Subject:
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Re: Adder/Subtractor revisited
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 4 Feb 1999 06:08:43 GMT
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Reply-To:
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bryan.beatty@/Spamless/autodesk.com
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Viewed:
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1176 times
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Johannes Keukelaar wrote:
> Right. This is what I was trying to get at. If one motor gives too
> little power, you can add the power of two together trough a
> differential. Power the axles of the differential by two different
> motors, and the added power comes out through the body. If you want to,
> you could of course use that power to drive an adder-subtractor
> construction. In that case you'd need three differentials.
>
> You need the extra differential to add the power of two motors, because
> they don't always rotate at exactly the same speed.
I can understand why you'd need a method like this if the two motors
were radically different types, but if you're dealing with two identical
motors (such as the 9V MindStorms motors), is this really necessary?
The tolerances may be a teensy bit different from one motor to the
other, but their speed is going to be limited by the load they're
pulling, not by their internal variations in manufacture: use them to
haul around a robot, and the motor shafts will turn somewhat slower than
if they were just spinning free. In this case, both motors will be able
to exert torque against the load, without the need for a differential.
Given that the Lego differential is a bit "sloppy" and seems to be
fairly inefficient (it seems to eat up a lot of torque due to friction,
although careful design can minimize this), I'd think that feeding motor
power through a differential for this purpose would lose you more than
you'd gain.
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Message has 1 Reply:
 | | Re: Adder/Subtractor revisited
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| Well, I don't know about your experiences, but I have had tracked vehicles with identical (as much as possible) construction on each side of the vehicle that deviat several degrees for each foot travelled. This was due to the characteristics of the (...) (26 years ago, 4-Feb-99, to lugnet.robotics)
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Message is in Reply To:
| | Re: Adder/Subtractor revisited
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| (...) Right. This is what I was trying to get at. If one motor gives too little power, you can add the power of two together trough a differential. Power the axles of the differential by two different motors, and the added power comes out through (...) (26 years ago, 2-Feb-99, to lugnet.robotics)
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