Propagate parameters via expandable connector?

[modelica-trac-importer]

Reported by ahaumer on 20 Nov 2015 18:29 UTC
I wonder whether it could be possible to propagate parameters via the bus (expandable connector); simple rule: one participant may set the parameter, all participants can get it. Would be a smart feature.

expandable connector Bus
  parameter Real p;
end Bus;

model A
  parameter Real p;
  Bus bus(p=p);
end A;

model B
  parameter Real p=bus.p;
  Bus bus;
end B;

model C
  A a(p=1);
  B b;
equation 
  connect(a.bus, b.bus);
end C;

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Migrated-From: https://trac.modelica.org/Modelica/ticket/1841

[modelica-trac-importer]

Comment by filip.jorissen on 26 Aug 2016 07:35 UTC
I'd like to also ask for this feature.

Right now it is possible to pass parameters through a bus by using fixed=false:

expandable connector Bus
  Real p;
end Bus;

model A
  parameter Real p;
  Bus bus;
equation
  bus.p=p;
end A;

model B
  parameter Real p(fixed=false);
  Bus bus;
initial equation
  p=bus.p
end B;

model C
  A a;
  B b;
equation 
  connect(a.bus, b.bus);
end C;

this however implies that a parameter value is only known at initialisation, which removes the possibility for simplifying code during translation for equations that depend on this parameter (e.g. using Evaluate=true in if/then/else statements). This is causing problems in the IDEAS library since we are forced to put certain equations in a different place than preferred, to be able to evaluate them efficiently.

The solution proposed by ahaumer seems good to me. I think this can be backwards compatible since it's a less strict implementation than what now exists.

[modelica-trac-importer]

Comment by filip.jorissen on 26 Aug 2016 07:39 UTC
The relevant IDEAS ticket for the concrete problem we are facing:
open-ideas/IDEAS#552

[modelica-trac-importer]

Comment by hansolsson on 6 Sep 2016 12:37 UTC
Modelica specification tickets.

[modelica-trac-importer]

Comment by hansolsson on 6 Sep 2016 12:48 UTC
Duplicate of #111 - which also includes discussion about e.g. using overconstrained connectors for this.