1. School of Automation, Nanjing University of Science and Technology, Nanjing, China
2. Department of Computer Science, Brunel University London, Uxbridge, Middlesex, U.K.
3. Key Laboratory of Advanced Perception and Intelligent Control of High-end Equipment, Ministry of Education, Anhui Polytechnic University, Wuhu, China
4. Department of Automation, Tsinghua University, Beijing, China