Subject:
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Re: rtlToronto19: Balance of Power and other upcoming events
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Newsgroups:
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lugnet.org.ca.rtltoronto
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Date:
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Tue, 1 Mar 2005 19:43:44 GMT
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Viewed:
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845 times
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On Tue, 1 Mar 2005 18:06:35 GMT, Iain Hendry <ihendry@ventax.com> wrote:
> In lugnet.org.ca.rtltoronto, Rob Antonishen wrote:
>
> > One option for the weight restriction is to use something like the
> > weighting currently in use for jockeys... but on a case by case basis.
> > Specifically, put two bots on the beam, then weight the end of the
> > lighter beam until the two start off balanced.
>
> I don't think that will work properly, though (from a fairness standpoint).
> Specifically because:
>
> 10 N @ 1 m = 10 Nm
>
> So a 1 kg mass (appr. 10 N) at the end of the beam generates a moment of 10 Nm
> at the fulcrum.
>
> Robot A weighs 25 N and robot B weighs 35 N.
>
> They both start out 0.1 m from the fulcrum.
>
> At the start, A generates a moment of 2.5 Nm, and robot B generates a moment of
> 3.5 Nm. The net moment at the fulcrum in the resting state is already 1 Nm, so
> difference of 1 Nm must be generated to keep the system in balance. So a 0.1 kg
> mass is placed 1 m from the fulcrum at the end of the beam to make up the
> difference (since 0.1 kg = appr. 1 N.)
>
> The robots move 1 m out at the same speed. It is desired in this situation for
> the system to remain balanced.
>
> The beam will not stay balanced, because, at 1 m:
>
> Robot A weighs 25 N and is now generating a moment of 25 Nm.
>
> Robot B weighs 35 N and is now generating a moment of 35 Nm.
>
> The beam will favour B, because the 1 N mass we placed 1 m from the fulcrum is
> making the net moment only 1 Nm less, while the net moment is now 10 Nm (instead
> of 1 Nm as it was when the robots were just 0.1 m from the fulcrum). B will
> have an unfair advantage.
>
> Iain
B has the advantage if and only if the assumption that the robots move
at the same rate holds true. Assuming that the two robots are are
similar in terms of battery and motor configurations, i.e. can deliver
the same power, robot A in the example would accelerate at 1.4 times
the rate of robot B, and should be able to shift it's moment that much
faster.
This is the exact trade off that I think would make this challenge
particularly interesting.
One big factor would be the pass of the beam and the friction at the
pivot. This would determine how responsive the whole system would be.
The ineriia of the beam should be kept low for the fastest response.
A T-beam made of, say 1/4" ply would also make for an interesting alternative.
-Rob A>
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