Model-based tracking and hybrid force/vision control for the UJI librarian robot

This paper describes design and implementation aspects of an autonomous robot that is intended to perform service tasks in a library. We first address problems concerning the arrangement of its components into a compact mobile manipulator suitable for our needs. Then, software issues are also discussed, related to the techniques that are necessary in order to navigate and to reliably manipulate books in a library. In this context, two methods are presented, concerning visual tracking and force/vision control. The first one is aimed at locating a book in a bookshelf by means of vision. For this, a tracking algorithm is implemented, which takes into account the spatio-temporal constraints of the problem. Book tags are located in the image and processed using open source optical character recognition (OCR) software, until the desired book is found. The second of the methods addresses the problem of extracting the book from the shelf. A hybrid force/vision control algorithm has been implemented, which uses vision for guiding the gripper to the correct book, and force for detecting contacts.