  A reliable estimation of 3D parameters is a must for several applications
like planning and control. Included in the latter is the Image-Based Visual
Servoing, whose control scheme depends directly on 3D parameters e.g. depth of
points, and depth and direction of 3D straight lines. Recently a framework for
Active Structure-from-Motion was proposed, addressing the former feature type.
However, straight lines were not addressed. These are 1D objects, which allow
for more robust detection and tracking. In this work, the problem of Active
Structure-from-Motion for 3D straight lines is addressed. An explicit
representation of this type of feature is presented, and a change of variables
is proposed, which allows the dynamics of the line to respect the conditions
for observability of the framework. The approach is validated first in
simulation for a single line, and second using a real robot. The latter set of
experiments are conducted first for a single line, and then for three lines,
which is the minimum required number of lines to control a 6 degree of freedom
camera.
