1. School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, PR China 150001
2. Department of Mechanical Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR, PR China 999077
3. State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, PR China 150001
4. Nano-Manufacturing Laboratory (NML), City University of Hong Kong Shenzhen Research Institute, Shenzhen, Guangdong, PR China 518057