How to calibrate compass and accelerometer ?

[Desoky01]

How to calibrate compass and accelerometer ?
What are those values refer to?
#Calibration
calib:
compass_min: [-28.451460, -42.645390, -38.086895]
compass_max: [68.179794, 48.143326, 57.744003]

accel_min: [ -1.004789, -1.014467, -1.015889 ]
accel_max: [ 0.995606, 1.002416, 0.996524 ]

[JeremieBourque1]

This document explains how the calibration works and what those min max values mean.
https://github.com/RTIMULib/RTIMULib2/blob/master/Calibration.pdf

[adityasivaraj]

This document explains how the calibration works and what those min max values mean. https://github.com/RTIMULib/RTIMULib2/blob/master/Calibration.pdf

Where do you store the settings file in this ROS package folder?

Thanks in advance!

[JeremieBourque1]

@adityasivaraj This package doesn't use the RTIMULib.ini calibration file generated by RTIMULib directly. Instead, all calibration data must is passed to the node with ROS parameters. These parameters are written in param/imu.yaml. If you don't want to manually copy all of the parameters one at a time, you can use a script I made to generate a yaml file automatically. You can find it here. You'll find instructions on how to use it in the README.

[adityasivaraj]

@JeremieBourque1 Thank you for the fast reply! Is covariance calculation of linear acceleration, orientation and angular velocity possible in this library? It is present in the program i2c_imu_node.cpp, but the calibration file does not seem to generate it...

[JeremieBourque1]

@adityasivaraj I'm afraid I don't know the answer to your question. The covariance might me calculated during runtime but I'm not sure since I haven't had the chance to use the library a lot yet. If it is, it would be availabe in the imu/data topic.

[adityasivaraj]

@JeremieBourque1 I am getting a linear acceleration of around 3m/s^2 even when the IMU is stationary. I think that it would affect my pose estimation. And, I think having covariance factor into the calculation would help my case. Do you think there is a way I can eliminate this bias out of the published message?

[JeremieBourque1]

@adityasivaraj If you get that acceleration when the IMU is resting wether the calibration wasn't done properly or there is something wrong with your IMU. I doubt a covariance would do much good if the measurement is very far from the right value. I'm not much of an expert in IMUs so I don't think I can help you more than that.