1. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001, China
2. School of Mechatronics Engineering, State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China e-mail:
3. School of Mechatronics Engineering, State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin 150001, China