Lakshmi,

You confused me because TransferFunctionModel takes a frequency domain expression and your expression looked like a frequency domain expression because time was called "s" (which is usually reserved for the complex variable in Laplace Transforms).

You should do this

exp = E^(-t/\[Tau])/\[Tau]
CreateSystemModel["myFilter", 
 TransferFunctionModel[Simplify[LaplaceTransform[exp, t, s]], s]]

Regards,

Neil

Lakshmi,

I’m confused. You refer to this as your transfer function and use it that way in the “TransferFunction” command in the way you would specify a frequency domain expression. However, now you say it’s a function of time. Is your expression an impulse response in time and not a transfer function in frequency ?

Regards,

Neil

Lakshmi,

To be clear, The model looks like this:

and the code is

model example
  Modelica.Blocks.Continuous.TransferFunction transferFunction1(a = {1, 0}, b = {0, 1}) annotation(Placement(visible = true, transformation(origin = {-55, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Nonlinear.FixedDelay fixedDelay1(delayTime = 1 / 1) annotation(Placement(visible = true, transformation(origin = {-5, 0}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
equation
  connect(transferFunction1.y, fixedDelay1.u) annotation(Line(visible = true, origin = {-30.5, 0}, points = {{-13.5, 0}, {13.5, 0}}, color = {1, 37, 163}));
  annotation(Diagram(coordinateSystem(extent = {{-150, -90}, {150, 90}}, preserveAspectRatio = true, initialScale = 0.1, grid = {5, 5})), Icon(coordinateSystem(extent = {{-100, -100}, {100, 100}}, preserveAspectRatio = true, initialScale = 0.1, grid = {10, 10}), graphics = {Rectangle(visible = true, lineColor = {0, 114, 195}, fillColor = {255, 255, 255}, extent = {{-100, -100}, {100, 100}}, radius = 25), Text(visible = true, textColor = {64, 64, 64}, extent = {{-150, 110}, {150, 150}}, textString = "%name")}));
end example;

The fixed delay is your exponent term.

Regards

Hi, Thank you. I created this transfer function using CreateSystemModel

RTFV2= CreateSystemModel[TransferFunctionModel[{{{E^(-s/\[Tau])}}, \[Tau]}, s]]

but when I used it in system model it gives me an error that there is no scope for variable s. Alternatively, I also tried to modify the in-built transfer function in modelica but was not sure how to use the exponent. What is the equation of y? Please let me know. Lakshmi

Hi Lakshmi,

You can check out the following videos in Wolfram U on creating custom components in SystemModeler. https://www.wolfram.com/wolfram-u/modeling-systems/

If you are interested in creating your component in Mathematica, see the documentation on CreateSystemModel here: https://reference.wolfram.com/language/ref/CreateSystemModel.html

Thanks, Ankit