Week 2- 2R Robotic Arm Challenge

Write a program in Matlab to simulate the forward kinematics of a 2R Robotic Arm, as shown in the video?

clc
close all 
clear all

%Two arm robotic kinematics manipulator
%Given datas

theta1=linspace(0,90,10);

theta2=linspace(0,90,10);


%I have used cos and sin to find the exact points of x and y for links
%For loop


ct=1

for i = 1:length(theta1);
THETA1=theta1(i);
for j =1:length(theta2);
THETA2=theta2(j);

L1=2;

L2=1;

x=0;
y=0;

x1=L1*cosd(THETA1);
y1=L1*sind(THETA1);

x2=x1+L2*cosd(THETA2);
y2=y1+L2*sind(THETA2);

%plotting the links

plot([x x1],[y y1],[x1 x2],[y1 y2],'linewidth',3)

axis([-1 3.5 0 3.5])

pause(.3)

M(ct)=getframe(gcf);

ct=ct+1

end 
end

movie(M)

videofile=VideoWriter('Forward_kinematics_for_challenge.avi','Uncompressed AVI');

open(videofile)

writeVideo(videofile,M)

close(videofile)

Video link of a 2R Robotic Arm

If this link was not redirecting to youtube, please copy the link and paste it into the youtube search box.

https://youtu.be/-hTRu6_qFxs

In that video we could get to know what are the possible positions can achieve using those two links.

CODING EXPLANATION

Clear all = It clears all the data on a workspace.

close all = It will close the all back end running process.

(eg): plots

CLC = It will clear all the history on the command window.

What are theta1 and theta2?

Theta1 represents the first link angle and Theta2 represents the second link angle.

Linspace?

Linspace is a command which will split numbers equally between starting range and ending range as we needed.

(eg):

linspace(starting range, ending range, number of values needed).

For loop?

For loop is a command which will repeat a certain syntax, again and again, depending on how much value we feed.

Here, I used a for loop command to provide more theta values to links, so my links could attain many positions each time it moves.

In this problem, I have two links and each link has to move independently from one another, so I have used for loop into the for loop as result both links move Independently.

L1 and L2?

L1 is the length of the first link and L2 is the length of the second link.

Coordinates?

x = It is the base point of the first link in the x axis.

y = It is the base point of the first link in the y axis.

x1 = It is the end point of the first link in the x axis and starting point of the second link in the x axis.

y1 = It is the end point of the first link in the y axis and starting point of the second link in the y axis.

x2 = It is the end point of the second link in the x axis.

y2 = It is the end point of the second link in the y axis.

Plot?

plot is also called a graph.

To make a plot we need to feed x and y values.

Linewidth is used to increase the width of the respective line.

Axis will represent the origin values and ending values of both the x and y axis.

SYNTAX FOR MAKING AN ANIMATION MOVIE :

M(ct)=getframe(gcf);

Here M is variable

gcf=get current frame

ct=ct+1

Here, I am gradually changing the frame one by one in a single plot and making as video.

movie(M)

M is variable, so the movie will be created according to the position or values of the variable M.

videofile=VideoWriter('FILE_NAME.avi','Uncompressed AVI');

Here, I am creating a file name for the movie and how want it to be either compressed or uncompressed.

open(videofile)

opening the videofile

writeVideo(videofile,M)

Feeding the M values into a video file by writing the video

close(videofile)

closing the videofile.

Applications :

2R robotic arm has wide usage in manufacturing industries such as

Painting

Welding

Inspection purpose

Cutting

Errors faced while programming :

L1=1;
L2=0.5;
theta1=linspace(0,90,10);
theta2=linspace(0,90,10);
ct=1

for i = 1:length(theta1)
    THETA1=theta1(i)
    for j =1:length(theta2)
        THETA2=theta2(j)


%calculating the coordinators using a input values

x=0;
y=0;
x1=L1*cosd(theta1);
y1=L1*sind(theta1);
x2=x1+L2*cosd(theta2);
y2=y1+L2*sind(theta2);

%plotting the coordinators 

hold on
plot([x x1],[y y1],'linewidth',3,'Color','r')
plot([x1 x2],[y1 y2],'linewidth',3,'Color','b')
axis([-1 2 0 1.5])

pause(.03)

ct=ct+1

end 
end

THE ERROR PLOT :

After the plot appeared, I got to know, I made some mistake in my coding.

I forget to change the theta1 and theta2 into a capital THETA1 and THETA2 in coordinates values.

Second error :

for i = 1:length(theta1);
THETA1=theta1(i);
for j =1:length(theta2);
THETA2=theta2(j);

L1=2;

L2=1;

x=0;
y=0;

x1=L1*cosd(THETA1);
y1=L1*sind(THETA1);

x2=x1+L2*cosd(THETA2);
y2=y1+L2*sind(THETA2);

%plotting the links 
ct=1

plot([x x1],[y y1],[x1 x2],[y1 y2],'linewidth',3)

axis([-1 3.5 0 3.5])

pause(.3)

M(ct)=getframe(gcf);

ct=ct+1

end 
end

movie(M)

videofile=VideoWriter('Forward kinematics_for_challenge.avi','Uncompressed AVI');

open(videofile)

writeVideo(videofile,M)

close(videofile)

THE ERROR PLOT :

When I run the code the plot works perfectly as I expected but when it comes to making an animation video I found nothing is playing. Only the last position of both links were appeared in video format.

The mistake I had made is ct=1

I mistakenly typed ct=1 above the plot instead of typing the ct=1 above the for loop command.

After fixing the issue, I did not encounter any other issues.

I had mentioned the final result as a video link which will redirect to youtube.

https://youtu.be/-hTRu6_qFxs