Buildings.Controls.OBC.CDL.Discrete

Package with discrete input/output blocks with fixed sample period

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 parameter startTime.
The output signals are computed from the sampled input signals.

Extends from Modelica.Icons.Package (Icon for standard packages).

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
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

Buildings.Controls.OBC.CDL.Discrete.DayType

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

Buildings.Controls.OBC.CDL.Discrete.FirstOrderHold

Information

Block that outputs the extrapolation through the values of the last two sampled input signals.

Parameters

Type	Name	Default	Description
Time	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 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

Buildings.Controls.OBC.CDL.Discrete.Sampler

Information

Block that outputs the input signal, sampled at a sampling rate defined via parameter samplePeriod.

Parameters

Type	Name	Default	Description
Time	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 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

Buildings.Controls.OBC.CDL.Discrete.TriggeredMax

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.TriggeredSampler

Triggered sampling of continuous signals

Buildings.Controls.OBC.CDL.Discrete.TriggeredSampler

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

Buildings.Controls.OBC.CDL.Discrete.UnitDelay

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		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

Buildings.Controls.OBC.CDL.Discrete.ZeroOrderHold

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		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;