1. School of Mechatronic Engineering, North University of China, Taiyuan Shan'xi 030051, People's Republic of China
2. Department of Mathematics, North University of China, Taiyuan, Shan'xi 030051, People's Republic of China
3. School of Information and Communication Engineering, North University of China, Taiyuan, Shan'xi 030051, People's Republic of China