Groudaut Posted September 12, 2024 at 12:14 PM Share Posted September 12, 2024 at 12:14 PM 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. Quote Link to comment Share on other sites More sharing options...

photron Posted September 12, 2024 at 12:34 PM Share Posted September 12, 2024 at 12:34 PM 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 Quote Link to comment Share on other sites More sharing options...

Groudaut Posted September 12, 2024 at 07:45 PM Author Share Posted September 12, 2024 at 07:45 PM 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. Quote Link to comment Share on other sites More sharing options...

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