orientation_imu_in_ars

Eigen::Quaterniond orientation_imu_in_ars = Eigen::Quaterniond::Identity()

Rotation from the IMU frame to the ARS frame.

The attitude reference system frame has +x forward, +y right and +z down, whereas our world frame has +x forward, +y left and +z up: https://github.com/mjbots/pi3hat/blob/ab632c82bd501b9fcb6f8200df0551989292b7a1/docs/reference.md#orientation