In Modelica, how to call a variable in a different block without wiring the 2 blocks? - modelica

Question

We are modeling various industrial component blocks, with each having CAPEX, labour cost, maintenance cost, total OPEX, etc. We would like to have 1 block, in the best case not wired to the other blocks, to account for the total OPEX, total CAPEX, total labour costs, etc. induced by the blocks present in a model : the number of blocks is not fixed. Is there a way of not connecting the blocks with a wire ?
In case there is no way, we found the solution of using the RealOutput y vector, as defined in Modelica.Blocks.Interfaces.MO : nout is defined as the number of actual variables we would like to add up (e.g. if CAPEX, OPEX and maintenance are of interest, then nout = n = 3). However, we struggle for 2 points :
How can we pass a matrix through this RealOutput ? This would be useful for instance when the CAPEX has 3 values : estimated, optimistic and pessimistic.
How can we take up this y in only 1 block ? For now we managed to use n Modelica.Blocks.Math.MultiSum blocks to take up each variable separately, but is there a way of adding them up respectively, but in the same block ?
Thank you already for your much appreciated help and answers !

Answer 1

I think you should be able to do this with the inner/outer construct and a custom connector with a flow variable for, e.g., your capex, as demonstrated in section 5.8 of Fritzson's book "Principles of Object-Oriented Modeling and Simulation with Modelica 3.3".
I could have sworn there is already an example around that sums masses of components to a total, but I could not find it anywhere...
package SO_69945088
model System
FinancialAggregator fin_totals() "Collects financial info";
inner CapexConn common_connection "autoshared connection";
Component comp1(capex_info.amount={0, 3, 5});
Component comp2(capex_info.amount={1, 10, 12});
Component comp3(capex_info.amount={5, 6, 7});
equation
//Conveniently collect financial info in fin_totals
connect(common_connection, fin_totals.agg_conn);
end System;
connector CapexConn
// the amount being a "flow" variables means all contributions
// sum at a connection point.
flow Real[3] amount;
// every "flow" variable should have a non-flow variable,
// at least for "physical" connections. Let's add a dummy:
Real [3] period;
end CapexConn;
model CapexEmitter
CapexConn conn;
Real[3] amount = fill(0, 3);
Real[3] period;
equation
// Here you could also have more logic, like computing emitted capex
// depending on the period
conn.amount = -amount; //negative because of sign of flow direction in connectors
conn.period = period;
end CapexEmitter;
model Component "Industrial component block with capex tracking"
// (you would extend your other components from this to use it)
outer CapexConn common_connection; // make outside connection visible
CapexEmitter capex_info;
equation
// all Component instances automatically connect, without manual wiring
connect(capex_info.conn, common_connection);
end Component;
model FinancialAggregator
CapexConn agg_conn;
Real[3] capexsum;
Real period[3] = {1,1,1};
equation
capexsum = agg_conn.amount;
period = agg_conn.period;
end FinancialAggregator;
end SO_69945088;
Simulating System gives a fin_totals.capexsum of {6, 19, 24} (optimistic, estimated, pessimistic).
This should give you a starting point showing the principles.