Robot cleaner and method for controlling the same

A robot cleaner comprising:

• a body provided with a suction portion;
• an auxiliary front wheel disposed at the body;
• a main wheel disposed at a rear side of the auxiliary front wheel and arranged such that a height of the main wheel is variable with respect to the body;
• and
• a driving unit to lower or raise the main wheel with respect to the body,
• wherein the driving unit lowers the main wheel when the auxiliary front wheel enters a stepped portion,
• wherein the driving unit comprises:
• an elastic member, one end of the elastic member being connected to one end of a main wheel housing adapted to accommodate the main wheel;
• and
• an actuator to pull the elastic member to lower the main wheel with respect to the body.

A robot cleaner comprising:

• a body provided with a suction portion;
• an auxiliary front wheel disposed at the body;
• a main wheel disposed at a rear side of the auxiliary front wheel and arranged such that a height of the main wheel is variable with respect to the body;
• a controller to control a driving unit adapted to lower or raise the main wheel with respect to the body;
• and
• a sensor to transmit a signal to the controller;
• wherein the controller lowers or raises the main wheel according to a signal transmitted from the sensor.