1. State Key Laboratory of Traction Power, Southwest Jiaotong University, No. 111, Second Ring Road, Sichuan, Chengdu 610031, China;
2. School of Mechanics and Engineering, Southwest Jiaotong University, No. 111, Second Ring Road, Sichuan, Chengdu 610031, China;
3. College of Mathematics and Statistics, Hanshan Normal University, Qiaodong, Guangdong, Chaozhou 521041, China e-mail:
4. State Key Laboratory of Traction Power, Southwest Jiaotong University, No. 111, Second Ring Road, Sichuan, Chengdu 610031, China
5. School of Mechanics and Engineering, Southwest Jiaotong University, No. 111, Second Ring Road, Sichuan, Chengdu 610031, China