Accelerometer coordinate frame

[oniht]

Hi, I have an issue with getting the simulated accelerometer and gyroscope measurements to match with a real life case. I'm trying to replicate IMU data that was recorded during a metro ride that includes 2 approx. 75 deg turns. First left then right. I flipped the IMU with initial pitch of 180 deg to get positive z-acceleration and assigned an initial velocity v_y = 20m/s. Then I simulated these 2 turns with constant yaw rate during 40 sec. (I ignored the acceleration periods in y-direction)

The results match pretty well with the real life case except that the acceleration in x-direction is negative during the left turn and positive during the right turn. I would assume that these should be opposite if the accelerometer coordinate frame follows the right hand convention?

[dxg-aceinna]

Could you provide a picture about how the IMU (in the simulation) is installed on the metro when you apply the pitch = 180deg flip? To me, usually ZYX sequence is used in the simulation by default. The range for the pitch angle should be [-90, 90]deg. Besides, even if pitch = 180, the X acceleration should still point along the motion direction of the metro. Without velocity amplitude change, X acceleration should be always zero while the Y acceleration should show acceleration due to rotation.