Engineering Projects/Robot arm/Howard Community College/Fall2011/502 TFCW

This is the Howard Community College Fall 2011 robot arm project.

Electronic Sections Expected

Problem Statement

Build a robot arm that is able to turn in all directions and pick up objects with an end effector.

Team Members

Summary

During this project Caleb Woo and Timothy Francis set out to build a functioning robot arm with and end effector. After the first week we decided that Timothy Francis would take on designing and building an end effector by using 123D and Caleb Woo would begin building the robot arm based off of a previous project except with a better, lighter and more flexible design. Although we were unable to get an end effector out of 123D and the 3D printer, we were able to complete a prototype Robot arm with a paper end effector. It is manually controlled by pushing and pulling the different wires and the bottom end of the arm and is able to pick up and drop objects by pulling and letting go of a string connected to the end effector.

Poster

Here are a few pictures and videos of the Robot arm and 123D end effector pieces:

123D model

Miniature arm with stand

Robot arm in grabbing station

End Effector

Robot Arm Picking up Lego

Wire holders

Links To Videos We Have Taken:

Robotic Arm Video #1 http://www.youtube.com/watch?v=JZa7Lc66-xg&feature=feedu

Robotic Arm Video #2 http://www.youtube.com/watch?v=Z-zSgx0VA98&feature=feedu

Robotic Arm Video #3 http://www.youtube.com/watch?v=3TWI68-86sg]

Links To Photos We Have Taken:

Robotic Arm Photo #1 [1]

Robotic Arm Photo #2 [2]

Robotic Arm Photo #3 [3]

Robotic Arm Photo #4 [4]

Robotic Arm Photo #5 [5]

Robotic Arm Photo #6 [6]

Robotic Arm Photo #7 [7]

Robotic Arm Photo #8 [8]

Robotic Arm Photo #9 [9]

Robotic Arm Photo #10 [10]

Robotic Arm Photo #11 [11]

Robotic Arm Photo #12 [12]

Robotic Arm Photo #13 [13]

Robotic Arm Photo #14 [14]

Robotic Arm Photo #15 [15]

Story

For this project we set out to try to build a robot arm that was able to turn in all directions and pick up objects with an end effector. We decided to split the project into two parts with Caleb Woo designing and building the robot arm, and Timothy Francis designing and building the end effector.In the first week of project robot our goal was to be able to understand how to build a working robot arm and end effector. we were able to find out that the previous team build a robot arm based off of the Festo design called the Bionic tripod 2.0 seen in the middle of this Video. The previous team however did not use as many rods and the rods themselves were too stiff and glued at too many points to provide almost no movement.The arm works by pulling and/or pushing the rods to make the arm turn in a desired direction. We then began building a miniature model of a three wired arm by using plastic wire and Lego mindstorm pieces. We connected the ends of the wire using a Lego tire rim piece a gluing them into the holes and we connected the center of the wire using a 6 holed piece and hot glue. During Week two of the project we set out to make the robot arm more flexible an sturdy. The problem was that the arm would bend only at the point were it was glued and the rest of the arm would be flimsy and not well held together. We was able improve it by adding three more connectors that would connect the wires wider the higher you went up. This would allow the connectors to naturally stay in place yet allow the wire to be passed through it to allow for more flexibility. We then were able to find a cardboard box and connect the end of the arm thought the cardboard box so that we could control the arm from the top.

During week three of the project we were still having problems with the 123D model of the end effector so we started drawing possible designs for a miniature end effector built from Legos and hard paper. We came up with an idea of duplicating the previous end effector but with smaller fingers, and less cross pieces in the fingers. Also instead of attaching strings to each finger we would attach all the fingers to a central circular Lego piece that would be pulled by a plastic wire. What we came up with is seen here. We then tried picking things up with it thinking the cross pieces weren't needed but it was very weak and it did not have the fin ray effect curling around an object so we soon added crosspieces. We then attached the end effector to the arm using tape as a temporary solution and we were able to pick up a Lego object with the arm. Here are three pictures of the arm picking up the piece: 1, 2, 3. During week four of project robot arm we set out to try to build a mechanized or manual system that would raise and lower the individual wires or the robot arm holding them in place. We began seeking multiple push and pull systems as well as railing systems and sliding systems. However, we were unable to implement any of theses systems due to lack of materials, time, and ways to control hold each of the sliders in place. We also tried connecting all the wires together like a puppet, but tuning and curling relied on turning and curling the piece holding the wires together which resulted in lack of flexibility and smoothness of control. Finally, we decided to add two Lego beams directly behind the two lateral wires. By adding peg like Lego pieces to the ends of the wires we were able place the wires at different levels while having them held in place by the Lego Beams. With this holding system it made it easier to control the direction of the arm while manually pushing or pulling the front wire. Essentially it gave us two extra hands to hold the side wires in place while we controlled the front wire and end effector with ours. We was unable to get any mechanized raising or lowering system but We plan on continuing the project to build such a system.

Decision List

At the beginning of this project we decided to somewhat replicate a previous project design of the robot arm but smaller, more flexible, and more sturdy. We also decided to split the project into two parts; timothy would take on designing the end effector and Caleb would take on building the robot arm. SEX!

Material List

Three strands of plastic wire that is straight, light, and flexible.
Lego mindstorm pieces
Hot glue for gluing the ends of the wire to the end Lego piece.
Cardboard box for grabbing station
Hard flexible paper material such as that from a cereal box for end effector
Tape for making end effector

Software List

Google for searching the festo robot arm.
123D.exe for designing parts of an end effector.

Time

4 week project.
Approx 18 hours designing and building Robot arm.

Tutorials

The Festo robot arm we modeled ours of off is seen in this Video

Start out by getting three plastic wires that can be bent straight and are flexible (We used the wire from the 3D printer and bent them as straight as possible).
Glue the ends of the straightened wire into three holes (all one hole away from each other) of a lego mindstorm tire rim piece.
Add about 4 connectors to the arm that all have three holes for the wires to feed trough. Make sure that as you move up the arm that the connectors connect the wires wider to keep them all in place yet be free flowing.
Make a base connector that can be attached to some box or stand.
Make holes in a box or stand (we used a cardboard box)so that the wires can be fed through.

For the end effector:

Cut three strips of some type of hard paper that is flexible (like from a cereal box)to desired length and width. Make sure they are all the same.
Bend each strip at about 2/3 the way up each strip.
Attach the longer half of each bent strip to a plastic gear (or some sort of desired piece with a hole in the center) and make sure each end is separated from the others evenly to create a claw like structure
Cut a small piece of hard plastic wire about 2" and attach the end of it to a small circular or triangular piece to create an umbrella looking component.
Slide the plastic piece through the hole in the center of the gear with the fingers pointing up.
Attach each end of the fingers to the center piece causing the piece to look like that of a claw.
Cut 3 square pieces of your hard paper material about the width of each finger and cut about a quarter the of the way into each square on two parallel sides of each square.
You should be able to bend two lips out of each cut. Bend one upward and the other downward, doing the opposite to the other side of the square (across from a lip that is bent up bend it the lip downward and vice versa)
Place each piece about halfway up the inside bend of each finger and about 2/3 the way up the outer bend. Tape the lips to both sides of the inside of each finger.
After this you should be able to open and close the claw by pushing and pulling the piece of plastic wire.
Glue some type of string to the end of the plastic wire and feed it and the wire through the end of the robot arm.
You can attach the end effector to the arm by using either tape, hot glue, or any other preferred means. Just make sure that the plastic wire and string can move freely between the arm and the end effector.
Pulling the string should close the end effector and letting the string go should open it back up.

Next Steps

Create a way to control the four wires and end effector effectively and more precisely then with your hands. This could be done with some raising and lowering system for all three wires at once and for each of them individually.