Model-based , Hierarchical Control of a Mobile Manipulation Platform

PR2 is a sophisticated mobile manipulation platform designed for operation in dynamic and unstructured indoor environments. In this paper we describe an experiment using TREX, a hierarchical control framework based on constraintbased temporal planning, to coordinate PR2 behavior. The experiment was part of a fully integrated demonstration of PR2 capabilities involving autonomous navigation, dooropening, and recharging using standard electrical outlets. The goal of this experiment was to evaluate the applicability of a model-based, planning centric approach for practical robotics on a large scale. The results were encouraging. Not only did TREX play an important role in accomplishing the milestone, which was in itself a significant achievement in autonomous robotics, but it did so with modest computatational overhead and system complexity. In this paper we outline the details of the milestone and how TREX was used to achieve it, providing a quantitative and qualititative evaluation of TREX performance. We believe this presents a promising pathway for deep integration of declarative models, and automated planning as a paradigm for practical robot programming. All software described in this paper, including TREX, is available under an Open Source license, via http://ros.sourceforge.net.