I have a problem in MATLAB Simulink.

So, I want to build the simulink model with "Matlab funcion" as a block. Which has input and output. Now, I have taken sine wave as an input. so "u = sin wave" here I have used "Sin wave" block. Now in function block i have added function as below,

I have attched screenshot of simulink model.

function y = fcn(u)

t_span = 5

y = u(t<t_span);

Here in order to calculate the value of y, I need time "t". So that I can compare it with "t_span". So, When I try to write parameter into "fcn(u)" as "fcn(u(t))" it creates another input port in function block.

So, My question is how can i use internal parameter "t" of sine wave block as a variable for different equations ??

Thank you.

[Sam Chak]

Hi @Shiv Nileshkumar Matliwala

If , then what is ?

I don't know how to interpret the function.

Can you make a basic plot for , so that it can be interpreted into the MATLAB Function block?

t = linspace(0, 2*pi, 2*1800+1);
u = sin(t);
plot(t, u, 'linewidth', 1.5), 
grid on, xlabel('\it{t}'), ylabel('\it{u}(\it{t})')

[Shiv Nileshkumar Matliwala]

In short, I want to have output sin(t) and t from sine wave block. So, is it possible to get "t" also as an output from sin wave block in simulink ??

And how can I make your code as simulation blocks in simulink.

t = linspace(0, 2*pi, 2*1800+1); u = sin(t); plot(t, u, 'linewidth', 1.5), grid on, xlabel('\it{t}'), ylabel('\it{u}(\it{t})')

Can you just show me how can I make this as simulink blocks in simulink model ?

[Sam Chak]

@Shiv Nileshkumar Matliwala, Before answering your queries, here is a straightforward request:

• Please sketch the desired output waveform of the MATLAB Function block.
• If you know the equation of the desired output, please display it here.

[Shiv Nileshkumar Matliwala]

ok. So,

function x=equa(u)
init_t=0;
final_t=10;
dt=0.001;
N= (final_t-init_t)/dt;
tspan=linspace(init_t,final_t,N)

x = u(tspan==max(tspan(t>=tspan)));

now, here i have written this code inside the "matlab function" block in simulink. So, now in order to run this function i have given input "u" which is coming from sine wave block. but as you can see to get the "x", I also need "t" so that i can compare it with "tspan".

So, in attchement you can see the model i have made. Now, when i run this model I get the following error.

% Undefined function or variable 't'.

% Function 'MATLAB Function' (#48.134.135), line 8, column 24:
% "t"
% Launch diagnostic report.
% Component:MATLAB Function | Category:Coder error

So, now you know my problem. So, if you have any solution to this "t" then please help me.

Answer 1

[Aditya]

Hi,

I understand that you are trying to get the parameters from which sine wave is calculated, particularly time “t”.

The sine wave output is calculated from the following formula:

y = amplitude*sin(frequency*t + phase) + bias;

amplitude, frequency, phase, and bias are all sine wave block parameters that are fixed.

For getting the time “t”, you can use the Clock block as discussed in Display and provide simulation time - Simulink (mathworks.com).

Here is an example of using a MATLAB function block to generate same waveform as a sine wave. You can see that the function uses the internal parameters of the sine wave block. You can have an extra input to your MATLAB function block from the clock block.

function y = fcn(t)
    frequency = 1; %Same as the sine wave block parameter
    amplitude = 1; %Same as the sine wave block parameter
    bias = 0; %Same as the sine wave block parameter
    phase = 0; %Same as the sine wave block parameter
    y = amplitude*sin(frequency*t + phase) + bias;
end

[Shiv Nileshkumar Matliwala]

That is the good idea to make sine wave as a function file. Thank you so much for that. I will try to implement this.

Thank you.

[Aditya]

@Shiv Nileshkumar Matliwala Just a clarification, you don't need to implement Sine wave as a block. You can get "t" directly from the Clock Block

[Shiv Nileshkumar Matliwala]

Yes. And I have posted one more question if you can solve it, it will be a great help sir.