Subject:
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Re: Pneumatic "One Leg at a Time" Robot Circuit
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Newsgroups:
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lugnet.technic
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Date:
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Tue, 13 Sep 2005 21:23:09 GMT
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Viewed:
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3722 times
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In lugnet.technic, Kevin L. Clague wrote:
> In lugnet.technic, Mark Bellis wrote:
> > A while ago I saw an electric robot on TV that had 6 legs in 2 rows of 3 and
> > moved one leg at a time forwards (lift, forward, down), then all back together.
> >
> > I thought this is an ideal application for Lego pneumatics.
(SNIP)
> >
> > http://www.brickshelf.com/gallery/mbellis/Technic/Pneumatics/Building-Blocks/pneumatic_one_leg_at_a_time_robot_circuit.jpg
> >
> > There are 5n+3 steps in the cycle, where n is the number of legs. The circuit
> > uses 3n+1 (or 4n+1) cylinders and 7n+2 valve switches.
> >
> > Load bearing is accommodated by the fact that all the legs share the weight, so
> > if a small pressure drop occurs when a raised foot is lowered, all the other
> > feet would rise a bit rather than one leg rising all the way, and it would equal
> > out by the time the raised foot was fully lowered.
> >
> > As well as walking robots, this circuit lends itself to any function that
> > requires several sub-systems to operate in sequence, with a global reset at the
> > end.
> >
> > Mark
>
> Hi Mark,
>
> Now I know what to build next..... a four legged walker that lifts one leg at
> a time. On paper it looks like I can get one made for 1+2n pistons and 2+4n
> switches. This assumes that legs mechanically lock when weight bearing. I don't
> use pneumatic differential pair logic when making walkers. I stick with single
> switch AND gates that Mark Terrabain turned me on to.
>
> In general I don't think that differential pair logic is the most cost
> effective way to build sequencers because they are so much more expensive to
> implement.
>
> Kev
This one has moved away from my usual differential logic. Each leg module has a
flip-flop for the foot and hip, which does 3 out of 4 movements and waits for
the fourth to be done all legs together.
I see how single switch AND gates work for several legs in parallel, but this
robot is one leg at a time, which has a greater overhead of pneumatic parts.
Perhaps using 3 leg modules with a few single switch AND gates would make a
decent 6-legged 2 at a time robot. It doesn't have the same steering capability
that you've added with reversers though, but it was directly modelled on the
robot I saw, rather than the ideal function.
I had a surprise the other day. Looking on my old computer I discovered that
I'd drawn a 1+4 AND gate for myself long before I joined the online community!
I wouldn't quibble about credits, though it just shows how great minds think
alike! The discovery was not a surprise in one sense, because I wondered how I
had developed my octopus arm without first making an AND gate. The octopus arm
is an old design too, but it combines single and differential logic. I think I
drew a first circuit sketch and then minimised it, probably removing a third of
the switches!
Mark
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Message has 1 Reply:
 | | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) I understand that leg 0 is moved up forward then down, leg 1 is moved up/forward/down, leg2 is moved up/forward/down, leg 3 is moved up/forward/down, and finally leg 0, leg 1, leg 2 and leg3 are moved back. I don't quite understand why you (...) (19 years ago, 13-Sep-05, to lugnet.technic)
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Message is in Reply To:
| | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) Hi Mark, Now I know what to build next..... a four legged walker that lifts one leg at a time. On paper it looks like I can get one made for 1+2n pistons and 2+4n switches. This assumes that legs mechanically lock when weight bearing. I don't (...) (19 years ago, 13-Sep-05, to lugnet.technic)
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