Obstacle following sensor scheme for a mobile robot

An autonomous coverage robot comprising:

• a robot housing defining a substantially cylindrical shape having an arcuate forward portion in a plane parallel to the floor surface;
• a drive system mounted on the robot housing and configured to maneuver the robot with respect to a surface;
• first and second edge cleaning heads carried on opposite sides of the robot housing and driven about a non-horizontal axis, each edge cleaning head extending substantially from the arcuate forward portion beyond a lateral extent of the robot housing to engage the surface while the robot is maneuvered across the surface;
• at least three cliff sensor components housed in the forward portion of the robot housing substantially near a forward edge and spaced from each other, each sensor component aimed downwardly toward the floor surface and comprising an optical emitter and a photon detector configured to receive emitter emissions reflected off the surface, each cliff sensor component has a detection volume defined by an intersection of an emission field of the optical emitter and a field of view of the photon detector, the detection volumes of the at least three downwardly-aimed sensor components being distributed along an arc defined by the arcuate forward portion of the robot housing;
• at least one wall sensor component housed in the forward portion of the robot housing and aimed outwardly substantially parallel to the floor surface;
• and
• a circuit in communication with the detector and the drive system for redirecting the robot when the photon detector of a respective sensor component ceases to detect the surface.