1. School of Automation, Nanjing University of Information Science and Technology, Nanjing 210044, China.
2. School of Computer Science and Engineering, South China University of Technology, Guangzhou 510641, China, and also with the Pazhou Lab, Guangzhou 510335, China (e-mail: philip.chen@ieee.org).
3. School of Automation Science and Engineering, South China University of Technology, Guangzhou 510641, China.