Hi, I have a robot and do FK and then use the Eigen library and convert the rotation matrix to quaternion. Here are the results: x-axis: red y-axis: green z-axis: up the quaternion is [1,0,0,0] in this state. Then I rotate the hand to the following state: and the quaternion is [0.7, 0.7, 0, 0]. The Z-direction of the world frame is toward up. Is it correct? I thought that I have to have some value in Z-direction. Maybe I'm wrong.