Challenge

Week 2- 2R Robotic Arm Challenge

HHarish Reddy G10 Mar 2022

% Program to simulate kinematics of a 2R Robotic arm

% 2R robotic arm i.e., 2 is no of links, R - rotation, 2 rotating links

% Consider Link 1 to be L1 and it makes an angle theta1 w.r.t x axis in counter clockwise direction
% Consider Link 2 to be L2 and it makes an angle theta2 w.r.t x axis in counter clockwise direction

% Link 1 is fixed to a base A and its movement is restricted to have only 1
% degree of freedom i.e, rotation about an axis perpendicular to the plane xy

% Link 2 is fixed to joint B and its movement is restricted to have only 1
% degree of freedom i.e, rotation about an axis perpendicular to the plane xy

% Projection of Link 1 on x axis = L1cos(theta1) 
% Projection of Link 1 on y axis = L2sin(theta1)

% Projection of Link 2 on x axis = L1cos(theta2)
% Projection of Link 2 on y axis = L2sin(theta2)


% Assigning input variables
L1 = 1;
L2 = 0.5;
% For a fixed lengths of L1 and L2, let us consider the multiple theta1 and theta2 values to generate a
% motion plot and also to create an animation video.

theta1 = linspace(0,90,10);
% linspace command - takes 10 values between 0 and 90 with equal intervals
theta2 = linspace(0,90,10);
% linspace command - takes 10 values between 0 and 90 with equal intervals


ct=1;
% ct - counter is used to generate plots one by one in a single figure so that it appears as a motion plot 
% To create multiple plots, "for loop" is used as this command does a
% repeat action of the same instructions with different inputs till the program terminates.
for i=1:length(theta1)
    % for loop is initiated, condition - variable 'i' goes through the no of values
    % assigned for theta1 i.e., a total of 10 values. Therefore, the
    % instructions or commands in the for loop are repeated 10 times with
    % different 'i' values.

    THETA1 = theta1(i);
    % for each iteration, THETA1 takes one value i.e., from theta1(1) to theta1(10)
    % theta1(1)=0, theta1(2)=10, theta1(3)=20, theta1(4)=30, theta1(5)=40,
    % theta1(6)=50, theta1(7)=60, theta1(8)=70, theta1(9)=80, theta1(10)=90

for j=1:length(theta2)
    % for loop is initiated, condition - variable 'j' goes through the no of values
    % assigned for theta1 i.e., a total of 10 values. Therefore, the
    % instructions or commands in the for loop are repeated 10 times with
    % different 'j' values.

    THETA2 = theta2(j);
    % for each iteration, THETA2 takes one value i.e., from theta1(1) to theta1(10)
    % theta2(1)=0, theta2(2)=10, theta2(3)=20, theta2(4)=30, theta2(5)=40,
    % theta2(6)=50, theta2(7)=60, theta2(8)=70, theta2(9)=80, theta2(10)=90

    % CODE WORKING:
    % The second for loop i.e., for 'j' is inside of the first for loop of
    % 'i'. The reason for creating code in this manner is to generate a
    % motion plot with L1 being fixed while L2 rotates. 
    % Working of code: 
    % for every 'i' value for THETA1, 10 'j' values will be considered for THETA2 
    % i.e., for every THETA1 of L1,  a number of 10 THETA2 values will be
    % considered to run the program and therefore, 10 plots will be generated for one angle of L1
    % a total of 100 plots will be generated by the end of the entire program.
    
  % Assigning coordinates for plotting links L1 & L2  
   x0 = 0;
   y0 = 0;
   % Let the starting/initial coordinates be at the origin

   x1 = L1*cosd(THETA1);
   % From trigonometric approach, the length of L1 along x axis is L1costheta1

   y1 = L1*sind(THETA1);
   % From trigonometric approach, the length of L1 along y axis is L1sintheta1

   x2 = x1+L2*cosd(THETA2);
   % From trigonometric approach, the length of L2 along x axis is L2costheta2. 
   % The ending point of L1 is starting point of L2, therefore the x coordinate of L2 is x1+L2costheta2

   y2 = y1+L2*sind(THETA2);
   % From trigonometric approach, the length of L2 along y axis is L2sintheta2. 
   % The ending point of L1 is starting point of L2, therefore the y coordinate of L2 is y1+L2sintheta2
   
   % NOTE: d is used before theta to mention the angle in degrees otherwise it
   % will be considered as radians while executing the program.

   plot ([x0 x1],[y0 y1],[x1 x2],[y1 y2],'linewidth',3);
   % plot - creates a 2D plot of links on xy plane
   % linewidth - creates a linewidth of 3 to the plot line 
   xlabel('x axis');
   % xlabel - to label the x axis
   ylabel('y axis');
   % ylabel - to label y axis
   axis([-0.1 2.5 0 2.5]);
   % axis - to create limits for x axis and y axis 
   % -0.1 to 2.5 - x axis limits, 0 to 2.5 - y axis limits
   title('kinematics of 2R robotic arm');
   % title - creates title for the plot on top of the graph
   pause(0.5);
   % pause - takes a pause 0.5 seconds after each run of the program
   M(ct)=getframe(gcf);
   % M - movie file name,ct - counter
   % getframe - records or captures the plot, each plot is one frame
   % gcf - gets the current figure or plot that is being executed
   % M(ct)=getframe(gcf) 
   %         M(1) = getframe(gcf) means first plot is captured
   %         M(2) = getframe(gcf) - second plot is captured and so on

   ct = ct+1;
   % after counter 1, it increments by one to execute the program for next plot 
   % and so on till the for loop terminates

end 
% end of for loop for 'j'
end
% end of for loop for 'i'

movie(M)
% movie - to play movie file M
videofile = VideoWriter('Test_moviefile2Rroboticarm_Harish.avi','Uncompressed AVI');
% Videowriter creates a videofile and file format on which video data can be written
% videofile is the name or variable assigned to videowriter
open(videofile)
% opens the videofile for writing video data
writeVideo(videofile,M)
% writevideo - writes the video data of M i.e., the frames captured by M onto the videofile
close(videofile)
% closes the videofile after writing video data

% Explanation of the output motion plot:
% With each angular rotation of L1 about base, L2 rotates about 10 angles about the joint connecting
% L1 and L2. Therefore, for 10 angular rotations of L1, L2 rotates about
% 100 angular rotations about joint connecting L1 and L2.
% The space covered by the links L1 and L2 by angular rotations from start
% point to end point is called the workspace of the robotic arm
% The motion plot does not have smooth transition from one plot to other as
% the pause provided between each plot is 0.5seconds.

% Explanation of the output  movie(M):
% By giving commmand movie(M), the video will be played once and the framerate is 12fps by default.

% Explanation of output video file saved in the folder:
% By creating a videofile name and format, an object is created so that
% video data can be written on it. Once the video data is written on it, it
% will be saved as a videofile in the format. The framerate is 30fps.

ERRORS FACED WHILE PROGRAMMING