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) * a_scale - a_offset

a_meas: value obtained form the IMU

a_zero: 'Acc Zero' calibration constant determined by calibration procedure

a_scale: 'Acc Scale' calibration constant determined by calibration procedure

a_offset: 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 form 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.