1. Robotics and Microsystems Center, College of Mechanical and Electrical Engineering, Soochow University, Suzhou, China
2. National Research Center for Rehabilitation Technical Aids, Beijing, China
3. Laboratory of Aerospace Servo Actuation and Transmission, Beijing Institute of Precision Mechatronics and Controls, Beijing, China
4. State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, China