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Tuesday, April 3, 2012

Omnibot can turn 360 degrees and go sideways too!

Translucent planetary gearbox test #2

Video Link...
http://www.youtube.com/watch?v=EfM46szNpeg&feature=player_embedded

Omnibot mkI (work in progress)

This page documents the work on Omnibot mkI. The goal of this project is to experiment with a novel configurable drivetrain that allows the robot to perform on-the-spot 360° turns, or to instantaneously switch to sideways motion - all while keeping a very accurate track of its position in almost any terrain. The design relies on just three $1.20 motors and four regular wheels, and is relatively easy to recreate even with Legos. The total price tag is under $120 or so.

Of course, robot designs capable of omnidirectional movement are not rare, but they usually employ very expensive and complex Mecanum wheels, or anywhere from 6 to 8 servomotors to independently position and operate regular wheels, in both cases resulting in a substantial price tag. Some low-budget alternatives exploit wheel slippage instead, but that approach is completely incompatible with many types of terrain, is inefficient, and makes accurate position tracking fairly difficult.

To be clear, the linkage-and-gear design used in this project is fairly simple and likely not unique. It's just that almost nobody seems to be using it, so I wanted to test out the idea.

Electronic components

This part is less exciting. The complete inventory for the planned design is:

Motors: 3 * Mabuchi RF-300FA-12350 ($1.20 each),
Motor drivers: 3 * Toshiba TA7291S/SG ($1.00 each),
Traction sensors: 3 * Toshiba TLP841 ($0.45 each),
Distance sensor: LV MaxSonar EZ4 ($27.00),
Microcontroller: AVR ATmega1284P ($5.90),
Display: Newhaven NHD-0216K1Z-NSW-FBW-L ($12.00),
Power supply: Zippy Flightmax 800 mAh 7.4V Li-poly ($6.20),
Supply watchdog: Maxim MAX8212 ($3.00) + STM STP12PF06 ($0.80),
Supply adjustment: Murata OKR-T3-W12-C ($6.20),
...plus several resistors, capacitors, switches, etc ($3.00).

The resulting robot should be a GCC-supported, libc-enabled compilation target running at up to 20 MHz, with 128 kB of program memory and 16 + 4 kB RAM. The system features very low power consumption - thanks to motors running with minimal losses (and consuming approx. 40 mA per motor).

Other materials and processes

Read More...
http://lcamtuf.coredump.cx/omni/

Now, if I could just make one, big enough to mount an Office Chair on and rig a Joy Stick to control it... I would be Rollin in Style!:) Seriously, wouldn't this make a great Base for an Electric Wheel Chair?...

Don