Vibration Isolation system

I'd have thought a computer and pneumatics woul'd be too slugish to damp out anything other than very slow movements...say the roll of a ship or maybe the priodic thump of a big machine ...but vibration...? I wouldn't bet a fiver on it.

I'm not sure about pneumatics but the idea worked for car suspension using hydraulics instead of springs, Lotus probably most famously employed it. The compressibility of gas mitigates against much of a quick repsonse, unless maybe it's at very high pressure?

Isn't a car suspension a relatively slow response compared with a vibration?

Does this tie in with what I was saying?...you may compenste for movement but will it be quick enough for vibration?

I can see this is going to degenerate into semantics...what constitutes vibration?..how fast is fast? How fast is your processor? What do we mean by 'what do we mean'? What is your shoe size?

Del

You're right, ....again! Suspension activity is probably only interesting up to 50Hz max I guess. Active noise cancellation works but I doubt it would if you needed to actuate your loadspeaker cones by air!!! (Wait a minute........

If you've ever done any bike road racing, the perfect suspension tracks the bumps and bounces like a good needle on vinyl. Too tight or too mushy and you'll be watching the end of your bike passing you in a hard turn.

Never, way too chicken. Oh no, not that 'tastes like...' thing again. Bike hasn't even run for probably 4 years poor thing.

Had a neigbour who's best effort was 17th in the senior TT though, dunno what lap time.

Brave bas****

I would think a sensitive detector feeding through a computer to pneumatics would be the equivalent of one of those "magic-fingers" beds you put a quarter into at a motel!

Take a look at the type of dampening strategies used for optical tables. If doing laser work, these things have to be insanely stable. It might give you an idea.

Good luck!!!

Damping is quite possible but responding to motion may require more effort.

Consider a linear encoder with a direct or indirect (via pneumatic or links) acting servo or stepper.

Sounds to me like a reactive system. I'd imagine if you can come up with something that reacts quick enough to vibration to actively eliminate it, industry would beat a path to your door!

Bear in mind the famous re-active suspicion Pioneered by F1 was in fact more programmable then reactive, they would do a run of the circuit, record the activity produced, and the next time out could program the car to set the suspension for each individual corner.

Hi Balraj,

I think that what you want to try is like what is used in heavy noise environment, active noise control.

see http://en.wikipedia.org/wiki/Active_noise_control for more infos on it.

Hope this helps...

Good luck for your thesis

You might want to check out some optical tables like these, they generally damp vibrations passively by having a large mass for the table top & elastomeric bearings.

That's what I said Oli'. Mmm mmm mmm!

But I added the nice link. We bought a used one of these tables from a local university earlier this year & found a specialist mover to deliver and install it. They moved a ton of table with 2 guys & made it look like child's play.

That's what a $50.00 tip and a six pack will get you!!!

We just get one of our ladies to ask them nicely.

air bearings?

Most of these isolation systems are comprised of a large mass supported on compiant springs to form a low pass mechanical filter. The springs are often columns of air. The only problem left is to keep the isolated platform level as the load location changes. Height sensing regulators are used at the supports to measure their elevation and admit or discharge air to keep the height constant. The details will be determined by what frquencies you need to isolate to, and how much isolation you require at those frequencies.

My first thoughts... Vibration in a machine is a frequency... may vary some.. noise cancelling headphones. set up a matching frequency, shift it to offset vibration. use computer to sense and shift. pneumatics to generate offsetting frequencys diaphram compressor with varible driver? If two are more sources of vibration are identified maybe two or more compressors may be used. Enter hormonics. Forget all of this if you are droping rocks onto the table or floor.. A nother thought, instead of compressors use woofers to generate air compression. Now my head hurts.

Hi

A few quick thoughts--"A table which will isolate the vibration from floor etc."--this is exactly the problem addressed by broadcast engineers when they needed to keep the needle from jumping on the old turntables. We used a lot of springs, foam rubber, sand bags, etc.

The easiest way to deal with vibration is to add floating support and enough mass to make the structure non-resonant over the troublesome frequency range. Obviously, when you get to low frequency, large displacement movement (like earthquakes or big trucks and locomotives rumbling by just outside), the amount of mass needed would be astronomical so you must find another approach.

Your pneumatic approach will work over some particular lower frequency band. Recognise that each physical mechanism you employ will have its own resonances which will contribute to the situation.

The audio compensation will likewise work across portions of the spectrum of audio frequencies--again most effectively at particular frequencies and requiring dynamic control continuously to operate in a "flat" manner.

Very powerful amplifiers (the modulator sections of '50s 10kw RCA
AM radio transmitters as I recall) were used to drive coils for vibrating test beds where the object was to test components to mechanical failure. With computer sensing and control, such a mechanism would again be effective over a particular frequency range.

Seems to me you might design a system starting with the pneumatics you have described to isolate a massive base supporting a platform designed to be non-resonant across a band of frequencies and use coil-driven compensation on the low end and audio freq compensation on the top end--what you might do from 20kHz to molecular vibration I don't know. At some frequency you get into surface wave deformations of the table top requiring an astute choice of construction materials, and ultimately the vibrational characteristics of molecules would probably drive you to cryogenic techniques such as cooling the whole thing with liquid helium...?

Interesting project. I expect you will need to limit the scope of your thesis to meet a particular level of stability over a particular range of vibrational frequencies.

Lonnie

Thank you everybody for your input. I will discuss further with my advisor to narrow down the topic. again thanks alot.