Subject:
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Re: Different motor speeds?
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 28 Dec 2000 23:59:45 GMT
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Original-From:
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Jeroen Stap <jv.stap@quicknet.[SayNoToSpam]nl>
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Viewed:
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841 times
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> I've build a very (VERY) simple robot that basically consists
> of two medium sized wheels coupled directly to the motors so I could
> begin to play around with the programing. I've noticed that one
> motor seems to go ever so slightly faster than the other even with
> the power setting to the motors A and C set identically. This
> causes my little 'bot to go in a wide circle when it is supposed
> to be going straight.
>
> Is this a fault in one of my motors or is it a basic flaw of
> design I can fix by using gears to couple the wheels to the motors or
> something?
No two motors give the exact same power output. In order to overcome that
you have the basic solution: you connect 1 motor to an differential, the
power is divided over both wheels. A side-effect of this method, is that if
one wheel has lesser friction than the other wheel, this wheel will spin
faster while the other wheel will slow down because of its friction. This
happens very often if your bot is driving over different sorts of surfaces,
resulting in a wide circle, which you were trying to get rid of in the first
place.
You can overcome this problem by making use of a so-called adder-subtracter.
This mechanism makes use of 2 differentials geared together so that 1
differential provides power to both wheels, and the other differential
determines the difference in power-output per axle. You can find building
instructions for such a device on my website: http://home.hccnet.nl/jv.stap/
This is extremely usefull if you're building caterpillar machines, because
you can have 1 output axle rotating in the other direction with this
mechanism. Steering is then possible, while real straight forward is no
problem anymore.
If you are interested on the exact working of differentials I could advise
you to take a look at http://www.howstuffworks.com
Good luck!
Jeroen.
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Message is in Reply To:
 | | Different motor speeds?
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| Folks: 1040EST 363-2000 Now that I'm "off and running" with regard to emailing to the list I thought I'd ask a question that's been going through my mind. I've build a very (VERY) simple robot that basically consists of two medium sized wheels (...) (24 years ago, 28-Dec-00, to lugnet.robotics)
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