Demonstration of units on signals and use of VehicleInterfaces

[dietmarw]

Just very simple concepts. Most likely not worth merging.

[kvid]

@dietmarw - How would you recommend combining an interface like Modelica.Blocks.Interfaces.RealOutput with a type like Modelica.Units.SI.AbsolutePressure to specify quantity, unit, displayUnit, min, nominal, etc. by just referring to the type identifier Modelica.Units.SI.AbsolutePressure without copying all parameters into the instantiation like this:

Modelica.Blocks.Interfaces.RealOutput y(quantity="Pressure", unit="Pa", displayUnit="bar", min=0.0, nominal=1e5);

Copying the other way is not much better:

output Modelica.Units.SI.AbsolutePressure y annotation(...);

Then all the graphical annotations from the interface Modelica.Blocks.Interfaces.RealOutput must be copied.
I'm seeking a way to combine the interface identifier with the type identifier. I would expect something like this should work, but it doesn't seem to compile (Syntax Error):

Modelica.Blocks.Interfaces.RealOutput y(type=Modelica.Units.SI.AbsolutePressure);

I use many combinations of interfaces and types, and want to combine existing declarations in an efficient way to avoid code duplication.

[dietmarw]

@kvid Ideally having to set the unit of an output should not be necessary and the tool should be able to deduce the type based on the (typed) variables and parameters involved in calculating the output's signal. Now that is the ideal solution which of course also needs support from the tool. OMEdit will check for unit conflicts (when you press "check model") but will (as of now) not go as far as propagate units so that for example plots show the units. For these cases you need to specify the unit manually but you do not really need to go as far as also specifying quantity and nominal.

So for now, the recommended way is

Modelica.Blocks.Interfaces.RealOutput y(unit="Pa", displayUnit="bar");

See also https://github.com/modelica/ModelicaStandardLibrary/pull/2197/files as an example how the MSL did it.