1. Department of Mechanical Engineering and Materials Science Yale University 9 Hillhouse Avenue New Haven CT 06511 USA
2. Department of Mechanical Engineering Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213 USA
3. Department of Mechanical Engineering Boston University 110 Cummington Mall Boston MA 02215 USA
4. School of Mechanical Engineering Southeast University Nanjing 211189 China
5. Jiangsu Engineering Research Center of Aerospace Machinery Southeast University Nanjing 211189 China
6. Robotics Institute Carnegie Mellon University 5000 Forbes Avenue Pittsburgh PA 15213 USA
7. Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology 50 Vassar Street Cambridge MA 02139 USA
8. Department of Mechanical Engineering and Materials Science University of California, Los Angeles 420 Westwood Plaza Los Angeles CA 90095 USA