at 5/2012 Methoden Constraint-Based Task Specification and Control for Visual Servoing Application Scenarios Beschränkungsbasierte Aufgabenspezifikation und -regelung für Visual-Servoing-Anwendungsszenarien Tinne De Laet, Ruben Smits, Herman Bruyninckx, Joris De Schutter, KU Leuven, Belgium Summary This paper reformulates image-based visual ser- voing as a constraint-based robot task, in order to integrate it seamlessly with other task constraints in image space, in Cartesian space, in the joint space of the robot, or in the “im- age space” of any other sensor (e. g. force, distance). This approach allows us to fuse various kinds of sensor data. The integration takes place via the specification of generic “feature coordinates”, defined in the different task spaces. Independent control loops are defined to control the individual feature co- ordinate setpoints, in each of these task spaces. The outputs of the control loops are instantaneously combined into joint vel- ocity setpoints for a velocity-controlled robot that executes the task. The paper includes experimental results for different ap- plication scenarios. ◮◮◮ Zusammenfassung In diesem Beitrag wird das Konzept des bildgestützten Visual-Servoing als eine beschränkungsbasierte Roboter-Aufgabe umformuliert, um es nahtlos mit anderen Aufgabenbeschränkungen im Bildkoor- dinatensystem, im kartesischen oder Gelenkkoordinatensystem integrieren zu können. Die Integration wird über die Spezi- fikation von Merkmalskoordinaten durchgeführt, die in den verschiedenen Aufgabenräumen definiert sind. In jedem dieser Aufgabenräume werden Regelungsschleifen definiert, um die einzelnen Sollkoordinaten der Merkmale selektiv zu steuern. Die Kombination der Ausgänge aller Teilregelkreise bilden die Sollwerte des geschwindigkeitsgeregelten Roboters. Experi- mentelle Ergebnisse für unterschiedliche Anwendungsszena- rien demonstrieren die Funktion und Leistungsfähigkeit des vorgeschlagenen erweiterten Visual-Servoing-Konzeptes. Keywords Visual servoing, constraint-based programming, task specification, robotics 1 Introduction This paper reformulates image-based visual servoing as a constraint-based robot task, in order to integrate it seamlessly with other task constraints in image space, in Cartesian space, in the joint space of the robot, or in the ‘‘image space’’ of any other sensor (e. g. force, distance). Previous work on specification of sensor-based robot tasks, such as force-controlled manipulation [9; 14 – 16] or force-controlled compliant motion combined with visual servoing [2], was based on the concept of the compliance frame [19] or task frame [4]. In this frame, different con- trol modes, such as trajectory following, force control, visual servoing, or distance control, are assigned to each of the translational directions along the frame axes and to each of the rotational directions about the frame axes. The task frame concept has proven to be very useful for the specification of a variety of practical robot tasks. However, the drawback of the task frame approach is that it only applies to task geometries with limited complexity, that is, task geometries for which separate control modes 260 at – Automatisierungstechnik 60 (2012) 5 / DOI 10.1524/auto.2012.0996  Oldenbourg Wissenschaftsverlag Brought to you by | Université Paris Ouest Nanterre La Défense Authenticated Download Date | 10/14/16 9:00 PM