Quote:
Originally posted by Al Skierkiewicz
Justin,
You are getting closer. Kevin will need to intervene here since he posed the original question. I have a hint running around in the back of my head for your bike tire analogy but I will wait for Kevin to rule on hints...
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Justin,
Yes, you are getting closer. The whole hitting-the-tire-of-an-upside-down-bike-with-the-palm-of-your-hand routine is something many kids do and therefore something that many people can relate to in the physical sense. This kind of explanation is the best kind of explanation because it takes advantage of the physical intuition that we start refining from an early age.
If I'm reading Al's mind correctly (it's scarey in there, BTW
), an Engineer would say your approach to spinning the tire (or any spinning object with mass) has a bit of a flaw. That flaw is that the error bars on the angular rate are really big. Getting beyond the Engineer-ese, this means that your RPMs aren't very close to being constant. Your approach involves hitting the tire, which causes a big jump in RPMs, then you wait a period of time while the RPMs drop to some level and then you hit it again. Imagine being in a car that had four wheels behaving like that bicycle tire -- it wouldn't be a fun way to travel.
So you need to refine your approach to spinning that tire using PWM (and what you've described *is* PWM). Remember you have two parameters to work with: frequency and duty cycle (percentage of the time the force is applied). Amplitude (amount of force, voltage, etc.) is another parameter, but it's a fixed value here.
Al: If this isn't the hint you were thinking of, feel free to jump in.
-Kevin