I have a problem in MATLAB Simulink.

Question

Shiv Nileshkumar Matliwala 2022-9-13

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1804460-i-have-a-problem-in-matlab-simulink

编辑： Shiv Nileshkumar Matliwala 2022-9-16

Screenshot 2022-09-13 at 5.27.30 PM.png

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.

4 个评论
显示 2更早的评论隐藏 2更早的评论

Sam Chak 2022-9-13

@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 2022-9-14

在 MATLAB Online 中打开

Capture.PNG

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.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Aditya 2022-9-16

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1804460-i-have-a-problem-in-matlab-simulink#answer_1054565

编辑：Aditya 2022-9-16

在 MATLAB Online 中打开

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