Human-robot physical interaction with dynamically stable mobile robots
Umashankar Nagarajan, George A. Kantor, Ralph L. Hollis · 2009
Developed by Prof. Ralph Hollis in the Microdynamic Systems Laboratory at Carnegie Mellon University, Ballbot is a dynamically stable mobile robot moving on a single spherical wheel providing omni-directional motion. Unlike statically stable mobile robots, dynamically stable mobile robots can be tall and skinny with high center of gravity and small base. The ball drive mechanism is a four motor inverse mouse-ball setup. An Inertial Measuring Unit (IMU) and encoders on the motors provide all information needed for full-state feedback. Ballbot has three legs that provide static stability when powered down and is capable of auto-transitioning from the statically stable state to the dynamically stable state and vice versa. It is also capable of yaw rotation about its vertical axis. An absolute encoder provides the relative angle between the IMU and the ball drive unit.