Robotic Arm: Team Stealth Squad

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Team Stealth Squad:

Overview

Our team created a dual-jointed robotic arm that would hold a pencil and draw a circle within a square within another circle. To do this we used a variety of Lynxmotion parts from the Engineering Lab classroom. The arm is attached to a surface using a c-clamp and is moved using two servo motors. The motors are controlled through a circuit board run with Matlab code. After calibrating the motors we went about creating an arm using aluminum tubes, servo brackets, and hubs. We initially used long (4"-6")tubes for the "upper arm" segment of our robotic arm, however this caused poor distibution of mass and led to an unbalanced and shaky product. Our final construct used 2" tubes for both segments of our robotic arm. After constructing the arm our team began to work on making a SolidWorks Model and creating Matlab commands that would control the arm and run the functions which we wanted with appropriate scale, speed, and accuracy.

Solid Works

Robot Arm




  • Our SolidWorks model shows the basic design and assembly of our robotic arm.
  • Fastners, pencil, and c-clamp are not included.
  • The SolidWorks file was created after completion of the physical arm.
  • It is thus more of a model/simulation than a design aid.





Matlab

Simulation

Simulated Circle
  %Define the arm
  la=4.5;  lb=4.3025;
  
  %Draw and animate the arm;
  numPts = 20;                    %the number of points in the animation
  phi = linspace(0,2*pi,numPts);  %angle goes from 0 to 2*pi.
  
  clf % clear the figure. 
  
  x0=0;  %Define center (x0,y0) of circle and radius (r)
  y0=7;
  r=1;
  
  % loop through all the values of phi
  for i=1:length(phi),
     x2=x0+r*cos(phi(i)); %x2 and y2 trace out a circle.
     y2=y0+r*sin(phi(i));
  
     %First do inverse kinematics to find angles...
     [theta_a, theta_b]= InverseKinematics(la, lb, x2, y2);
  
     %Then do forward kinematics to find arm locations.
     [xa ya xb yb] = forwardKinematics(la, lb, theta_a, theta_b);
  
     subplot(1,2,1);   %generate 1x2 plots, choose plot 1
     plot([0 xa xb],[0 ya yb],'b','LineWidth',2);
     axis([-10 10 0 10]);
  
     subplot(1,2,2);   %choose second plot
     plot(xb,yb,'ro')  %plot red circle
     axis([-10 10 0 10]);
     hold on;          %don't erase this plot.
  
     pause(0.1);       %delay 1/10 second
  end

This code simulates our robotic arm drawing a circle in MatLab. The code is essentially the same as the simulation from MatLab Lab 1, only with the arm lengths changed to correspond with the arm lengths of our robot.