I keep getting 'Undefined function or variable 't' ' after running the code
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I am following an example in a MATLAB sliding mode control book, however the book does not do a good job of explaining how to follow the examples. the code from the book is:
function [sys,x0,str,ts]=spacemodel(t,x,u,flag)
switch flag
case 0
[sys,x0,str,ts]=mdlInitializeSizes;
case 1
sys=mdlDerivatives(t,x,u);
case 3
sys=mdlOutputs(t,x,u);
case {2,4,9}
sys=[];
otherwise
error(['Unhandled Flag =',num2str(flag)]);
end
function [sys,x0,str,ts]=mdlInitializeSizes
sizes=simsizes;
sizes.NumContStates=0;
sizes.NumDiscStates=0;
sizes.NumOutputs=1;
sizes.NumInputs=3;
sizes.DirFeedthrough=1;
sizes.NumSampleTimes=0;
sys=simsizes(sizes);
x0=[];
str=[];
ts=[];
function sys=mdlOutputs(t,x,u)
J=2;
thd=u(1);
th=u(2);
dth=u(3);
e=th-thd;
de=dth;
c=10;
s=c*e + de;
xite=1.1;
k=0;
%k=10;
ut=J*(-c*dth-1/J*(k*s+xite*sign(s)));
sys(1)=ut;
This part 1 of 3 .m scripts for this example. When I run the .m file I get the 'Undefined function or variable 't' ' message.
Also there is a SIMULINK model in the book that I am also trying to get working.
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Risposte (2)
Stephen23
il 29 Set 2018
Modificato: Stephen23
il 29 Set 2018
You do not explain how you are calling the function, but that is likely to be the problem. Perhaps you are trying to call it by copy-and-pasting the function definition and trying to run that?:
[sys,x0,str,ts] = spacemodel(t,x,u,flag)
The function requires four input arguments: you cannot just "run" it (e.g. by clicking the big green "Run" button) or "run" the file, you have to call it with all four input arguments, which have to be variables that exist in the workspace, e.g.:
A = 2;
B = 2;
C = 3;
function [sys,x0,str,ts] = spacemodel(A,B,C,1)
All well-written code also includes a help section at the beginning which explains what the code does, and specifies the input and output arguments. Note that this code will throw errors for some different flag input values when not all of the output arguments are defined... this is not very well written code.
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Stephen23
il 29 Set 2018
@Anas Din: Read my answer again. You call the function from the command window like this:
But where have you defined t, x, u and flag ? What values do you expect them to have, if you have not defined them?
If you are expecting to use this function with Simulink, then you should read the documentation about how to call function from Simulink. While trying things and experimenting is a great idea, it is no replacement for actually reading the documentation:
mohammed lubbad
il 8 Ott 2018
Modificato: mohammed lubbad
il 8 Ott 2018
do you have this book anas ?? i f you need anything contact me @ lubbad1991@gmail.com i have something
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