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#166
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Re: Team Update #18
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The only assumptions used in the calculation were to ignore friction (which was explicit, not implied) and to ignore additional stored kinetic energy (rotational). These tend to cancel each other out. Over very short distances (such as 1/4"), the stored rotational KE easily overcomes friction, so it's actually a conservative assumption. You can demonstrate this for yourself, if you like: with the wheels raised, power your minibot with 12V and then remove the power. Observe how much the wheels turn after the power is removed. If you have questions about the mecanum analysis I would be glad to discuss those, but not in this thread. |
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#167
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Re: Team Update #18
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2.) Light sensors are subject to noise and calibration. These may work better than proximity sensors since the noise is most likely easy to isolate, yet the tolerances in spacing would have to be tight to ensure even the slightest movement of the plate triggers the sensor. The designers simply may not have the time to implement something so quickly across all of the regional events for this week or even next week. This one seems the most feasible to me from a technical perspective though. 3.) Any instant replay sets a dangerous precedent. There will always be those who make assumptions based upon what's happened before, regardless of what's stated in the manual and regardless of what's talked about at driver meetings. I think FIRST just doesn't want to go there unless there's more thought put into it. That desire is reasonable in the longer term just to simply avoid stress during competition. Yet assuming a photo finish for 1 specific aspect of every game could probably also open up the types of activities we'd perform in future games. So I'm with you on this one ... subject to that caveat. |
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#168
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Re: Team Update #18
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*dangerous because the process of coming to the conclusions would then be acceptable to use elsewhere. I can't characterize the friction with numbers or equations, which I will concede. Interestingly, that's the very specific reason we [industry] do shock testing for our real world complex systems. The equations simply don't match the results of the real implementation. Last edited by JesseK : 17-03-2011 at 11:01. Reason: clarity |
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#169
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Re: Team Update #18
I'm counting the days down until Waterloo. Get your popcorn ready.
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#170
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Re: Team Update #18
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#171
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Re: Team Update #18
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Logically one would think that a setup using limit switches would be momentary-ie not having to be triggered for some finite time period. We should have foreseen that there was not enough real world testing done to show how robots hitting the towers would affect the response of the triggers? In the future I guess when we see things like this you're saying we should assume FIRST will not be able to implement them properly and as such we should ask way more questions than necessary to ensure that everything works right? |
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#172
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Re: Team Update #18
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So the refs, judges, and staff at the events are VOLUNTEERS. According to the people who don't see it my way, they should be forgiven any and all shortcomings, because they're VOLUNTEERS. Everyone claims that a cornerstone of the FIRST program is the tenet of GRACIOUS PROFESSIONALISM. To me, doing your job poorly, or worse, outright incorrectly (as in 2008 SVR Finals Match 2), is UNPROFESSIONAL. Not only that, but each and every team has mentors. All of whom are, themselves, VOLUNTEERS. The mentors are expected to know and follow the rules, because if they don't, and their teams robot doesn't comply with the rules, they don't get to play. This isn't even what this argument is about, though. FIRST HQ is NOT run by volunteers. Many of the staff at FIRST HQ take a salary, paid for by our entry fees, and the sponsorships provided by industry. They are being paid to provide the teams with a product, a competition. While I might be able to be convinced to forgive the shortcomings of a ref based on the "volunteer" argument, I will never be able to be convinced to forgive FIRST HQ for shamelessly doing things at the expense of their customers, the teams. |
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#173
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Re: Team Update #18
Does a standard scale, such as the ones used to inspect the robots at competition, give us the weight or mass of the robot? In other words, is the number we see equal to mass*[accel due to gravity] or equal to only mass?
Using a direct weight-equals-mass calculation, I get 0.586 feet stopping distance and 488N for stopping @ 1/4". Dividing by the acceleration of gravity, I get a stopping distance of 0.060 feet (~3/4") and ~50N to stopping @ 1/4". |
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#174
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Re: Team Update #18
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If you measure something on Earth, then you can use that force to calculate the mass, as follows: kilograms = pounds * 0.4535924 If you use the same scale on the Moon, you will get a force reading about 1/6 of what you got on Earth, even though the mass is the same. |
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#175
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Re: Team Update #18
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#176
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Re: Team Update #18
I wouldn't say I'm a whiner, but I did propose a solution: http://www.chiefdelphi.com/forums/sh...57#post1040957
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#177
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Re: Team Update #18
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(I was asked to itemize it out this year because we're doing budget negotiations and it looks like the admins are trying to cut compensation for extracurricular advisors, so I did the math and discovered that when it comes down to brass tacks I get paid about $0.07/hour if we keep it to only one summer project, but still...) |
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#178
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Re: Team Update #18
@pfreivald: ok, so maybe not ALL the mentors on FRC teams are 100% volunteers, but my point is still valid since you're in the overwhelming minority.
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#179
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Re: Team Update #18
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(I hope you realize I was just playing with you.) |
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#180
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Re: Team Update #18
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Just kidding. Quote:
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Real engineering specifications are pretty explicit, I'm working on a project here at work that has an entire page explaining that the power LED must turn on when I apply power to the system. It even states how fast the LED must turn on when power is applied. The 'spec' we got from FIRST, if you can even call it that, was most definitely incomplete, and yes we should have foreseen complications from a lack of real world test data. I stand by my original argument, both the teams and FIRST are responsible for this. Matt |
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