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Honda P Series |
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| P1 | P2 | P3 | P4 |
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P4
Never officially announced, P4 was a prototype that existed sometime between 1998 and 2000. The development was lead by Toru Takenaka. There have only been a few sightings of this robot since the knowledge of it's existence, all of which I will list. It's first and most showing appearance was in an NHK documentary series called Beyond the Century. The episode "How Human-Like Robots Can We Get?" (ロボット どこまで人間に近づけるのか) aired on October 15th, 2000, and showed a detailed look into the labratory and testing methods used for P4 and other Honda robots. It's second appearance was on Honda's Japanese website in November of 2000 and went by a different name, "P3 Improved Prototype" (P3改良型試作機)[1]. The third appearance was in a PBS documentary special called "Beyond Human", which showed some more testing footage in the lab. It's final appearance was in 2010 where it was put on display (along with other Honda robots) in the Honda Collection Hall at Twin Ring Motegi.
To speculate on P4, based on it's years in development, it was mostlikely co-developed alongside ASIMO, if not just ahead of ASIMO. You can see a lot of similarities between the two; smaller body, rounder exerior, astronaut-style front visor (similar but different to P3). The seperate development teams would have cross polinated ideas and technical improvements.
Hardware
P4's height is 160 cm, and weights 80 kg. Compaired to P3's 30 DoF, P4 now has 34 Dof. The shoulders are mounted at a slight angle for greater range of motion, and can now most likely raise it's arms higher than it's shoulders.
The first newly added DoF is located at the hips, acting as a waist roll. This enables smooth walking.
Another new DoF, located in the mid chest region, acts as a spine twisting motion. It now has a greater working range of motion.
You can see that the backpack is split into two, allowing P4 to twist it's upperbody freely.
The last 2 DoF are on the hands. The thumbs can now actuate in or out from the hand, similar to a thumb MCP flection.
A patent was filed by Honda for a "Bipedal robot with storage battery"[2], using P4 as an example. While you can't take what patents describe to mean absolute truth, there are some interesting findings. The battery is modular by design and is located in the upper torso to raise the center of gravity. It also claims that they were atleast considering using Lithium-ion cells in the battery, a change from the nickel-zinc batteries used on P1, P2, and P3.
I/O, power switches, emergency shutoff, and wireless antennas are located at the top of the backpack.
From observation, the stereo camera/tilt head mount seem to be very similar to P3, though the cameras could be different.
Software
Not much is known about the software used on P4, however we do know that it's walking control software must be very similar to ASIMO 2000 because of it's ability to change directions while walking smoothly.
You can catch a small glimpse of a P4 CAD model on the screen behind Toru Takenaka.
References
Full Image Gallery (including many unused images)