MATLAB: How to transform a DCM axes to an axis-angle representation in the Aerospace Toolbox 2.4 (R2009b)

Question

Given the Direction Cosine Matrix, I want obtain the rotation vector, i.e. the Euler axis/angle? This transformation is common in multi-body dynamics, but I cannot find this same functionality in either the Aerospace Blockset or the Aerospace Toolbox.

Answer 1

It is possible to express an orientation represented as a Direction Cosine Matrix by a single rotation axis and a single rotation angle, this can be done with the DCM2QUAT function in the Aerospace Toolbox, or with the "Direction Cosine Matrix to Quaternions" block in the Aerospace Blockset.

Given the quaternion, it is straightforward to extract the axis of rotation (Euler axis), as well as the angle of rotation (Euler angle).