The Robotics Institute

RI | Seminar | September 15, 2006

Robotics Institute Seminar, September 15, 2006
Time and Place | Seminar Abstract | Speaker Biography | Speaker Appointments


Ralph Hollis

Research Professor

Carnegie Mellon University


Time and Place

Mauldin Auditorium (NSH 1305)
Refreshments 3:15 pm
Talk 3:30 pm


Multi-wheeled statically-stable robots tall enough to interact meaningfully with people must have low centers of gravity, wide bases of support, and low accelerations to avoid tipping over.  These conditions present a number of performance limitations that make it difficult to maneuver through doorways and around furniture and people.  Accordingly, we are developing an inverse of this type of mobile robot that is the height, width, and weight of a person, having a high center of gravity, that balances on a single spherical wheel.  Such machines, which we refer to as ballbots, appear to be a hitherto unstudied class of mobile robots. Unlike balancing 2-wheel platforms which must turn before driving in some direction, our single-wheeled ballbot can move directly in any direction.  In this talk I will present the overall design, actuator mechanism based on an inverse mouse-ball drive, control system, and initial results including dynamic balancing, station keeping, and point-to-point motion.  In conclusion, I will discuss plans for future enhancements including body yaw rotation and the addition of a pair of dynamically-significant arms.

Speaker Biography

Ralph Hollis received the B.S. and M.S. degrees in physics from Kansas State University, Manhattan, in 1964 and 1965, and the Ph.D. degree in solid state physics from the University of Colorado, Boulder, in 1975. From 1965 to 1970, he was engaged in computer simulation of space-flight vehicles at the Autonetics Division of North American Aviation.  He was a National Science Foundation / Centre Nationale de la Reserche Scientifique Exchange Scientist at the Universite de Pierre et Marie Curie, Paris, for part of 1976-77.  He joined IBM in 1978 at the Thomas J. Watson Research Center as a Research Staff Member, where he worked in magnetism, acoustics, and robotics.  From 1986 to 1993, he was Manager of Advanced Robotics in the Manufacturing Research Department. Dr. Hollis joined the faculty at Carnegie Mellon University in 1993 where he is a Research Professor in the Robotics Institute, School of Computer Science.  Dr. Hollis is a member of the American Physical Society and a Fellow of IEEE.  He has served on several government panels, and the editorial boards of the Journal of Micromechanics and Microengineering: Structures, Devices, and Systems, and the IEEE Transactions on Robotics and Automation.  At IBM, he received five Invention Achievement Awards and an Outstanding Technical Achievement Award for work in precision robotic positioning.  He was recipient of the Nakamura Prize for best paper at the International Symposium on Intelligent Robots and Systems in 1995 and 2001, IEEE Robotics and Automation Society Best Video award in 1999, and was a Christopher Columbus Fellowship Foundation Discover Award Finalist in 2000.  He is founding director of the Microdynamic Systems Laboratory at Carnegie Mellon University where his research centers on haptics, agile manufacturing, and dynamically-stable mobile robots.

Speaker Appointments

For appointments, please contact Virginia Arrington (

The Robotics Institute is part of the School of Computer Science, Carnegie Mellon University.