Much like its predecessors Aibo and Aibo II, Sony's 50cm-tall, 50kg prototype SDR-3X has been designed to entertain. It can perform a variety of relatively high-speed, autonomous movements, including walking at a speed of 15 meters a minute and dancing to a tune with a quick tempo. It's equipped with speech- and image-recognition functions.The SDR-3X gave a demonstration by walking at a high speed, moving its body like a gymnast, dancing to a disco tune with a quick tempo and kicking a ball into a goal net as instructed by voice. The SDR-3X model employs the same OPEN-R architecture as Sony's autonomous entertainment canine robot "AIBO." Similar to AIBO, the SDR-3X model recognizes human voices and images. It has an 18,000-pixel CCD color camera in its head area. The SDR-3X model can maintains its balance in the upper half of the body by twisting its body and moving its arms, thereby realizing stable walking movements with alternating feet. The SDR-3X model has 24 joints, with actuators for each joint that help move the joints. It has two joints in the neck, two in the trunk, four in each arm and six in each leg. Two 64-bit RISC processors enable real-time control of the joints to realize autonomous movement.Sony's original real-time operating system called "Aperios" is used for the SDR-3X.The biggest challenge for a humanoid robot is to keep its body in full balance. The SDR-3X keeps balance by moving its arms and twisting at the waist to counteract the yaw-axis moment, the force needed to turn the body right and left, which is generated from the lower half of the body every time the robot takes one step forward in the high-speed walking movement.And the robot's posture is controlled in real-time, to prevent it from falling over. It uses a variety of information, such as the angle of the floor, gathered from contact sensors in the torso section as well as from a "dual-axis accelerometer" and a "dual-axis angular rate sensor" in the waist section, whenever the robot walks up slopes and moves its whole body.It can (1) move forward or backward and walk sideways at a speed of up to 15 meters a minute; (2) turn left or right when walking (with the maximum 90 degrees of freedom for each step forward); (3) get up from the position of lying on its stomach or its back; (4) stand on one leg (possible even on inclined ground); (5) walk on a bumpy road; (6) kick a ball; and (7) dance to a wide range of tunes.