Page 320 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Android hand 16

IN THIS CHAPTER WE WILL CONSTRUCT A HUMANLIKE OR
android hand. The actuator we will use to move the fingers in the an-
droid hand is the air muscle introduced in Chap. 3.
The air muscle is a pneumatic device that produces linear motion
with the application of pressurized air. Much like a human muscle, it
contracts when activated. You may think, well, pneumatic cylinders
have been around quite a while and do the same thing. True, but the 299
air muscle represents a boon to hobbyists and robotists because it is
lower in cost, extremely lightweight, flexible, and easier to use.
The air muscle has a power-to-weight ratio of about 400:1. Since
most of its components are plastic and rubber, the air muscle can
work while wet or underwater. The flexible nature of the air muscle
allows it to be connected to and contract on/off axis pulleys and
levers. The air muscle can contract even when bent around curved
surfaces. These easy-to-use features make the air muscle the exper-
imenter’s choice over standard pneumatic cylinders.

Of course, being a pneumatic device it needs a supply of com-
pressed air. Compressed air is not as readily available as electric
current. When I first learned about the air muscle, I thought that a
small air system would be too much of a hassle to build. I was
wrong. A simple air system can be put together for about $25.00,
and a small electric air system for about $50.00.
Overall efficiency is lost when using electric power to compress air.
However, the air muscle consumes little air volume per activation
and the compressed air can be stored. The air muscle’s response
and cycle times are fast. A small 6" 10-gram (g) air muscle can lift
6.5 pounds (lb).

Team LRN Android hand

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