If removable components like securement bands are attached to the device, then the device usability is improved, but the magnetic distortion changes require recalibration
Solution Approach 1:
The system continuously monitors for changes in magnetic distortion patterns and triggers recalibration when deviations are detected, creating a feedback loop that maintains accuracy despite component changes
Solution Approach 2:
The calibration model is made dynamic and adaptive, allowing the system to update its distortion compensation parameters in response to changing device configurations rather than relying on static calibration
3Measurement precision
If magnetic field data is collected at high sampling frequency for calibration, then the calibration accuracy is improved, but the data collection time and processing complexity increase
Solution Approach 1:
The system collects more calibration data than the minimum single-point measurement, gathering data over at least 2 minutes at high sampling frequency to ensure sufficient statistical accuracy for robust distortion modeling
4Volume of moving object
If the magnetometer is placed near removable components for compact device design, then the device size is reduced, but the magnetic interference from these components increases
Solution Approach 1:
The harmful magnetic interference from removable components is extracted and characterized as a separate distortion pattern through calibration, allowing the system to mathematically remove its effect from the measurements
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 enables the magnetometer to provide accurate directional information by accounting for changes in magnetic distortions caused by removable components, ensuring reliable navigation and orientation calculations.
Implementation Method 1
The electronic compass can obtain a measurement of the magnetic field that is present in its immediate surroundings as a three-component vector
Implementation Method 2
the magnetic field associated with the device's reference frame can be distorted by 'soft' magnetic components of or near the device
Data Source
AI summary
A method for calibrating a magnetometer of an electronic device can include detecting a change in a magnetism of the electronic device, collecting a first magnetic field data from the magnetometer at sampling frequency of at least 1 hertz, generating an elliptical calibration model based at least partially on the collected first magnetic field data, collecting a second magnetic field data from the magnetometer, and fitting the collected second magnetic field data to a sphere using the elliptical calibration model.