Mechatronics Zone

Can Pneumatics Play a Bigger Role in Mechatronics Designs?

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apresher   7/24/2012 7:39:49 AM
Chuck, I don't have a handle on a percentage but I think it is very small as well.

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Re: Pneumatics
Sunstream   7/26/2012 4:13:04 AM
In short, yes, the compressibility challenges posed by air have been resolved.

Modern servopneumatic actuators can move heavy loads (30kg+) at high velocity without overshoot.

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Re: Pneumatics
Sunstream   7/26/2012 4:21:26 AM
ttemple -


It sounds as if you've had a frustrating experience with a poorly designed pneumatic servo system.

Modern, well designed systems are able to rapidly position heavy vertical loads without overshoot, without high levels of valve control activity, and to high levels of repeatability.  The 0.005" accuracy you mentioned is readily achievable in many systems.

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Re: Really competitive with electric?
pnachtwey   7/26/2012 7:48:22 AM
I/we mostly deal with hydraulics.  Pneumatic servo control is a very small part of our business because there are usually better solution.  However, we use pneumatics as a means of testing hydraulic algorithms.   If one can control pneumatics the hydraulics and servo motors are even easier.

Here is an example of what can be done.


You may need to download the mp4 file before viewing depenind on your browser.

We have controlled pneumatics in some low pressure testing applicaitons.

Besides the energy lost in compressing and decompressing air the second problem is that feedback devices are still needed and the controller can't be a simple cheap PID controller.  It takes some complicated math to do the control shown and this isn't cheap.  For small jobs little linear motors are tough to beat.




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Re: Pneumatics
ttemple   7/26/2012 8:12:23 AM
I would compare moving a load with air to using a rubber bat to play baseball, or a rubber stick to play hockey.  You could do it, but why would you?  ("Because I can" is not a good reason.)

What are the selling points for such a system?

If the system is not exponentially less expensive to purchase and operate, I don't see the advantage.  I doubt if the systems are much less expensive to purchase than a comparable electric solution, and I seriously doubt whether the operation cost is lower, when the cost of clean compressed air is factored in.  Then have one incident where the dryer floods the air line with contamination and see what the cost of repair is.

For explosive environments I can concede that air is compelling.  Otherwise, I don't get it, and I wouldn't design it in over an electric servo system.

For grippers, clamping cylinders, and a host of other short stroke, bang-bang actuators, I'm all for pneunatics.  It is also great for certain counterbalancing systems. I just don't see it for positioning systems.

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Re: Pneumatics
Sunstream   7/26/2012 2:24:23 PM
You could play hockey with a chop stick too.  Maybe you'd do so to handicap a much less capable opponent?  But it's a false analogy to the pneumatic - electric - (hydraulic) debate.

In applications with high cycle rates and high masses, pneumatic servos can be 25% the cost of a linear motor solution, and 30-50% of the cost of an electromechanical solution - while requiring less space.

For many applications that require a combination of controlled, rapid translation (12" in 100ms) coupled with a high force joining operation (think resistance welding, hot melt, etc.), servo pneumatics again has a similar big cost advantage.  

Generally speaking, if you look into many of the positioning, general automation applications in packaging and similar industries, you can replace a linear electric axis with servo pneumatics with the benefit of 50% less installation cost, and a 50% increase in cycle rates.



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