HOME  |  NEWS  |  BLOGS  |  MESSAGES  |  FEATURES  |  VIDEOS  |  WEBINARS  |  INDUSTRIES  |  FOCUS ON FUNDAMENTALS
  |  REGISTER  |  LOGIN  |  HELP
Page 1/3  >  >>
Sunstream
User Rank
Iron
Re: Pneumatics
Sunstream   7/26/2012 2:24:23 PM
NO RATINGS
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.

 

 

ttemple
User Rank
Platinum
Re: Pneumatics
ttemple   7/26/2012 8:12:23 AM
NO RATINGS
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.

pnachtwey
User Rank
Iron
Re: Really competitive with electric?
pnachtwey   7/26/2012 7:48:22 AM
NO RATINGS
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.

http://deltamotion.com/peter/Videos/PneuMove.mp4

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.

 

 

 

Sunstream
User Rank
Iron
Re: Pneumatics
Sunstream   7/26/2012 4:21:26 AM
NO RATINGS
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.

Sunstream
User Rank
Iron
Re: Pneumatics
Sunstream   7/26/2012 4:13:04 AM
NO RATINGS
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.

apresher
User Rank
Blogger
Pneumatics
apresher   7/24/2012 7:39:49 AM
NO RATINGS
Chuck, I don't have a handle on a percentage but I think it is very small as well.

Charles Murray
User Rank
Blogger
Re: Pneumatics
Charles Murray   7/23/2012 9:21:13 PM
NO RATINGS
Thanks, Al. One more question for you: Do you have any idea what percentage of oneumatics systems today are servo? I would imagine the percentage is very small.

ttemple
User Rank
Platinum
Re: Pneumatics
ttemple   7/23/2012 9:05:04 AM
NO RATINGS
The last pneumatic positioner I worked on was in a vertical orientation, which created additional challenges for the actuator.  The systems I have worked on used "magnetostrictive" position feedback ("Temposonics" would be one trade name).  This feedback system is based upon timing pulses transmitted down a rod that get reflected back by a magnetic ring, or something like that.  The time is converted to an analog output of some resolution.  The resolution doesn't change as the length of the transducer gets longer, so the system resolution is typically affected by the transducer length.

The controls on this system were essentially analog in nature, comparing setpoints to the transducer position, and throttling air valves to try to keep the actuator in the correct position, and move it to new positions, etc.

The end result was less than what I would have desired (Fortunately I didn't pick the equipment, I was just called on to get it to work.).  There was a tendency to overshoot significantly (large fractions of inches at least), especially when moving down.  I don't know what the final position tolerance was, but it was not comparable to an electric servo actuator.  It is also relatively noisy, due to the air valves constantly fighting with each other to try to position the load.  I couldn't help but think that there would soon be a mechanical failure in the valves because of the frequency of the switching, etc.

Having worked with literally hundreds of servo systems of many different flavors, and a small number of pneumatic positioners (less than 10 probably), I would favor an electric solution unless there is some overwhelming reason to not use electric (explosive environment?).

Under ideal circumstances pneumatic positioners talk about 0.005" positioning resolution.  That might be achievable under some circumstances, but if I were designing the system, I would be thinking a quarter of an inch and designing in energy absorbers and positive stops at the desired stopping points.

As a general substitution for this type of actuator, I would favor the belt drive style slides offered by a number of vendors.  They offer high speed capability in a similar form factor, and the precision of a completely digitally controlled electric servo system.

mrdon
User Rank
Gold
Re: Pneumatics
mrdon   7/22/2012 6:18:40 PM
NO RATINGS
Pneumatics is becoming an important component in the field of Mechatronics for efficiency and motion control precision. Festo is a leader in pneumatic based robotics with their gripper and arm products. I remember taking a Pneumatics class at community college back in the early 80s. I didn't see the importance of this class because of my fascination with electronics. I which more emphasis on system integration was discussed in class as it relates to Mechatronics, maybe I would have considered working for engineering companies like Festo who makes great and cool pneumatics based robots instead of just electronic/semiconductor jobs.

apresher
User Rank
Blogger
Pneumatics
apresher   7/19/2012 9:01:55 AM
NO RATINGS
Chuck, Forgot the second part of your question.  I don't think pneumatics is too costly. The precision limits are a reflection of the underlying technology, especially when compared to electromechanical solutions which can achieve very high precision, resolution and repeatable accuracy.

Page 1/3  >  >>


Partner Zone
Latest Analysis
This Gadget Freak review looks at a cooler that is essentially a party on wheels with a built-in blender, Bluetooth speaker, and USB charger. We also look at a sustainable, rotating wireless smartphone charger.
Texas Instruments is rolling out a new microcontroller that could make the design of sensor networks and data logging systems simpler and less costly.
Made By Monkeys highlights products that somehow slipped by the QC cops.
From pitchers and forwards to quarterbacks and defensemen, we offer a peek at some of the more memorable engineers in sports history.
IBM announced it is dedicating $3 billion of funding over the next five years to research and development of new processor technologies.
More:Blogs|News
Design News Webinar Series
7/23/2014 11:00 a.m. California / 2:00 p.m. New York
7/17/2014 11:00 a.m. California / 2:00 p.m. New York
6/25/2014 11:00 a.m. California / 2:00 p.m. New York
5/13/2014 10:00 a.m. California / 1:00 p.m. New York / 6:00 p.m. London
Quick Poll
The Continuing Education Center offers engineers an entirely new way to get the education they need to formulate next-generation solutions.
Jul 21 - 25, Design Products With Bluetooth Low Energy
SEMESTERS: 1  |  2  |  3  |  4  |  5  |  6


Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.
Next Class: August 12 - 14
Sponsored by igus
Learn More   |   Login   |   Archived Classes
Twitter Feed
Design News Twitter Feed
Like Us on Facebook

Sponsored Content

Technology Marketplace

Copyright © 2014 UBM Canon, A UBM company, All rights reserved. Privacy Policy | Terms of Service