1. a Biomedical Robotics Laboratory, Campus Bio-Medico University, 00128 Rome, Italy
2. b Department of Information Engineering, University of Padova, 35131 Padova, Italy
3. c Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA
4. d Department of Mechanical Engineering, University of Delaware, Newark, DE 19716, USA
5. e Biomedical Robotics Laboratory, Campus Bio-Medico University, 00128 Rome, Italy