IMU calibration - what exactly does it do

ArduCopter
1

I have been trying to understand how IMU calibration works. My specific questions are :

  1. Does it just calibrate each of the XYZ accelerometers so that the reading is 1G when the accelerometer is lined up with the gravity force ? How about zeroing ? is it done at all ?
  2. Are the gyros calibrated in any ways ?

I have done some searching but was unable to find any documentation on the subject. If anyone can point my to any relevant on-line resources, it will be very much appreciated.

2

The accelerometers are scaled and zeroed (offset) during the calibration process. The gyro’s are zeroed (offset) on boot during the calibration phase.

1 Like
3

Thanks for the reply. I am still curious about how the accelerometers can be zeroed when there is no way to ensure that the flight controller is exactly vertical or level in the calibration process. Is some smart computation used or there are some other ways ?

4

I’ve found it to be quite important to get the Level Horizon correct, you can come back and do this at any time. We do it as if “the whole craft, prop plane, is level” like you’d want to see the aircraft flying - not as if just the flight controller is level because it may not be.

5

This doesn’t matter. The FC can be in many different orientations relative to the crafts frame, there is a parameter to set for that. Then it learns the offsets, relative to the frame, during the calibration process.

That’s it, there is nothing more to it. Scaling is done from 1G acceleration from gravity in each axis.