Subject:
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Re: moving in a straight line with two motors?
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Newsgroups:
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lugnet.robotics
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Date:
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Sat, 14 Nov 1998 08:46:15 GMT
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Original-From:
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Ben Laurie <BEN@ALGROUP.saynotospamCO.UK>
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Viewed:
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2154 times
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Scott Furman wrote:
>
> > Here's an exercise for someone with an RCX: Create a chassis that
> > consists of one drive motor to the wheels and an angle sensor geared to a
> > 2-d inverted pendulum on top. Write a program that moves the chassis to
> > keep the pendulum straight vertical.
>
> Believe it or not, I've been working on exactly this problem for the last few
> days. I built an angle sensor using a 500K potentiometer wired directly to an
> RCX input port. (Lego's angle sensor doesn't have sufficient angular
> resolution unless it's geared down and adding those gears adds too much
> mechanical resistance for the pendulum to swing freely.)
>
> The problems I am still facing are:
>
> * The acceleration provided by two motors isn't sufficient to keep the
> pendulum erect if it's only slightly perturbed from vertical. Partly,
> this is due to the tires slipping when the machine accelerates from rest,
> but I think that, even with that corrected, the motors may not be
> powerful enough.
I think making the pendulum longer should cure this...
> * Although there's programmatic control of the motor power, there doesn't
> seem to be control over the motor velocity. As a result, the motor tends
> to jerk when it starts or changes direction. When the pendulum is
> leaning slightly, the motor turns on briefly to correct it, but the
> application of full velocity tends to cause overcompensation and the
> pendulum swings the other way. In a few cycles, the pendulum
> oscillations increase beyond the motor's ability to compensate.
Possibly making it heavier will cure this...
Cheers,
Ben.
--
Ben Laurie |Phone: +44 (181) 735 0686| Apache Group member
Freelance Consultant |Fax: +44 (181) 735 0689|http://www.apache.org/
and Technical Director|Email: ben@algroup.co.uk |
A.L. Digital Ltd, |Apache-SSL author http://www.apache-ssl.org/
London, England. |"Apache: TDG" http://www.ora.com/catalog/apache/
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Message is in Reply To:
 | | Re: moving in a straight line with two motors?
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| (...) Believe it or not, I've been working on exactly this problem for the last few days. I built an angle sensor using a 500K potentiometer wired directly to an RCX input port. (Lego's angle sensor doesn't have sufficient angular resolution unless (...) (26 years ago, 14-Nov-98, to lugnet.robotics)
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