the-risk-taker / matlab-magnetometer-hard-and-soft-iron-compensation-algorithm

MATLAB Algorithm for getting Soft and Hard Iron compensation parameters for magnetometer sensor

Magnetometer Soft and Hard Iron magnetic compensation

MATLAB script and data plotter for calculating Hard and Soft Iron magnetic compensation parameters.

This script is intended to work with the HMC5883L magnetometer, however, the results from this script can easily be adapted to work with other magnetometers or implementations.

Results

Getting Started

If you just want to see the results of the algorithm, there are sample measurements in the file myData. Just run main.m script in MATLAB and change fileName variable to see another result.

If you want to get results for your implementation or my HMC5883L magnetometer see next paragraph.

How to generate data for calibration

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Use my HMC5883L example or make your own program to generate data in the specific manner provided in next paragraph.

Requirements for data file and script usage

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• data should be scaled in miliGauss [mGs] use HMC5883L::getScaled(); from here with the HMC5883L_EXTENED_CALIB_PROCEDURE define set to 0x01 in HMC5883L.h file,
• column should be separated by tabs: "\t",
• data order:

TIME[ms]   X-AXIS     Y-AXIS      Z-AXIS

Example of data:

798       -151.84     332.88      -275.94
805       -148.19     330.69      -277.40
811       -144.54     329.96      -281.78
818       -141.62     324.12      -281.05
825       -138.70     321.93      -284.70
831       -137.24     323.39      -286.89
838       -136.51     319.01      -285.43
...

• file with data can be in the same folder as main.m file or in other, but the path should be provided in filename variable,
• change myData/afterCallib1.txt to yours in filename variable in main.m file,
• run script,
• copy output from MATLAB command window:

const float magn_ellipsoid_center[3] = {2.74731, -15.5597, 5.48397};
const float magn_ellipsoid_transform[3][3] = {{0.979956, 0.00991353, 0.00841591}, {0.00991353, 0.93923, -0.00647764}, {0.00841591, -0.0064776}}

into void HMC5883L::useHardAndSoftIronCompensationParameters(void) and replace data in ellipsoidCenter and ellipsoidTransMatrix matrixes.

• set HMC5883L_EXTENED_CALIB_PROCEDURE define to previous value 0x00.

Author

• 2018, Mateusz Patyk, [e-mail]

based on the work:

• 2013 Peter Bartz from Razor AHRS project,
• 2011-2012 Quality & Usability Lab, Deutsche Telekom Laboratories, TU Berlin from Razor AHRS project,
• 2009 Yury Petrov, Northeastern University, Boston, MA.