1. School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, No. 37, Xueyuan Road, Haidian District, Beijing 100191, China e-mail:
2. School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, No.37, Xueyuan Road, Haidian District, Beijing 100191, China
3. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China