1. Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, USA
2. Department of Aerospace Engineering and Coordinated Science Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, USA
3. Department of Aeronautics and Astronautics, Stanford University, Stanford, CA, USA
4. Intelligent Robotics Group, NASA Ames Research Center, Moffett Field, CA, USA