An autonomous robot comprising: a robot body defining a forward drive direction, the robot body having a bottom surface and a top surface located at a robot height above a floor surface ; a drive configured to propel the robot over a floor surface; a sensor system disposed on the robot body; and a navigation controller circuit in communication with the drive and the sensor system, the controller circuit configured to process a signal received from the sensor system and to control the drive as a function of the processed signal; wherein the sensor system comprises at least one proximity sensor (510 a-d) comprising: a sensor body , and a receiver housed by the sensor body, wherein the receiver is arranged to detect radiation reflected from objects in a bounded detection volume (V) of the receiver field of view aimed outward and downward beyond a periphery of the robot body, characterized in that the sensor system further comprises a first emitter and a second emitter , wherein the receiver is disposed above and between the first and second emitters, the first and second emitter having a twice-reshaped emission beams (523 a, b), the twice-reshaped emission beams being angled upward with respect to the floor surface to intersect the receiver field of view at a fixed range of distances from the periphery of the robot body to define the bounded detection volume, wherein the receiver is configured to generate a signal in response to receiving reflected radiation produced by the first and second emitters as the first and second emitters are activated sequentially, and wherein the first and second emitters are spaced from the top surface of the robot body by a distance of less than 35-45% of the robot height, and the receiver is spaced from the top surface of the robot body at a distance of less than 20-35% of the robot height. a robot body defining a forward drive direction, the robot body having a bottom surface and a top surface located at a robot height above a floor surface ; a drive configured to propel the robot over a floor surface; a sensor system disposed on the robot body; and a navigation controller circuit in communication with the drive and the sensor system, the controller circuit configured to process a signal received from the sensor system and to control the drive as a function of the processed signal; wherein the sensor system comprises at least one proximity sensor (510 a-d) comprising: a sensor body , and a receiver housed by the sensor body, wherein the receiver is arranged to detect radiation reflected from objects in a bounded detection volume (V) of the receiver field of view aimed outward and downward beyond a periphery of the robot body, a sensor body , and a receiver housed by the sensor body, wherein the receiver is arranged to detect radiation reflected from objects in a bounded detection volume (V) of the receiver field of view aimed outward and downward beyond a periphery of the robot body, characterized in that the sensor system further comprises a first emitter and a second emitter , wherein the receiver is disposed above and between the first and second emitters, the first and second emitter having a twice-reshaped emission beams (523 a, b), the twice-reshaped emission beams being angled upward with respect to the floor surface to intersect the receiver field of view at a fixed range of distances from the periphery of the robot body to define the bounded detection volume, wherein the receiver is configured to generate a signal in response to receiving reflected radiation produced by the first and second emitters as the first and second emitters are activated sequentially, and wherein the first and second emitters are spaced from the top surface of the robot body by a distance of less than 35-45% of the robot height, and the receiver is spaced from the top surface of the robot body at a distance of less than 20-35% of the robot height. <EOS>