doubt regarding a for loop

k11=28.21;
k21=-4.23;
k12=-18.133;
k22=2.59;
k13=20.815;
k23=-2.97;

for i=1:5
    
    tdot1=k11+2*k21*t(i);
    tdot2=k12+2*k22*t(i);
    tdot3=k13+2*k23*t(i);
    
    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,O1O2);
    v3=R32*(v2+cross(w2,O2O3));
    uV2(i)=norm(v2);
    uV3(i)=norm(v3);
    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]');
end

I want to understand this code. I am unable to get how can i define t(i) in order to get the code to work. Please help me.

Answer 1

[Walter Roberson]

k11=28.21;
k21=-4.23;
k12=-18.133;
k22=2.59;
k13=20.815;
k23=-2.97;

%some variables were left undefined
R21 = randn()

R21 = 1.2025

R32 = randn()

R32 = -0.8773

O1O2 = randn(1,3)

O1O2 = 1×3

-0.0390 -0.7938 -0.8864

O2O3 = randn(1,3)

O2O3 = 1×3

1.5511 -0.5591 -1.2109

%end of undefined variables

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);
    
    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,O1O2);
    v3=R32*(v2+cross(w2,O2O3));
    uV2(i)=norm(v2);
    uV3(i)=norm(v3);

end
    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]');

[Vinay Basagare]

Thanks a lot. Really appreciate it.