1. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China;
2. Department of Mechanical Engineering, Northwestern University, Evanston, IL 60208
3. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, Heilongjiang, China
4. School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065, Sichuan, China