1. Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, USA
2. Department of Mathematics and Statistics, University of Minnesota Duluth, Duluth, USA
3. School of Astronautics, Harbin Institute of Technology, Harbin, China
4. Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, ON, Canada
5. Institute of Flight System Dynamics, Technical University of Munich, Garching, Germany
6. Robotics and Mechatronics Laboratory, Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA