Active Structure-from-Motion for 3D Straight Lines

A reliable estimation of 3D parameters is a must for several applications like planning and control, in which is included Image-Based Visual Servoing. This control scheme depends directly on 3D parameters, e.g. depth of points, and/or 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 these features is presented, and a change of variables is proposed. The latter allows the dynamics of the line to respect the conditions for observability of the framework. A control law is used with the purpose of keeping the control effort reasonable, while achieving a desired convergence rate. The approach is validated first in simulation for a single line, and second using a real robot setup. The latter set of experiments are conducted first for a single line, and then for three lines.