Version_3_0

Description

Version 3.0 is not backward compatible to previous versions.A conversion script is provided to transform models and librariesof previous versions to the new version. Therefore, conversionshould be automatic.

The following changes are present for the whole library:

• In the Modelica language version 3.0, several restrictions have been introduced to allow better checking, e.g., models on all levels must be balanced (number of equations = number of unknown variables - unknown variables that have to be defined when using the component). A few models of the Modelica Standard Library did not fulfill these new restrictions and had either to be moved to library ObsoleteModelica3 (e.g., Blocks.Math.TwoInputs) or had to be differently implemented (e.g., Media.Interfaces.PartialMedium.BaseProperties). The Modelica Standard Library version 3.0 fulfills all the restrictions of the Modelica Language version 3.0.
   
• The graphical annotations describing the layout of icon and diagram layer are changed from Modelica language version 1 to Modelica language version 3. This gives several significant improvements:
  Especially, the coordinate systems of icon and diagram layers are no longer coupled and therefore the size of the icon layer can be changed independently of the size of the diagram layer. Also it can be defined that the aspect ratio of a component icon is kept when changing its size in a model. This flag is set so that all icons of the Modelica Standard Library keep its aspect ratios. This is slightly non-backward compatible: If the aspect ratio was not kept when using a component from the Modelica Standard Library, it is now resized so that the aspect ratio is maintained.
   
• All non-standard annotations removed by:
  (1) Removing the annotation since without effect (e.g., "__Dymola_experimentSetupOutput", "Window", "Terminal" removed).
  (2) Renaming the annotation to a standard name (e.g., "Hide" renamed to "HideResult").
  (3) Renaming the annotation to a vendor specific name (e.g., "checkBox" renamed to "__Dymola_checkBox").
   
• All emulated enumerations (defined via packages and constants) have been replaced by "real" enumerations. User models are automatically correctly converted, provided the user models used the package constants previously. Existing models that use directly literal values for enumerations, might give in some cases wrong results (if the first constant of the emulated enumeration had value zero, whereas the first value of an enumeration is one).
   
• The operator "cardinality" will be removed in one of the next versions of the Modelica language, since it is a reflective operator and its usage significantly reduces the possibilities of advanced model checks (e.g., to guarantee that a model is "balanced", i.e., the number of equations and unknowns is identical, for all valid usages of the component). As a preparation for this change, all models that contain the "cardinality(..)" operator are rewritten: If possible the operator is removed. If this is not possible, it is only used in asserts to check that, e.g., a connector is connected at least once or is connected exactly once. In the next Modelica language version new language elements will be introduced to specify such a property check without the cardinality operator. Once these language elements are available, the cardinality operator will be removed completely from the Modelica Standard Library.
  The changes with respect to the cardinality(..) operator are usually not backward compatible. This is the reason for the changes of the Rotational and Translational library (see below).
   
• The design of the Rotational and Translational libraries have been changed (especially to remove the cardinality(..) operator, see above):
  • Components have a useSupport flag to enable or disable a support flange. If the support flange is enabled, it must be connected. If it is disabled, it must not be connected and the component is then internally grounded. The grounding is visualized in the icon.
  • The relative angle/distance and the relative speed of all force/torque elements (that need the relative speed) are by default defined with "StateSelect.prefer", i.e., to use these variables as preferred states. This improves the numerics if the absolute angle or the absolute distance are continuously increasing during operation (e.g., driving shaft of the wheels of a car). The effect is that relative angles/distances and speeds are used as states and the size of these variables is limited. Previously, the default was to use the absolute angle/distance and absolute speed of every inertia/mass which has the disadvantage that the absolute angle and or distance are state variables that grow in size continuously.
    A significant advantage is also, that default initialization is usually better, because a default value of zero for a relative angle/distance is usually what the user would like to have. Previously, say, the load was initialized to a non-zero angle and then the elastically coupled motor inertia had to be explicitly also initialized with this value. This is now, no longer needed. Since the default nominal value of 1 is usually too large for a relative quantity, the nominal values of the relative angle/distance was changed to 1e-4.
  • The two libraries have been restructured in sublibraries to cope with the growing number of components.
  • Finally, the Translational library has been made as similar as possible to the Rotational library by, e.g., adding missing components.
     
• The initialization of the MultiBody, Rotational and Translational libraries have been significantly simplified by removing the "initType" parameters and only using start/fixed values. This design assumes that a tool has special support for start/fixed values in the parameter menu.
   
• Nearly all parameters defined in the Modelica Standard Library had been defined with a default equation, e.g.,

     parameter Modelica.SIunits.Resistance R=1; 

  Physical parameters, such as a resistance, mass, gear ratio, do not have a meaningful default and in nearly all cases, the user of the corresponding component has to provide values for such parameters. If the user forgets this, a tool cannot provide diagnostics, since a default value is present in the library (such as 1 Ohm for the resistance). In most cases the model will simulate but will give wrong results due to wrong parameter values. To improve this situation, all physical parameter declarations in the Modelica Standard Library have been changed, so that the previous default becomes a start value. For example, the above declaration is changed to:

     parameter Modelica.SIunits.Resistance R(start=1);  

  This is a backward compatible change and completely equivalent from the perspective of the Modelica language. It is, however, advised that tools will print a warning or optionally an error message, if the start value of a parameter is defined, but no value for the parameter is given via a modification. Furthermore, it is expected, that the input field of a parameter menu is empty, if no default equation is defined, but only a start value. This shows clearly to the modeler that a value has to be provided.

The following new components have been addedto existing libraries (note, the names in parenthesesare the new sublibrary names that are introduced in version 3.0):

The following existing componentshave been changed in anon-backward compatible way(the conversion script transforms models and librariesof previous versions to the new version. Therefore, conversionshould be automatic):

The following existing componentshave been improved in abackward compatible way:

The following critical errors have been fixed (i.e., errorsthat can lead to wrong simulation results):

The following uncritical errors have been fixed (i.e., errorsthat do not lead to wrong simulation results, but, e.g.,units are wrong or errors in documentation):