how to deal with the error "Attempted to access t(5001); index out of bounds because numel(t)=2000."

if true
clc;
clear all;
close all;
to=0;
tf=2;
d=0.001;
n=tf/d;
y=zeros(1,n);
r=zeros(1,n);
x=zeros(4,n);
s=zeros(1,n);
v=zeros(1,n);
t=zeros(1,n);
e=zeros(4,n);
g=0.2;
M=0.005;
v(1)=0;
k1=0.1689;
k2=0.6785;
k3=0.0237;
k4=1;
u=zeros(1,n);
h=zeros(1,n);
a=-0.5;
b=0.5;
u(1,1)=0;
h(5001)=a;
for i=1:5000
 u(i)=a;
end
for i=5001:15000
  u(i)=t(i);
  t(i+1)=t(i)+d;
end
for i=15001:20001
  u(i)=b;
end

for i=1:(n+1)

    r(1,1)=g*1.75;
    r(1,(i+1))=g*1.75;
    dx1=-8.376*x(1,i)-34.97*x(2,i)-4.14*x(3,i)-32.7*x(4,i)+108.77*(v(1,i));
    dx2=2.54*x(1,i)-7.89*x(2,i)+77.75*(v(1,i));
    dx3=-7.198*x(1,i)+3.36*x(2,i)-11.05*x(3,i)-87.2*x(4,i)+93.48*(v(1,i));
    dx4=x(3,i);
    x(1,(i+1))=x(1,i)+(d*dx1);
    x(2,(i+1))=x(2,i)+(d*dx2);
    x(3,(i+1))=x(3,i)+(d*dx3);
    x(4,(i+1))=x(4,i)+(d*dx4);
    t(1,(i+1))=t(1,i)+d;
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    e(1,(i+1))=-x(1,(i+1));
    e(2,(i+1))=-x(2,(i+1))+r(1,(i+1));
    e(3,(i+1))=-x(3,(i+1));
    e(4,(i+1))=-x(4,(i+1));
    s(1,(i+1))=k1*e(1,(i+1))+k2*e(2,(i+1))+k3*e(3,(i+1))+k4*e(4,(i+1));
    a=(-108.77*k1-77.75*k2-93.48*k3);
    b=(-8.376*k1+2.54*k2-7.198*k3);
    c=(-34.97*k1-7.89*k2+3.36*k3);
    d=(-4.14*k1-11.05*k3+k4);
    p=(-32.7*k1-87.2*k3);
    v(1,(i+1))=((b*e(1,(i+1))+c*(e(2,(i+1)))+r(1,(i+1))+d*e(3,(i+1))+p*e(4,(i+1)))/a)-(M*sign(s(i)));
    y(1,(i+1))=0.4419*x(3,(i+1))+3.98*x(4,(i+1));

end plot(t(1,:),y(1,:),'r'); ylabel('sliding surface'); xlabel('time(sec)*10^-3'); hold on; grid;

      end

Answer 1

[Geoff Hayes]

Biswajit - the error message is telling you that you are trying to access an index that exceeds the dimension of your array t. You have defined t as

 t=zeros(1,n);

where n is 2000, yet the code that uses this array is doing

 for i=5001:15000
    u(i)=t(i);
    t(i+1)=t(i)+d;
 end

So either you have to increase the size of t to 5000 elements, or change the code here so that you don't begin iterating at 5001.

Why has t been initialized to an array of all zeros with dimension 1x2000, and yet now the code is treating it as if it were an array of at least 5000?