hopping humanoids, continued



I'm doing that - Bioloid kit, with the Sparkfun 5 axis IMU. For balance, you really don't need the yaw axis on the IMU, although I suppose it would be helpful, but I think the 5-axis setup would be fine. The nice thing about the 5-axis board is how tiny it is, and the fact that you can hook it up to a tiny ATMega128, and build a sensor module that can just be another device on the Bioloid bus.
I was originally going to use a gumstix for on-board, but I decided instead to use a Wifi module with the "brain" being developed (and deployed) on my laptop. It will make the robot a little less portable, but it will make development and testing 100x easier, plus give me a lot more resources (more memory, dual core CPU, big hard drive).
Later, Jon
http://www.huv.com/blog
-------------------------------------------------------------- Jon Hylands snipped-for-privacy@huv.com http://www.huv.com/jon
Project: Micro Raptor (Small Biped Velociraptor Robot) http://www.huv.com/blog
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Jon Hylands wrote:

Very nice. I'd noticed a few months ago that the ICs for that were available, but hadn't been integrated into systems. 5DOF is sort of OK, although not having yaw rate means you may have trouble controlling spin (rotation about the vertical axis) while running. But that's a second order problem. You now have enough hardware to do running. And a platform that can survive falling down.
                John Nagle
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Indeed, I'm pretty sure that some of the Robo-One competitors are already using IMUs, but I can't back that up with any references at the moment.

That's a very interesting question. I think they just have a cultural tradition of more interest in humanoid robots, whereas the U.S. has traditionally focussed on more "practical" robotics (like industrial robots, though there's evidence that we're losing our edge even there).
In addition, they have several years' head start on us on the small humanoid robots, simply because Robo-One started there. But it's starting to catch on here too -- c.f. Matt Bauer and his "Rook's Pawn" robot (a heavily modified Robonova). I think Jon Hylands's Bioloid-based robodino will be very interesting too, for that matter.
I suspect that within a few years these small humanoids will be the dominant form of hobby robot here too, and then maybe every new advance in humanoid robotics won't be prefaced with "Over in Japan, they've just demonstrated..." :)
Best, - Joe
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Joe Strout wrote:

Not quite. A few have been using single axis rate gyros run through servo mixers to increase standing stability, but not a full IMU.
This is the point at which control moves from hacking to heavy math. The same thing happened in the video game world when graphics went 3D. Early 2D games were all about clever hacks in assembler to make the hardware do interesting things. Then came 3D, and everybody had to learn matrix algebra. Which game programmers did. Robotics hobbyists are going to be spending more time reading math books and theory papers over the next few years.
                John Nagle                 Animats                 www.animats.com
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kert wrote:

There is a new book out called "Loving the Machine: The Art and Science of Japanese Robots" which explains a lot about japanese culture of robotics ...
http://www.google.com/custom?q=%22loving+the+machine%22
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But is regenerative braking even possible with servos? I thought the reducing geartrain would, if not completely prevent transferring power in the reverse direction, make the efficiency very bad. Bad enough to be not worth doing.
--
snipped-for-privacy@iki.fi
Tomi T. Salo
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Tomi T. Salo wrote:

I would think that depends on your gearing type and ratios. Some types of gears allow for back-driving with moderate efficiency, harmonic drive and some types of planetary gearing come to mind. To get really complicated and expensive, you could employ a magnetic clutch arrangement and have separate coils as motor/generator on different gearings. Overall efficiency could be higher, could be lower, dont know. Also, some prototypes of newer electric vehicles use wheel motors with really high starting torques without any gearing at all, these also function as generators when braking. I dont know if similar designs could be applied to servos and scaled down, but it seems that motor technology is not standing still. http://www.pmlflightlink.com/motors/wheelmotors.html
-kert
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