Subject:
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Re: why won't my biped walk?
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Newsgroups:
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lugnet.technic
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Date:
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Sun, 22 Aug 2004 19:02:57 GMT
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Viewed:
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3517 times
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In lugnet.technic, Joe Strout wrote:
> A newbie needs some help here... I tried to make a biped COG-shifting walker,
> based on the many excellent examples found in the archives here. But it doesn't
> walk -- it just tips up onto the edges of its feet.
>
> Here's the starting position (both feet flat, one slightly ahead of the other):
> <http://www.strout.net/temp/bot1-start.jpg>
>
> After a quarter-cycle advancement, it should have itself tipped over onto one
> foot and the other one in the air, like this:
> <http://www.strout.net/temp/bot1-desired.jpg>
>
> But here's what actually happens (if I don't give it a nudge with my finger):
> <http://www.strout.net/temp/bot1-actual.jpg>.
>
> It makes sense that this happens -- as the lifting foot starts to lift, the bot
> (whose is in the middle at that point) naturally shifts over slightly onto the
> lifting foot. So it never manages to get it off the ground. It seems like for
> that to happen, the lifting foot would have to push a little to get the weight
> over onto the supporting foot, before it lifts into the air. But I don't see
> how the simple mechanisms posted here can accomplish that.
>
> Can you more experienced biped builders give me a clue?
Good explanations so far. Here are some additions.
The problem is that you are not truly getting the center of gravity inside the
footprint of the down foot. The critical part is to get the center of gravity
past the inside edge of each foot.
This is harder when the inside edge of the foot is not close enough to the
center line of the bot. Your feet might be too far apart. Try to go for zero
or one studs between feet instead of two.
As pointed out, shoot for symmetry.
I also suggest that you walk your walker on a hard surface, instead of running
it on a cloth placemat. Soft surfaces make it harder to drive the inside edge
of the foot so it has leverage.
>
> Thanks,
> - Joe
Kevin
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Message has 1 Reply:
 | | Re: why won't my biped walk?
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| (...) I'll try that. Though if it works, I may still be baffled as to why. What is it that causes the CG to move over the down foot at all? At the start of a walk cycle (when we go from both feet flat to one foot lifting), you have one foot lifting (...) (20 years ago, 22-Aug-04, to lugnet.technic)
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Message is in Reply To:
| | why won't my biped walk?
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| A newbie needs some help here... I tried to make a biped COG-shifting walker, based on the many excellent examples found in the archives here. But it doesn't walk -- it just tips up onto the edges of its feet. Here's the starting position (both feet (...) (20 years ago, 22-Aug-04, to lugnet.technic)
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