Subject:
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Re: Rotational Sensor & Gearing Down
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 24 Jan 2001 12:36:15 GMT
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Viewed:
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1605 times
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"Dean Husby" <nntp@akasa.bc.ca> wrote in message
news:3A6E7170.F38BA60@akasa.bc.ca...
> > In my experience, rotational sensors are accurate to within +/-5%. 100% • accurate sensors would
> > be great, but 95% accurate sensors are still very useful. You can • compensate for the inaccuracy
> > in various ways, e.g. in the software. IMHO, this is no reason to be • disappointed or not to use them.
> > YMMV (literally).
> How do you compensate in software?
Exactly... you can't. Unless you use another sensor, which totally defeats
the purpose. For linear positioning, I've always used a light sensor looking
at a grey-coded bar, with a touch sensor multiplexed on the same port for
homing. That works fine... and uses just one port per axis (perfect!). But
I've wanted to do a SCARA-typ robot for quite some time. Accuracy is of
utmost importance, and I can't have rotation sensors missing a few counts
every hundred steps. That could mean a difference of a millimetre or two
every cycle; and when I'm doing accurate pick-and-place, that is
unacceptable. :(
Absolute encoders would be utterly fantastic... :)
(I supose that can be emulated with potentiometers?)
Iain
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Message has 2 Replies:
 | | Re: Rotational Sensor & Gearing Down
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| I guess I didn't word that very well. I didn't mean that you can make an inaccurate sensor look like an accurate sensor via software. What I meant is that you write your software to know that the sensor is not accurate, i.e. the software doesn't act (...) (25 years ago, 24-Jan-01, to lugnet.robotics)
| | | Re: Rotational Sensor & Gearing Down
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| What kinds of sprocket(s) does Lego currently use with tracks? A long time ago (in decades), I remember a set that used Caterpillar-link-style tracks, and they used a long-toothed sprocket to drive the tracks. It might work to put one of those (...) (25 years ago, 25-Jan-01, to lugnet.robotics)
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