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Big Dog Robotic Dog/Mule Gordon McComb 03-22-2008
Posted by Curt Welch on March 24, 2008, 4:16 pm
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> Curt Welch wrote:
> > However, one thing I noticed in that video is that it seemed to be
> > using very different walking gaits in each segment. My assumption is
> > that they are developing and testing different gait algorithms for
> > different tasks. That's a fine thing to do, but stringing the different
> > tests together on the video gives the illusion that the robot is better
> > than it is - because it looks like it "knows" how to deal with all
> > those different terrains by using different walking (or jumping)
> > techniques. No doubt, they still have to work out how to combine
> > multiple walking algorithms, all probably very different, into one
> > general system that can adjust to the task at hand based on the
> > situation. I suspect they still have a lot of work to do to make that
> > happen.
>
> No, it looks like they have that figured out. I suspect the
> whole system is primarily gaitless - legs are viewed as an asset to be
> used to accomplish a goal. Gait is an emergent behavior.
>
> Step through the sequence where it slips on ice and recovers, and
> pay attention to when the feet lift, when they slip and when they don't,
> and the primacy of slip control over balance control over foot sequencing
> over direction control. Don't think gait; think adaptive feedforward
> control. Read Raibert's old "Legged Robots that Balance" and my
> work from 1995.
>
> Finally, someone is doing this right.
>
> John Nagle
> Animats

I do agree that the "gait" algorithms are far from fixed sequences. It's
clear they have a lot of very advanced adaptive balancing and movement at
work (they aren't called Boston _Dynamics_ for nothing :)). The examples
of them kicking the animal off balance show that nicely. And, as you say,
the slipping on the ice is priceless in that it shows just how adaptive the
system is.

But that doesn't explain the _extreme_ difference in behavior between the
videos of it walking outside (where it never stops moving the legs and it
is constantly prancing even when standing in place), and the video of it
walking over the pile of concrete cinder blocks where it keeps 3 legs on
the ground and only moves one at a time, and the video of it hopping and
doing the jump at the end. That very much looks to me like three
completely different locomotion algorithms. I can't imagine that their
adaptive algorithm which keeps the feet moving would work very well at all
on that pile of concrete blocks for example where the legs could get stuck
between blocks or knock the blocks off balance when it trys to "dance" on
them.

--
Curt Welch http://CurtWelch.Com/
curt@kcwc.com http://NewsReader.Com/

Posted by dan michaels on March 25, 2008, 10:56 am
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On Mar 23, 12:55=A0pm, c...@kcwc.com (Curt Welch) wrote:
> > I may have linked to an older video, as I wanted one on a mainstream
> > site. There is a new version of the robot, and new videos. But here's
> > one of the new vids that's now on YouTube:
>
> >http://www.youtube.com/watch?v=3DW1czBcnX1Ww
>
> > The payload of the new version has been increased to 340 pounds, BTW.
> > Even more impressive!
>
> > -- Gordon
>
> I was really impressed with that new work as well.
>
> However, one thing I noticed in that video is that it seemed to be using
> very different walking gaits in each segment. =A0My assumption is that the=
y
> are developing and testing different gait algorithms for different tasks.
>


Quadrupeds have a range of different gaits they use for different
situations, depending upon speed and terrain characteristics,
ranging from slow creep to diagonal walk to trot to canters and
a couple of types of gallop. Not all quads use the same range.

http://en.wikipedia.org/wiki/Horse_gait

The 1-legattatime is the creep gait, used widely by cats, but
not so characteristic of dogs or horses, and is the most stable
for going over rough terrain. The slower gaits differ mainly by
relative leg timing, so it's not too difficult to change over between
creep and diagonal walk or trot. The gallops OTOH are quite
different leg sequencing,

As John indicated, Raibert [honcho at Boston Dynmaics] has
been working on "dynamic" adaptive walking gaits since the
early 1980s, since his time at the MIT leg lab. Lots of gimbals
and gyros.

http://www.ai.mit.edu/projects/leglab/robots/3D_hopper/3D_hopper.html
http://www.ai.mit.edu/projects/leglab/robots/2D_biped/2D_biped.html
http://www.ai.mit.edu/projects/leglab/robots/quadruped/quadruped.html
http://www.ai.mit.edu/projects/leglab/robots/robots.html




>
> That's a fine thing to do, but stringing the different tests together on
> the video gives the illusion that the robot is better than it is - because=

> it looks like it "knows" how to deal with all those different terrains by
> using different walking (or jumping) techniques. =A0No doubt, they still h=
ave
> to work out how to combine multiple walking algorithms, all probably very
> different, into one general system that can adjust to the task at hand
> based on the situation. =A0I suspect they still have a lot of work to do t=
o
> make that happen.
>
> --
> Curt Welch =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0=
=A0 =A0 =A0 =A0 =A0 =A0http://CurtWelch.Com/
> c...@kcwc.com =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0http://NewsReader.Com/


Posted by pogo on March 22, 2008, 4:15 pm
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> This thing has me thinking that the field of robotics is about to take a
> giant leap. It's got fantastic mechanics, and a walking/balancing
> algorithm that should win its programmers a Nobel Prize. It is truly
> amazing!
>
> http://video.google.com/videoplay?docid=5349770802105160028
>
> -- Gordon

This one's pretty cool, too:
http://video.google.com/videoplay?docid=-8194319473624563718
And this one skitters about so much it is also cool:
http://video.google.com/videoplay?docid=-8194319473624563718

Can you imagine the psychological impact these things might have in dark jungles
or deserts with the appropriate covering & sound
effects ? Would either start or stop you from drinking !!! :-)

JCD


Posted by pogo on March 23, 2008, 8:45 pm
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> This thing has me thinking that the field of robotics is about to take a
> giant leap. It's got fantastic mechanics, and a walking/balancing
> algorithm that should win its programmers a Nobel Prize. It is truly
> amazing!
>
> http://video.google.com/videoplay?docid=5349770802105160028
>
> -- Gordon

Here is yet another video - showing it going uphill, downhill, and even running
jumping and kicking up its heels at the end of the
movie! COOL!

http://www.coasttocoastam.com/gen/page2490.html?theme=light


Posted by Shawn B. on April 8, 2008, 3:13 pm
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I totally agree with you Gordon. There will be huge changes in the next
10 years. I Live 35 minutes from this company. I can't even begin to
tell you how badly I want to work there. I'd sweep the floors if I had
to. ;-) I hope those guys read this thread.

Shawn



Gordon McComb wrote:
> This thing has me thinking that the field of robotics is about to take a
> giant leap. It's got fantastic mechanics, and a walking/balancing
> algorithm that should win its programmers a Nobel Prize. It is truly
> amazing!
>
> http://video.google.com/videoplay?docid=5349770802105160028
>
> -- Gordon

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