Title :
On continuous null space projections for torque-based, hierarchical, multi-objective manipulation
Author :
Dietrich, Alexander ; Albu-Schäffer, Alin ; Hirzinger, Gerd
Author_Institution :
Inst. of Robot. & Mechatron., German Aerosp. Center (DLR), Wessling, Germany
Abstract :
The technological progress in the field of robotics results in more and more complex manipulators. However, having an increasing number of degrees of freedom raises the question of how to use them effectively. In turn, establishing manipulators in human environments, e.g., as service robots, calls for the fulfillment of various constraints and tasks at the same time. In the context of torque controlled robotic systems, we provide an approach to simultaneously deal with a multitude of tasks and constraints which are arranged in a hierarchy, utilizing the large number of actuated joints of the manipulator. To this end, we propose a continuous null space projection technique to consider unilateral constraints, singular Jacobian matrices and dynamic variations of the priority order within the hierarchical structure. We show that activating and deactivating tasks as well as crossing singularities does not lead to a discontinuous control law. Simulations and experiments on the humanoid Justin of the German Aerospace Center (DLR) validate our approach. The presented concept is supposed to contribute to whole-body control frameworks.
Keywords :
Jacobian matrices; continuous systems; humanoid robots; manipulator dynamics; sampled data systems; service robots; torque control; German Aerospace Center; actuated manipulator joints; continuous null space projection technique; continuous null space projections; crossing singularity; deactivating tasks; degrees of freedom; discontinuous control law; dynamic variations; hierarchical manipulation; hierarchical structure; human environments; humanoid Justin; multiobjective manipulation; robotics; service robots; singular Jacobian matrices; technological progress; torque controlled robotic systems; torque-based manipulation; unilateral constraints; whole-body control frameworks; Collision avoidance; Jacobian matrices; Joints; Manipulators; Null space; Torque;
Conference_Titel :
Robotics and Automation (ICRA), 2012 IEEE International Conference on
Conference_Location :
Saint Paul, MN
Print_ISBN :
978-1-4673-1403-9
Electronic_ISBN :
1050-4729
DOI :
10.1109/ICRA.2012.6224571