Week 2- 2R Robotic Arm Challenge

• Program in Matlab to simulate the forward kinematics of a 2R Robotic Arm

• clear all
  close all
  clc
  % Forward kinematics of a 2R Robotic Arm
  
  x0 = 0;
  y0 = 0;
  l1 = 1;
  l2 = .5;
  theta1 = linspace(0,90,10);
  theta2 = linspace(0,90,10);
  ct = 1;
  for i = 1:length(theta1)
      THETA1 = theta1(i);
      x1 = l1*cosd(THETA1);
      y1 = l1*sind(THETA1);
  for j = 1:length(theta2)
      THETA2 = theta2(j);
      x2 = x1 + l2*cosd(THETA2);
      y2 = y1 + l2*sind(THETA2);
      plot([x0 x1],[y0 y1],[x1 x2],[y1 y2],'LineWidth',2);
      axis([-.1 1.5 0 1.5]);
      title('Forward kinematics of a 2R Robotic Arm');
      xlabel('X_.AXIS');
      ylabel('Y_.AXIS');
      M(ct) = getframe(gcf);
      ct = ct + 1;
     
  end
  end
  movie(M)
  videofile = VideoWriter('Forward kinematics of a 2R Robotic Arm.avi');
  open(videofile)
  writeVideo(videofile,M)
  close(videofile)

• Step-wise explanation of codes used.

1. clear all - To clear all the variables from work space
2. close all - To close all opened figures in the screen
3. clc - To clear all commands and texts from the command window
4. Let a robotic arm; in which link l1 and manipulator l2 moves from an angles of 0 - 90 degrees in x-y axis
5. 
6. x0 = 0,y0 = 0 - the starting co-ordinates of robotic arm link l1
7. l1 =1,l2 = .5 - The lengths of 2 links of robotic arm
8. theta1 = linspace(0,90,10),

   theta2 = linspace(0,90,10)
   -These are the angles of link l1 and l2 with respect to x-axis respectively .'linspace' command generates linear arrays with 10 equally intervaled points between 0 - 90
9. ct = 1 - count of frame
10. for i = 1:length(theta1)

    for j = 1:length(theta2) - Its a command used to start a loop in which the values of 'i' and 'j' takes the values from '1' to(:) length of 'theta1' and 'theta2' respectively,that is '10'.Second loop(for j = 1:length(theta2)) is inside the first loop(for i = 1:length(theta1)) in which '10' loops are being made in each 10 frames of first loop.
11. THETA1 = theta1(i)
    THETA2 = theta2(j) - These are the angles used instead of 'theta1' and 'theta2' respectively for loops and the values varies from 1 - 100 (since theta1 and theta1 is 10; & i and j are 10)
12. 

    x1 = l1*cosd(THETA1),
    y1 = l1*sind(THETA1) - These are the ending co-ordinates of link 'l1' and starting co-ordinates of link 'l2' (co-ordinates equations are formed in the above figure)
13. x2 = x1 + l2*cosd(THETA2),
    y2 = y1 + l2*sind(THETA2) - These are the ending co-ordinates of link 'l2' (co-ordinates equations are formed in the above figure)
14. plot([x0 x1],[y0 y1],[x1 x2],[y1 y2],'LineWidth',2) - It plots the links of robotic arm in X-Y axis as 2D with the help of co-ordinates of the links ,'linewidth'-it helps to create the desired width for the plot
15. axis([-.1 1.5 0 1.5]) - Command used to set the x-axis limits and y-axis limits
16. title('Forward kinematics of a 2R Robotic Arm') - Command used to put the title for the plot
17. xlabel('X_.AXIS') - Command used to label the x axis
18. ylabel('Y_.AXIS') - Command used to label the y axis
19. M(ct) = getframe(gcf) - Command used to get seperate frames for each round of loops and saved in M(ct)
20. ct = ct + 1 - Command used to create succeeding frames in each frames 1 loop is saved
21. end - command used to close the loop ,2 ends are used since there are 2 loops
22. movie(M) - Command used to create a movie with frames saved in 'M'
23. videofile = VideoWriter('Forward kinematics of a 2R Robotic Arm.avi') - Command used to create video ,in which the 'video name-Forward kinematics of a 2R Robotic Arm' and 'video format -avi' is edited in paranthesis ,it can also be made into uncompressed video by editing the videowriter as -'Forward kinematics of a 2R Robotic Arm.avi','uncompressed AVI'- where the video will have the size of 64 plus mega bytes ,since i got it in 1.30 mega bytes without much quality difference in the animation video
24. open(videofile) - Command used to open the videofile
25. writeVideo(videofile,M) - Command used to write down all the frames which had been created using programming into the videofile
26. close(videofile) - Command used to close the videofile
27. semicolons are used to close the function in order to not show the output in the command window

• Outputs
• youtube link - https://youtu.be/DMVtki_kRG0
• google drive - https://drive.google.com/file/d/1aVcLczUOJ-oLD2_cNEX8kxxI-c-OFQ_U/view?usp=drivesdk
  
• 
  
• Errors

1. 1st error - I tried to plot 2 lines in a single command and tried to give them seperate 'linewidth' & 'color' and got error.So i gave them both single command for linewidth , for the color it automatically had seperate color so i didnt give any commands for that.The error -

2. 2nd error - When i was plotting, i tried to group together three x co-ordinates and three y co-ordinates in one 'square bracket'; so i got undesired plot. Then i gave them seperate sqaure brackets (since i was plotting a line so i should have given accordingly) and got desired result. The error -

3. 3rd error - When i was labeling the x-axis and y-axis for the plot ,after the underscore(_)the first alphabet was getting subscripted so i added a dot after the underscore. The error -