1. Beijing Key Lab of Precision/Ultra-Precision Manufacturing Equipments and Control, Tsinghua University, Beijing 100084, China;
2. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405 e-mails: ;
3. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China e-mail:
4. George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405
5. Department of Mechanical and Energy Engineering, South University of Science and Technology of China, Shenzhen 518055, China