1. School of Automation, Nanjing University of Science and Technology, Nanjing, P. R. China
2. Key Laboratory of Information Perception and Cooperative Control of Multi-Mobiles, Nanjing, P. R. China
3. School of Electrical and Automation Engineering, Nanjing Normal University, Nanjing, P. R. China
4. School of Science, Huzhou Teachers College, Huzhou, P. R. China