Problem loading variables to Simulink

I have a Simulink model that uses variables set in Matlab code. However it keeps giving me the same error.

I have this function

function y = tclabsim(t, x0, u, p)
    % Ensure input sizes match
    if length(t) ~= length(u)
        error('Time vector t and input profile u must have the same length.');
    end
    
    % Extract parameters from p
    U = p(1);    % Heat transfer coefficient
    alpha = p(2); % Ambient heat loss parameter
    tau = p(3);  % Time constant
    
    % Initial conditions
    x0_T = x0; % Initial temperature
    
    % Ensure t and u are column vectors
    t = t(:);
    u = u(:);
    
    % Create input matrices
    inputMatrix = [t, u];
    U_matrix = [0, U];
    alpha_matrix = [0, alpha];
    tau_matrix = [0, tau];
    x0_T_matrix = [0, x0_T];
   
    
    % Set simulation stop time
    stopTime = t(end);
    
    % Assign all required variables to base workspace
    assignin('base', 'x0_T', x0_T_matrix);
    assignin('base', 'U', U_matrix);
    assignin('base', 'alpha', alpha_matrix);
    assignin('base', 'tau', tau_matrix);
    assignin('base', 'inputMatrix', inputMatrix);
    
    % Run the Simulink model
    simOut = sim('SingleHeaterTCLab_1.slx', 'SrcWorkspace', 'current', ...
        'StopTime', num2str(stopTime));
    
    % Extract the output from the simulation
    y = simOut.Ts; % Sensor temperature output
end

And I call the function like this

% Time vector (0 to 1000 seconds with 1-second steps)
t = (0:999)'; % Make sure t is a column vector

% Initial temperature (20°C)
x0 = 20;

% Heater input (step response: 50% heater power after 100s)
u = zeros(size(t));
u(t >= 100) = 50;

% Parameters [U, alpha, tau]
p = [0.01, 0.01, 200]; % Example values for U, alpha, tau

% Simulate the system
y = tclabsim(t, x0, u, p);

However, every time I try to run it gives the same error.

I have tried to load them as simple double and I have also tried a matrix with t on the first column and the same value in every line of the second column. They also gave the same error.

The block in Simulink has these properties. And I have also tried to change the sample time to -1.

This is the entire simulink if it helps.

How can I fix it?

Thank you

Answer 1

[Walter Roberson]

function y = tclabsim(t, x0, u, p)
%...
    x0_T = x0; % Initial temperature

The size of x0 is uncertain at this point.

    x0_T_matrix = [0, x0_T];

That would only work if x0_T is empty or scalar or a row vector. The result x0_T_matrix will be a scalar or a row vector.

    assignin('base', 'x0_T', x0_T_matrix);

So that will be scalar or a row vector.

You then import it with a From Workspace block. From Workspace allows a few different datatypes, but when the data is numeric, it needs to be a 2D array. You are specifying a scalar or row vector instead of a 2D array.

If you are trying to import x0_T as a constant scalar, then import x0 as the initial value of a Constant block.

[Dinis]

Thank you!

That made a lot of sense and it worked.