1. The State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing 400044, China
2. College of Automotive Engineering, Chongqing University, Chongqing 400044, China
3. Department of Civil and Environmental Engineering, University of California, Berkeley, CA 94720, USA
4. The State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China
5. The Cho Chun Shik Graduate School for Green Transportation, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Republic of Korea