1. School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, Sichuan, China
2. Robotics Research Center, Xihua University, Chengdu 610039, Sichuan, China
3. Control Engineering College, Chengdu University of Information Technology, Chengdu 610225, Sichuan, China
4. Centre for Computational Intelligence, School of Computer Science and Engineering, De Montfort University, Leicester, UK