Active Vibration Suppression

How about active dampening systems for earthquake and wind compensating for large buildings such as this

http://www.takenaka.co.jp/takenaka_e/quake_e/seishin/seishin.htm

Hello Techno, thank you for your link!

As far as I know,

Moving masses, like Crystal tower, change the resonant peak of the building, trying to dodge the most destructive frequencies of the earthquake, or extreme wind.

Friction dampers attenuate the high frequency cases, absorbing the energy in its movement.

The way I understand it, this would be acting like a filter or a prefilter to the system, modifying the plant, the building + wind + earthquake, so that the damage level is hopefully lowered.

In my previous post I was thinking of active control suppressing the vibrations, moving or changing something by means of a sensor feedback, by means of piezoelectric materials or regular motors at the flexible link...

Maybe the moving masses can be thought as a kind of controller. I will look deeper in to it.

Bose has been researching active suspension using electric linear actuators for a couple of decades.

http://www.bose.com/controller?event=VIEW_STATIC_PAGE_EVENT&url=/learning/project_sound/bose_suspension.jsp

Very cool

Hello Techno, thank you for your answer.

As far as I know on the topic :

- friction dampers, act as a filter for the vibrations for high frequencies absorbing, hopefuly, the danger associated to them, just as a low band pass filter in a motor tracking system.

- Moving masses, like in Osaka's Crystal tower, modify the frequency resonant peak of the building, in order to adapt itself to the perturbation. In this way the damaging frequencies are attenuated, but the energy is still there and the structure still moves.

I was thinking more of piezoelectric actuation on the system, moving the structure with the vibration, which is I think not the case for a building, but for a machine that is under a known(not so many perturbations) enviroment.

Maybe there is not a single big application for this kind of active vibration suppresion yet.

Thanks again, I will keep on searching

What scale are you talking about (size of the structure you are working with, range and speed of actuation, what frequencies are you working around about?). What do you mean by 'known (not so many perturbations) environment'? If it is a well known environment, it might be less work to use elastomeric isolator supports or otherwise tune the natural frequency of your structure away from the vibration you want to suppress. Passive is always more reliable than active.

I took a class on active materials and smart structures - piezo systems certainly can be used as both sensing and actuating elements at different times, or even simultaneously. Are you thinking of supporting a structure on piezos that will actively isolate it from vibration, or making piezo elements embedded as part of the structure at various points to control vibration within the structure? You can absolutely do either, but I'd be really surprised if you could find an off the shelf system to do so.

The wikipedia article on piezos is accurate, or at least appears to be after a quick look through the math (http://en.wikipedia.org/wiki/Piezoelectric). The links also seem good.

I would recommend finding a relatively local piezo manufacturer and talking to an engineer there.

Thank you very much for your answers Butcher,

I have been having several problems with my computer lately, so I have not been able to answer before.

Regarding scale, I am thinking or a large scale machine-tool, several m on every dimension; very fast speeds ,several m/s, with also big jerks, m/s3. And therefore, the resonant peaks are just inside the bandwidth.

Therefore my elastic body is elastic due to large kinetic variations, and the projecting mass and length of the tool head.

The best apriori solution is as you say using passive methods, but I fear this won't be enough, for the projecting length of the tool head is too large and the resonant vibration peaks are dependent off both position and time.

Then I thought about using piezos, but before starting with the complex partial diferential ecuations, I was just wondering if it would be possible to have large actuations on big structures.

Again as you said, my next step will be talking to piezolectric manufacturers to see the size of the needed actuators, its costs... and so forth before deciding if it feaseble this way.

It is good to see that my reasoning is the same as yours, thank you very much again

Here are a few good sites

http://www.hse.gov.uk/noise/casestudies/soundsolutions/

http://www.flightcom.net/pdf/2004_Denali_manual.pdf