Subject:
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Re: Adder/subtractor mod
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 4 May 2001 02:22:08 GMT
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Viewed:
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672 times
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In lugnet.robotics, Clayton Epps writes:
> Does anyone know if there is a way to use the adder/subtractor in such a way
> that tank/treaded vehicle moves forward at the sum of the two motor speeds
> (A+B) and can still rotate (in place) left and right and move backwards.
>
> My understanding of the adder/subtactor is that tank forward direction is
> still obtained by using one motor turning both axles at the same speed
> (drift problem solved). I need the sum (of both motors) turning both axles
> at the same speed while still having all other movement functions (backward,
> turn-in-place-left, turn-in-place-right).
>
> I'm looking to use Brian Long's wormgear mod to adder/subtractor at the
> bottom of Denis Cousineau page
> (http://prelude.psy.umontreal.ca/~cousined/lego/1-Varia/adder/adder.html) to
> develop a powerful transmission with some speed to power a treaded vehicle.
>
> I just don't know how to build the transmission around the adder/subtractor
> to make this happen.
>
> Any help would be appreciated.
Clayton, I recently built a tracked vehicle with a motor driving each set of
tracks via a worm and wheel. The 'other' end of the drive shaft for each
side inputs to a differential. With both tracks going in the same direction
the differential would be their sum and the casing would rotate twice as
fast. However, one drive runs backwards so the sum is zero. The left drive
runs forward and the right backward. The final connection to the tracks is
via a small-link chain drive with the left chain overslung and the right
chain underslung.
The result is that both the left and right tracks go forward.
The casing of the differential is connected to a rotation sensor. When one
drive runs slower than the other, the rotation sensor stops the *other*
track for 15/100 of a second each time through the loop. The effect is that
the vehicle does track a straight line and also can be steered.
However, nothing is perfect. The rotation sensor, even at close to zero
rpm, skips counts and gains counts in an unpredictable manner (well
documented in other threads in this newsgroup).
This might be what you are trying to do. The key is to use chain drives so
that both tracks can go forward even while one drive motor is forward and
the other reversed... so that the differential yields zero sum.
This is hard to visualize. When I get time I will post some pics on my web
page.
Jerry
>
> Clayton
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Message is in Reply To:
 | | Adder/subtractor mod
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| Does anyone know if there is a way to use the adder/subtractor in such a way that tank/treaded vehicle moves forward at the sum of the two motor speeds (A+B) and can still rotate (in place) left and right and move backwards. My understanding of the (...) (24 years ago, 3-May-01, to lugnet.robotics)
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