SURFACE TYPE DETECTION

A robotic cleaning appliance includes a housing, surface treatment item, surface type detection sensor, and processor. The sensor emits sonic signals toward a surface being traversed and receives corresponding returned signals from the surface. The returned signals are used for surface type detection and include directly reflected primary returned signals and multi-path reflected secondary returned signals which return at a later time than the primary returned signals. The processor selects a window of time after transmission of a sonic signal such that the returned signals in the window comprise at least a portion of the secondary returned signals, wherein the window is related to round trip time-of-flight of the returned signals; processes the returned signals falling in the window to achieve a reflectivity metric; compares the reflectivity metric to a stored value; and based on the comparison, determines which surface type of a plurality of surface types has been detected.