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nkhadar1-Visitor
1-Visitor
May 7, 2018
Solved

need solution for piece wise differential equation in matcad

Hello, I'm Mathcad newbie and I am unable to solve the attached problem in mathcad. 

how to plot voltage vs df/dt and voltage vs f

-MFra-Answer
21-Topaz II
May 11, 2018

The for loop begins from j=1 not 0:

RK4.jpg

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8 replies

Fred_Kohlhepp23-Emerald I
23-Emerald I
May 7, 2018

Attached is how to do it; but I don't like the result. . .

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LucMeekes23-Emerald V
23-Emerald V
May 7, 2018

This may be a start. (Note, a value for Vo is needed, I just put in 2).

LM_20180507_Piecewise1.png

This is your df/dVin. Note that it is discontinuous!

Then you find f by simple integration:

LM_20180507_Piecewise2.png

So now you have the function f(Vin...), You can put in any value, or function, for Vin.

 

Success!
Luc

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Fred_Kohlhepp23-Emerald I
23-Emerald I
May 7, 2018

That's great!

 

Plot f(t) vs t  ??

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-MFra-21-Topaz II
21-Topaz II
May 7, 2018

Hi,

I've used the fourth order Runge-Kutta method, the result is below depicted:

answer for nkhadar.jpg

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Werner_E
Werner_E25-Diamond I
25-Diamond I
May 8, 2018

You could define the function that way

B1.png

But it would be the same as

B2.png

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-MFra-21-Topaz II
21-Topaz II
May 8, 2018

Hi, nhkadar,

I can give you an image:

RK4 for nkhadar.jpg

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-MFra-21-Topaz IIAnswer
21-Topaz II
May 11, 2018

The for loop begins from j=1 not 0:

RK4.jpg

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LucMeekes23-Emerald V
23-Emerald V
May 11, 2018

I should think that Fred solved it here: https://community.ptc.com/t5/PTC-Mathcad-Questions/solution-for-the-attached-paper-to-get-figure-2-results-in/m-p/548325#M180502

 

Luc

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