A robotic vacuum cleaner includes a casing with a motor-driven wheel unit mounted on a lower major wall thereof, and a tactile sensor unit yieldable radially relative to the casing. An electrical control unit is operable to control the wheel unit to operate in a starting mode in which the casing is moved along a spiral path, and, upon receipt of a switching signal generated by the sensor unit in response to a contact of the sensor unit with an obstacle, controls the wheel unit to operate in an edge-cleaning mode in which the wheel unit is initially turned to a normal angle, is then driven to move forward a predetermined distance, is subsequently turned to an activating angle, and is moved towards the obstacle to permit contact of the sensor unit with the obstacle so as to result in generation of switch signal enabling the wheel unit to continue to operate in the edge-cleaning mode.