Login | Register

Previous in Forum: Manual for Atlas Copco Compressor ZR315VSDFF   Next in Forum: Coatings for Underground NG Pipelines
Close

Comments Format:






Close

Subscribe to Discussion:

CR4 allows you to "subscribe" to a discussion
so that you can be notified of new comments to
the discussion via email.

Close

Rating Vote:







6 comments
Guest

Sinusoidal Vibration

10/29/2009 7:20 AM

PPl i want to generate vibration from 0hz to 150hz. i have decided to use a cam where we can accurately obtain the required frequency, But the vibration should be sinosidal can anybody suggest a good idea.

Send to a friend Digg this Add to del.icio.us
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing. Kettle's on.
Posts: 8653
Good Answers: 163
#1

Re: vibration

10/29/2009 8:25 AM

<...vibration should be sinosidal ...>

How about a sine-wave signal generator, an amplifier and a loudspeaker instead, then?

__________________
The elephant is a funny bird. It flits from bough to bough. It lays its eggs in a rhubarb tree and whistles, like a cow - Spike Milligan.
Power-User

Join Date: May 2007
Location: Ohio. USA
Posts: 385
Good Answers: 15
#2

Re: vibration

10/29/2009 8:35 AM

Use a shaft with an offset weight. Vary the frequency by changing the shaft rotation speed (this may also vary the amplitude). Vary the amplitude by adjusting the weight's distance to the shaft centerline.

The advantage of this over the cam method is only one moving part with no wear surface. The cam method may provide better amplitude control based on your application.

If you need cam like control, study an IC engine valve train arrangement. Movement of a cam, cam follower, and return spring that maintains cam to follower contact can be set up for a very specific movement.

__________________
Duct tape is like the force. It has a light side, a dark side and it holds the universe together.
Guru

Join Date: Dec 2008
Location: Long Island NY
Posts: 942
Good Answers: 51
#3

Re: vibration

10/29/2009 9:32 AM

You span an awkward frequency range to recommend one vibration technique. Spinning an offset counterweight will give you an excellent low frequency vibration control in both frequency and amplitude. Since the counterweight will be spinning in a circle, the vibrations must be sinusoidal. Amplitude can be controlled by changing the counterweight mass or the length of the offset. Frequency can be controlled by changing the motor speed. (Oh by the way, if you choose the motor to be an induction motor you will need a variable frequency drive to be able to change the speed.) But 150 hertz is 9000 RPM for a motor shaft speed. You're not going to find many motors capable of that speed that can spin an offset counterweight without destroying some bearings.

Now the speaker approach will easily be able to vibrate at 50 hertz and into higher frequencies. You will have to have some mechanical linkage between the voice coil and the object you are vibrating to transfer this energy. But lower than 50 hertz gets to be very difficult for a voice coil to move air, let alone whatever you are shaking. (Yes, those of you familiar with Velodyne, Hsu Research, Caton, PSB and the makers of other fine sub-woofers know, this can be done. But it isn't easy. )

So I suggest you use two shakers for your earth quake test rig. (Just a wild guess on the test rig.)

__________________
There are 10 types of people. People who understand binary and those who don't.
Power-User

Join Date: Jan 2008
Location: NY
Posts: 348
Good Answers: 18
#4

Re: Sinusoidal Vibration

10/29/2009 10:26 PM

That is a fairly large range.

What Mass are you trying to vibrate?

What Amplitude at what Frequency?

Guru

Join Date: Dec 2006
Location: Germany 49° 26' N, 7° 46' O
Posts: 1408
Good Answers: 76
#5

Re: Sinusoidal Vibration

10/30/2009 3:20 AM

Hi,

any decentered circular cam will give a pure sine motion if this motion is guided with a linear stage.

This is pur geometry with inertial forces and deformations neglected.

RHABE

Commentator

Join Date: Dec 2008
Location: Anthem, AZ
Posts: 62
Good Answers: 4
#6

Re: Sinusoidal Vibration

10/30/2009 11:45 AM

Hydraulic actuators were designed for just that purpose. You can probably buy one cheap off EBAY.

6 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

DaveB (1), mjb1962853 (1), PWSlack (1), redfred (1), RHABE (1), WoodwardDL (1)

Previous in Forum: Manual for Atlas Copco Compressor ZR315VSDFF   Next in Forum: Coatings for Underground NG Pipelines
You might be interested in: Gearmotors , Gearboxes and Gearheads, Linear Position Sensors, Eddy Current