1. Faculty of Applied Sciences, Macao Polytechnic University, Macao SAR 999078, China
2. Department of Computer Science and Engineering, University of Bologna, 40126 Bologna, Italy
3. Autonomous Robotics Research Center, Technology Innovation Institute (TII), Abu Dhabi P.O. Box 9639, United Arab Emirates
4. Macao Polytechnic University, Macao SAR 999078, China
5. Samueli Computer Science Department, University of California, Los Angeles, CA 90095, USA