Quote:
Originally Posted by Ether
Thanks for posting this. Very interesting!
See attached screenshot. The friction has a lot of "noise" (to be expected) but it appears to be independent of velocity. So I fit a least-squares line instead of a quadratic. I'd say the friction is darn close to 6 Newtons.
Arghh. Won't let me attach screenshot. I'm going to upload it with the paper attachments.
OK, here's a link to the screenshot:
http://www.chiefdelphi.com/media/papers/download/2999
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Thanks Again!
We've been doing more testing to analyze the model accuracy.
I think the largest remaining error is the phenomena of sliding friction that occurs when the power is first applied.
The model suggest that the robot should move its first half inch within 0.05 seconds of applying the power.
We see it taking about .3 seconds based on video analysis.
It's approximately 0.2-0.3 seconds whether we turn the motors on after the mininbot is attached to the pole or if we start the motors up prior to attaching to the pole.
After accounting for the time of this initial sliding friction, the model you produced accurately predicts the measured time of our minibot!
I'd be curious if anyone else would be willing to share their results.
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I would think a ramp bot could be better able to minimize this initial sliding friction and also immediately start doing "work" (some of which that will be turned into vertical momentum) as soon as it turns on. The pole bot has to wait until it reaches the pole to have any of its work being used for creating vertical momentum, Thus, I'm a firm believer that theoretically, a ramp bot can obtain a better time than a pole bot.