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 |
|---|---|
 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.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 |
|---|---|---|---|
| Real | samplePeriod | 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 Real samplePeriod(
final quantity="Time",
final unit="s",
min=1E-3)
"Sample period of component";
Interfaces.RealInput u
"Continuous input signal";
Interfaces.RealOutput y
"Continuous output signal";
protected
parameter Real t0(
final quantity="Time",
final unit="s",
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";
Real tSample(
final quantity="Time",
final unit="s")
"Time of sample";
Real uSample
"Value of sample";
Real pre_uSample
"Value of previous sample";
Real c
"Slope";
initial equation
t0=Buildings.Utilities.Math.Functions.round(
x=integer(time/samplePeriod)*samplePeriod,
n=6);
pre(tSample)=t0;
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;
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 |
|---|---|---|---|
| Real | samplePeriod | 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 Real samplePeriod(
final quantity="Time",
final unit="s",
min=1E-3)
"Sample period of component";
Interfaces.RealInput u
"Continuous input signal";
Interfaces.RealOutput y
"Continuous output signal";
protected
parameter Real t0(
final quantity="Time",
final unit="s",
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=Buildings.Utilities.Math.Functions.round(
x=integer(time/samplePeriod)*samplePeriod,
n=6);
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 |
| input BooleanInput | trigger | Connector for trigger |
| output RealOutput | y | Connector with a Real output signal |
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.BooleanInput trigger
"Connector for trigger";
Interfaces.RealOutput y
"Connector with a Real output signal";
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 | 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
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";
discrete Real ySample[n](
start=zeros(n),
each fixed=true)
"Vector of samples to be averaged";
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 |
| input BooleanInput | trigger | Signal that triggers the sampler |
| output RealOutput | y | Connector with a Real output signal |
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.BooleanInput trigger
"Signal that triggers the sampler";
Interfaces.RealOutput y
"Connector with a Real output signal";
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 |
|---|---|---|---|
| Real | samplePeriod | 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 Real samplePeriod(
final quantity="Time",
final unit="s",
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 Real t0(
final quantity="Time",
final unit="s",
fixed=false)
"First sample time instant";
output Boolean sampleTrigger
"True, if sample time instant";
initial equation
t0=Buildings.Utilities.Math.Functions.round(
x=integer(time/samplePeriod)*samplePeriod,
n=6);
y=y_start;
equation
// Declarations that are used for all discrete blocks
sampleTrigger=sample(
t0,
samplePeriod);
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 |
|---|---|---|---|
| Real | samplePeriod | 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 Real samplePeriod(
final quantity="Time",
final unit="s",
min=1E-3)
"Sample period of component";
Interfaces.RealInput u
"Continuous input signal";
Interfaces.RealOutput y
"Continuous output signal";
protected
parameter Real t0(
final quantity="Time",
final unit="s",
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=Buildings.Utilities.Math.Functions.round(
x=integer(time/samplePeriod)*samplePeriod,
n=6);
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;