Omni wheels
November 13, 2009 – 2:09 pmJust a quick post to prove the project isn’t dead… I’ve been very busy with my PhD research, but have slowly been making plans and purchases for a significant hardware upgrade based around the YeRobot 4WD base I detailed last time.
A comment on that entry from the manufacturers suggested I’d have more success with a 12V power supply, so I managed to solder one together using AA battery boxes (holding 10 1.2V rechargeables in series) and the connector from a dead R/C battery. That indeed gave the motors enough bite to enable turning on the spot (as opposed to just steering), but I’ve now taken a different approach- by using Omni Wheels I’m able to get the desired results with the usual 7.2V battery. Which is preferable as I can charge that in 30 minutes, whereas it takes me nine hours to top up eight AAs- and I need ten!
The Omni wheels were part of an order I made with DAGU through LMR; the universal hub they offer looked like it’d fit the motors used in the YeRobot kit, which turned out to be mostly true… I’ve had to file the axles down a bit to attach the hubs, and there isn’t enough clearance with the case to push the wheels all the way on, so on a couple of runs one has fallen off! Still, the video shows that it essentially works, with the existing QwerkBot build inelegantly balanced on top; the next task is to strip off the old motors and figure out how best to attach the board to the rover base.
I took the opportunity to remove the switch and power supply connector from the YeRobot base, which leaves some holes I can hopefully fit a sensor of some description to, ideally a bumper switch for cheap collision detection. I also ordered an IR compound eye from DAGU, with the ultimate goal of using that for object tracking on the camera pan/tilt assembly and moving the existing sharp rangefinder to another servo for obstacle avoidance. So, plenty of plans as always!
4 Responses to “Omni wheels”
Hi about the Omni Wheel you’re using is it the 60mm Omni wheel?
By Mark on Mar 6, 2010
Yes, they are the 60mm ones.
By Graeme on Mar 7, 2010
The 60mm Dagu Omni Wheels I see have hex axel hubs, while the universal adapter is round, did you make some sort of “converter” beside filing it down?
Or did I miss something? Could you post pictures of the omniwheel mounted in the adapter? I’m interested in doing the same!
By Mark on Mar 10, 2010
Hi Mark, the adaptors are double ended, with a round end for servos and an oblong one fo the gear motors: after some filing (and, er, glue), I’ve been able to make the latter fit the motors from the A4WD kit. DAGU supply universal hubs appropriate to the wheels, so although the one in this picture – http://letsmakerobots.com/files/userpics/u1533/Hub_geared_motor_omni_wheel1__small_.jpg – is round, for the 60mm wheel they’re hexagonal.
By Graeme on Mar 10, 2010