1. School of Mechanical Engineering, Xihua University, Chengdu, Sichuan, China
2. School of Mechanical Engineering, Southwest Jiaotong University, Chengdu, Sichuan, China
3. State Key Laboratory of Rail Transit Vehicle System, Southwest Jiaotong University, Chengdu, Sichuan, China
4. Institute of Railway Research, University of Huddersfield, Huddersfield, U.K.