MATLAB: How to control a contant/ trigger signal in simulink FROM an m-file

simulink

Hi! I'm using an m file to control a simulation (simulink slx file). The user enters the stop time. When the simulation time reaches its half value, (ie halfway through the simulation,) I need to change a constant from 0 to 1. when it reaches 75%, I need to change the (same) constant source from 1 to 0.

so my question is, how do we control the value of the constant block (or any other block that can produce a const, eg. a step block, or signal generator) with respect to the simulation time from an m file?

Please help me.. I googled a lot but couldn't find a solution thanks

Best Answer

oh I myself found the soln :) kinda dumb of me ;)

you simply need the FROM WORKSPACE block. enter a 2-columned matrix in it, 1st column contains time with respect to stop time and 2nd contains const values........

not removing this question in case anybody needs it

Related Solutions

MATLAB: Matlab M-File

You should review the documentation on how to write a function, since your above code is not a correctly written function. First, come up with a name for your function, e.g. myFunction. Then create a new file called myFunction.m somewhere on the MATLAB path (e.g. your working directory). Then in that file put your code. E.g.,

function result = myFunction(V)
result = V;  % <-- allocate the result variable, copying all elements
%

% Insert your code here to create the result variable from the V variable
%
return
end

I will give you some hints about correcting your code:

Change this loop:

for i=1:1:6;  % <-- hard coded for exactly 6 elements

to this

for i=1:numel(V)  % <-- allows any size input

The following test has an error in the logic (compare this carefully with the requirement):

if [V(i)<0 | mod(V(i),2)==0 | mod(V(i),4)==0]

The following line has an error on the right hand side calculation (compare this carefully with the requirement):

    V(i)=i*i;

If you don't see what the errors are, step through a small example by hand and compare that to the code result. E.g., at the command line type this:

V=[10,4,7,-8,-3,-12];
myFunction(V)

MATLAB: M-file function

Your function is calling itself without approaching any convergance or something that will allow it to end. Therefore it will run forever and eventually out of memory (hence the error). Try splitting it up into a script and a function as so:

Script:

 %creating window of plot from -5 to 50 using stepsize 0.25 for t x-axis
 %t should be on the x axis, v should be on the y axis
 k=0; 
for i= -5:.25:50
    k = k+1;
    t(k)=i;
    v(k)=vPieceWise(t(k));
end 
plot(t,v);
 
figure
plot(t,v);
hold on

Function:

%Part A: Mfile function to compute v as a function of t
function v = vPieceWise(t)
 if (t < 0)
        v = 0;
    elseif (0 <= t)&&(8<=16)
        v = -5*t+10*t.^2;
    elseif (8<=16)&&(t<=16)
        v = 624 - 3*t;
    elseif (t<=16)&&(t<=26)
        v = 12*(t-16).^2+36*t;
    elseif (26<t)
        v = 2136*exp(-0.1*(t-26));
 end

Best Answer

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MATLAB: M-file function

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