Tracking unobservable rotations by cue integration

Model based object tracking has earned significant importance in areas such as augmented reality, surveillance, visual servoing, robotic object manipulation and grasping. Although an active research area, there are still few systems that perform robustly in realistic settings. The key problems to robust and precise object tracking are outliers caused by occlusion, self-occlusion, cluttered background, and reflections. Two most common solutions to the above problems have been the use of robust estimators and the integration of visual cues. The tracking system considered in this paper achieves robustness by integrating model-based and model-free cues. As model-based cues, we consider a CAD model of the object known a priori and as model-free cues, automatically generated corner features are used. The main idea is to account for relative object motion between consecutive frames using integration of the two cues. The particular contribution of this work is the integration framework where not only polyhedral objects are considered. In particular, we deal with spherical, cylindrical and conical objects for which the complete pose cannot be estimate using only CAD like models. Using the integration with the model-free features, we show how a full pose estimate can be obtained. Experimental evaluation demonstrates robust system performance in realistic settings with highly textured objects