[simscape] how can I write a difference between output and input?

Hello all,

I've modelize a thermal component. my system put a heat flow Q at the node A. my component has to consume a part of this heat flow (Qcons) and i need to put out the rest of the heat flow at a node B.

the equation i want to put is B.Q == A.Q - Qcons

but i have an error :"Unexpected function or variable 'B'.

i have this in my variable: Q = { 0, 'J/s' };

and this in the fonction setup: through ( Q, A.Q, B.Q );

What can I do?

Thanks

[Babak]

Please post all your code. The error says that you have not defined B before using it. So MATLAB doesn't recognize it!

[leclercq]

thanks for your response

here is my code:

component Consomateur
% Consomateur
% Ce composant symbolise un consomateur de chaleur.

    nodes
      M = foundation.thermal.thermal; % :top
      U = foundation.hydraulic.hydraulic; % :top
      N = foundation.thermal.thermal; % :bottom
      V = foundation.hydraulic.hydraulic; % :bottom
    end

    parameters
      Cp = { 4180, 'J/(kg*K)' };   % Cp eau
      rho = { 1000, 'kg/m^3' };   % rho de l'eau
      Qcons = { 1000, 'J/s' };     % Puissance consommée
      resistance = { 5000 'Pa/(m^3/s)' }; % resistance lineique consomateur
      Tini = { 343.15, 'K' }; % Temperature initiale
      pini = { 500000, 'Pa' }; % p initiale
    end

    variables
      Q = { 0, 'J/s' };
      q = { 0, 'm^3/s' };
      p = { 0, 'Pa' };
      T = { 0, 'K' };
    end

    function setup
      through ( Q, M.Q, N.Q );
      through ( q, U.q, V.q );
      across ( p, U.p, V.p );
      across ( T, M.T, N.T);
      N.T = Tini;
      U.p = pini;
    end

    equations
      N.Q == M.Q - Qcons;
      M.Q == q * rho * Cp * T;
      p == resistance * q;
    end

end

A and B of my example are transformed into N and M.

On my opinion, N.Q and M.Q are defined with through ( Q, M.Q, N.Q ) but i'me maybe wrong.

Answer 1

[Babak]

 M = foundation.thermal.thermal;

M is defined as an element of a structure. The structure names are fixed. I don't know if your M is also by itself a structure or not. But if it is then it might have its subelements like M.a and M.b

In your code we don't see how the foundation structure is fully defined. If it has an element like foundation.thermal.thermal.Q then M.Q would be meaningful, but if foundation.thermal.thermal.Q is not defined then M.Q is not defined either.

Now, you cannot change Q before calling M.Q. If structure M has an element named Q, it is a fixed name and you cannot change Q to

 Q = { 0, 'J/s' };

or this Q doesn't have anything to do with the Q in M.Q