Dynamic Time, Dynamic Frequency, Oh My

[Twoballcane]

Hi,
I have posted this already in the ProM forum with no luck. So Im posting here to see if anybody in this forum can help me. Thanks you for your time.

Hello,

How would you handle a continues sin wave of maybe 25Hz at 1G in ProM? Im trying to simulate a vibe table with a UUT on it. And then using measures like response accelerometers to monitor points in question. So basicly I want to "vib" the table with a sin wave of 25Hz at 1G and then get the responses. I would like to simulate that in ProM. I have used Dynamic randome before but that will excite all of the frequencies. Dynamic frequencies seems it will do the same. Dynamic time seems the best way to do it by inputing "if(time<.040,1*sin(pi*time/.020),0)" but this looks like a shock input (not contiunes) than a vib input (continues).

Thank you in advance for your help.


Tobalcane
"If you avoid failure, you also avoid success."

 

[GregLocock]

use just

sin(pi*time/.020)


as your input, BUT be aware that you will get a starting transient, as there is a discontinuity between t<0 and t=0, where you are literally jerking the structure into motion.

So in the real world we either ddrive the system via a compliant stinger, or we ramp up drive signals slowly.




Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Twoballcane]

Thanks Gregfor responding. Yup, I have actually found out last night that to have a continues sin wave I just adjust the time in "time<#" to any time length I wanted...duhhh, since the dynamic time uses time domain. And yes, from 0 to .1 you can see the "jerk" of the table and uut and then smooths out to steady state.

Thanks

Tobalcane
"If you avoid failure, you also avoid success."