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modelicadymola

smooth the curve in Dymola

In Dymola, after plotting the result, how could I smooth the curve? enter image description here

Solution

  • I don't know a way of doing it in the plot window, but smoothing a curve could be done in multiple ways. You have to be aware that you are manipulating the actual simulation result with that.

    I would recommend using a filter yourself and just create a smoothed signal without influencing the actual simulation. I made a small sample model with an original and filtered signal using a Butterworth filter from the MSL.

    I just copied and modified an example slightly, please disregard most of the inline comments. You have to fiddle a bit with the f_cut such that it cuts the correct high frequencies for your case. 

    model FilterTest "Demonstrates the Continuous.Filter block with various options"
  extends Modelica.Icons.Example;

  Real original = add.y;
  Real filtered = Butterworth.y;
  protected
  parameter Integer order=3;
  parameter Modelica.SIunits.Frequency f_cut=2;
  parameter Modelica.Blocks.Types.FilterType filterType=Modelica.Blocks.Types.FilterType.LowPass
    "Type of filter (LowPass/HighPass)";
  parameter Modelica.Blocks.Types.Init init=Modelica.Blocks.Types.Init.SteadyState
    "Type of initialization (no init/steady state/initial state/initial output)";
  parameter Boolean normalized=true;
  Modelica.Blocks.Continuous.Filter Butterworth(

    analogFilter = Modelica.Blocks.Types.AnalogFilter.Butterworth,
    f_cut= 100,
    f_min=1,
    filterType=Modelica.Blocks.Types.FilterType.LowPass, gain = 1,
    init=init,normalized=normalized,
    order=order)
    annotation (Placement(visible = true, transformation(extent = {{38, 18}, {58, 38}}, rotation = 0)));
  Modelica.Blocks.Sources.Sine sineHigh(freqHz = 200)  annotation(
    Placement(visible = true, transformation(origin = {-62, 54}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Sources.Sine sineLow(amplitude = 10, freqHz = 3)  annotation(
    Placement(visible = true, transformation(origin = {-56, 2}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
  Modelica.Blocks.Math.Add add annotation(
    Placement(visible = true, transformation(origin = {-8, 28}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
equation
  connect(add.u1, sineHigh.y) annotation(
    Line(points = {{-20, 34}, {-20, 55}, {-51, 55}, {-51, 54}}, color = {0, 0, 127}));
  connect(add.u2, sineLow.y) annotation(
    Line(points = {{-20, 22}, {-33.5, 22}, {-33.5, 2}, {-45, 2}}, color = {0, 0, 127}));
  connect(Butterworth.u, add.y) annotation(
    Line(points = {{36, 28}, {3, 28}}, color = {0, 0, 127}));
  annotation(
    experiment(StopTime = 0.9),
    Documentation(info = "<html>

<p>
This example demonstrates various options of the
<a href=\"modelica://Modelica.Blocks.Continuous.Filter\">Filter</a> block.
A step input starts at 0.1 s with an offset of 0.1, in order to demonstrate
the initialization options. This step input drives 4 filter blocks that
have identical parameters, with the only exception of the used analog filter type
(CriticalDamping, Bessel, Butterworth, Chebyshev of type I). All the main options
can be set via parameters and are then applied to all the 4 filters.
The default setting uses low pass filters of order 3 with a cut-off frequency of
2 Hz resulting in the following outputs:
</p>

<img src=\"modelica://Modelica/Resources/Images/Blocks/Filter1.png\"
   alt=\"Filter1.png\">
</html>"),
    uses(Modelica(version = "3.2.2")));
end FilterTest;