Why does my red lines on the graph stop?

For code, the red lines (vl and rvr) on the graph need to reach a certain point, which I have defined as 50, then it should remain constant. When I get the graph, the red lines stop when it reaches 50 instead of continuing constantly for the remainder of the time. How can I get the lines to show that it is constant until the end?

Any help would be greatly appreciated.

%Constants
m = 300
rw = 0.356
Iw = 2.7
N = m*9.81
Td1 = 1.134826021738053e+03
Td2 = 1200
%Magic Formula
B_1 = 10
C_1 = 1.9
D_1 = 1
E_1 = 0.97


t = [0:0.1:10]



al1= NaN(1,length(t));%empty acceleration vector
al2= NaN(1,length(t));%empty acceleration vector
vl1= NaN(1,length(t));%empty velocity vector
vl2= NaN(1,length(t));%empty velocity vector

rar1= NaN(1,length(t));%empty acceleration vector
rar2= NaN(1,length(t));%empty acceleration vector
rvr1= NaN(1,length(t));%empty velocity vector
rvr2= NaN(1,length(t));%empty velocity vector

slip1 = NaN(1,length(t));
slip2 = NaN(1,length(t));
CF_1 = NaN(1,length(t));
CF_2 = NaN(1,length(t));

vl1(1) = 0
vl2(1) = 0
rvr1(1) = 0
rvr2(1) = 0

slip1(1) = 0.16
slip2(1) = 0.16
for i = 2:100
    
    CF_1(i) = D_1*sin(C_1*atan(B_1*slip1(i-1)-E_1*(B_1*slip1(i-1)-atan(B_1*slip1(i-1)))))
    CF_2(i) = D_1*sin(C_1*atan(B_1*slip2(i-1)-E_1*(B_1*slip2(i-1)-atan(B_1*slip2(i-1)))))
    
    al1(i) = (1/m)*(CF_1(i)*N)
    al2(i) = (1/m)*(CF_2(i)*N)
    vl1(i)=vl1(i-1)+al1(i)*0.1;
    vl2(i)=vl2(i-1)+al2(i)*0.1;
    
    rar1(i) = (1/Iw)*(Td1-(CF_1(i)*N*rw))*rw;
    rar2(i) = (1/Iw)*(Td2-(CF_2(i)*N*rw))*rw;
    rvr1(i)=rvr1(i-1)+rar1(i)*0.1;
    rvr2(i)=rvr2(i-1)+rar2(i)*0.1;
    if rar1(i)<0
        rar1(i)=0
    end
     if vl1(i)>50
         al1(i) = 0
         vl1(i) = vl1(i-1)
         rar1(i) = 0
        rvr1(i) = rvr1(i-1)
     end
   
    slip1(i) = (rar1(i)-al1(i))/rar1(i)
    slip2(i) = (rar2(i)-al2(i))/rar2(i)
end

figure,plot(t,vl1,'r',t,rvr1,'r',t,vl2,'b',t,rvr2,'b')
% figure,plot(t,rar1)
% figure,plot(t,slip)
% figure,plot(t,CF_1)

[KSSV]

It is because, vl1 is taking a value NaN. You should recheck your code.

[Charles Steyn]

How would I then get vl1(i) to be vl1(i-1) for every loop? In this way vl1 would remain constant and not take on the value NaN

Answer 1

[Karthik Malisetty]

Hi Charles Steyn,

My understanding is that in the ‘if’ section, you are setting the values of al1(i) and rar1(i) to zero.

if vl1(i)>50 
  al1(i) = 0 
  vl1(i) = vl1(i-1) 
  rar1(i) = 0 
  rvr1(i) = rvr1(i-1) 
end 

This would make the expression

slip1(i) = (rar1(i)-al1(i))/rar1(i)

as 0/0 which is ‘NaN’ in Matlab.

So, slip1(i) is set to NaN (precisely at i=53) which in turn will set vl1(i) = ‘NaN’ (at i=54). So, the if condition fails at i = 54.

Therefore, the values of vl1 will remain as NaN for i=55 to 100. These NaN values can’t be reflected in plot.

Hence, the red line plots in the graph are stopped.

Removing the lines al1(i)=0 and rar1(i)=0 would give you those horizontal lines. Although, you should check that it wouldn’t effect any other program (if any)

[Charles Steyn]

Thank you so much. This makes total sense!