Simulink user defined function: undefined variable or function

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Martijn
Martijn 2012-6-10
评论： Sumukh Bharadwaj 2018-3-21
Dear all,
When using a user defined Matlab function in Simulink, with the following structure:
function xdot = fcn(x,u)
%VEHICLE PROPERTIES (removed here)
%%Dea
xdot(1)=V*cos(x(1));
xdot(2)=V*sin(x(1));
xdot(3)=V*1/l(1)*tan(u);
xdot(4)=-xdot(3)-V/l(2)*sin(x(4))-xdot(3)*(c(1)/l(2))*cos(x(4));
V(1)=V;
for k=2:n-1
ratep=xdot(3)+sum(xdot(4:k+2)); %yaw-rate precessing unit
V(k)=V(k-1)*cos(x(k+2))-ratep*c(k-1)*sin(x(k+2)); %velocity precessing unit
xdot(k+3)=-ratep-V(k)/l(k+1)*sin(x(k+3))-ratep*(c(k)/l(k+1))*cos(x(k+3));
end
end
I get the errors: Undefined function or variable 'xdot'. The first assignment to a local variable determines its class.
As you can see, I want to assign a value to xdot, so I do not understand where the error comes from. Can anyone help?

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采纳的回答

Walter Roberson
Walter Roberson 2012-6-11
Start the routine with
xdot = zeros(1, n+2);
  2 个评论
Martijn
Martijn 2012-6-11
Thank you, the function variable are not allowed to change size to be able to generate code.
Sumukh Bharadwaj
Sumukh Bharadwaj 2018-3-21
Hi,
I'm facing the same problem! "Undefined function and first assignment........
How did you overcome it?

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