pic: off season chassis

[Chris Fultz]

From the video, it looks like most of the weight is on the back, and the robot is acting like a 4 WD, with the omni's being the "front" wheels. The other "front" wheels do not appear to be in contact with the surface.

When it spins, it is turning around a center somewhere between the back and middle wheels - hard to tell by just doing stop frames on the video.

As others said - try it on carpet. The carpet will give a little and absorb the wheels, whick may allow all 6 to have some surface contact.

[PAR_WIG1350]

It did seem to oversteer a bit and hit the pole in the beginning, but that could be due to lag or driver error.

[JVN]

Interesting. Not quite what I expected.

My guess as to what we're seeing:
Is the CG very close to the center? This would put so much weight on the center wheels it would offset the "zero" lateral traction affects of the omni wheels and shift the CG back towards where you'd expect for a "standard" 6WD.

-John

[IKE]

Very cool. Thank you so much for the testing and videotaping. Another really cool attribute to the video was the voice explaining what the driver should do as opposed to random driving around.

As far as turning goes, I was impressed that the turing center was so closely loacted to the center of the wheels (most notable at the spin near the end of the clip). I would tend to concur with JVN that maybe most of the weight is on those center wheels.

As fat as my over-steer under-steer comments from before, it would likely take a little more speed for these behaviours to show up. The bot appeared to be traveling at or below 4 ft/s.

Published lateral grip on those wheels is supposed to be around 0.2. I would expect the oversteer understeer stuff to come up when attempting at turn that would have lateral forces around 1/5th a G to 0.5 G. Lateral acceleration is equal to the centripetal force. V^2/r for 4 fps, this would be 16/r = 0.2 to 0.5 or r of 3 to 1 ft.
I will need to review the clip again. From what I remember, most of the turns were done after it had stopped.

Thanks again for trying this.