Like all of us, [Jonathan Guberman] has a list of projects and builds that ‘will get done when I have time.’ His Kiwi drive robot is no exception. It’s intended to be one piece of a much larger project, but he decided to document it anyway (we think in the hope of getting is rear in gear).
The robot uses a holonomic drive to get around. A holonomic drive uses three fixed wheels placed 120 degrees apart. The wheels can be independently controlled and with some vector addition the robot can move in any direction and rotate 360º inside its own wheelbase. Of course the wheels will have to be able to roll in two dimensions, so an omniwheel is used. Everything is controlled with a Wiimote nunchuck, and the movement is very smooth.
[Jonathan] has had a few projects featured on Hack A Day before, like his Mechanical Pac-Man and his adorable Portal turret plushie. [Jonathan] really demonstrates his artistry and skill in his project, so we’re really wondering what his ‘larger project’ actually is. Take a guess in the comments section, that might get [Jonathan]’s rear in gear.
Check out the video of the omnidirectional robot after the break.
[vimeo=http://vimeo.com/26250459]
very cool and interesting. But seems like a very inefficient way to move forward.
It creates a lot of drag when you use 3 wheels in those angles even with omni wheels trya 3 wheels in a row crossing through the center and have “rollers” for support in the needed areas but good work keep the project going!
I made one of these a couple of months back, I’d recommend using powerful servos because weak ones tend to stick solid when moving slowly.
I used miniature ones (converted to standard geared motor configuration) and they performed pretty badly. But if you get the mechanics of it right they can be a really fun way to move your project around.
And they only work on flattish surfaces like linoleum or thin carpet. Plus you need to add a rubber paint finish to the omniwheels otherwise they get zero traction.
Not to be a pedant, but…a holonomic drive is *any* drive system that offers at least as many axes of control as the platform has degrees of freedom. So, while a kiwi drive *is* a holonomic drive, it is by no means the only such system. Others in the category include the venerable four or six-wheel omniwheel drive, the newer mecanum drive, various forms of ball drives, and even (arguably) a swerve/crab drive. http://en.wikipedia.org/wiki/Holonomic#Robotics
“(we think in the hope of getting is rear in gear).”
Should be…
“(we think in the hope of getting his rear in gear).”
Mechanum wheels would be a better replacement omni wheels and have a 4 wheel drop center with that (you need 4 mechanum wheels) and have them faced opposilty than the ones on their left and righ but mark directions and include a lot center falling idlers for a structural rotation point the process may take a little longer but it worth it for its manuverability and lack of drag!
What about threaded tri-star wheels? I’ve always had a soft spot for those, and they aren’t as difficult to fabricate as omniwheels.
You can drop the 12v encoder signals down to TTL levels with a resistor and an LED (used as a zener diode voltage regulator). Depending on LED color, you get different voltage out. Common red LEDs are fine for 3.3v or 5v TTL logic.