Class UnitModel

Simulatable "default" process model.

This is a model that can be either dynamic or static, have one or multiple inputs and can be either linear in inputs or have inputs nonlinearity described by a second-order polynominal. Dynamics can be either 1. order time-constant, time-delay or both. The model also supports "additive" signals added to its output (intended for modeling disturbances).

The model is designed to lend itself well to identification from industrial time-series datasets, and is supported by the accompanying identification method UnitIdentifier.

This model is also intended to be co-simulated with PidModel by PlantSimulator to study process control feedback loops.

It is assumed that most unit processes in industrial process control systems can be described sufficiently by this model, and thus that larger plants can be modeled by connecting unit models based on this model structure.

It would be possible to extend this model to also describe second-order dynamics along the same principles by the introduction of one additional parameter in future work.

See also: UnitParameters
Inheritance
object
ModelBaseClass
UnitModel
Implements
Inherited Members
Namespace: TimeSeriesAnalysis.Dynamic
Assembly: TimeSeriesAnalysis.dll
Syntax
public class UnitModel : ModelBaseClass, ISimulatableModel

Constructors

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UnitModel()

Empty constructor

Declaration
public UnitModel()
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UnitModel(UnitParameters, string)

Constructor

Declaration
[JsonConstructor]
public UnitModel(UnitParameters modelParameters, string ID = "not_named")
Parameters
Type Name Description
UnitParameters modelParameters

model parameter object
string ID

a unique string that identifies this model in larger process models
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UnitModel(UnitParameters, UnitDataSet, string)

Initalizer of model that for the given dataSet also creates the resulting y_sim.

Declaration
public UnitModel(UnitParameters modelParameters, UnitDataSet dataSet, string ID = "not_named")
Parameters
Type Name Description
UnitParameters modelParameters
UnitDataSet dataSet
string ID

a unique string that identifies this model in larger process models

Fields

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modelParameters

The parameters of the UnitModel.

Declaration
public UnitParameters modelParameters
Field Value
Type Description
UnitParameters

Methods

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Clone(string)

Create a deep copy of itself

Declaration
public ISimulatableModel Clone(string IDexternal = null)
Parameters
Type Name Description
string IDexternal
Returns
Type Description
ISimulatableModel

deep copy
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GetFittedDataSet()

Returns a copy of the dataset against which the model was fitted.

Declaration
public UnitDataSet GetFittedDataSet()
Returns
Type Description
UnitDataSet
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GetLengthOfInputVector()

Returns the number of external inputs U of the model. Note that this model may have a disturbance signal added to the output in addition to the other signals.

Declaration
public override int GetLengthOfInputVector()
Returns
Type Description
int
Overrides
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GetModelParameters()

Get the object of model parameters contained in the model.

Declaration
public UnitParameters GetModelParameters()
Returns
Type Description
UnitParameters

Model parameter object
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GetOutputSignalType()

Get the type of output signal.

Declaration
public override SignalType GetOutputSignalType()
Returns
Type Description
SignalType
Overrides
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GetSteadyStateInput(double, int, double[])

Calcuate the steady-state input if the output and all-but-one input are known.

Declaration
public double? GetSteadyStateInput(double x0, int inputIdx = 0, double[] givenInputs = null)
Parameters
Type Name Description
double x0

If no additive inputs y=x, otherwise subtract additive inputs from y to get x
int inputIdx
double[] givenInputs
Returns
Type Description
double?
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GetSteadyStateOutput(double[], double)

Get the steady state output y for a given input (including additive terms).

Declaration
public double? GetSteadyStateOutput(double[] u, double badDataID = -9999)
Parameters
Type Name Description
double[] u

vector of input values
double badDataID
Returns
Type Description
double?
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InitSim(UnitParameters)

Initalize the process model with a sampling time.

Declaration
public void InitSim(UnitParameters modelParameters)
Parameters
Type Name Description
UnitParameters modelParameters

model parameters object
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IsModelSimulatable(out string)

Answers if the model can be simulated with the inputs provided.

Declaration
public bool IsModelSimulatable(out string explainStr)
Parameters
Type Name Description
string explainStr

a string that explains why the model cannot be simulated if that is the case
Returns
Type Description
bool
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IsModelStatic()

Is the model static or dynamic?

Declaration
public bool IsModelStatic()
Returns
Type Description
bool

Returns true if the model is static(no time constant or time delay terms),otherwise false.
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Iterate(double[], double, double)

Iterates the process model state one time step, based on the inputs given.

Declaration
public double[] Iterate(double[] inputs, double timeBase_s, double badValueIndicator = -9999)
Parameters
Type Name Description
double[] inputs

vector of inputs U. Optionally the output disturbance D can be added as the last value.
double timeBase_s

the time in seconds between samples
double badValueIndicator

value in U that is to be treated as NaN
Returns
Type Description
double[]

the updated process model state (x) - the output without any output noise or disturbance. NaN is returned if model was not able to be identfied, or if no good U values have been given yet. If some data points in U inputs are NaN or equal to badValueIndicator, the last good value is returned
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RemoveAdditiveInputs()

Removes the addtive inputs.

Declaration
public void RemoveAdditiveInputs()
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SetFittedDataSet(UnitDataSet)

Store the fitted dataset.

Declaration
public void SetFittedDataSet(UnitDataSet dataset)
Parameters
Type Name Description
UnitDataSet dataset
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SetModelParameters(UnitParameters)

Update the parameter object of the model.

Declaration
public void SetModelParameters(UnitParameters parameters)
Parameters
Type Name Description
UnitParameters parameters
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ToString()

Create a nice human-readable summary of all the important data contained in the model object. This is especially useful for unit-testing and development.

Declaration
public override string ToString()
Returns
Type Description
string
Overrides
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WarmStart(double[], double)

Warm-starting.

Declaration
public void WarmStart(double[] inputs = null, double output = 0)
Parameters
Type Name Description
double[] inputs

not used, leave as null
double output

not used, leave as null

Implements