I want to make a simulation model of the given function. Can you help me ??

function y = fcn(u,t)
t_span = 10
y = u(t_span-t) ;

%input u = sin-wave

Here, this is the matlab function inside the matlab function block in simulink. Now as an input I have given sine wave with simulation time as a parameter not external signal as time. But now i want to use the time 't' inside the equation like given above inside the function equation. Then how can i define time 't' and use it inside the equation ??

Answer 1

[Walter Roberson]

If t is simulation time, then it will likely be non-integer, and you would be trying to index by a non-integer.

If u were the sine function instead of being a signal, then

sin(t_span - t) = -sin(t - t_span)

which is negative of sin with a delay. It would probably be easier to take a sine wave generator and put it through a delay of t_span and then take the negative of the delayed signal -- which are all things you can do without using a MATLAB Function Block.

[Shiv Nileshkumar Matliwala]

I understand you totally. But, here I want the internal parameter of sine block which is time "t". So, how can i extract that and i can use in other equation as well.

[Walter Roberson]

@Shiv Nileshkumar Matliwala

here I want the internal parameter of sine block which is time "t".

If you are referring to the Sine Wave source https://www.mathworks.com/help/simulink/slref/sinewave.html , then it does not have an internal parameter which is time "t". It uses Simulation Time unless you configure an external signal for the time. You can get the Simulation Time using a Clock block. https://www.mathworks.com/help/simulink/slref/clock.html

If you are trying to delay the sine wave by tspan seconds, then you can convert the time into radians for the Phase parameter of the Sine Wave block.

[Shiv Nileshkumar Matliwala]

Yeah. I understand you correctly. And one more question is how can I implement function handler inside the simulink "Matlab function" block ??

[Walter Roberson]

I do not think I know what you mean by "function handler"?

[Shiv Nileshkumar Matliwala]

You know it but yeah i can show you what i mean. So, As you can see in the below code I have written the function starting from "@(t,x)" which is called as function handler. this will handle the function with input "x" with internal time variable "t".

@(t,x) ODE(t, x, u, t_span)

So, This is not supporting into the "Matlab Function" block in simulink. So, I am asking for any way i can implement this in calling the function.

[Walter Roberson]

https://www.mathworks.com/help/simulink/ug/code-generation-for-anonymous-functions.html says that anonymous functions are supported in MATLAB Function Blocks (as of R2016b if I understand correctly)

[Shiv Nileshkumar Matliwala]

Yes. I got it. Thank you so much for your help.