For loop in for loop

k11=28.21;
k21=-4.23;
k12=-18.133;
k22=2.59;
k13=20.815;
k23=-2.97;
t=0:0.1:3;
num_t=length(t);
t4=0;
t3=-0.3588;
t2=0.2433;
t1=-0.81;

R21 = [cos(t2) -sin(t2) 0;
    sin(t2) cos(t2) 0;
    0 0 1];
R32=[cos(t3) -sin(t3) 0;
    sin(t3) cos(t3) 0;
    0 0 1];
D4=[0 0 0.450+0.092];
D3=[0.440 0 0];
D2=[0; 0.33; 0];
D1=[0.05; 0; 0];
t = 0:.1:3;
num_t = length(t);
for i=1:num_t
    
    tdot1=k11+2*k21*t(i);
    tdot2=k12+2*k22*t(i);
    tdot3=k13+2*k23*t(i);
    t2dot1=2*k21;
    t2dot2=2*k22;
    t2dot3=2*k23;
    w1=[0;0;tdot1*2*pi/360];
    w2=R21*w1+[0;0;tdot2*2*pi/360];
    w3=R32*w2+[0;0;tdot3*2*pi/360];
    
    uW1(i)=w1(3,1);
    uW2(i)=w2(3,1);
    uW3(i)=w3(3,1);
    
    v2=R21*cross(w1,D1);
    v3=R32*(v2+cross(w2,D2));
    uV2(i)=norm(v2);
    uV3(i)=norm(v3);
    W1=[0;0;w1(i)];
    alfa1=t2dot1;
    Tdot2=[0;0;tdot2(i)];
    alfa2=t2dot2+R21*alfa1+R21*cross(W1,Tdot2);
    W2=[0;0;w2(i)];
    Tdot3=[0;0;tdot3(i)];
    alfa3=t2dot3+R32*alfa2+R32*cross(W2,Tdot3);
    ua2(i)=alfa2(3,1);
    ua3(i)=alfa3(3,1);
    
end

Index exceeds the number of array elements. Index must not exceed 1.

hold on
figure(1)
plot(t,uW1,'-*')
xlabel('time[s]');
ylabel('w1[rad/s]');
figure(2)
plot(t,uW2,'*')
xlabel('time[s]');
ylabel('w2[rad/s]');
figure(3)
plot(t,uW3,'*')
xlabel('time[s]');
ylabel('w3[rad/s]');
figure(4)
plot(t,uV2,'.')
xlabel('time[s]');
ylabel('v2[m/s]');
figure(5)
plot(t,uV3,'.')
xlabel('time[s]');
ylabel('v3[m/s]');
hold on 
figure(1)
plot(t,ua2,'*')
xlabel('time[s]');

ylabel('alfa2[rad/s^2]');
figure(2)
plot(t,ua3,'*')
xlabel('time[s]');

ylabel('alfa3[rad/s^2]');

Should I be using another For loop for the plot of Alpha vs time? I am unable to understand how can I get rid of the error at line 48.Please help me. Thanks in advance.

[Walter Roberson]

    w1=[0;0;tdot1*2*pi/360];

That only has 3 elements

    W1=[0;0;w1(i)];

That asks for the i'th element of the vector of length 3, which is going to fail when i becomes 4.

    tdot1=k11+2*k21*t(i);

Those are all scalars, so tdot1 is a scalar. Likewise for tdot2

   Tdot2=[0;0;tdot2(i)];

There you ask for the i'th element of that scalar.

You do not use tdot1 or tdot2 or tdot3 after the loop, so it is not obvious that you want to store all of the tdot* values as they are calculated. It would seem to make more sense to just use

   Tdot2 = [0;0;tdot2];

That would hint that you should do the same for w1(i), just leave off the (i) indexing. But w1 and w2 and w3 are vectors of length 3: does it make sense to calculate W1=[0;0;w1]; where w1 is a vector of length 3? Are you expecting a vector of length 3 result, or are you expecting a vector of length 5 result?

[Vinay Basagare]

I understood and I am expecting a vector of length 3.

[Vinay Basagare]

I just want to take it as the first element of w(i) should be taken when the first element of tdot1 is taken and thats why i thought to use it that way. but, i got your point. Thanks for the whole explaination. I really apprecaite it.

Answer 1

[VBBV]

 k11=28.21;
k21=-4.23;
k12=-18.133;
k22=2.59;
k13=20.815;
k23=-2.97;
t=0:0.1:3;
num_t=length(t);
t4=0;
t3=-0.3588;
t2=0.2433;
t1=-0.81;
R21 = [cos(t2) -sin(t2) 0;
sin(t2) cos(t2) 0;
0 0 1];
R32=[cos(t3) -sin(t3) 0;
sin(t3) cos(t3) 0;
0 0 1];
D4=[0 0 0.450+0.092];
D3=[0.440 0 0];
D2=[0; 0.33; 0];
D1=[0.05; 0; 0];
t = 0:.1:3;
num_t = length(t);
for i=1:num_t
tdot1=k11+2*k21*t(i);
tdot2=k12+2*k22*t(i);
tdot3=k13+2*k23*t(i);
t2dot1=2*k21;
t2dot2=2*k22;
t2dot3=2*k23;
w1=[0;0;tdot1*2*pi/360];
w2=R21*w1+[0;0;tdot2*2*pi/360];
w3=R32*w2+[0;0;tdot3*2*pi/360];
uW1(i)=w1(3,1);
uW2(i)=w2(3,1);
uW3(i)=w3(3,1);
v2=R21*cross(w1,D1)
v3=R32*(v2+cross(w2,D2))
uV2(:,i)=norm(v2)
uV3(:,i)=norm(v3)
W1=[0;0;w1];
alfa1=t2dot1;
Tdot2=[0;0;tdot2];
alfa2=t2dot2+R21*alfa1+R21*cross(w1,Tdot2);
W2=[0;0;w2];
Tdot3=[0;0;tdot3];
alfa3=t2dot3+R32*alfa2+R32*cross(w2,Tdot3);
ua2(i)=alfa2(3,1)
ua3(i)=alfa3(3,1)
end;
figure(1)
plot(t,uW1,'-*')
xlabel('time[s]');
ylabel('w1[rad/s]');
figure(2)
plot(t,uW2,'*')
xlabel('time[s]');
ylabel('w2[rad/s]');
figure(3)
plot(t,uW3,'*')
xlabel('time[s]');
ylabel('w3[rad/s]');
figure(4)
plot(t,uV2,'.')
xlabel('time[s]');
ylabel('v2[m/s]');
figure(5)
plot(t,uV3,'.')
xlabel('time[s]');
ylabel('v3[m/s]');
figure(6)
plot(t,ua2,'*')
xlabel('time[s]');
ylabel('alfa2[rad/s^2]');
figure(7)
plot(t,ua3,'*')
xlabel('time[s]');
ylabel('alfa3[rad/s^2]');

You might not need additional for loop

[Vinay Basagare]

Thanks a lot for the answer and your time.