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Subject: 
Re: Analogue Control of Pneumatics
Newsgroups: 
lugnet.build, lugnet.general, lugnet.technic, lugnet.robotics.rcx
Date: 
Thu, 22 Mar 2001 16:23:58 GMT
Viewed: 
772 times
  
In lugnet.build, Mario Ferrari writes:
I am interested in trying to build mechanisms found in read life things • like
cars and was thinking about power steering servos when I started playing
about with pneumatics. Perhaps this is a bit hard for Lego:-)

Hi Al,

what you ask is not possible because the Lego pneumatic system is,
precisely, *pneumatic*. In real life cylinders that are designed for
position control are hydraulic and not pneumatic ones. This difference is
very important because you can compress a gas but cannot compress a liquid.
A pneumatic system has a very high degree of elasticity, and in practical
terms this means that position is a function of both the applied pressure
AND the encountered resistance.

Ok. So you can't do it with pneumatics.

Looking around for alternative ways of making a power steering mechanism, I
found this link  http://www.umbra.demon.co.uk/power_steering.html which gives
an RCX based motor driven mechanism that might be of interest to others.

Al Telanco



Message has 2 Replies:
  Re: Analogue Control of Pneumatics
 
(...) I wouldn't say that at all. Its just that you'd need a good supply of compressed air (there's plenty of compressor designs about) and a good feedback mechanism. This is by no means impossible - just a bit tricky. ROSCO trimmed lugnet.general (...) (24 years ago, 22-Mar-01, to lugnet.build, lugnet.technic, lugnet.robotics.rcx)
  Re: Analogue Control of Pneumatics
 
Whoa. Not entirely correct. You can do accurate positioning with pneumatics, it's just harder to do than with hydraulics, because you have to take air compressiblity and seal "stiction" into account if you want to hit an arbitrary position that's (...) (24 years ago, 22-Mar-01, to lugnet.build, lugnet.general, lugnet.technic, lugnet.robotics.rcx)

Message is in Reply To:
  Re: Analogue Control of Pneumatics
 
"Alvin Telanco" <78of560001@sneakemail.com> wrote (...) like (...) Hi Al, what you ask is not possible because the Lego pneumatic system is, precisely, *pneumatic*. In real life cylinders that are designed for position control are hydraulic and not (...) (24 years ago, 21-Mar-01, to lugnet.build, lugnet.general, lugnet.technic)

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