Week 2- 2R Robotic Arm Challenge

Video link : https://youtu.be/AIVqNIe3urw

Code :

clear all
close all
clc

% Simulating Forward_Kinematics of a 2R Robotic Arm Manipulator
% Alloting length values to LINK 1(l1) and LINK 2(l2)  
l1=1; 
l2=0.5;

% Defining an array of 5 values between 0 to 90 degrees for different orientations of the links
% Decreasing the resolution for demostration purpose 
alpha1 = linspace(0,90,15);
alpha2 = linspace(0,90,15);

s=1; % defining counter variable as 1 to keep a count on number of frames.
% for loop is used for changing the orientation of LINK 1
% Loop counter variable for "1st for loop"
for i = 1 : length(alpha1)
    ALPHA1 = alpha1(i)
% Executing each value of alpha1 at a time and saving it in variable ALPHA1
% 2nd for loop is used to show all possible orientaions/inclinations of LINK 2 for a given position of LINK 1 
    for j = 1:length(alpha2)
        ALPHA2 = alpha2(j);
% COORDINATES OF END POINTS OF THE LINKS:
% 1st point :
            x0=0;
            y0=0;
% 2nd point : 
            x1 = l1*cosd(ALPHA1);
            y1 = l1*sind(ALPHA1);
% 3rd point : 
            x2 = x1 + l2 *cosd(ALPHA2);
            y2 = y1 + l2 *sind(ALPHA2);
           
% Replacing two line commands with a single plot command            
% PLot command takes the color of the most recent used plot,that's y
% we're seeing a single blue color when plot 
%'figure' command can be removed bcoz the movie can be shown in a single plot command
% For avoiding overwriting of plots 
            
            plot([x0 x1],[y0 y1],[x1 x2],[y1 y2],'linewidth',3)
            axis([-0.1 2 0 2]) 
            % Removing 'pause' command since it pauses the code which is not very efficient
           
            % getting individual frame and saving it in an array M
            % 's' represents each frame
            % 'getframe' command is getting every individual figure window
            % and saving it in array M
            M(s)=getframe(gcf);
            s=s+1; % Incrementing the frame after saving it   
        end
end
            
            
            movie(M) % Matlab is going to create a movie with all the frames in M
            %creating avi files to dump out all the frames
            % Creating videofile using commmand ,VideoWriter'
            videofile=VideoWriter("Forward_Kimematics_Simulator.avi",'Uncompressed AVI');
            open(videofile) % Opening this videofile
            writeVideo(videofile,M) % Writing in the frames that we captured in the videofile  
            close(videofile) % closing the videofile
            
            % First an animation and then a movie will be shown.

Report :

1. Firstly,the length of the links were assigned to a variable named as l1 and l2.
2. Then,two arrays of inclination angle that the links l1 and l2 will make with the x-axis during the entire simulation is generated.
3. Now,for changing these angle that the links makes with x-axis needs to be changed automatically & for we used for loop.
4. 1st for loop is used to change the orientation of the link 1 between 0 and 90 degrees and for each orientation of the link 1,link 2 is needs to be varied between 0 and 90 degrees.
5. So,2nd for loop is used for this variation i.e., for each value of alpha1,we're looping through the values of alpha2 and performing the above operations as shown above.
6. Initially,for generating plots,two "line" commands were used,which generated 9 plots in total showing different positions of the Robotic Arm & clearly that was not convenient way to represent the plot because we're in need of a single animation that shows the entire motion of the links
7. And also, for storing different no. of these plots,figure command is used along with a counter variable 's' defined & initially set to 1 just before the 1st for loop and is incremented by 1 after execution of each plot.
8. So,plot command is employed instead of 'line' command and still it yield 16 plots in total and just a single red link is shown now which represents both the links.
9. This is because the plot command uses the most recent plot it executed which is red here.
10. So,to avoid overwriting of the plots,we'll use 'hold on' before the plot command.
11. Advantage of using 'plot' command is we can remove 'figure(s)' and use 'pause' command to give a pause between various orientations of the robotic arm.
12. But,even this is not enough because visualizing all the postions in single plot seems a bit confusing.
13. Using a single 'plot' command even gives almost the same plot of different colors which changes randomly.
14. Removing 'hold on' command ,we'll get an animation showing for each value of alpha1,how alpha2 varies.
15. Now,fixing the x and y axes for getting a clear animation.
16. Increase the size apha1 and alpha2 array for getting a smoother plot and now we get to know how to create an animation on screen.
17. Usage of 'pause' comand is not recommended because it pause the code which is not very efficient.
18. Creating a Movie out of this program:
19. Getting individual frame which is represented by' s' variable and saving it in and array 'M' defined just after plot command.
20. 'Movie(M)' command is used to create a movie with all the frames
21. Creating a videofile using VideoWriter command with the filename 'Forward_Kinematics_Simulator.avi' and profile as 'Uncompressed AVI'.
22. Opening this videofile using open command.
23. Writing in the frames we captured to this videofile using command writeVideo command.
24. Finally,closing this videofile by close command.
25. Decreasing the resolution ultimately for demostration purpose.i.e.,array size is decreased to 15.
26. After performing the above steps an animation will be shown and a movie will be played.

Plots :

The below screenshots shows various plots obtained at different stages of the code execution:

When a single plot was obtained without the use of For loop:

Refer point 12 : A simulation showing all the possible variations of the links in a single plot.

Refer point 13 : Using a single plot command instead of two.

Refer point 26 :

• Removing hold on command and setting my axes to get a clear animation followed by a movie.

Errors:

• The error came on the command window because I haven't defined the 's' variable and using it for saving it in the array M,so defining it outside the 1st for loop.