Subject:
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Re: NXT Program: How to avoid stop-and-go? (US-Sensor Test Values)
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 27 Dec 2007 12:41:42 GMT
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Original-From:
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bigboss97 <bigboss97.geo@yahoo.com(ihatespam)>
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Viewed:
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5675 times
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I tried to use a program to log the distance while the US-sensor is moving
forward. Unfortunately, it doesn't go straight all the time. So, I simply
display the US value and put the vehicle in different position manually.
Here are my test values for distance from 60cm-10cm:
90 degree to the wall: 60, 49, 41, 30, 22, 14
45 degree: 46, 39, 32, 25, 23, 166
The values for 90 degree are nearly perfect. The 1st 5 values for 45 degree
are acceptable because the sensor position is closer to the wall than the
pointing distance. But the value for 10cm (166) is crazy. I did some more
investigations. When I moved the sensor between 20 and 10cm I noticed that
the value never went lower than 22. Sometimes I got 28 for 10cm. In this
section, the value can suddenly go crazy just by doing a minimal turn in the
senor.
Conclusion, if you want to allow your NXT approach a wall from different
angles do not use an US value less than 25. That also explains my initial
problem. My vehicle has no problem to slow down with 30cm to the wall. But
it often failed to turn around when it came closer than 20cm.
Phuoc Can HUA
bigboss97 wrote:
>
> I found a very interesting (and beautiful) site:
> http://www.tik.ee.ethz.ch/tik/education/lectures/PPS/mindstorms/sa_nxt/index.php?page=tests_us
>
>
> bigboss97 wrote:
> >
> > Strangely, it slows down, i.e. it detects the further distance (less
> > reflection?) in the same angle.
> > I tried to put the US-sensor vertically. It still shows the same effect.
> > I also notice the closer it comes the larger angle it needs to get a
> > reaction. I observed...
> > When the vehicle hits the wall with a flat angle and I leave it running,
> > it keeps on pushing to the wall. I noticed that it only turns around when
> > the vehicle has been pushed to a position of almost 90 degree. The sensor
> > is almost covered by the all. The angle range is even smaller than if it
> > comes from a distance.
> >
> >
>
>
--
View this message in context: http://www.nabble.com/NXT-Program%3A-How-to-avoid-stop-and-go--tp14446433p14512573.html
Sent from the LEGO Robotics mailing list archive at Nabble.com.
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