This was an attempt to build a robot that was directly connected to a person.
I just got my new pneumatics mini pump and cylinder and of course, wanted to test them right away, so this "hand" was a good start.
Even though it's not really automatic or independent (can you see an RCX/Scout?), it has some interesting features. The arm can move up and down in an angle of about 45°, the hand can open/close and rotate.
The basic idea of this creation was that a human could put his/her hand inside the robot to operate it using electric polarity switches and pneumatic valves. I will describe more about this topic later.
The compressor mounted on the bottom is an exact replica of the one shown on Ralph Hempel's page (link here). If you watch closely you will see it's actually hanging upside down.
The only difference is that the two pumps are not connected. Each one pumps air independently. The pump with the blue tube provides the pressure needed to raise and lower the arm, while the other one fills an air tank that allows the grabber hand to operate.
The hand mechanism itself is not very complicated, and there are much better pneumatic arms and hands that can be found on the internet (see the one made by Philippe Hurbain here), but the main challenge for this invention was to make it ergonomic, that is, comfortable for the user.
I tried to use a few rounded pieces for the parts where the user would place his/her hand (as you know, LEGO pieces have pretty sharp corners and edges), together with flex tubes. The yellow lever (index finger) controls the rotation of the hand using the polatiry switch. The red one (middle finger) activates the grabber. Notice that I was holding the arm in the wrong way (duh). The thumb is supposed to be in the blue valve lever visible in the upper right corner of the picture, controlling the "elbow" joint.
Another shot of the "human interface", or what you wish to call it. By the way, the hand is inserted between the two green tubes you see on the bottom of the picture.
The arm is pretty useless in most cases (unless you are dealing with toxic jellyfish, an extremely ugly spider or something of the kind) considering that it's much easier, faster and less battery consuming to grab something with your hands, not mentioning the weakness of the pneumatic cylinder's grip. But the "control glove" was an interesting thing to build and test, and I guess there could be some smarter use for that.
The "elbow joint" takes ages to move because i did not have enough pneumatic "T-junctions" to be able to drive both the elbow and the grabber from the air tank, I hope I will improve this some day.
I used the large Technic turntable for the rotating motion of my grabber hand; it is geared down quite a bit. The pneumatic tubes run through the hole in the center of the turntable. Therefore it is possible to let the hand make a couple of rotations before it gets stuck.
Some of the advanced pneumatic builders might cry when they see the poor design of the grabber, but hey, it's my first try! ;-)
One last shot of the "glove". The battery box powers the compressor and feeds the polarity switch for the turntable, which turns in one direction when you push the yellow lever forward and the other when you pull it back.
In the first pictures you can see that the pneumatic tubes go inbetween the yellow L-shaped bricks (between the red and the yellow levers), I guess they got messed up during the photoshooting; that's why on this picture they are a little out of place.
I hope I get to build another robot with a similar glove-like interface, come back often to see when it's finished.
Green