Wearable imu calibration

Hi, I am using a BNO055 imu of Adafruit to record the yaw of the hip during a walking gait.
Firstly I needed to calibrate the ACC, MAG, and GYRO. I did it successfully, indeed the yaw is not present I shall say. There is weird behavior based on the inversion walk. Imagine being in a room doing a walk forward, then rotate yourself and you come back. During the inversion, the coordinate system of the start is changed. That's the reason why I think that I have to calibrate the imu to the anatomical position. Has someone of you some Github link for some special repositories? Also, some tips could be great to have better ideas.

Thank you all

  1. Yes, it is "present". Yaw can be derived at any time from the quaternion.

During the inversion, the coordinate system of the start is changed.

  1. No, it has not changed. The base coordinate system for navigation is by definition fixed to the Earth.

You are right. Indeed I can see it from the first graph of euler.x and at the bottom the trend of quaternion.w (I knew that they can vary only in [-1;1] but I was wrong maybe)
I don't want for now a logic that works in real-time, but what could be at this point the solution to recognize with a threshold the maximum and minimum of the swing with BNO055, in your opinion, please? Do you have some help theory for me?

If you can clearly describe what it is that you actually want to measure (a clear diagram would help a lot), forum members will be in a position to contribute useful suggestions.

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This is the graph of what we were discussing about it. In the black section, the sensor is just calibrated totally. Then it is worn at the level of the thigh more or less and I start to walk. The red indicates the walk in a direction and the green in the opposite one (where each wave indicates a step). All of them of course include the inversion of gait at the end of each color. I need to put some thresholds to let the sensor recognize the maximum and minimum of each wave. Note that the sensor is not properly fixed. Anyway, for sure there will be some noise.