1. Robotic Intelligence Lab, Department of Engineering and Computer Science, Universitat Jaume-I, 12071 Castellón, Spain
2. Interaction Science Department, Sungkyunkwan University, Seoul 110-745, Republic of Korea
3. Department of Informatics, Bioengineering, Robotics and System Engineering (DIBRIS), University of Genoa, 16145 Genoa, Italy