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 18:26:08 GMT
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Viewed:
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3808 times
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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
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Message has 3 Replies:
 | | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) hi, why do you wanne build a thing that lifts one leg a time?.... i did it but it dont have any advanges. it isn't much more stable. it isn't faster (my cat 343 was not to slow) but stil i don't see any inprovments. the only thing is that it (...) (19 years ago, 13-Sep-05, to lugnet.technic)
| | | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) (SNIP) (...) 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 (...) (19 years ago, 13-Sep-05, to lugnet.technic)
| | | Re: Pneumatic "One Leg at a Time" Robot Circuit
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| (...) 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 (...) (19 years ago, 3-Oct-05, to lugnet.technic)
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Message is in Reply To:
| | Pneumatic "One Leg at a Time" Robot Circuit
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| 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 (...) (19 years ago, 13-Sep-05, to lugnet.technic)
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