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uclphd1-Visitor
1-Visitor
January 15, 2013
Solved

Help please - plotting curve as a series of functions

  • January 15, 2013
  • 10 replies
  • 4284 views

Hi,

Attached is a mathcad worksheet - when you scroll down you will see a set of questions to my problem and a plot of the function that I have produced to try and plot the curve that I want. The curve I wish to plot should look something like the sketch attached (see curve_sketch file) Plot points on the sketch refer to the nomenclature in the mathcad file.

Can you please read the questions in matchad file and advise how best to plot the individual functions of the curve?

Many thanks

Omar

Best answer by AndyWesterman

If you normalise the x parameter for each stage

Capture.PNG

here mod(x)-Xeb then the start point needs a constant added, equal to the result from the previous stage at Xeb in this case already calculated as Rub.

If you calculate everything as mod(x) here, saving the result as a local variable (r).

Then the final answer can be returned as

Capture.PNG

Regards

Andy

10 replies

Werner_E
Werner_E25-Diamond I
25-Diamond I
January 15, 2013

I'll take a look when I have some more time.

In the meantime maybe the following link will be of help concerning plotting of piecewise defined functions.

http://communities.ptc.com/message/170411#170411

U
uclphd1-VisitorAuthor
1-Visitor
January 15, 2013

Thanks Werner

F
Fred_Kohlhepp23-Emerald I
23-Emerald I
January 15, 2013

See if this helps.

    U
    uclphd1-VisitorAuthor
    1-Visitor
    January 15, 2013

    Hi Fred, thanks for your approach it solves plotting the curve correctly. If you read my response below to Andy I upload a further file - there is a scaler issue in my differential equation that I need to fix to solve my problem.

    Many thanks

    Omar

    A
    AndyWesterman12-AmethystAnswer
    12-Amethyst
    January 15, 2013

    If you normalise the x parameter for each stage

    Capture.PNG

    here mod(x)-Xeb then the start point needs a constant added, equal to the result from the previous stage at Xeb in this case already calculated as Rub.

    If you calculate everything as mod(x) here, saving the result as a local variable (r).

    Then the final answer can be returned as

    Capture.PNG

    Regards

    Andy

      U
      uclphd1-VisitorAuthor
      1-Visitor
      January 15, 2013

      Hi Andy,

      That's great you've solved the problem for plotting the curve. However I encounter another problem when I apply the curve to my differential equation which I solve using the Runge Kutta method. I have attached an updated version of the mathcad file - if you can please take a look and let me know how I resolve the scaler issue so it solves the differential equation.

      Many thanks

      Omar

      A
      AndyWesterman12-Amethyst
      12-Amethyst
      January 15, 2013

      Hi Omar,

      2 problems:

      1

      Capture.PNG

      You have Rmu * (...

      It should be just Rmu(...

      & 2

      Capture.PNG

      Rmu is set for parameter in m and returning value as N

      All the other functions only return number results (no units)

      If you remove the units from Rmu (as above) you get an answer.

      However, I have tried adding units to the other equations & still get errors!!

      So possible that the answer given may not be correct.

      Regards

      Andy

      U
      uclphd1-VisitorAuthor
      1-Visitor
      January 15, 2013

      Hi Andy

      I have tried removing Rmu units as shown however don't get an answer. Can you please provide your worksheet with answer?

      Thanks

      Omar

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