Subject:
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Re: Rotaion Sensor Sampling Speed?
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 14 Oct 1999 17:47:36 GMT
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Viewed:
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585 times
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Ralph,
I don't know about the specific issues with pbForth, but this summer I
was working on a large gear train (for a problem that we have recently
"proven" is computationally intractable for the RCX) and dropped about 20
counts out of every 1,000 when I was running it at very high speed (say,
maybe 12,000 counts per minute.)* So, there should be no problem with the
speed.
If you are being jumpy, have you checked the raw values? Perhaps
with the axle being moved slightly up and down as well as being rotated,
slight transients are being generated, which are screwing up your count?
-Luis "bitterly frustrated at rotation sensors today" Villa
*125:1 gear ratio, 16 counts per rotation (2,000 counts per rotation of
the largest gear, then) and two half-rotations (to check for drops) in 10
seconds.
On Thu, 14 Oct 1999, Ralph Hempel wrote:
> Date: Thu, 14 Oct 1999 16:40:18 GMT
> From: Ralph Hempel <rhempel@bmts.com>
> To: lugnet.robotics@lugnet.com
> Subject: Rotaion Sensor Sampling Speed?
>
> Hi all,
>
> I'm putting together a mazebot for Mindfest, and ran into a
> bit of a funny with the rotation sensor. I THINK it has to
> do with the sample speed, but I'm not positive.
>
> I'm using pbFORTH and sampling the rotation sensor in a tight
> loop. The idea is to make it go to a certain count and back
> again a number of times to see if I lose counts. If I can't
> accurately figure out where I am, the maze problem is REALLY
> hard...
>
> I'm driving a suspended light sensor on a rack with a micromotor
> and an 8 tooth gear. The axle of the micromotor drives the
> gear and goes right through to the rotation sensor. The assembly
> is solid, but does vibrate a bit, and I think this is where
> my problem is.
>
> Since pbFORTH can sample VERY quickly,I'm wondering if the
> slow turning rotation sensor and the vibrations might cause
> some "jumping" of the values to the rotation sensor processing
> code as it transitions through the steps.
>
> If I run the gantry manually (smoothly) the problem goes away...
>
> If I add some DELAY between samples, say 40-50 msec, the problem
> goes away....
>
> Anyone else noticed this if you are using rotation sensors and
> smapling at very high speeds? This is probably only an issue with
> custom firmware, but I'm curious to see if the micromotor to
> the rotation sensor is a problem with regular Mindstorms firmware...
>
> Cheers,
>
> Ralph Hempel - P.Eng
>
> --------------------------------------------------------
> Check out pbFORTH for LEGO Mindstorms at:
> <http://www.hempeldesigngroup.com/lego/pbFORTH>
> --------------------------------------------------------
> Reply to: rhempel at bmts dot com
> --------------------------------------------------------
>
>
#######################################################################
Profanity is the one language that all programmers understand.
-Anonymous
#######################################################################
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Message is in Reply To:
 | | Rotaion Sensor Sampling Speed?
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| Hi all, I'm putting together a mazebot for Mindfest, and ran into a bit of a funny with the rotation sensor. I THINK it has to do with the sample speed, but I'm not positive. I'm using pbFORTH and sampling the rotation sensor in a tight loop. The (...) (25 years ago, 14-Oct-99, to lugnet.robotics)
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