Subject:
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Re: more on the rotation sensor
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Sat, 29 Jan 2000 22:23:31 GMT
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Viewed:
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2343 times
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In lugnet.robotics.rcx.legos, Philip Brown writes:
> Ben (ben@ben.com) wrote:
> > The order of the states (as defined by legOS, in order of increasing raw • value)
> > is: 2, 1, 3, 0.
>
> I think I have an idea what is going on.
> Consider the sensor rotating forwards. If typical readings for states 0 to 3
> are
> 3, 1, 0, and 2 (ordered as in your message) the input goes through the
> series:
The order is numerical, either 0->1->2->3->0... or 0->3->2->1->0... That's why
legOS has them enumerated that way. The Mindstorms fw numbers them
differently, which is why I mentioned it.
> state : 0 -> 1 -> 2 -> 3 -> 0 ->...
> input : 3 -> 1 -> 0 ->* 2 -> 3 ->...
>
> As the input is an analog signal, if you read it while it is changing from
> state
> 2 to 3 and the input is changing from 0 to 2 (marked with a * above) you may
> get a reading corresponding to a 1.
I don't think your specific example is correct because of what I mentioned
above. I agree that there is probably some analog signal which is a linear
combination of two adjacent inputs that appears to be something else.
For example:
actual: 0 -> 1 -> 2 -> 3
samples: 0003111122222333333
So in that case you see what should be "forward 1" translated into "back 1",
"forward 2" (ignored). I think I have observed this in practice, because it
shows up as an offset of -2 from the correct position. The other case would
be:
actual: 3 -> 2 -> 1 -> 0
samples: 33322221111113000
In this case what should be backward 1 turns into "forward 2" (ignored)"
"forward 1". An offset of +2.
In both cases ignoring a state 3 when it would result in a 2-state transition
should fix the problem. I thought I had tried that...
--Ben
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 | | Re: more on the rotation sensor
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| (...) of (...) not (...) value) (...) all (...) These (...) of (...) or (...) are (...) the (...) range (...) the (...) strength (...) to (...) I think I have an idea what is going on. Consider the sensor rotating forwards. If typical readings for (...) (25 years ago, 29-Jan-00, to lugnet.robotics.rcx.legos)
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