Index in position 1 is invalid. Array indices must be positive integers or logical values. can anyone help me solve the problem?

this is a code of electromechanic system , when I run it without writing transfer function code (T_1 , T_2 , ... ) ,it runs . but when I write transfer function it errors. can you help me solve this problem?

x0=[0;0;0];
t0=0;
tf=20;
global k_m J_m J R L N k_t;
k_m=0.05; %constant 
R=1.2; %ohm
L=0.05; %henry
J_m=8e-4; %Moment of inertia on the motor side
J=2e-2; %Moment of inertia on the load side
N=12; %constant
k_t=50 ; %N/m
J_e=J+(N^2*J_m);
A=[0 1 0; N^2*k_t/J_e 0 N*k_m/J_e; 0 -N*k_m/L -R/L];
B=[0 0;0 -1/J_e; 1/L 0];
C=[1 0 0 ; 0 1 0];
D=zeros(2,2);
G=ss(A,B,C,D);
[num1,den1]=ss2tf(A,B,C,D,1);
[num2,den2]=ss2tf(A,B,C,D,2);
T_1=tf(num1(1,:),den1);
T_2=tf(num1(2,:),den1);
T_3=tf(num2(1,:),den2);
T_4=tf(num2(2,:),den2);

%% functions 
function [xdot]=electromechanic(t,x)
global k_m J J_m R L N k_t ;
J_e=J+(N^2*J_m);
%x1=teta ; x2=omega ; x3=i;
v=2; %voltage
T_L=5 ;%load torque
u_1=v; %first input
u_2=T_L;%second input
xdot=zeros(3,1);
xdot(1)=x(2);
xdot(2)=(N^2*k_t/J_e)*x(1)+(N*k_m/J_e)*x(3)-(1/J_e)*u_2;
xdot(3)=(-N*k_m/L)*x(2)-(R/L)*x(3)+(1/L)*u_1;
end

Answer 1

[KSSV]

T_1=tf(num1(1,:),den1);

The above line is ridiculous. Points to note:

1. tf is a scalar whose value is 20. Why indexing?
2. num1 has all elements which are fractions and you cannot use them as indexing.
3. den1 also all the elements which are fractions.

So whn you index, you should use the indices as either logicals or posittive integers. In your case, the indices are fractions which is wrong. Also you need to index for arrays not for scalars.

[Tina M]

tnx for answering .but what should I do now?

because I've been learning MATLAB for a month , I can't solve it.

can you help me?

[wassim bidi]

Answer me please.

Excuse me,i can't ask

so, i have porblem and i need to help

the problm with :Error using plot

Vectors must be the same lengths.

clc

clear

sys1 = tf(1,[0.1 1])

t=0:0.1:10;

step(sys1)

y=step(sys1);

plot(t,y)

[Steven Lord]

Tina M:

While the variable tf exists you will not be able to call the tf function. Attempts to call the function will be interpreted instead as an attempt to index into the variable.

Rename or remove that variable.

wassim bidi:

This question is not related to Tina M's original question. Please post it as a separate question (using the Ask link just below the blue bar at the top of this page.)