1. State Key Laboratory of Robotics and Systems, Harbin Institute of Technology, Harbin, China
2. School of Mechatronics Engineering, Harbin Institute of Technology, Harbin, China
3. Helen and John C. Hartmann Department of Electrical and Computer Engineering, New Jersey Institute of Technology, Newark, NJ, USA
4. Teachers College for Vocational and Technical Education, Guangxi Normal University, Guilin, Guangxi, China