A robot lawmnower includes a body, a drive system carried by the body, at least one caster wheel supporting the body, a grass cutter carried by the body, a controller in communication with the drive system, and a bump sensor in communication with the controller. The controller is configured to maneuver the robot to turn in place and to redirect the robot in response to the bump sensor sensing contact with an obstacle. The drive system is configured to maneuver the robot across a lawn and includes differentially driven right and left drive wheels positioned rearward of a transverse center axis defined by the body. The at least one caster wheel is positioned substantially forward of the right and left drive wheels, and the grass cutter is positioned at least partially forward of the right and left drive wheels and at least partially behind the at least one caster wheel.