MPU-9250 madgwick filter drift

[Jl06CTEP]

For my project i need a way to determine correct orientation of the rocket.

I took code for Madgwick filter from here

https://github.com/morgil/madgwick_py

for collecting data i used Arduino Nano + MPU9250 sensor. This setup sends packets every 12ms to my PC via Serial.

I calibrated magnetometer by calculating biases to "align" axis origin and center of sphere, created by set of measurements.

Then i drew coordinate axis with blender: 

and coded some script for it - quaternion.py It just reads values from serial, feeds them into Filter, and then rotates my axis object using quaternion rotation mode.

I screwed up with orientation of model's X axis a little bit, so when i rotate my board clockwise, axis on the screen rotates counter-clockwise. I flipped signs of all X components, and it became fine.

According to this picture 

 i flipped X and Y axis and sign of Z axis, to align axis of magnetometer with gyroscope + accelerometer

And it almost works with one small exception - when after "stabilization" i tilt i.e. X axis downwards (or Y axis, doesnt matter) this axis starts drifting toward global X-Y plane. If i tilt axis upwards, remaining axis starts drifting around global O-Z axis, like this 

X axis downwards

And when x axis upwards

Speed of that drift depends on Beta of Madgwick filter - the more beta the more drift.

What can be done there?

Edited July 1, 2018 by Jl06CTEP
add code for script