The function 'velocity_update_first_order' of RigidBody

[huizi-sui]

In the update of angular_velocity, I found the process may be exist an error.

Should the variable "relRot" be in the following form?

relRot = (Eigen::Quaterniond)(predicted_rotation.coeffs() - rotation.coeffs()) * rotation.conjugate();

If I understand wrong, I'm sorry, and please tell me why. Thanks.