Robotic Arm 2.0

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Revision as of 22:11, 3 December 2008 by Kbertau1 (Talk | contribs) (Current Status)

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For our final project we will be improving the hardware and controls for the robotic arm.

Group Members


  • Hardware:
    • Add in vertical support for the arm in the form of something that can slide/roll over the paper so the arm does not sag so much that the pen cannot be lifted far enough off the paper.
    • Make the arm less wiggly
      • Improve fasteners
      • Increased rigidity in "elbow" joint, using a bracket
  • Software:
    • Better coding style for increased readability of the code
    • Integrate the two programs
    • If possible add functionality for increased user-friendliness editing capabilities

Proposed Time Line

  • Allow the user to draw lines and free paths--Sunday 11/23
  • Add saving and opening of files containing lines and free paths--Tuesday 11/25
  • Write in code to allow the arm to draw what the user has designed--Friday 11/28 (will not be tested until we are back)
  • Add the ability to draw rectangles and other regular polygons--Saturday 11/29
  • Improve the rigidity of the arm using a bracket at the elbow and tighten all the joints--Sunday 11/30
  • Add in a brace that will allow the pen to be lifted clear of the paper--Monday 12/1
  • Test and debug code to allow the arm draw what the user has designed--Tuesday 12/2
  • Include curve drawing to the GUI and to paper--Friday 12/5
  • Implement circles and arcs as well--Sunday 12/7
  • Final testing--Monday 12/8

Current Status


Currently the arm has a solenoid to allow the pen to be lifted, as well as a brace that slides across the paper to reduce the vertical give in the arm so that the pen can be lifted completely off of the paper. A bracket has been added to the elbow joint, and the servo mounting brackets are doubled to increase their rigidity.


For the project we are using Processing, an open-source JAVA-based language designed specifically with graphics in mind. Currently our code allows the user to draw line paths and free lines, as well as store and retrieve them from files. There is an arm that follows the cursor around the screen and can also traverse previously drawn lines. There is a status bar at the bottom which displays the cursor coordinates, the number of objects, and a message containing brief instructions for the user. Serial commands can be sent to the servo controller and these commands are displayed in a separate info box. Curves are in the process of being implemented, however that is not yet finished.

Updates from Meetings

Wednesday 12/3

Today we added in the brace and taped all the wires so that they would not get caught. We decided to double up the servo mounting brackets as they seemed to be too thin. In an attempt to fix the bug in the code we changed slightly how the commands to raise and lower the pen are sent to the controller and we made sure that the program closed the serial when the program was exited. Finally, we started to implement curves, which can now be drawn but not traversed or stored in/read from files.

Tuesday 12/2

Today we meet in Hicks to work on the hardware for the arm. We reconfigured the elbow joint to use a bracket and we discussed the design of the brace. Once we had determined the specifications for the brace we submitted a request to have the part machined. On the software side we added the solenoid controller to the code, so that the pen is only in the down position when it is actually drawing a line. Unfortunately, we also determined that sometimes when we start sending to the serial our code crashes for an unknown reason. We wonder whether it is an error in the Processing Serial library.

Monday 12/1

We added code to allow the program to send serial signals to the servo controller, and then a small information box that displays the device and the command to be sent. We decided to store our messages in a HashMap, making it much easier to modify the Strings. In addition, we added interpolation so the arm can smoothly transition in and out of trace mode and between paths.

Monday 11/24

We squished a few little code-bugs and then added a status bar at the bottom of the screen. We also added the ability to re-trace previously drawn lines using the virtual arm.

Saturday 11/22

We added code to allow the user to draw more than one line path and to draw in "free line" mode. We also added some file I/O and made the robotic arm display and follow the cursor around the screen.

Friday 11/21

Today we started in a fresh file (we will be adding in functionality from the two previous files). We decided to store our data as a linked list per object, and wrote in code that allows us to do so. We then added in the ability to draw a line path to the screen (however right now only one line path can be drawn).

At the Start

Before the official start of the project we created two programs where we tested out the ideas we were thinking of implementing, not spending too much time on organization. The first of these programs allows the user to draw free lines and then ask the arm to trace on paper what has been drawn. SVG files of only short lines can be imported. The second of these allows the user to draw straight lines, circles, polygons, rectangles, and line paths to the screen. On the hardware side, our arm has a pen attached to a solenoid at the end, however this does not lift the pen up far enough to hold it clear of the paper--additional support for the arm is needed. Also, there is more wiggle in the arm that we would like.