Subject:
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Re: Advice on Rotation sensors and steering please.
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 21 Sep 2000 18:15:40 GMT
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Viewed:
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646 times
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In lugnet.robotics, sjbaker1@airmail.net writes:
>
> * I heard that the rotation sensor can lose count if it rotates too
> fast for software to keep up. Can anyone give me an idea of what
> a 'sensible' rate is? I guess it's a compromise between precision
> and risk of count lossage.
I have run into "count loss" using the rotation sensors also. I found that
anything above 40RPM is somewhat problematic. I imagine the exact numbers
depend upon the size of the program you are running and how it is designed.
But no matter what the speed I seem to loose counts occasionally. To get
around this I use a touch sensor to home the rotation sensor every once in a
while.
> * In the pseudo-code, I have 'slow down wheel-N'. There seems to be
> a suprising variety of ways to do that..although there isn't actually
> a 'speed' control! :
>
> + I can set the motor output to 'Off'.
> + I can momentarily apply 'OnRev'
> + I can reduce the 'power' from 7 to something
> smaller...either suddenly or gradually.
> + I can 'float' the motor output.
> + I can do a combination of these things.
>
> Which of these things works best? Does the choice depend on the wheel
> size/tyre type/gearing/robot weight - or this there simply 'one best
> way' ?
You are correct in that it depends greatly upon the design of the robot. If
it doesn't require much energy to spin the gear train, varying the motor power
has almost no effect. Just think of riding your bike along a flat road on a
calm day. Your speed doesn't vary greatly if you peddle continuously, or for
short bursts with coasting in between. So use motor power only if you have a
lot of friction, or are lifting something.
Floating the motor has a greater effect than adjusting motor power. I have
found this technique to work very well for wheeled vehicles with a caster.
Turning the motor off is nice in that the response is immediate. Sometimes I
use this in conjunction with floating. Picking which mode to use dependant on
how much steering is required.
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Message is in Reply To:
 | | Advice on Rotation sensors and steering please.
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| OK - so I am now the proud owner of three rotation sensors. I've built a really basic two-wheeled robot with a caster at the back for the purposes of getting in some programming experience with these things. Each wheel has a rotation sensor (...) (24 years ago, 21-Sep-00, to lugnet.robotics)
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