Patent ID: 8634960

Claim:
A robot lawnmower swath edge detector system comprising: a controller carried by a body of a robot; and a grass length sensor carried by the body of the robot and in communication with the controller, the grass length sensor comprising: a sensor housing defining a cavity and a cavity opening directly downward configured to allow grass entry into the cavity while inhibiting direct sunlight into the cavity; an emitter carried by the housing in the cavity and configured to emit an emission across the cavity opening; and a receiver carried by the housing and configured to receive a grass-reflected emission, the receiver positioned in the cavity in a position where the housing blocks direct sunlight and the receiver positioned in the cavity on substantially the same side of the housing as the emitter in a location relative to the emitter such that the receiver receives emissions reflected from grass penetrating into the cavity; wherein the controller compares outputs from multiple ones of the grass length sensors to determine a swath edge location.