How to draw a true robot trajectory ?

Hello everyone !

I work on two-wheels robot mobile project. One part of the project is making a visualization of trajectory like a plot in Matlab. The plot shows how robot ride along black line in line follower mode and it is scalled to centimeters. The problem is with coordinate Y. In reality Y oscillate between 0-3 cm but plot shows even 20 cm. Do you know maybe how to deal with this inaccuracy ?

this link contains excel file with encoders values https://megawrzuta.pl/download/2c94ed93d2e8675ba2388cecff7bc53e.html

[Talat Buyukakin]

Hello Adam, The link you give above can not be open because of deleted or missing. Can you please mail me encoder values that you have worked with. I'm working on kind of this project. [e-mail] Thank You

[Walter Roberson]

Talat: note that Adam will not have been notified about your comment.

I happened to have downloaded the file while testing the code. I have attached it.

[Talat Buyukakin]

Walter:Thank you so much for your help. I download it.

[Adam Stepniak]

Walter was faster ;), good luck with your project Talat.

[Talat Buyukakin]

Thank you too Adam :)

Answer 1

[Walter Roberson]

It is difficult for us to test with a picture of code, so I typed it in, but skipped the comments.

Your alfa (angle) has been calculated based upon difference in linear distance traveled, rather than based upon angular distance traveled. When I divided alfa by R to get angular distance, the results looked plausible.

modified version that looks plausible:

filename='encoders.xlsx';
encoders=xlsread(filename);
el=encoders(:,1);
er=encoders(:,2);
R=3.25;
L=16;
n=192;
dr=er.*((2*pi*R)/n);
dl=el.*((2*pi*R)/n);
d=(dr+dl)/2;
alfa=(dr-dl)/L/R;
c=cos(alfa);
s=sin(alfa);
x=d.*c;
y=d.*s;
plot(x,y);
title('trajectory');
xlabel('X')
ylabel('Y')
axis([0 200 -50 50])
hold on
grid on

[Adam Stepniak]

Thank you for fast resposnse, in fact the plot shows more realistic results in case of following straight line.