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acceleration to displacement

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Hi

 

I have an acceleration signal

 

I can integrate it twice using Labview VI as shown in the attached file in order to find out velocity and displacement signals.

 

But how do I calculate the INITIAL CONDITIONS for velocity and displacement????

 

And how to include such initial conditions in the VI

 

Thanks in advance

 

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Message 1 of 34
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You can't calculate an initial position or an initial velocity.  You have to define them.  Do you want to assume your object is as a position of x=0 and a velocity of zero when you start acquiring data and integrating it?  Or do you want to assume it is at a position x0 and/or already moving at a velocity V0 when the acquisition starts.

 

 

Message 2 of 34
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Hi ...thanks for reply... so nice of you

 

I got your point....I want to define the initial condition.

 

My acceleration, velocity and displacement are 0.1, 0.2 and 0.3 at time t=-1 seconds

 

Please tell how to integrate this information into the INTEGRATION VI shown in the attached file

 

Have a nice day

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Message 3 of 34
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Hi Sehgal,

 

get rid of the ExpressVI, use "real" VIs/functions from the palettes instead and you will be able to supply start conditions to your integration...

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
Message 4 of 34
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Thanks but how to set the initial condition such the CONSTANT OF INTEGRATION becomes zero?

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Message 5 of 34
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These initial conditions are relative offsets to the results of each of the integral operations, ie

The result of the integration of the acceleration signal is your velocity distribution, which is relative to the initial condition 0.2 to t=0.

The result of the intergration of the velocity distribution is your displacement distribution, which is relative to the initial condition 0.3 at t=0.

 

Therefore, just add the initial condition to the distribution.

 

Double_Integration.png

Thoric (CLA, CLED, CTD and LabVIEW Champion)


Message 6 of 34
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Thanks a lot 

 

But I tried it and got a problem that the displacement signal is drifting downwards. It should be a sine wave but it is not coming like that. Please see the attached VI file for details. Here acceleration signal is of 1Hz frequency. Pic.JPG

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Message 7 of 34
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Hi Sehgal,

 

did you read my message #4?

Best regards,
GerdW


using LV2016/2019/2021 on Win10/11+cRIO, TestStand2016/2019
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Message 8 of 34
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Of course it is. If you intergrate a sinusoidal signal with a non-zero meanline then you will see shifted result biased towards that meanline. Therefore, if the centre plot has a meanline of -0.159 (as dictated by the initial condition), then the integral result will slope downwards. This is an expected outcome.

Thoric (CLA, CLED, CTD and LabVIEW Champion)


Message 9 of 34
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Hi GerdW

 

I have tried that also but the same problem persists......the double integral drfits downwards as shown in the third scope

Can you please send the VI file to me...I will be very thankful to you....i have already spent 50 odd hours on this problem.

Please help

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Message 10 of 34
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