// Get the quaternion first derivative from the vector of angular acceleration with a specified in _absolute_ coords.
public static ChQuaternion Qdtdt_from_Aabs(ChVector a,
ChQuaternion q,
ChQuaternion q_dt)
{
ChQuaternion ret = new ChQuaternion(1, 0, 0, 0); //QNULL;
ret.Qdtdt_from_Aabs2(a, q, q_dt);
return(ret);
}