Cleaning robot and controlling method therefor

A robot cleaner comprising:

• a main body;
• a wheel motor configured to provide power;
• a wheel configured to be drivable by the power provided by the wheel motor to move the main body on a surface;
• a brush motor configured to provide power;
• a brush configured to be rotatable by the power provided by the brush motor to scatter foreign substances on the surface as the main body moves on the surface;
• a suction fan configured to provide a suction force to suction the foreign substances scattered by the brush;
• an encoder configured to detect a revolutions per minute (RPM) of the wheel motor as the wheel is driven by the power provided by the wheel motor to move the main body on the surface;
• and
• a controller configured to
• calculate
• a gradient g indicating how the detected RPM changes in response to changes in a duty ratio of the wheel motor, where the gradient g=(encoder output)/(duty ratio), or
• ΔDiff, where ΔDiff=E−Δg, E is the encoder output, (Δg) is a gradient variation and (Δg)=g*Δw, and Δw is a weight based on linear velocity,
• determine whether the calculated gradient or the calculated ΔDiff indicates that the main body is moving on to a soft surface from a hard surface or on to the hard surface from the soft surface and produce a corresponding determination result, and control the suction force provided by the suction fan based on the determination result.

A method of controlling a robot cleaner that includes a main body, a wheel motor configured to provide power, a wheel configured to be drivable by the power provided by the wheel motor to move the main body on a surface, an encoder configured to detect a revolutions per minute (RPM) of the wheel motor, a brush configured to be rotatable to scatter foreign substances on the surface as the main body moves on the surface, and a suction fan configured to provide a suction force to suction the foreign substances scattered by the brush, the method comprising:

• by the robot cleaner,
• detecting revolutions per minute (RPM) of the wheel motor by the encoder, as the wheel is driven by the power provided by the wheel motor to move the main body on the surface,
• adjusting a duty ratio of the wheel motor to compensate for a variation in the detected RPM,
• calculating
• a gradient g of a relationship between the detected RPM and the adjusted duty ratio, where the gradient g=(encoder output)/(duty ratio), or
• ΔDiff, where ΔDiff=E−Δg, E is the encoder output, (Δg) is a gradient variation and (Δg)=g*Δw, and Δw is a weight based on linear velocity,
• determining whether the calculated gradient or the calculated ΔDiff is higher than, or lower than, a predetermined reference value, and
• controlling the suction force provided by the suction fan based on the determining of whether the calculated gradient is higher than, or lower than, the predetermined reference value.