Seminole Ridge SECME: End Effectors for Robotic Arms

Thursday, November 11, 2010

End Effectors for Robotic Arms

Humans and Robots Educational Brief
Have your students build an end effector similar to the one on the Orbiter’s robotic arm with simple, everyday materials.

Objectives:
• Students will learn how the end effectors for the robotic arms used on the Space Shuttle and the International Space Station work.
• Students will design and construct a grapple fixture that will enable the end effector to pick up an object.
http://quest.arc.nasa.gov/test/speakersnotes/ITP/78/examples_tech.html

Will it work, Norman?

Will it work, Ronit?

Will it work, Tavo?

Will it work, Sean, Eric and Alex?

Will it work, Yiro and AJ?

Yes! Yes it will!

Activity:

End Effector instructions
1. Nest the two coffee cups together. Using the plastic picnic knife, saw through the sides of both cups to make two rings (See illustration 1). Try to make the cut level through both cups (Based on the age of the student, teachers may want to do this part). Smooth away any rough edges left from the cuts.
2. Cut three pieces of string 12 cm long. Tape each string around the outside of cup 1 (See illustration 2). Leave a little bit of string hanging out from the tape. You will need to adjust the strings later by pulling on the ends.
3. Tape the long end of each string to the inside of cup 2. This will form three loops going from the outside of cup 1 to the inside of cup 2 (See illustration 3).
4. Begin the adjustment procedure by rotating cup 1 only 120 degrees (1/3) of the way around cup 2. This will realign the two tape points of each string across the opening of the cups. Gently pull on the ends of each string so that the strings stretch straight across the opening (See illustration 4). Your end effector is ready for service.
5. To see how the end effector works, rotate cup 1 back to its original position. The strings will loosen up. Have a partner hold out an index finger (grapple fixture). Slide the end effector over the finger past the first knuckle. While holding cup 2 still, rotate cup 1. The snare strings will wrap tightly around the finger. You have capture. You can tug on your partner but be careful. Your end effector is only made from tape, string, and Styrofoam cups!