Method of controlling biped walking robot

A method of controlling a biped walking robot which has a main body, legs movably combined to lower opposite sides of the main body, and an actuator to drive the legs, and which controls the actuator to balance the robot based on a sensed ground reaction force, the method comprising:

• assigning X and Y coordinates to respective positions of a plurality of sensors attached to a sole of the leg, each sensor sensing the ground reaction force at one of the respective positions;
• assigning a Z coordinate value to each of the respective positions based on the sensed ground reaction force sensed at the respective position;
• specifying a ground reaction force plane based on at least three of the assigned XYZ coordinates, and calculating a normal vector perpendicular to the ground reaction force plane;
• specifying an XYZ coordinate system based on the positions of the plurality of sensors;
• calculating a roll angle about the X-axis of the XYZ coordinate system and a pitch angle about the Y-axis of the XYZ coordinate system;
• and
• driving the actuator in correspondence to the roll angle and the pitch angle to align the normal vector with a reference vector of the gravity direction.