CreateSystemModel

CreateSystemModel[sys]

creates a Modelica SystemModel from the systems model sys.

CreateSystemModel[eqns,t]

creates a model for the system equations eqns with independent variable t.

CreateSystemModel[,tspec]

creates a model with type specification tspec for variables and parameters.

CreateSystemModel[,spec]

creates a model with spec for parameter values, initial values and model relations.

Details

  • CreateSystemModel returns SystemModel[].
  • CreateSystemModel["NewModel",] gives the created model the name "NewModel".
  • CreateSystemModel["PackageA.NewModel"] inserts "NewModel" into "PackageA".
  • Possible systems models sys include TransferFunctionModel and StateSpaceModel. »
  • Possible equations eqns include ordinary differential equations (ODE), differential algebraic equations (DAE), initial value equations and event specifications given by WhenEvent. »
  • Parameters in eqns and sys are taken to be variables that do not explicitly depend on t.
  • Type specifications tspecs for variables and parameters {tspec1,}, where each tspeci has the form:
  • paritypeiparameter type typei
    varitypeivariable type typei
  • The types typei can be basic Reals, Integers and Booleans, or any Modelica type including units. »
  • SystemModels["Modelica.SIunits.*","type"] can be used to find built-in standard units.
  • Modelica models are typically built by combining many models into a larger system. The interaction between these models is described by the Modelica concept connector. »
  • A connector consists of effort and flow variables. When connecting multiple connectors, flow variables are summed to 0, while effort variables are set equal.
  • As an example, an electrical circuit connector, commonly called a pin, consists of a voltage variable v and a current variable i.
  • Connecting pins n and p sums the flow variables, in this case currents i, to 0 and sets the efforts, in this case voltages v, equal:
  • All flow variables are positive in the direction flowing into a component.
  • Effort and flow variables for different domains include:
  • DomainEffort VariablesFlow Variables
    electrical circuitsvoltagecurrent
    magnetic circuitsmagnetic potentialmagnetic flux
    translational mechanicspositionforce
    rotational mechanicsangletorque
    3D mechanicsposition vector, orientation objectcut force vector, cut torque vector
    fluid flow systemspressure, specific enthalpymass flow rate, enthalpy flow rate
    heat transfer systemstemperatureheat flow rate
    block diagramsreal, integer, Boolean-
  • Possible connectors conni for a domain are usually defined in an Interfaces package. For example, SystemModels["Modelica.Electrical.Analog.Interfaces.*","connector"] can be used to find connectors for the built-in electrical library.
  • The specification variconni can be used to specify that a variable vari refers to a connector of type conni.
  • Variables vi in a connector c can be referred to in eqns with cvi, where the "" character is input as \[UpPointer].
  • The variables defined by a connector conn can be listed with SystemModel[conn,"SystemVariables"].
  • In CreateSystemModel[,spec], spec is an Association with the following keys:
  • "ParameterValues"{p1val1,}parameter values
    "InitialValues"{v1val1,}initial values
    "ExtendsModels"{partial1,}partial models to build on
    "DiscreteVariables"{v1,v2,}variables changing only at events
    "SimulationSettings"{opt1val1,}model simulation options
  • Libraries often contain partial models called interfaces for building new component models. These interfaces usually consist of connectors and equations describing the basic relationships between them.
  • With CreateSystemModel[,"ExtendsModels"partial], the new model is combined with the existing partial SystemModel defined in Modelica. »
  • A model can extend multiple models using "ExtendsModels"{"partial1",}.
  • Partial models to build on are usually defined in an Interfaces package. For example, SystemModels["Modelica.Electrical.Analog.Interfaces.*","model"|"block"] can be used to find partial models for the built-in electrical library.
  • "InitialValues" correspond to the start property in the Modelica model.
  • Allowed options in "SimulationsSettings"->{opt1val1,} include:
  • "Method"simulation method
    "StartTime"simulation start time
    "StopTime"simulation stop time
  • Available adaptive step "Method" values include:
  • "DASSL"DASSL DAE solver
    "CVODES"CVODES ODE solver
  • Options for adaptive-step methods include:
  • "InterpolationPoints"number of interpolation points
    "Tolerance"tolerance for adaptive step size
  • Available fixed-step "Method" values include:
  • "Euler"explicit Euler's method of order 1
    "Heun"Heun's method of order 2
    "RungeKutta"explicit RungeKutta method of order 4
  • Options for fixed-step methods include:
  • "StepSize"fixed step size

Examples

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Basic Examples  (3)

Create a model based on a StateSpaceModel:

Create a model based on a TransferFunctionModel, giving it a custom name:

Build a model around an existing interface using equations:

Scope  (41)

Systems Models  (11)

Create a model of a single-input, single-output TransferFunctionModel:

Create a model of a single-input, single-output StateSpaceModel:

Multiple input, multiple output:

Create a model with parameters in a transfer-function model:

Specify parameters in a state-space model:

Define parameter values in a transfer-function model:

Give parameter values in a state-space model:

Give the types and values of parameters:

Create a model from a discrete transfer-function model:

Create a model from a discrete state-space model:

Use a descriptor system:

Create a model from an affine state-space model:

Create a model from a nonlinear state-space model:

A function is converted into an input-output block:

Differential Equations  (12)

Create a single-equation ODE system:

Specify any order equation. Reduction of higher-order derivatives is done automatically:

Define a system of multiple equations:

Define a system with an algebraic constraint, resulting in a high-index problem:

Hybrid equations can be specified using WhenEvent:

Declare a variable a that only changes at discrete times:

Simulate and plot the model of a bouncing ball on stairs:

Wolfram Language functions are automatically translated to their Modelica equivalent:

Specify a default parameter value:

Specify a start value:

Specify types for variables and parameters:

Arrays are expressed using Indexed:

Functions used in equations are translated into functions in Modelica:

Naming Models  (3)

Give a custom name to the created model:

Show the model name:

Create a model inside a package:

Show the model name:

If no name is given, a unique name is generated:

Show the generated model name:

Give the model a custom name:

Show the new model name:

Types and Connectors  (4)

Create a single output block:

Return it as a real:

Create the model:

Create a derivative block:

Define input and output connectors:

Create the model:

Create a resistor using connectors from the Electrical library:

Use the short form to refer to connectors:

Initial and Parameter Values  (6)

Give a start value for a variable:

Give a start value for a parameter:

With both a start value and an initial equation, the initial equation has higher priority:

Use a parameter as an initial value:

Give a parameter value:

Give a parameter depending on another parameter:

Build on Partial Models  (2)

Create a block that adds 1 to the input:

Create the block, extending a SISO block interface:

Use the short form to refer to an existing interface:

Simulation Settings  (3)

Give a start and a stop time to a model:

Simulate the model and plot:

Pick a RungeKutta method for simulation:

Show the model simulation settings:

Set real-time synchronization for a model:

Show the model simulation settings:

Applications  (5)

Define the equations for a bouncing ball:

Create the model:

Simulate with a restitution of 95%:

Plot the height over time:

Create a model of the LotkaVolterra equations, modeling a predator-prey relationship:

Define initial values for the two states:

Define parameter values:

Create the model:

Show the levels of predators and prey over time:

A higher prey growth parameter speeds up the cycles in the system:

Model two connected tanks with a leak in the second tank:

Set up the equations, which include initial equations and parameters:

Create the model, using a given set of parameter values as the default:

Simulate:

Both tanks drain over time, because the second tank is leaking:

Create a mechanical translational damper with damping in only one direction:

Define the damping constant:

Create the damper using a partial interface from the Translational Mechanics library:

Compare with a bidirectional damper:

Create a digital lowpass filter:

Convert the filter into a transfer function:

Create a model of the filter:

Create a signal generating source:

Connect the signal source to the filter:

Simulate and plot the signal output and the filtered signal:

Properties & Relations  (3)

SystemModel properties can be used to extract information from a model:

Create a new model with equations from an existing model, changing a parameter:

Simulate and compare the two models:

Special characters are translated into their long form:

Subscript is translated into _:

Possible Issues  (2)

Models are not saved unless explicitly saved:

After quitting the Wolfram Language kernel, the model is gone:

CreateSystemModel supports a subset of Wolfram Language functions:

Introduced in 2018
 (11.3)
 |
Updated in 2020
 (12.1)