Rise time of a half sine pulse

[varistor]

Hi,

Not sure if this is the correct place to ask this but here goes.

I am trying to work out a equation for calculating the rise time of a half sine, assuming peak and period is known and working on 10-90%

Any takers

 

[electricpete]

I don't know what 10-90% was.

You can obviously figure out the rise time of a half sin pulse if you know the frequency.

I expect in your case you are using a half sin pulse of acceleration.

The integral under the half sin pulse of acceleration must be equal to the change in velocity.

Let's say the pulse is Amax*sin(2*Pi*t/T)
where T is twice the length of the pulse

The integral from t=0 to T/2 is
T*Amax/Pi

T and Amax must satisfy:
V0 = T*Amax/Pi

Again the time of the peak (if that's what you're calling rise time) would be T/2


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[electricpete]

Sorry: T is one period of the sinusoid. So the peak occurs at 1/4 of that. Should be corrected as follows:

"the time of the peak (if that's what you're calling rise time) would be T/4"



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[varistor]

electricpete

The 10-90% I referred to is the time taken for the amplitude to rise from 10% to 90% of the peak amplitude (at least that is how it is defined in electronics)
I guess it is the same when talking about acceleration pulses?

I can calculate this graphically, but thought there must be a formula

 

[GregLocock]

Yes. You learned it when you were 14.

What is the asin(0.1) ?

what is asin (0.9) ?



Cheers

Greg Locock

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

 

[James9999z]

I think the answer is not that straight-forward. For a half sine acceleration shock, the control system will actually apply the pre- and post- compensation to the main pulse. How the velocity and displacement behave will largely depend on how the compensations are applied. In fact, different compensation will result in different rising time, given the same half sine shock pulse.

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