Buildings.Controls.OBC.CDL.Discrete
Package with discrete blocks
Information
This package contains discrete control blocks with fixed sample period. Every component of this package is structured in the following way:
- A component has continuous Real input and output signals.
- The input signals are sampled by the given sample period
defined via parameter
samplePeriod. The first sample instant is defined by the parameterstartTime. - The output signals are computed from the sampled input signals.
Package Content
| Name | Description |
|---|---|
 DayType
|
Block that outputs a signal that indicates week-day or week-end |
 FirstOrderHold
|
First order hold of a sampled-data system |
 Sampler
|
Ideal sampler of a continuous signal |
 TriggeredMax
|
Output the maximum, absolute value of a continuous signal at trigger instants |
 TriggeredMovingMean
|
Triggered discrete moving mean of an input signal |
 TriggeredSampler
|
Triggered sampling of continuous signals |
 UnitDelay
|
Output the input signal with a unit delay |
 ZeroOrderHold
|
Output the input signal with a zero order hold |
 Examples
|
Collection of models that illustrate model use and test models |
Buildings.Controls.OBC.CDL.Discrete.DayType
Block that outputs a signal that indicates week-day or week-end
Information
This block outputs a signal that indicates the type of the day. It can for example be used to generate a signal that indicates whether the current time is a work day or a non-working day. The output signal is of type Buildings.Controls.OBC.CDL.Types.Day.
The parameter nout determines how many days should be
sent to the output. For applications in which only the current day
is of interest, set nout=1.
For applications in which the load is predicted for the next 24 hours,
set nout=2 in order to output the type of day for today and for
tomorrow.
The transition from one day type to another always happens when the simulation time is a multiple of 1 day. Hence, if the simulation starts for example at t=-3600 seconds, then the first transition to another day will be at t=0.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | nout | 2 | Number of days to output. Set to two for one day predictions |
| Day | days[:] | {Buildings.Controls.OBC.CDL.... | Array where each element is a day indicator |
| Integer | iStart | 1 | Index of element in days at simulation start |
Connectors
| Type | Name | Description |
|---|---|---|
| output DayTypeOutput | y[nout] | Type of the day for the current and the next (nout-1) days |
Modelica definition
model DayType "Block that outputs a signal that indicates week-day or week-end"
parameter Integer nout = 2
"Number of days to output. Set to two for one day predictions";
parameter Buildings.Controls.OBC.CDL.Types.Day[:] days={
Buildings.Controls.OBC.CDL.Types.Day.WorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.WorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.WorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.WorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.WorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.NonWorkingDay,
Buildings.Controls.OBC.CDL.Types.Day.NonWorkingDay}
"Array where each element is a day indicator";
parameter Integer iStart(min=1, max=size(days, 1)) = 1
"Index of element in days at simulation start";
Interfaces.DayTypeOutput y[nout]
"Type of the day for the current and the next (nout-1) days";
protected
parameter Modelica.SIunits.Time samplePeriod=86400
"Sample period of component";
output Integer iDay(min=1, max=size(days, 1))
"Pointer to days that determines what day type is sent to the output";
parameter Modelica.SIunits.Time firstSample(fixed=false)
"Time when the sampling starts";
output Boolean sampleTrigger "True, if sample time instant";
output Boolean skipIDayIncrement
"If true, don't increment iDay in first sample";
initial equation
iDay = iStart;
firstSample = ceil(time/86400)*86400;
// skipIDayIncrement is true if the simulation starts at midnight.
skipIDayIncrement = abs(firstSample-time) < 1E-8;
equation
for i in 1:nout loop
y[i] = days[ mod(iDay+i-2, size(days, 1))+1];
end for;
sampleTrigger = sample(firstSample, samplePeriod);
when sampleTrigger then
skipIDayIncrement = false;
if pre(skipIDayIncrement) then
iDay = pre(iDay);
else
iDay = mod(pre(iDay), size(days, 1))+1;
end if;
end when;
end DayType;
Buildings.Controls.OBC.CDL.Discrete.FirstOrderHold
First order hold of a sampled-data system
Information
Block that outputs the extrapolation through the values of the last two sampled input signals.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | samplePeriod(min=1E-3) | Sample period of component [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block FirstOrderHold "First order hold of a sampled-data system"
parameter Modelica.SIunits.Time samplePeriod(min=1E-3)
"Sample period of component";
Interfaces.RealInput u "Continuous input signal";
Interfaces.RealOutput y "Continuous output signal";
protected
parameter Modelica.SIunits.Time t0(fixed=false)
"First sample time instant";
output Boolean sampleTrigger "True, if sample time instant";
output Boolean firstTrigger(start=false, fixed=true)
"Rising edge signals first sample instant";
Modelica.SIunits.Time tSample "Time of sample";
Real uSample "Value of sample";
Real pre_uSample "Value of previous sample";
Real c "Slope";
initial equation
t0 = time;
pre(tSample) = time;
pre(uSample) = u;
pre(pre_uSample) = u;
pre(c) = 0.0;
equation
// Declarations that are used for all discrete blocks
sampleTrigger = sample(t0, samplePeriod);
when sampleTrigger then
firstTrigger = time <= t0 + samplePeriod/2;
end when;
// Declarations specific to this type of discrete block
when sampleTrigger then
tSample = time;
uSample = u;
pre_uSample = pre(uSample);
c = if firstTrigger then 0 else (uSample - pre_uSample)/samplePeriod;
end when;
/* Use pre_uSample and pre(c) to break potential algebraic loops by an
infinitesimal delay if both the continuous and the discrete part
have direct feedthrough.
*/
y = pre_uSample + pre(c)*(time - tSample);
end FirstOrderHold;
Buildings.Controls.OBC.CDL.Discrete.Sampler
Ideal sampler of a continuous signal
Information
Block that outputs the input signal, sampled at a sampling rate defined
via parameter samplePeriod.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | samplePeriod(min=1E-3) | Sample period of component [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block Sampler "Ideal sampler of a continuous signal"
parameter Modelica.SIunits.Time samplePeriod(min=1E-3)
"Sample period of component";
Interfaces.RealInput u "Continuous input signal";
Interfaces.RealOutput y "Continuous output signal";
protected
parameter Modelica.SIunits.Time t0(fixed=false)
"First sample time instant";
output Boolean sampleTrigger "True, if sample time instant";
output Boolean firstTrigger(start=false, fixed=true)
"Rising edge signals first sample instant";
initial equation
t0 = time;
equation
// Declarations that are used for all discrete blocks
sampleTrigger = sample(t0, samplePeriod);
when sampleTrigger then
firstTrigger = time <= t0 + samplePeriod/2;
end when;
// Declarations specific to this type of discrete block
when {sampleTrigger, initial()} then
y = u;
end when;
end Sampler;
Buildings.Controls.OBC.CDL.Discrete.TriggeredMax
Output the maximum, absolute value of a continuous signal at trigger instants
Information
Block that outputs the input signal whenever the trigger input
signal is rising (i.e., trigger changes to
true). The maximum, absolute value of the input signal
at the sampling point is provided as the output signal.
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Connector with a Real input signal |
| output RealOutput | y | Connector with a Real output signal |
| input BooleanInput | trigger | Connector for trigger |
Modelica definition
block TriggeredMax
"Output the maximum, absolute value of a continuous signal at trigger instants"
Interfaces.RealInput u "Connector with a Real input signal";
Interfaces.RealOutput y "Connector with a Real output signal";
Interfaces.BooleanInput trigger "Connector for trigger";
initial equation
y = u;
equation
when trigger then
y = max(pre(y), abs(u));
end when;
end TriggeredMax;
Buildings.Controls.OBC.CDL.Discrete.TriggeredMovingMean
Triggered discrete moving mean of an input signal
Information
Block that outputs the triggered moving mean value of an input signal.
At the start of the simulation, and whenever the trigger signal is rising
(i.e., the trigger changes to true), the block samples
the input, computes the moving mean value over the past n samples,
and produces this value at its output y.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Integer | n | n(min=1) | Number of samples over which the input is averaged |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| input BooleanInput | trigger | Boolean signal that triggers the block |
| output RealOutput | y | Discrete averaged signal |
Modelica definition
block TriggeredMovingMean
"Triggered discrete moving mean of an input signal"
parameter Integer n(min=1)
"Number of samples over which the input is averaged";
Interfaces.RealInput u "Continuous input signal";
Interfaces.BooleanInput trigger "Boolean signal that triggers the block";
Interfaces.RealOutput y "Discrete averaged signal";
protected
parameter Modelica.SIunits.Time t0(fixed=false) "First sample time instant";
Integer iSample(start=0, fixed=true) "Sample numbering in the calculation";
Integer counter(start=0, fixed=true)
"Number of samples used for averaging calculation";
Integer index(start=0, fixed=true) "Index of the vector ySample";
Real ySample[n](
start=zeros(n),
each fixed=true) "Vector of samples to be averaged";
initial equation
t0 = time;
equation
when {initial(), trigger} then
index = mod(pre(iSample), n) + 1;
ySample = {if (i == index) then u else pre(ySample[i]) for i in 1:n};
counter = if pre(counter) == n then n else pre(counter) + 1;
y = sum(ySample)/counter;
iSample = pre(iSample) + 1;
end when;
end TriggeredMovingMean;
Buildings.Controls.OBC.CDL.Discrete.TriggeredSampler
Triggered sampling of continuous signals
Information
Samples the continuous input signal whenever the trigger input
signal is rising (i.e., trigger changes from false to
true) and provides the sampled input signal as output.
Before the first sampling, the output signal is equal to
the initial value defined via parameter y_start.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | y_start | 0 | Initial value of output signal |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Connector with a Real input signal |
| output RealOutput | y | Connector with a Real output signal |
| input BooleanInput | trigger | Signal that triggers the sampler |
Modelica definition
block TriggeredSampler "Triggered sampling of continuous signals"
parameter Real y_start=0 "Initial value of output signal";
Interfaces.RealInput u "Connector with a Real input signal";
Interfaces.RealOutput y "Connector with a Real output signal";
Interfaces.BooleanInput trigger "Signal that triggers the sampler";
initial equation
y = y_start;
equation
when trigger then
y = u;
end when;
end TriggeredSampler;
Buildings.Controls.OBC.CDL.Discrete.UnitDelay
Output the input signal with a unit delay
Information
Block that outputs the input signal with a unit delay:
1
y = --- * u
z
that is, the output signal y is the
input signal u of the
previous sample instant. Before the second sample instant,
the output y is identical to parameter y_start.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | samplePeriod(min=1E-3) | Sample period of component [s] |
| Real | y_start | 0 | Initial value of output signal |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block UnitDelay "Output the input signal with a unit delay"
parameter Modelica.SIunits.Time samplePeriod(min=1E-3)
"Sample period of component";
parameter Real y_start=0 "Initial value of output signal";
Interfaces.RealInput u "Continuous input signal";
Interfaces.RealOutput y "Continuous output signal";
protected
parameter Modelica.SIunits.Time t0(fixed=false)
"First sample time instant";
output Boolean sampleTrigger "True, if sample time instant";
output Boolean firstTrigger(start=false, fixed=true)
"Rising edge signals first sample instant";
initial equation
t0 = time;
y = y_start;
equation
// Declarations that are used for all discrete blocks
sampleTrigger = sample(t0, samplePeriod);
when sampleTrigger then
firstTrigger = time <= t0 + samplePeriod/2;
end when;
// Declarations specific to this type of discrete block
when sampleTrigger then
y = pre(u);
end when;
end UnitDelay;
Buildings.Controls.OBC.CDL.Discrete.ZeroOrderHold
Output the input signal with a zero order hold
Information
Block that outputs the sampled input signal at sample time instants. The output signal is held at the value of the last sample instant during the sample points. At initial time, the block feeds the input directly to the output.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Time | samplePeriod | samplePeriod(min=1E-3) | Sample period of component [s] |
Connectors
| Type | Name | Description |
|---|---|---|
| input RealInput | u | Continuous input signal |
| output RealOutput | y | Continuous output signal |
Modelica definition
block ZeroOrderHold "Output the input signal with a zero order hold"
parameter Modelica.SIunits.Time samplePeriod(min=1E-3)
"Sample period of component";
Interfaces.RealInput u "Continuous input signal";
Interfaces.RealOutput y "Continuous output signal";
protected
parameter Modelica.SIunits.Time t0(fixed=false)
"First sample time instant";
output Real ySample(fixed=true, start=0)
"Sampled value of input";
output Boolean sampleTrigger "True, if sample time instant";
output Boolean firstTrigger(start=false, fixed=true)
"Rising edge signals first sample instant";
initial equation
t0 = time;
equation
// Declarations that are used for all discrete blocks
sampleTrigger = sample(t0, samplePeriod);
when sampleTrigger then
firstTrigger = time <= t0 + samplePeriod/2;
end when;
// Declarations specific to this type of discrete block
when {sampleTrigger, initial()} then
ySample = u;
end when;
/* Define y=ySample with an infinitesimal delay to break potential
algebraic loops if both the continuous and the discrete part have
direct feedthrough
*/
y = pre(ySample);
end ZeroOrderHold;