August 20, 2008

GrabBob, a 4 fingers wiimote controlled grabber




Hi Everyone!

It' s been a long time since I have not built a grabber. And this time, I tried to do an unsusual one:

Most LEGO grabber arms use 2 different axis to open or close the hand. It actually is the most eficcient way to make a good grabber, and I first wanted to do one like it. Still, a friend of mine asked me if I could build a grabber like the one in the movie "Iron Man" : the main character has a small cute fellow grabber, whith 3 fingers on different axises. Considering that it' s very hard to deal with triangles in LEGO geometry, I decided to make it 4 fingers.

I had to use a small trick for the linear actuator to open or close the hand, as you can see on the video below, but building the grabber was not the main difficulty.
I actually had a lot of trouble to make the grabber rotate on its base, because of the high torque that was applied on the axis. I didn' t use the part 48542 because it involved way too much friction. So I decided to tinker something, still the result is pretty lousy.

The wiimote has 3 sensors : an hitechnic accelerometer, for the wii-like control, a light sensor, to control the opening of the fingers, and a touch sensor, only to stop the robot ( I only use the touch sensor to put the robot back in its initial position).

Obviously, it is not a good grabber! Anyway, I had a lot of fun building and programming it, and it' s kind of a pretty robot. ^^

Bobly yours