Subject:
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Re: New technique: three position piston control
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Newsgroups:
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lugnet.technic, lugnet.robotics
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Date:
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Sun, 2 Oct 2005 15:31:58 GMT
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Viewed:
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378 times
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In lugnet.technic, Sigurd van Strakenburg wrote:
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I already have a paper design for a six legged walker with three leg
groups using forward/mid/back leg sweeps (what a surprise!) It walks
using a 9 step sequence. It only uses mid-stop on expansion, but not on
contraction.
Please let me know what you think.
Kev
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6 legs and 3 leg groups is a great idea!!
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Interesting stuff! Should make walkers move more smoothly, with the
possibility of more groups of legs. The trick will then be reversing all
the groups, since it was easier with just two, using two polarity
reversers.
I have a centre-stop mechanism for pneumatic steering for a JCB. It’s not
part of an automatic system though, since I don’t yet have an application
for that.
Does your centre stop cylinder stop accurately in the same place every
time, even under different pressure conditions? I thought if you put a lot
of source pressure into the cylinder it might overshoot the mid-point,
whereas with low pressure it would creep up to it. Accurate repeatable
positioning is one of the challenges of this scheme.
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The center stop is not the same spot when expanding vs. decoration I did not
try it at different pressures. I just pumped a hand pump as fast as I could
to make the sequencer go.
I’ve not seen it overshoot the mid point.
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I’ve think about overshooting the mid point and i don’t know sure but i think
it will overshoot the mid point whan you link them in serie isn’t it?... and
when you build it into a walking beast i think it whil need 2 cilinders don’t
you?... and then you also can link those 2 to make a 3 position joint
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I tried to make a sequencer using two mid-stop piston configurations, and it
didn’t work out on paper (at least the cases I tried.)
Hmmm...... I think that with a walker, you probably need to add one more switch
to instrument full expansion/contraction. Four switches is typically the limit
for one medium piston. Things operate pretty slowly with five switches on one
piston, because of the force required to flip the switches vs. the force created
by the piston. At high pressures a single piston can flip more than four
switches, but it talkes a long time to build the pressure suficiently high.
Why do you think you will need two pistons for mid-stop. The pistons that run
the OR gates to get you out of mid-stop combined with the the switches needed
for instrumentation, might push you to two pistons.
Is this what you were thinking?
Most certainly you can connect two pistons together to create mit-stop. You
have four possible combinations of expand/contract for the two pistons:
Piston1 Piston2
contract contract shortest
contract expand mid
expand contract mid
expand expand longest
The size of the combined pistons is twice as large as the single mid-stop
configuration.
Kevin
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