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Make Ramp a continuous source #4121

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Make Ramp a continuous source #4121

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832d5d3
Guarantee continuity of Ramp output
henrikt-ma Apr 24, 2023
8c970d5
Require positive 'duration' to ensure continuity
henrikt-ma Apr 24, 2023
d659e66
Use Step instead of Ramp in BranchingDynamicPipes
henrikt-ma Apr 26, 2023
961e4c7
Move smooth(...) to top of equation
henrikt-ma Apr 26, 2023
bfaec28
Update description string
henrikt-ma Apr 27, 2023
e582b8f
Remove statement about ramp becoming step when duration is 0
henrikt-ma Feb 9, 2026
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12 changes: 4 additions & 8 deletions Modelica/Blocks/Sources.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -244,13 +244,13 @@ The Real output y is a step signal:
block Ramp "Generate ramp signal"
parameter Real height=1 "Height of ramp"
annotation(Dialog(groupImage="modelica://Modelica/Resources/Images/Blocks/Sources/Ramp.png"));
parameter SI.Time duration(min=0.0, start=2)
"Duration of ramp (= 0.0 gives a Step)";
parameter SI.Time duration(min=Constants.small, start=2)
"Duration of ramp";
extends Interfaces.SignalSource;

equation
y = offset + (if time < startTime then 0 else if time < (startTime +
duration) then (time - startTime)*height/duration else height);
y = smooth(0, offset + (if time < startTime then 0 else if time < (startTime +
duration) then (time - startTime)*height/duration else height));
Comment on lines +252 to +253
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@HansOlsson HansOlsson Feb 10, 2026

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If one necessarily wants to rewrite it, obviously want to avoid evaluating duration, and use smooth when appropriate why not write:

Suggested change
y = smooth(0, offset + (if time < startTime then 0 else if time < (startTime +
duration) then (time - startTime)*height/duration else height));
y = offset+(if duration>0 then smooth(0, (if time < startTime then 0 else if time < (startTime +
duration) then (time - startTime)*height/duration else height)) else (if time < startTime then 0 else height);

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@henrikt-ma henrikt-ma Feb 10, 2026

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At least I wouldn't know what to do with the smoothness information unless duration > 0 was evaluated.

annotation (
Icon(coordinateSystem(
preserveAspectRatio=true,
Expand Down Expand Up @@ -281,10 +281,6 @@ The Real output y is a ramp signal:
<img src=\"modelica://Modelica/Resources/Images/Blocks/Sources/Ramp.png\"
alt=\"Ramp.png\">
</div>

<p>
If parameter duration is set to 0.0, the limiting case of a Step signal is achieved.
</p>
</html>"));
end Ramp;

Expand Down
7 changes: 3 additions & 4 deletions Modelica/Fluid/Examples/BranchingDynamicPipes.mo
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Original file line number Diff line number Diff line change
Expand Up @@ -81,17 +81,16 @@ replaceable package Medium=Modelica.Media.Air.MoistAir constrainedby
p=100000) annotation (Placement(
transformation(extent={{10,-10},{-10,10}}, rotation=90,
origin={0,60})));
Modelica.Blocks.Sources.Ramp ramp1(
Modelica.Blocks.Sources.Step step1(
offset=1e5,
startTime=2,
height=1e5,
duration=0) annotation (Placement(transformation(extent={{-40,70},{-20,90}})));
height=1e5) annotation (Placement(transformation(extent={{-40,70},{-20,90}})));
Modelica.Thermal.HeatTransfer.Sources.FixedHeatFlow[
pipe2.nNodes] heat2(Q_flow=200*
pipe2.dxs, alpha=-1e-2*ones(pipe2.n))
annotation (Placement(transformation(extent={{-60,-20},{-40,0}})));
equation
connect(ramp1.y, boundary4.p_in) annotation (Line(
connect(step1.y, boundary4.p_in) annotation (Line(
points={{-19,80},{-8,80},{-8,72}},
color={0,0,127},
thickness=0.5));
Expand Down