Modelica.Blocks.Discrete.UnitDelay does not delay input

[JayHuLBL]

The Modelica.Blocks.Discrete.UnitDelay does not delay the input as described in its documents.

Given an example model as below, where the unitDelay_MSL is the delay block from MSL and the unitDelay_Corrected is the one with correction. It has the results as:

The unitDelay_MSL.y is the same as the output from the sampling block, while the unitDelay_Corrected .y is the expected one.

[casella]

@JayHuLBL where do we find the corrected model?

Could you please post the code that allows to replicate the issue?

Thanks!

[JayHuLBL]

@casella Thanks for your response.

Please see the test model as below:

model UnitDelayAndSampleBlock "Example model for the UnitDelay block"
  Buildings.Controls.OBC.CDL.Reals.Sources.Ramp ramp1(
    duration=1,
    offset=0,
    height=6.2831852)
    "Block that generates ramp signal"
    annotation (Placement(transformation(extent={{-60,-10},{-40,10}})));
  Buildings.Controls.OBC.CDL.Reals.Sin sin1
    "Block that outputs the sine of the input"
    annotation (Placement(transformation(extent={{-20,-10},{0,10}})));

  Buildings.Controls.OBC.CDL.Discrete.Sampler sam(
    samplePeriod=0.05)
    "sampler of a continuous signal"
    annotation (Placement(transformation(extent={{40,-50},{60,-30}})));
  Modelica.Blocks.Discrete.UnitDelay unitDelay_MSL(
    samplePeriod=0.05)
    "Unit delay from MSL"
    annotation (Placement(transformation(extent={{40,40},{60,60}})));
  Buildings.Controls.OBC.CDL.Discrete.UnitDelay unitDelay_Corrected(
    samplePeriod=0.05,
    y_start=1)
    "Unit delay with correction"
    annotation (Placement(transformation(extent={{40,-10},{60,10}})));

equation 
  connect(ramp1.y,sin1.u)
    annotation (Line(points={{-38,0},{-22,0}}, color={0,0,127}));
  connect(sin1.y, unitDelay_Corrected.u)
    annotation (Line(points={{2,0},{38,0}}, color={0,0,127}));
  connect(sin1.y, sam.u)
    annotation (Line(points={{2,0},{20,0},{20,-40},{38,-40}}, color={0,0,127}));
  connect(sin1.y, unitDelay_MSL.u)
    annotation (Line(points={{2,0},{20,0},{20,50},{38,50}}, color={0,0,127}));

annotation (
    Icon(graphics={
        Ellipse(lineColor={75,138,73}, fillColor={255,255,255},
          fillPattern=FillPattern.Solid, extent={{-100,-100},{100,100}}),
        Polygon(lineColor={0,0,255}, fillColor={75,138,73}, pattern=LinePattern.None,
          fillPattern=FillPattern.Solid, points={{-36,60},{64,0},{-36,-60},{-36,60}})}),
     uses(Modelica(version="4.0.0")),
     experiment(StopTime=1, __Dymola_Algorithm="Dassl"));
end UnitDelayAndSampleBlock;

The corrected unit delay is from here.