why do i get '' Error using / Arguments must be numeric, char, or logical.'' for the line where i have f=

L = 2;

N = 500;

a = 0;

b = L;

Ra = 300;

Rb = 400;

h = (b-a)/N;

k = @(xj) (5 + (1/6)*xj.^2);

xj = (a+h):h:(b-h);

A = zeros(N-1, N-1);

for i = 2:(N-2)

A(i,i-1)=-1/h^2;

A(i,i) = 2/h^2;

A(i,i+1)=-1/h^2;

end

A(1,1)=2/h^2;

A(1,2)=-1/h^2;

A(N-1,N-2)=-1/h^2;

A(N-1,N-1)=2/h^2;

f = [(1/k)*300*exp(-(( xj - (L/2)).^2))]';

f(1) = (1/k)*300*exp(-(( 0.0080 - (L/2))^2))+(Ra/h^2);

f(N-1)=(1/k)*300*exp(-(( L-0.0080 - (L/2))^2))+(Rb/h^2);

T = A\f;

T=[300, T' , 400];

x=[0:h:2];

plot( x, T)

MaxT=max(T')

Answer 1

[Dave B]

You get this error on the line:

f = [(1/k)*300*exp(-(( xj - (L/2)).^2))]';

because you're trying to perform the division 1/k, but k is a function handle.

You defined k as:

k = @(xj) (5 + (1/6)*xj.^2); 

This says 'take an input xj and then use that input in the equation'

Maybe you wanted:

f = [(1./k(xj))*300.*exp(-(( xj - (L/2)).^2))]';

I'd also suggest that you consider changing the definition of k to use a different variable name to make more clearly differentiate k's local variable and the outer xj.

I'm also not sure what you intended for the next two lines (which look like scalars so maybe should take in xj(1) and xj(N-1)?

[Alexander Singh]

i get a new error after your changes

Error using /

Matrix dimensions must agree.

i get this for the same line as before

[Dave B]

did you catch the two places where I added a . to your code? I'm guessing you want element-wise multiplication and division...

[Alexander Singh]

thank you Dave B

everything is working now

Answer 2

[Ahmad A]

Error evaluating 'InitFcn' callback of block_diagram 'imfp'.

Callback string is 'f=50;

Ns=(120*f)/P;

w=2*pi*0;

Lls=0.754/1000;

Llr=0.754/1000;

Lm=24/1000;

W=(2*pi*Ns*P)/120;

Vp=230*sqrt(2);

Rr=0.953;

Rs=1.5856;

P=4; J=0.089;

Vdc=500;

ts=10e-6;

Ls=Lm+Lls;

Lr=Lm+Llr;'

Caused by: Arguments must be numeric, char, or logical.

in sumulink for induction motor I get this error, would you please help me?