1. School of Information and Electronics, Beijing Institute of Technology, Beijing, P. R. China
2. College of Information and Control Engineering, Xi'an University of Architecture and Technology, Xi'an, P. R. China
3. School of Automation, Northwestern Polytechnical University, Xi'an, P. R. China
4. School of Artificial Intelligence, Optics and Electronics (iOPEN), Northwestern Polytechnical University, Xi'an, P. R. China