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robotics : legs and wheels Answered

Hi !

Generally, wheeled robots sound limited, and legged robots too much complicated.
So, wheels or legs ?

Well, seems it's possible to take the best of the two worlds : Look at this robot !

http://www.dailymotion.com/cluster/tech/featured/video/x3g2y3_rhex



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CameronSS (author)2008-01-10

Owww...My stomach lurched painfully when that robot tumbled down the rocks.

...I have got to get out of the lab more.

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Kiteman (author)2008-01-09

Have you seen the three-pronged versions of these - called whegs. I've seen them used as the landing gear of an entomopter.

Hey! They're cheating - the swimming legs are flexible and the walking legs are rigid!

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royalestel (author)Kiteman2008-01-09

Really? The first shot of the robot going into the water looked like he was using the same legs.

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Kiteman (author)royalestel2008-01-09

The swimming legs seem quite flexible, and are a different colour. Watch the way the walking legs don't flex at all in the clip immediately after.

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royalestel (author)Kiteman2008-01-09

The two shots between 1:09 and 1:24 look like "dog-paddling" with the land legs. After that I saw the robot with yellow flippers on in a pool. Is that what you meant about color change and flexible legs?

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Kiteman (author)royalestel2008-01-10

Yes - the dog-paddling seems to be just splashing about in "hip" deep water. Just after the 'bot falls down the cliff, there is a moment when it tries to turn it's legs backwards, and they don't bend when they hit the ground - it has to reverse the direction to be able to lift off the ground.

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royalestel (author)Kiteman2008-01-10

Ah, I was under the impression that it was floating when at rest, but now I see you are right. Well, it's still pretty spiffy, but not as.

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Kiteman (author)royalestel2008-01-10

Maybe they're working on a compromise leg? Stiff enough to walk on, flexible enough to swim. Methinks a wider "foot" would make for more efficient swimming, applying a greater bending force to the limb, and giving better grip in mushy ground.

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chooseausername (author)Kiteman2008-01-09
Whegs !
I wonder why they did not use this technology for martians robots =o/


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Kiteman (author)chooseausername2008-01-09

Because that would mean admitting that you can produce decent systems without spending several billion dollars. (Such as the DC-X - the whole rocket cost the same as a single shuttle toilet)

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chooseausername (author)Kiteman2008-01-10

Yes ... Why doing simple when doing complicated makes one seems smarter, justify one's enormous salary and makes one's job more durable ...

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royalestel (author)Kiteman2008-01-09

(Such as the DC-X - the whole rocket cost the same as a single shuttle toilet)

Is that an unwittingly ironic comment? ;)

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Kiteman (author)royalestel2008-01-09

No, it's true.

The DC-X worked, and showed up NASA quite badly - it's turn-around was less than 24 hours (not a 6-12 month rebuild) and it could be flown from any reasonably level area (not a specially-built launch-pad and extra-long runway). It needed a ground-crew of half-a-dozen (not 20,000), and was monitored by three men in a semi-trailer, using normal PCs (rather than several hundred men in a massive, specially-built command centre).

When human error caused an accident that blew the side out of the ship, it returned to it's launch-site automatically, and landed safely under autopilot (rather than flying to pieces within a minute or two).

NASA refused to buy DC-X as a shuttle-replacement for two reasons - when it had one crash, it caught fire (as opposed to exploding into several million pieces?), and it's engines were based on an old design (that works).

Instead, they went for the aerospike engine, which cost billions to develop and still has not managed to get a vehicle off the ground.

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royalestel (author)Kiteman2008-01-09

Wow. Cool story.

But I was kidding before! No wonder NASA's head is on the chopping block lately.

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Kiteman (author)royalestel2008-01-09

No problem, just a raw nerve.

As far as I am concerned, DC-X could have been an important link to the permanent, self-sufficient scientific base that could have been put on Mars five or more years ago at a fraction of the cost of the ISS that was supposed to be a stepping stone to Mars.

http://en.wikipedia.org/wiki/Mars_Direct
http://en.wikipedia.org/wiki/The_Case_for_Mars (excellent book)

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royalestel (author)Kiteman2008-01-09

Oh, man. That would have been AWESOME.

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royalestel (author)Kiteman2008-01-09

I read more on Wikipedia. Very cool aircraft. Hate it when you see great projects like these bite the dust due to bureaucracy.

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royalestel (author)2008-01-09

I love watching this little guy run! It's like an auto-muppet or something. For some reason it makes me smile. Intrepid little guy! My brother had an R/C truck as a kid that would extend claws from the wheels when the wheels had a hard time turning. Thought this might be something like that.

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royalestel (author)royalestel2008-01-09

Did a quick search, but couldn't find a picture of the thing.

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