Covering mobility robot

An autonomous robot (100, 200, 258, 270, 300) comprising: a chassis (102); a pull system (104) mounted on the chassis (102) and configured to maneuver the robot a proximity sensor floor (140) located on the chassis (102) and configured to detect a surface adjacent floor sensor (140 ) comprises: a beam emitter (148) configured to direct a beam toward the floor surface; and lightning receptor (150) responsive to a reflection beam directed from the floor surface and mounted in a receptacle facing downwards (144, 146) of the chassis (102); and transparent to the rays (152) having a front edge (158) and a trailing edge (159) disposed through a lower end of the receptacle (144, 146) to prohibit accumulation of sediment in the receptacle housing, front (158) edge raised above the trailing edge (159).