Why cant I use a custom MATLAB function in Simscape equation section?

component fou_bv_elem

nodes

p = fouriernet.FourierNet; % +:left

n = fouriernet.FourierNet; % -:right

end

parameters

R = { 8.314, 'J/mol/K'};

F = { 96485, 'A*s/mol'};

T = { 298, 'K'};

i_bv = { 0.8734, 'A'};

alpha_a = 0.5;

alpha_k = 0.5;

end

variables(Access=private)

fU = { zeros(1,p.numb), 'V' }; % Voltage

fI = { zeros(1,p.numb), 'A' }; % Current

end

branches

fI : p.fI -> n.fI;

end

equations

fU == p.fU - n.fU;

fI == fouriernet.computeCurrent(fU,p.numb,R,F,T,i_bv,alpha_a,alpha_k); %I want to use this function

end

end

Answer 1

[Abhishek]

Hi @Julian Ulrich,

To use custom MATLAB function in ‘Simscape’, there are two available approaches, depending on whether the function is defined as a main or local function:

• Main function: Create a separate ‘.ssc’ file with the same name as the function. This file can then be called within the custom block definition.
• Local function: Define the function after the final ‘end’ keyword in the main function file which is then accessible only within the scope of that specific file.

For detailed examples and further information, refer to the MATLAB documentation below:

https://www.mathworks.com/help/releases/r2025a/simscape/lang/function.html