New Servo Feedback Type/$100 Robotic Arm

[tusavision]

I just posted a topic on physics forums but the more I thought about it, the more I thought this forum was the right place to ask.

http://builders.reprap.org/2009/09/b...boo-robot.html I want to see this design move forward. Before I can work on the mechanical engineering aspects of the motors: I want to work on my position control system. (Cheap geared DC motors like those from solarbotics/chinese drill motors seem ideal if I can convert them in to servos somehow. I'm also considering DIY worm wheels drawing from the astronomy or http://en.wikipedia.org/wiki/Magnetorheological_fluid between clutch plates to manage the holding torque issue with DC, but that's getting ahead of myself.) Rather than going with the potentiometer/optical encoder positioning that seems popular on many systems/servos: for ultra-low budget reasons: I'm inclided to go with a CCD active motion capture setup wiimote style. http://www.chinavasion.com/product_i...-audio-camera/ Now: If I put and IR filter on several of these cameras and affix them to the arm on each axis of movement: I imagine I can keep the robotic arm in a room with line of sight to multiple reference IR LEDs, and I can use this code: http://code.google.com/p/lasertraq/ to translate the video feed in to positional feedback on the arm. I guess is what I'm looking for is suggestions/constructive criticism. Trouble you anticipate I might run in to from your experience in such things. Not being a CS/Mechatronics expert, I have no experience to draw from on the: "in over my head" scale. Flame away.

I'll elaborate here on my motivations:
From a philosophical standpoint I think the robotic arm is a better direction for the reprap project due to the high speed/low precision/LOW RIGIDITY requirments.

Those considerations in mind: a cartesian bot seems like overkill/over-engineering to me.

If these solarbotics motors can be servo'ed in to an acrylic arm with a lightweight MIG welder/plastic extrusion head attatchments: rapid prototyping could make a major leap in access/price.


I'm playing with a pair of Harbour Freight digital calipers as we speak and it's awfully tempting to try and strap one to a syringe/lead screw and make a regulated pump for hydraulics. I guess that brings me to the stepper vs. servo debate which I just started reading.

This is the parrallel discussion if anyone cares to follow both.
http://www.physicsforums.com/showthread.php?t=370180