Patent ID: 8469131

Claim:
A wheel drive vehicle comprising a main body having a rotatable arm and an arm driving unit for driving the arm, a wheel rotatably mounted to the arm, and a sensing unit for sensing a non-contact state of the wheel from a ground, wherein the sensing unit comprises: a spring installed between the arm driving unit and the arm, and extended or compressed in response to a relative rotary motion of the arm with respect to an output shaft of the arm driving unit; first and second sensors configured to detect rotation drive information related to the arm with respect to the main body and attitude information related to the main body; and a controller configured to measure a reference length of the spring or a reference angle of the arm in the non-contact state based upon at least one of the rotation drive information related to the arm and the attitude information related to the main body, and detect the non-contact state of the wheel based upon the measured length of the spring and the reference length thereof or based upon a rotary motion angle of the arm and the reference angle thereof.