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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Mon, 3 Oct 2005 20:09:36 GMT
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Viewed:
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3967 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.
> >
> > I don't still have it built, but my prototype leg used parallelograms to lift
> > the foot vertically, keeping its track constant but allowing it to swing forward
> > and back. The hip joint was based on a technic turntable. I used one cylinder
> > for the foot and two for the hip, working in opposite directions on bevel geared
> > axles to turn the turntable.
> >
> > Here's the pneumatic circuit diagram that will allow the above function to be
> > realised, whilst allowing a variable number of legs to be used. The diagram has
> > 2 leg modules in it, but the table shows enough columns for four legs. I
> > suggest that four legs is probably the minimum for stability but I'd be
> > interested to see a stable tripod.
> >
> > 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
For a hexapod, I've revised the design and implemented it. The cost savings
were not quite as high as I thought, but......
Pistons = 2n+1 (13)
Switches = 5n+2 (32)
I'll be posting pictures, movies, timing diagrams and schematics in a different
post.
Kev
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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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