Calibrating Magnetic Field Data for Rotating Bezel Sensors
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Solution Overview
Problem
The rotation of a bezel in electronic devices, such as smartwatches, causes magnetic field disturbances, leading to varying offsets in geomagnetism sensing values. This results in errors when calculating azimuth based on uncompensated geomagnetic data.
Innovation Solution
An electronic device is equipped with a rotating body having multiple magnets, a pair of Hall sensors in the bezel to sense magnetic fields, a magnetic sensor inside the device, and a processor to calibrate the magnetic field data. The processor generates first magnetic field data from the Hall sensors and second magnetic field data from the magnetic sensor, calculates a compensated offset value based on the angular position and first magnetic field data, and then calibrates the second magnetic field data using this offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If magnets are disposed on the rotating bezel to enable rotation detection, then the bezel rotation can be detected, but magnetic field disturbance occurs causing varying offsets in geomagnetism sensing values
Solution Approach 1:
The patent divides the magnetic sensing function into two separate systems: Hall sensors dedicated to detecting the rotating bezel's magnetic field, and a magnetic sensor dedicated to sensing geomagnetism. This segmentation isolates the interference source from the geomagnetic measurement, allowing each sensor to perform its specific function without mutual interference.
Solution Approach 2:
The patent introduces an intermediary calibration process that uses the Hall sensor data to calculate offset values, which then serve as correction factors for the magnetic sensor readings. This intermediary calibration mechanism mediates between the interfering bezel magnets and the geomagnetic measurements, eliminating the harmful effects of magnetic disturbance.
2Device complexity
If geomagnetic data is used without offset compensation, then the calculation process is simple, but azimuth calculation includes errors
Solution Approach 1:
The patent performs preliminary calibration by calculating offset values based on Hall sensor data before using the magnetic sensor for azimuth calculation. This preliminary action of offset compensation ensures that subsequent geomagnetic measurements are already corrected, maintaining measurement precision while keeping the actual azimuth calculation process simple.
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 solution effectively compensates for magnetic field disturbances caused by bezel rotation, reducing errors in azimuth calculation and providing more accurate geomagnetic sensing.
Implementation Method 1
The Hall sensor, used to measure magnetic force, may sense magnetic field using the Hall effect. The 'Hall effect' may refer to the effect where when magnetic field is applied to a conductor in which current is flowing, a force (e.g., Lorentz force) is generated in a predetermined direction, the flow of the current is changed by the force, and a voltage difference (hereinafter, referred to as 'a Hall voltage') between two detection terminals caused by the change in the flow of the current is generated.
Implementation Method 2
a magnetic sensor disposed in an internal space within a circumference of the rotating body
Data Source
AI summary
An electronic device includes a rotating body coupled to a bezel part to be rotatable and including a plurality of magnets, a pair of Hall sensors configured to sense a magnetic field caused by the plurality of magnets, a magnetic sensor disposed in an internal space, and a processor configured to calibrate, based on first magnetic field data, second magnetic field data based on a calculated offset value.