Modeling a resistor using custom Simscape block and lookup tables using data from an excel sheet.

Hey, I am trying to model a resistor but whenever I try to read the specific columns from the excel sheet, Matlab gives an error 'Invalid use of non-parametric value 'Data'. All entities referenced in member declarations must be parameters'. I have specified the excel file in the same folder as the .ssc file. My execution steps are correct, there is only something wrong with my code. I am affixing the code below, can you pls rectify it. I have commented the error. I am also attaching the excel file 'Battery_Parameters.xlsx'. Pls fix any other errors if you feel so and give feedback if I'm doing anything wrong.

Code:

component Cell
    nodes
        p = foundation.electrical.electrical; %+:left
        n = foundation.electrical.electrical; %-:right
    end
    variables
        i = {0,'A'};
        v = {0,'V'};
        SOC = {0,'Pa'}; % Provided simply as a unit is required
        Data = xlsread('Battery_Parameters.xlsx');
        R_Discharge = {0,'Ohm'}; % resistance
    end
 parameters (Size=variable)
   xd = Data(2:end,1) %Error
   yd = Data(2:end,4) %Error
 end
  function setup
        if R_Discharge<0
            pm_error('simscape:GreaterThatOrEqualToZero','Resistance')
        end
  end
  branches
      i: p.i -> n.i;
  end
  equations
     v == p.v - n.v;
     R_Discharge == tablelookup(xd, yd, SOC, interpolation=linear, extrapolation=nearest);
 end
end

Answer 1

[Zeng]

In my opnion, you should read the file in "Setup".

Answer 2

[Pramil]

Hi Pranav,

For loading external data in a SSC file you can use "MATLAB Declaration Functions". Here is the link for the following:

https://www.mathworks.com/help/simscape/lang/declaration-functions.html

Here is the updated code that works in both MATLAB R2024a as well as R2018a:

component Cell
    nodes
        p = foundation.electrical.electrical; %+:left
        n = foundation.electrical.electrical; %-:right
    end
    variables
        i = {0,'A'};
        v = {0,'V'};
        SOC = {0,'Pa'};
        
        R_Discharge = {0,'Ohm'}; % resistance
    end
 parameters (Access = private)
   [xd,yd] = my_fcn();
 end
  branches
      i: p.i -> n.i;
  end
  equations
     assert(R_Discharge>=0); 
     v == p.v - n.v;
     R_Discharge == tablelookup({xd 'Pa'}, {yd 'Ohm'}, SOC, interpolation=linear, extrapolation=nearest);
 end
end

Where "my_fcn" is:

function [xd,yd] = my_fcn()
    Data = xlsread('Battery_Parameters.xlsx');
    xd = Data(2:end,1);
    yd = Data(2:end,4);
end

Hope it helps.