Subject:
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Re: Tilt Sensors
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 19 Dec 2000 06:37:08 GMT
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Original-From:
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Steve Baker <sjbaker1@airmailSTOPSPAM.net>
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Reply-To:
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sjbaker1@airmail.net/NoSpam/
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Viewed:
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735 times
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"Boorman, Mathew" wrote:
>
> Steve Baker Wrote
> > (I was trying to build a 2 wheeled vehicle like a bicycle and needed the
> > pendulum to balance it - both designs of pendulum worked well - but the
> > bike didn't :-(
>
> Thats another thought provoking project. It makes it tricky once you
> realise that the pendulum will stay on centre even when turning.
Yes - exactly - that was my plan - keep the pendulum in the center - even
when intentionally turning. I think that actually makes the software
quite a bit simpler.
I started off with a pendulum which was black on one half and white
and the other. I was planning on steering the front wheel to keep
the light sensor producing a mid-level reading - turning left for
black and right for white.
However, my Lego construction skills are still in their infancy
and building a motorized steering wheel and a powered rear wheel
resulted in such a heavy bike that it wouldn't move fast enough
to balance upright. It would just fall over - steering frantically
to try to stay upright. This really was a TOTAL failure - not
something I'm proud of!
I thought at first that the light sensor was taking too long to
produce a changed reading from the pendulum before the bike
fell over - so that's when I tried to connects gears to the
pendulum's axle and use a rotation sensor to detect the swing.
Unfortunately, rotation sensors are quite coarse in
resolution - and I had to gear up the mechanism in order to get
the sensitivity up high enough. The gearing slowed down the swing of
the pendulum considerably - and the whole contraption responded
even slower than the light sensor. Adding more weight to the pendulum
to give it more power to drive the gear train made it still worse.
I think that real cyclists lean using their body weight to stay
vertical until they have enough speed to correct small wobbles
using the steering - that's why it's so hard to ride slower than
a certain speed. Moving the RCX left and right and using all
that battery weight to balance with might have worked - but I'd
given up in disgust by the time I thought of that!
Part of the constructional difficulties I got myself into was
in trying not to have the steering column be vertical. I think
that like a real bike, the front forks and column should lean
backwards. Lego parts make it REALLY hard to build things like
that and the amount of structure I ended up with was just
too much. I also wanted it to *look* like a bike - so I used
a chain drive on the rear wheel - that must have wasted a chunk
of drive power that would have been better used in making the
bike run faster.
I should probably try again sometime - I have a lot more construction
time under my belt now and I could probably make it a lot lighter
this time.
It would be really cool to see it work.
Perhaps this would be a good subject for a future competition?
"Build a machine that runs on two wheels that are mounted one
behind the other like a standard bicycle. To win, you have to
drive in a controlled figure-8 without falling over. No
part of the machine is allowed to touch the ground except for
the two wheels."
> Has anyone achieved such a beasty?
It would be interesting to find out.
--
Steve Baker HomeEmail: <sjbaker1@airmail.net>
WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sourceforge.net
http://tuxaqfh.sourceforge.net
http://tuxkart.sourceforge.net
http://prettypoly.sourceforge.net
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Message has 2 Replies:
 | | Re: Tilt Sensors
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| I had a couple of thoughts while reading the posting on the bicycle. I am currently working on an adjustable mercury tilt sensor. The size is 2x4, with a height of 1 brick and 2 plates. While it doesn't give the degree of tilt, it will give a closed (...) (24 years ago, 19-Dec-00, to lugnet.robotics)
| | | Re: Tilt Sensors
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| (...) Also, as I mentioned in another post, legOS had a bug where it would gain or lose total counts sometimes. I don't know if the default fw is susceptable to this but I'm sure I tested it and mentioned it if you search the legOS archives from (...) (24 years ago, 23-Dec-00, to lugnet.robotics)
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