US Patent 8935005 Operating a mobile robot

A method of operating a mobile robot to traverse a threshold includes detecting a threshold proximate the robot. The robot includes a holonomic drive system having first, second, and third drive elements configured to maneuver the robot omni-directionally. The method further includes moving the first drive element onto the threshold from a first side and moving the second drive element onto the threshold to place both the first and second drive elements on the threshold. The method includes moving the first drive element off a second side of the threshold, opposite to the first side of the threshold, and moving the third drive element onto the threshold, placing both the second and third drive elements on the threshold. The method includes moving both the second and third drive elements off the second side of the threshold.