1. a TAMS Group, Department of Computer Science, University of Hamburg, Vogt-Koelln-Strasse 30, 22527 Hamburg, Germany
2. b TAMS Group, Department of Computer Science, University of Hamburg, Vogt-Koelln-Strasse 30, 22527 Hamburg, Germany; Robotics Institute, School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, 37 Xueyuan Road, 100083 Beijing, PRC
3. c Control and Telematics Systems Lab, School of Engineering, Universidad Autonoma de Madrid, Ctra. de Colmenar Km. 15, 28049 Madrid, Spain
4. d TAMS Group, Department of Computer Science, University of Hamburg, Vogt-Koelln-Strasse 30, 22527 Hamburg, Germany