1. Robotics Institute, State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, R. 301, Mechanical Building B, 800 Dong Chuan Road, Shanghai 200240, China e-mail:
2. Robotics Institute, State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, R. 914, Mechanical Building A, 800 Dong Chuan Road, Shanghai 200240, China e-mail: