Robot cleaner and control method thereof

A robot cleaner comprising:

• a main body;
• moving units configured to move the main body;
• a cleaning unit mounted on the main body and configured to contact a surface to perform cleaning;
• a water supply unit configured to contain water in a housing of the water supply unit and to supply the contained water to the cleaning unit, the housing including an inclined portion extending upward from a horizontal bottom surface of the housing and provided at an interior portion of the housing;
• and
• a sensing unit provided on at least a portion of the water supply unit and configured to sense an amount of the water contained within the water supply unit,
• wherein the sensing unit includes:
• a transmission part outside the water supply unit such that the transmission part is separated from water, and configured to radiate electromagnetic waves toward the inclined portion of the housing of the wafer supply unit, and
• a reception part outside the water supply unit such that the reception part is separated from water, and configured to receive the electromagnetic waves radiated by the transmission part through the inclined portion of the housing of the water supply unit,
• wherein an inclination angle of the inclined portion of the housing adjacent to the horizontal bottom surface of the housing is less than 90 degrees from the horizontal bottom surface of the housing.