Rotation Matrix for Yaw, Pitch and roll with IMU bricklet 3.0

[Groudaut]

Hello,

I have IMU bricklet 3.0 and get Yaw, Pitch and Roll data. I want to calculate the position [X Y Z] in earth frame of a given point (x, y, z coordinates in IMU reference frame is [1, 0, 0] ) according to Pitch, Roll and Yaw data from IMU.

I have difficulties to find the rotation matrix R (3x3) to get X,Y,Z. The formula is [X,Y,Z]= [x,y,z] * R.

I worked for hours on this and tried many differents rotation matrix according to this source : https://en.wikipedia.org/wiki/Euler_angles.

I don't know in witch order the 3 rotations are done (around IMU axes) and I don't know which axes are used for Pitch Yaw and roll reference in the IMU...

I think IMU use extrinsic references axes : for example when roll is about 30°, if I change the pitch the heading change also.

I found this discussion about BNO055 sensor (used in IMU 3.0) but it doesn't solve my problem ! https://community.bosch-sensortec.com/t5/MEMS-sensors-forum/BNO055-How-to-use-Euler-angles/td-p/45085

Does someone has the correct rotation matrix ? or could help me (ideas to proceed some tests, some references....)

Thanks

Gil.

[photron]

Euler angles are problematic, as you already found out. The IMU Bricklet also provides the oriantation in form of a quaternion and Wikipedia explains how to convert a quaternion into a rotation matrix:

https://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation#Quaternion-derived_rotation_matrix

[Groudaut]

Thanks for the answer. Well, It's seems a little bit more complicate, but maybe not... I have to go through and, archive quaternions from IMU3.0, get or write some codes and make some new tests. I will come back when I will proceed to all of this steps.

If anyone else have other solutions, or already solve this orientation problem, please tell me.

Gil.