Magnetic Sensor Calibration for Cross-Talk Error Reduction
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Solution Overview
Problem
Existing magnetic sensing systems for position sensing suffer from inaccuracies due to cross-talk between the magnetic fields of the master and nonius tracks, leading to errors in detecting the absolute angular position.
Innovation Solution
A method and system that utilize a two-track coded multi-pole magnet with a master and nonius track, where the number of multipoles differs between the two tracks, and a magnetic sensor to measure at least four components of the magnetic field. The system includes a calibration method that uses periodic correction functions to minimize position errors over a calibration range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two multipole magnetic tracks with different number of poles are used to reconstruct the full 360° range, then absolute angular position information is recovered, but cross talk between the fields causes inaccuracies in the detected position
Solution Approach 1:
The patent extracts and compensates for the harmful cross-talk effect by measuring it separately using a sensorless mode, then removing its influence from the position measurement through calibration coefficients
Solution Approach 2:
The patent changes the operating parameters by switching between sensorless mode (for cross-talk measurement) and sensing mode (for position measurement), and uses calibration coefficients to adjust the measurement results
2Measurement precision
If complex calibration methods with lengthy series and multiple terms are used to correct position errors, then measurement accuracy is improved, but processing power and computational requirements increase
Solution Approach 1:
The patent uses a simplified calibration approach with limited terms in the Fourier series (typically just the fundamental harmonic) rather than exhaustive complex corrections, achieving sufficient accuracy with reduced computation
Solution Approach 2:
The patent performs calibration offline during manufacturing or setup, storing the resulting coefficients for simple runtime application, rather than performing complex calculations during operation
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
The proposed solution significantly reduces errors induced by cross-talk, allowing for high-accuracy position measurements with low processing power and computational requirements, achieving 13 bits of absolute accuracy and 17 bits of resolution over a full 360° range.
Implementation Method 1
measuring at least four components of the magnetic field generated by the magnetic structure
Data Source
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AI summary
A method of calibrating a magnetic sensor system and a sensor system are provided. The position of a magnetic structure with a master and nonius tracks is changed over a calibration range while measuring at least four components of the magnetic field generated by the magnetic structure. Uncorrected positions of the structure are determined and compared with corresponding reference positions. A periodic function is obtained by calculating two coefficients of the function, such that the function applied to the uncorrected positions minimize the error from the comparison with the reference positions.