1. Ph.D. Student, Robotics Institute, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213 (corresponding author).
2. B.S. Student, Robotics Institute, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
3. Research Professor, Robotics Institute, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.
4. University Professor, Robotics Institute, Carnegie Mellon Univ., 5000 Forbes Ave., Pittsburgh, PA 15213.