Calibration Model

The STorM32 controller implements a relatively simple calibration model for the accelerometers and gyros.

Accelerometer

Each axis is converted as follows:

$a=(a_{meas}-a_{zero})\cdot a_{scale}-a_{ofs}$

$a_{meas}$: value obtained from the IMU

$a_{zero}$: 'Acc Zero' calibration constant determined by calibration procedure

$a_{scale}$: 'Acc Scale' calibration constant determined by calibration procedure

$a_{ofs}$: offset entered in the GUI ("Pitch Offset" or "Roll Offset" or "Yaw Offset")

Gyro

Each axis is converted as follows:

$g=g_{meas}-g_{zero}$

$g_{meas}$: value obtained from the IMU

$g_{zero}$: bias determined during gyro calibration at startup, or 'Gyro Zero' calibration constant determined by calibration procedure

IMU Orientation

The calibration constants are with respect to the IMU frame, i.e., applied before the rotation into the gimbal frame as specified by the IMU orientation settings. The offset value is however applied after this rotation, i.e., is with respect to the gimbal frame. This makes it possible to calibrate the IMU and then to mount it in any desired orientation without having to recalibrate (the offsets may have to be adjusted however, but these should normally not be needed).