Modelica.UsersGuide

Package Modelica is a standardized and pre-defined package that is developed together with the Modelica language from the Modelica Association, see https://www.Modelica.org. It is also called Modelica Standard Library. It provides constants, types, connectors, partial models and model components in various disciplines.

This is a short User's Guide for the overall library. Some of the main sublibraries have their own User's Guides that can be accessed by the following links:

Package Content

Name	Description
Overview	Overview of Modelica Library
Connectors	Connectors
Conventions	Conventions
ParameterDefaults	Parameter defaults
ModelicaLicense2	Modelica License 2
ReleaseNotes	Release notes
Contact	Contact

Modelica.UsersGuide.Overview

The Modelica Standard Library consists of the following main sub-libraries:

Library Components	Description
	Analog Analog electric and electronic components, such as resistor, capacitor, transformers, diodes, transistors, transmission lines, switches, sources, sensors.
	Digital Digital electrical components based on the VHDL standard, like basic logic blocks with 9-value logic, delays, gates, sources, converters between 2-, 3-, 4-, and 9-valued logic.
	Machines Electrical asynchronous-, synchronous-, and DC-machines (motors and generators) as well as 3-phase transformers.
	FluxTubes Based on magnetic flux tubes concepts. Especially to model electro-magnetic actuators. Nonlinear shape, force, leakage, and material models. Material data for steel, electric sheet, pure iron, Cobalt iron, Nickel iron, NdFeB, Sm2Co17, and more.
	Translational 1-dim. mechanical, translational systems, e.g., sliding mass, mass with stops, spring, damper.
	Rotational 1-dim. mechanical, rotational systems, e.g., inertias, gears, planetary gears, convenient definition of speed/torque dependent friction (clutches, brakes, bearings, ..)
	MultiBody 3-dim. mechanical systems consisting of joints, bodies, force and sensor elements. Joints can be driven by drive trains defined by 1-dim. mechanical system library (Rotational). Every component has a default animation. Components can be arbitrarily connected together.
	Fluid 1-dim. thermo-fluid flow in networks of vessels, pipes, fluid machines, valves and fittings. All media from the Modelica.Media library can be used (so incompressible or compressible, single or multiple substance, one or two phase medium).
	Media Large media library providing models and functions to compute media properties, such as h = h(p,T), d = d(p,T), for the following media: 1240 gases and mixtures between these gases. incompressible, table based liquids (h = h(T), etc.). compressible liquids dry and moist air high precision model for water (IF97).
	FluidHeatFlow, HeatTransfer Simple thermo-fluid pipe flow, especially to model cooling of machines with air or water (pipes, pumps, valves, ambient, sensors, sources) and lumped heat transfer with heat capacitors, thermal conductors, convection, body radiation, sources and sensors.
	Blocks Input/output blocks to model block diagrams and logical networks, e.g., integrator, PI, PID, transfer function, linear state space system, sampler, unit delay, discrete transfer function, and/or blocks, timer, hysteresis, nonlinear and routing blocks, sources, tables.
	StateGraph Hierarchical state machines with a similar modeling power as Statecharts. Modelica is used as synchronous action language, i.e., deterministic behavior is guaranteed
A = [1,2,3; 3,4,5; 2,1,4]; b = {10,22,12}; x = Matrices.solve(A,b); Matrices.eigenValues(A);	Math, Utilities Functions operating on vectors and matrices, such as for solving linear systems, eigen and singular values etc., and functions operating on strings, streams, files, e.g., to copy and remove a file or sort a vector of strings.

Modelica.UsersGuide.Connectors

The Modelica standard library defines the most important elementary connectors in various domains. If any possible, a user should utilize these connectors in order that components from the Modelica Standard Library and from other libraries can be combined without problems. The following elementary connectors are defined (the meaning of potential, flow, and stream variables is explained in section "Connector Equations" below):

domain	potential variables	flow variables	stream variables	connector definition	icons
electrical analog	electrical potential	electrical current		Modelica.Electrical.Analog.Interfaces Pin, PositivePin, NegativePin
electrical multi-phase	vector of electrical pins			Modelica.Electrical.MultiPhase.Interfaces Plug, PositivePlug, NegativePlug
electrical space phasor	2 electrical potentials	2 electrical currents		Modelica.Electrical.Machines.Interfaces SpacePhasor
quasi stationaray single phase	complex electrical potential	complex electrical current		Modelica.Electrical.QuasiStationary.SinglePhase.Interfaces Pin, PositivePin, NegativePin
quasi stationary multi-phase	vector of quasi stationary single phase pins			Modelica.Electrical.QuasiStationary.MultiPhase.Interfaces Plug, PositivePlug, NegativePlug
electrical digital	Integer (1..9)			Modelica.Electrical.Digital.Interfaces DigitalSignal, DigitalInput, DigitalOutput
magnetic flux tubes	magnetic potential	magnetic flux		Modelica.Magnetic.FluxTubes.Interfaces MagneticPort, PositiveMagneticPort, NegativeMagneticPort
magnetic fundamental wave	complex magnetic potential	complex magnetic flux		Modelica.Magnetic.FundamentalWave.Interfaces MagneticPort, PositiveMagneticPort, NegativeMagneticPort
translational	distance	cut-force		Modelica.Mechanics.Translational.Interfaces Flange_a, Flange_b
rotational	angle	cut-torque		Modelica.Mechanics.Rotational.Interfaces Flange_a, Flange_b
3-dim. mechanics	position vector orientation object	cut-force vector cut-torque vector		Modelica.Mechanics.MultiBody.Interfaces Frame, Frame_a, Frame_b, Frame_resolve
simple fluid flow	pressure specific enthalpy	mass flow rate enthalpy flow rate		Modelica.Thermal.FluidHeatFlow.Interfaces FlowPort, FlowPort_a, FlowPort_b
thermo fluid flow	pressure	mass flow rate	specific enthalpy mass fractions	Modelica.Fluid.Interfaces FluidPort, FluidPort_a, FluidPort_b
heat transfer	temperature	heat flow rate		Modelica.Thermal.HeatTransfer.Interfaces HeatPort, HeatPort_a, HeatPort_b
blocks	Real variable Integer variable Boolean variable			Modelica.Blocks.Interfaces RealSignal, RealInput, RealOutput IntegerSignal, IntegerInput, IntegerOutput BooleanSignal, BooleanInput, BooleanOutput
complex blocks	Complex variable			Modelica.ComplexBlocks.Interfaces ComplexSignal, ComplexInput, ComplexOutput
state machine	Boolean variables (occupied, set, available, reset)			Modelica.StateGraph.Interfaces Step_in, Step_out, Transition_in, Transition_out
Connectors from other libraries
hydraulic	pressure	volume flow rate		HyLibLight.Interfaces Port_A, Port_b
pneumatic	pressure	mass flow rate		PneuLibLight.Interfaces Port_1, Port_2

In all domains, usually 2 connectors are defined. The variable declarations are identical, only the icons are different in order that it is easy to distinguish connectors of the same domain that are attached at the same component.

Hierarchical Connectors

Modelica supports also hierarchical connectors, in a similar way as hierarchical models. As a result, it is, e.g., possible, to collect elementary connectors together. For example, an electrical plug consisting of two electrical pins can be defined as:

connector Plug
   import Modelica.Electrical.Analog.Interfaces;
   Interfaces.PositivePin phase;
   Interfaces.NegativePin ground;
end Plug;

With one connect(..) equation, either two plugs can be connected (and therefore implicitly also the phase and ground pins) or a Pin connector can be directly connected to the phase or ground of a Plug connector, such as "connect(resistor.p, plug.phase)".

Connector Equations

The connector variables listed above have been basically determined with the following strategy:

1. State the relevant balance equations and boundary conditions of a volume for the particular physical domain.
2. Simplify the balance equations and boundary conditions of (1) by taking the limit of an infinitesimal small volume (e.g., thermal domain: temperatures are identical and heat flow rates sum up to zero).
3. Use the variables needed for the balance equations and boundary conditions of (2) in the connector and select appropriate Modelica prefixes, so that these equations are generated by the Modelica connection semantics.

The Modelica connection semantics is sketched at hand of an example: Three connectors c1, c2, c3 with the definition

connector Demo
  Real        p;  // potential variable
  flow   Real f;  // flow variable
  stream Real s;  // stream variable
end Demo;

are connected together with

   connect(c1,c2);
   connect(c1,c3);

then this leads to the following equations:

  // Potential variables are identical
  c1.p = c2.p;
  c1.p = c3.p;

  // The sum of the flow variables is zero
  0 = c1.f + c2.f + c3.f;

  /* The sum of the product of flow variables and upstream stream variables is zero
     (this implicit set of equations is explicitly solved when generating code;
     the "<undefined>" parts are defined in such a way that
     inStream(..) is continuous).
  */
  0 = c1.f*(if c1.f > 0 then s_mix else c1.s) +
      c2.f*(if c2.f > 0 then s_mix else c2.s) +
      c3.f*(if c3.f > 0 then s_mix else c3.s);

  inStream(c1.s) = if c1.f > 0 then s_mix else <undefined>;
  inStream(c2.s) = if c2.f > 0 then s_mix else <undefined>;
  inStream(c3.s) = if c3.f > 0 then s_mix else <undefined>;

Modelica.UsersGuide.ParameterDefaults

In this section the convention is summarized how default parameters are handled in the Modelica Standard Library (since version 3.0).

Many models in this library have parameter declarations to define constants of a model that might be changed before simulation starts. Example:

model SpringDamper
parameter Real c(final unit="N.m/rad")    = 1e5 "Spring constant";
parameter Real d(final unit="N.m.s/rad")  = 0   "Damping constant";
parameter Modelica.SIunits.Angle phi_rel0 = 0   "Unstretched spring angle";
...
end SpringDamper;

In Modelica it is possible to define a default value of a parameter in the parameter declaration. In the example above, this is performed for all parameters. Providing default values for all parameters can lead to errors that are difficult to detect, since a modeler may have forgotten to provide a meaningful value (the model simulates but gives wrong results due to wrong parameter values). In general the following basic situations are present:

1. The parameter value could be anything (e.g., a spring constant or a resistance value) and therefore the user should provide a value in all cases. A Modelica translator should warn, if no value is provided.
2. The parameter value is not changed in > 95 % of the cases (e.g., initialization or visualization parameters, or parameter phi_rel0 in the example above). In this case a default parameter value should be provided, in order that the model or function can be conveniently used by a modeler.
3. A modeler would like to quickly utilize a model, e.g.,
   • to automatically check that the model still translates and/or simulates (after some changes in the library),
   • to make a quick demo of a library by drag-and-drop of components,
   • to implement a simple test model in order to get a better understanding of the desired component.
   In all these cases, it would be not practical, if the modeler would have to provide explicit values for all parameters first.

To handle the conflicting goals of (1) and (3), the Modelica Standard Library uses two approaches to define default parameters, as demonstrated with the following example:

model SpringDamper
parameter Real c(final unit="N.m/rad"  , start=1e5) "Spring constant";
parameter Real d(final unit="N.m.s/rad", start=  0) "Damping constant";
parameter Modelica.SIunits.Angle phi_rel0 = 0       "Unstretched spring angle";
...
end SpringDamper;

SpringDamper sp1;              // warning for "c" and "d"
SpringDamper sp2(c=1e4, d=0);  // fine, no warning

Both definition forms, using a "start" value (for "c" and "d") and providing a declaration equation (for "phi_rel0"), are valid Modelica and define the value of the parameter. By convention, it is expected that Modelica translators will trigger a warning message for parameters that are not defined by a declaration equation, by a modifier equation or in an initial equation/algorithm section. A Modelica translator might have options to change this behavior, especially, that no messages are printed in such cases and/or that an error is triggered instead of a warning.

Modelica.UsersGuide.ModelicaLicense2

All files in this directory (Modelica) and in all subdirectories, especially all files that build package "Modelica" and all files in "Modelica/Resources/*" and "Modelica/help" are licensed by the Modelica Association under the Modelica License 2 (with exception of files "Modelica/Resources/C-Sources/win32_dirent.*, ModelicaMatIO.*, ModelicaStandardTables.*").

Licensor:
Modelica Association
(Ideella Föreningar 822003-8858 in Linköping)
c/o PELAB, IDA, Linköpings Universitet
S-58183 Linköping
Sweden
email: Board@Modelica.org
web: https://www.Modelica.org

Copyright notices of the files:
Copyright © 1998-2013, ABB, Austrian Institute of Technology, T. Bödrich, DLR, Dassault Systèmes AB, Fraunhofer, A. Haumer, ITI, Modelon, TU Hamburg-Harburg, Politecnico di Milano, XRG Simulation.

The Modelica License 2
Frequently Asked Questions

The Modelica License 2

Preamble. The goal of this license is that Modelica related model libraries, software, images, documents, data files etc. can be used freely in the original or a modified form, in open source and in commercial environments (as long as the license conditions below are fulfilled, in particular sections 2c) and 2d). The Original Work is provided free of charge and the use is completely at your own risk. Developers of free Modelica packages are encouraged to utilize this license for their work.

The Modelica License applies to any Original Work that contains the following licensing notice adjacent to the copyright notice(s) for this Original Work:

Licensed by the Modelica Association under the Modelica License 2

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Frequently Asked Questions

This section contains questions/answer to users and/or distributors of Modelica packages and/or documents under Modelica License 2. Note, the answers to the questions below are not a legal interpretation of the Modelica License 2. In case of a conflict, the language of the license shall prevail.

Using or Distributing a Modelica Package under the Modelica License 2

What are the main differences to the previous version of the Modelica License?

1. Modelica License 1 is unclear whether the licensed Modelica package can be distributed under a different license. Version 2 explicitly allows that “Derivative Work” can be distributed under any license of Your choice, see examples in Section 1d) as to what qualifies as Derivative Work (so, version 2 is clearer).

2. If You modify a Modelica package under Modelica License 2 (besides fixing of errors, adding vendor specific Modelica annotations, using a subset of the classes of a Modelica package, or using another representation, e.g., a binary representation), you must rename the root-level name of the package for your distribution. In version 1 you could keep the name (so, version 2 is more restrictive). The reason of this restriction is to reduce the risk that Modelica packages are available that have identical names, but different functionality.

3. Modelica License 1 states that “It is not allowed to charge a fee for the original version or a modified version of the software, besides a reasonable fee for distribution and support”. Version 2 has a similar intention for all Original Work under Modelica License 2 (to remain free of charge and open source) but states this more clearly as “No fee, neither as a copyright-license fee, nor as a selling fee for the copy as such may be charged”. Contrary to version 1, Modelica License 2 has no restrictions on fees for Derivative Work that is provided under a different license (so, version 2 is clearer and has fewer restrictions).

4. Modelica License 2 introduces several useful provisions for the licensee (articles 5, 6, 12), and for the licensor (articles 7, 12, 13, 14) that have no counter part in version 1.

5. Modelica License 2 can be applied to all type of work, including documents, images and data files, contrary to version 1 that was dedicated for software only (so, version 2 is more general).

Can I distribute a Modelica package (under Modelica License 2) as part of my commercial Modelica modeling and simulation environment?

Yes, according to Section 2c). However, you are not allowed to charge a fee for this part of your environment. Of course, you can charge for your part of the environment.

Can I distribute a Modelica package (under Modelica License 2) under a different license?

No. The license of an unmodified Modelica package cannot be changed according to Sections 2c) and 2d). This means that you cannot sell copies of it, any distribution has to be free of charge.

Can I distribute a Modelica package (under Modelica License 2) under a different license when I first encrypt the package?

No. Merely encrypting a package does not qualify for Derivative Work and therefore the encrypted package has to stay under Modelica License 2.

Can I distribute a Modelica package (under Modelica License 2) under a different license when I first add classes to the package?

No. The package itself remains unmodified, i.e., it is Original Work, and therefore the license for this part must remain under Modelica License 2. The newly added classes can be, however, under a different license.

Can I copy a class out of a Modelica package (under Modelica License 2) and include it unmodified in a Modelica package under a commercial/proprietary license?

No, according to article 2c). However, you can include model, block, function, package, record and connector classes in your Modelica package under Modelica License 2. This means that your Modelica package could be under a commercial/proprietary license, but one or more classes of it are under Modelica License 2.
Note, a “type” class (e.g., type Angle = Real(unit=”rad”)) can be copied and included unmodified under a commercial/proprietary license (for details, see the next question).

Can I copy a type class or part of a model, block, function, record, connector class, out of a Modelica package (under Modelica License 2) and include it modified or unmodified in a Modelica package under a commercial/proprietary license

Yes, according to article 2d), since this will in the end usually qualify as Derivative Work. The reasoning is the following: A type class or part of another class (e.g., an equation, a declaration, part of a class description) cannot be utilized “by its own”. In order to make this “usable”, you have to add additional code in order that the class can be utilized. This is therefore usually Derivative Work and Derivative Work can be provided under a different license. Note, this only holds, if the additional code introduced is sufficient to qualify for Derivative Work. Merely, just copying a class and changing, say, one character in the documentation of this class would be no Derivative Work and therefore the copied code would have to stay under Modelica License 2.

Can I copy a class out of a Modelica package (under Modelica License 2) and include it in modified form in a commercial/proprietary Modelica package?

Yes. If the modification can be seen as a “Derivative Work”, you can place it under your commercial/proprietary license. If the modification does not qualify as “Derivative Work” (e.g., bug fixes, vendor specific annotations), it must remain under Modelica License 2. This means that your Modelica package could be under a commercial/proprietary license, but one or more parts of it are under Modelica License 2.

Can I distribute a “save total model” under my commercial/proprietary license, even if classes under Modelica License 2 are included?

Your classes of the “save total model” can be distributed under your commercial/proprietary license, but the classes under Modelica License 2 must remain under Modelica License 2. This means you can distribute a “save total model”, but some parts might be under Modelica License 2.

Can I distribute a Modelica package (under Modelica License 2) in encrypted form?

Yes. Note, if the encryption does not allow “copying” of classes (in to unencrypted Modelica source code), you have to send the Modelica source code of this package to your customer, if he/she wishes it, according to article 6.

Can I distribute an executable under my commercial/proprietary license, if the model from which the executable is generated uses models from a Modelica package under Modelica License 2?

Yes, according to article 2d), since this is seen as Derivative Work. The reasoning is the following: An executable allows the simulation of a concrete model, whereas models from a Modelica package (without pre-processing, translation, tool run-time library) are not able to be simulated without tool support. By the processing of the tool and by its run-time libraries, significant new functionality is added (a model can be simulated whereas previously it could not be simulated) and functionality available in the package is removed (e.g., to build up a new model by dragging components of the package is no longer possible with the executable).

Is my modification to a Modelica package (under Modelica License 2) a Derivative Work?

It is not possible to give a general answer to it. To be regarded as "an original work of authorship", a derivative work must be different enough from the original or must contain a substantial amount of new material. Making minor changes or additions of little substance to a preexisting work will not qualify the work as a new version for such purposes.

Using or Distributing a Modelica Document under the Modelica License 2

This section is devoted especially for the following applications:

1. A Modelica tool extracts information out of a Modelica package and presents the result in form of a “manual” for this package in, e.g., html, doc, or pdf format.

2. The Modelica language specification is a document defining the Modelica language. It will be licensed under Modelica License 2.

3. Someone writes a book about the Modelica language and/or Modelica packages and uses information which is available in the Modelica language specification and/or the corresponding Modelica package.

Can I sell a manual that was basically derived by extracting information automatically from a Modelica package under Modelica License 2 (e.g., a “reference guide” of the Modelica Standard Library):

Yes. Extracting information from a Modelica package, and providing it in a human readable, suitable format, like html, doc or pdf format, where the content is significantly modified (e.g. tables with interface information are constructed from the declarations of the public variables) qualifies as Derivative Work and there are no restrictions to charge a fee for Derivative Work under alternative 2d).

Can I copy a text passage out of a Modelica document (under Modelica License 2) and use it unmodified in my document (e.g. the Modelica syntax description in the Modelica Specification)?

Yes. In case you distribute your document, the copied parts are still under Modelica License 2 and you are not allowed to charge a license fee for this part. You can, of course, charge a fee for the rest of your document.

Can I copy a text passage out of a Modelica document (under Modelica License 2) and use it in modified form in my document?

Yes, the creation of Derivative Works is allowed. In case the content is significantly modified this qualifies as Derivative Work and there are no restrictions to charge a fee for Derivative Work under alternative 2d).

Can I sell a printed version of a Modelica document (under Modelica License 2), e.g., the Modelica Language Specification?

No, if you are not the copyright-holder, since article 2c) does not allow a selling fee for a (in this case physical) copy. However, mere printing and shipping costs may be recovered.

Modelica.UsersGuide.Contact

The Modelica Standard Library (this Modelica package) is developed by many people from different organizations (see list below). It is licensed under the Modelica License 2 by:

 

Modelica Association

(Ideella Föreningar 822003-8858 in Linköping)

c/o PELAB, IDA, Linköpings Universitet

S-58183 Linköping

Sweden

email: Board@Modelica.org

web: https://www.Modelica.org

  

The development of this Modelica package, starting with version 3.2.1, is organized by:

Anton Haumer

Technical Consulting & Electrical Engineering

A-3423 St.Andrae-Woerdern, Hadersfelderweg 21

Austria

email: A.Haumer@Haumer.at

  

The development of this Modelica package up to and including version 3.2.1 was organized by:

Martin Otter

German Aerospace Center (DLR)

Robotics and Mechatronics Center (RMC)

Institute of System Dynamics and Control (SR)

Postfach 1116

D-82230 Wessling

Germany

email: Martin.Otter@dlr.de

Since end of 2007, the development of the sublibraries of package Modelica is organized by personal and/or organizational library officers assigned by the Modelica Association. They are responsible for the maintenance and for the further organization of the development. Other persons may also contribute, but the final decision for library improvements and/or changes is performed by the responsible library officer(s). In order that a new sublibrary or a new version of a sublibrary is ready to be released, the responsible library officers report the changes to the members of the Modelica Association and the library is made available for beta testing to interested parties before a final decision. A new release of a sublibrary is formally decided by voting of the Modelica Association members.

The following library officers are currently assigned:

The following people have directly contributed to the implementation of the Modelica package (many more people have contributed to the design):