Week 3.2 - 2R Robotic Arm Challenge

AIM:

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

OBJECTIVE:

• Create an animation file of the plot.
• Step-wise explanation of your code.
• Mention the errors faced while programming.
• Steps taken to overcome those errors.
• Screenshots showing errors thrown in command window.

ROBOTIC ARM:

• A ROBOTIC ARM is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot.
• The links of such a manipulator are connected by joints allowing either rotational motion (such as in an articulated robot) or translational (linear) displacement.
• he links of the manipulator can be considered to form a kinetic chain.
• The terminus of the kinematic chain of the manipulator is called the end effector and it is analogous to the human hand.

INPUTS:

• length of link (l1) is l1 = 1.

• length of link (l2) is l2 = 0.5.

COORDINATES:

(x0,y0)

• The starting point of the link 1 is attached to the base as the base is fixed, so the starting point of the link 1 cannot move as it is in fixed position so the value of 'X' and 'Y' will be '0'.
• x = 0.
• y = 0.

(x1,y1)

• The ending point of the link 1 is the starting point of the link 2. The length of link 1 is l1 and the angle between the base and link 1 is represented by an angle 'theta1'.
• x1 = l1*cosd(θ1).
• y1 = l1*sind(θ1).

(x2,y2)

• It is the ending point of link 2. The angle between link 1 and link 2 It is represented by an angle θ2">θ2 and length of link 2 is l2. The equation x and y will be,
• X2=X1+l2*cosd(θ2).
• Y2=Y1+l2*sind(θ2).

MATLAB CODE:

1. CODE FOR 2R ROBOTIC ARM (θ1 & θ2) ARE GIVEN MANUALLY

close all
clear all
clc
% matlab code for 2R robotic arm 
% inputs
% for fixed theta 1 & 2 values

l1 = 1;
l2 = 0.5;

% the values are changed manually
theta1 = 45;
theta2 = 60;

% coordinates
x0 = 0;
y0 = 0;

x1 = l1*cosd(theta1);
y1 = l1*sind(theta1);

x2 = x1+l2*cosd(theta2);
y2 = y1+l2*sind(theta2);

% ploting
line([x0 x1],[y0 y1],'linewidth',3,'color','b')
line([x1 x2],[y1 y2],'linewidth',3,'color','r')

2. CODE FOR 2R ROBOTIC ARM FOR MULTIPLE VALUES (θ1 & θ2) (USING NESTED FOR LOOP)

close all
clear all
clc
% 2R robotic arm cahallenge
% For multiple values of theta 1& 2
% initializing inputs for theta 1 & 2
l1 = 1;
l2 = 0.5;

theta1 = linspace(0,90,20);
theta2 = linspace(0,90,20);

% using nested for loop for geting values for different values of theta 
ct = 1;
for i = 1:length(theta1)
    THETA1 = theta1(i)

    for j = 1:length(theta2)
        THETA2 = theta2(j)
        x0 = 0;
y0 = 0;

x1 = l1*cosd(THETA1);
y1 = l1*sind(THETA1);

x2 = x1+l2*cosd(THETA2);
y2 = y1+l2*sind(THETA2);

% ploting
plot([x0 x1],[y0 y1],[x1 x2],[y1 y2],'linewidth',3)
axis([0 2 0 2])
pause(0.03)
M(ct) = getframe(gcf);
ct = ct+1;
    end
end

% creating movie using matlab
movie(M)
videofile = VideoWriter('robotic arm.avi','Uncompressed AVI')
open(videofile)
writeVideo(videofile,M)
close(videofile)

EXPLANATION:

1. Matlab code is started with clear all, close all, clc command .
2. The input value for θ1 & θ2 IS determined with a command linspace in this we create a degree of freedom from 0 to 90 with 20values between the degree of freedom.
3. Then initialize the counter command using ct.
4. To move the robotic arm continuously we are using for loop.
5. Then enter the values of co-ordinates ([X0 X1], [Y0 Y1],[X1 X2], [Y1 Y2]).
6. Then plot the values of ([X0 X1], [Y0 Y1],[X1 X2], [Y1 Y2]) with the 'linewidth',3.
7. Then axis command is used for fixing axes - changing x-limits and y-limits.
8. Then use pause command to slow down the output.
9. Then we use getframe command to get individual frame and stored in variable M .
10. (ct = ct+1; )Then incrementing the counter value by 1.
11. The end command is used to end the for loops, this terminates the set of instructions.
12. Using movie command we can create a movie with the help of individual frame.
13. Using the different individual frames a new uncompressed avi file is created using videofile command.
14. Then we are opening the videofile using the open command and closing the videofile using the close command.

ANIMATION VIDEO LINK:

https://youtu.be/eregx6qHDCI

ERRORS:

CASE SENSITIVE ERROR 1

After changing the 'J' to small'j' the error is solved.

ERROR 2

As i used double '==' the error poped up ,so removing one '='the error is resolved.

ERROR 3

In the line 33 the command was typed worngly as 'geframe' instead of 'getframe' after changing the error was resolved.