Subject:
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Re: SSClagorpion
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 4 May 2004 22:54:56 GMT
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Viewed:
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12043 times
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In lugnet.technic, Steve Hassenplug wrote:
> In lugnet.technic, Steve Hassenplug wrote:
> >
> > I just came up with an idea for how to make the legs work. It should make it so
> > the pneumatic cylinder doesn't have to support the weight of the creature.
>
>
> Now, I have a question about the "logic" behind walking sideways. When
> SSClagorpion is done walking sideways, and it starts walking forward, will the
> legs all be in the same position in/out, or will 1/2 be in, while 1/2 are out?
Below is a diagram of the 8 legs as one of the two points where all eight feet
are down.
A\_
\B
_/D
C/
E\_
\F
_/H
G/
Assuming that all the hips sweeps are the same, for example compressed means
swept backwards, and expanded means swept forward, then....
Hip pistons A, D, E, and H start out expanded and
hip pistons B, C, F, and G start out contracted.
Also assuming that contracted sideways pistons means feet away from body, and
expended sideways pistons means feet closer to the body.....
In normal walking we expect that the sideways walking leg pistons will be all
expanded. When we switch to sideways walking, we subsititute sideways sweep for
hip sweep. We leave the hips as they are, and then drive the sidways pistons.
This means that D and H sidways pistons will expand. As we progress through the
sequence, we see the legs go up, sideways walking change, legs go doen, sideways
walking change. Given the hip orientation shown above, the sideways walking
would be forward/left for A,D,E and H, and backward/left for B, C, F, and G.
When we decide to switch back to forward/backward walking we'll have to contract
all the sideways pistons, and start driving the hip pistons again.
>
> Assuming the legs start at vertical, and push out to walk sideways, is there
> ever a time when all legs are vertical, or will that require even more switches?
> Right now, there will be a time when all legs are down, but they are not
> required to be vertical, I think.
Hmmm..... Did you look at this sequence?
http://www.kclague.net/SSCorpion/ssclagorpion_seq.JPG
I think that the legs are *never* statically vertical. They are either swept
out, or in. The sweep needs to be symmetric between "in to out" transitions and
"out to in" transitions, When walking left, the power stroke for the legs on
the left side of the body are "out to in", and the power stroke for the legs on
the right side of the body are "in to out". Because of this, both sweeps need
to be of equal length.
Also vertical component of the sideways part of the leg needs to be the same at
either limit, otherwise you are creating a gravity well.
In the image shown above, notice the two extremes of the third degree of freedom
are mirrors of each other? This avoids gravity wells.
>
> When walking forward/back, there will be a time when all legs are straight out
> from the body, but they will never be stopped in that postion. They can only be
> stopped (reliably) when they are forward, or back, right?
Correct, unless we double the number of pistons for leg sweep.
>
> Same with in/out. They "could" be stopped at 1/2 way, but not reliably, and
> that would not be vertical.
Why is vertical so critical? Isn't it sufficient that the feet are out as far
as they can get? Vertical is not needed for your "leg lock" strategy.
>
> This could make walking kind of funky.
The two sequences in the image above never assume that the leg is vertical.
>
> Steve
Kevin
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Message has 3 Replies:
 | | Re: SSClagorpion
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| (...) ... (...) ... (...) Will it be possible to expand or contract all sideways walking pistons at the same time? Or is that like walking forward, where 1/2 will be expanded, while the other 1/2 are contracted? (20 years ago, 5-May-04, to lugnet.technic)
| | | Re: SSClagorpion
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| (...) slight problem. When SSClagorpion is walking sideways, due to the LEG SWEEP the legs will be positioned as show above. However, when he takes a step left, legs A, B, E & F would be stepping forward(up)/left and C,D,G & H are stepping (...) (20 years ago, 8-May-04, to lugnet.technic)
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Message is in Reply To:
| | Re: SSClagorpion
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| (...) Now, I have a question about the "logic" behind walking sideways. When SSClagorpion is done walking sideways, and it starts walking forward, will the legs all be in the same position in/out, or will 1/2 be in, while 1/2 are out? Assuming the (...) (20 years ago, 4-May-04, to lugnet.technic)
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