1. Specific Research Center CS2AC , Polytechnic University of Catalonia (UPC) , Rbla. Sant Nebridi 22, 08222 Terrassa , Spain
2. Institute of Robotics and Industrial Informatics (CSIC-UPC) , Polytechnic University of Catalonia (UPC) , Llorens i Artigas 4–6, 08028 Barcelona , Spain