1. College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao, China, 999001 (e-mail: liangxiao_sdu@163.com)
2. Institute of Complexity Science, School of Automation, Qingdao University, Qingdao, China, 266071 (e-mail: qiqy123@163.com)
3. College of Electrical Engineering and Automation, Shandong University of Science and Technology, Qingdao, China, China, 250061 (e-mail: hszhang@sdu.edu.cn)
4. School of Elect. & Electr. Eng., BLK S2, Nanyang Tech. Univ., Singapore, Singapore, Singapore, 639798 (e-mail: elhxie@ntu.edu.sg)