1. a Institute for Robotics and Process Control, Technical University of Braunschweig, Hamburger Strasse 267, 38114 Braunschweig, Germany
2. b Institute for Robotics and Process Control, Technical University of Braunschweig, Hamburger Strasse 267, 38114 Braunschweig, Germany
3. c Institute for Robotics and Process Control, Technical University of Braunschweig, Hamburger Strasse 267, 38114 Braunschweig, Germany