Evolution of ASIMO
To maintain balance while increasing walking speed and preventing the feet from slipping or from rotating while in mid-air, Honda developed new posture control logic that employs active use of the bending and twisting of the upper body, as well as highly responsive hardware. This has enabled ASIMO to run at 6 km/h, and also improved the walking speed to 2.7 km/h.
There were two challenges in making ASIMO run. One was to obtain an accurate jump function and absorb shock when landing, and the other was to prevent the rotation and slipping as a result of the increased speed.
In order for ASIMO to run, it had to be able to repeat the movements of pushing off the ground, swinging its legs forward, and landing within a very short time cycle and without any delay, absorbing the instantaneous impact shock of landing. ASIMO is a piece of hardware equipped with a newly developed high-speed processing circuit, highly-responsive and high-power motor drive unit, and lightweight and highly rigid leg structure.
Due to reduced pressure between the bottom of the feet and floor, spinning and slipping are more likely to happen right before the foot leaves the floor and right after the foot lands on the floor. Combining Honda's independently developed theory of bipedal walking control with proactive bending and twisting of the torso, ASIMO achieved stable running while preventing slipping.
When a human runs, the step cycle is 0.2 to 0.4 seconds depending on one's speed, and the leap time, when both feet are off the ground, varies between 0.05 to 0.1 seconds. The step cycle of ASIMO is 0.32 seconds with a leap time of 0.08 seconds, which are equivalent to that of a person jogging.
* Distance ASIMO moves forward while both feet are off the ground
Running in a circular pattern at high speed was achieved by tilting the center of gravity of ASIMO's body inside of the circle to maintain balance with the amount of centrifugal force experienced. A tilting ASIMO changes its speed according to the radius of the circle and controls its tilted posture.