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 17:00:32 GMT
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Original-From:
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Medical Informatics Consulting <MEDINFO@antispamAROS.NET>
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Viewed:
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1013 times
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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 motors used to drive each side and the
angular velocity of each motor. I was able to verify difference between
the motors with a simple, non-Lego angular velocity measuring device.
Matt
medinfo@aros.net
On Thu, 4 Feb 1999, Bryan Beatty wrote:
> 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.
> --
> Did you check the web site first?: http://www.crynwr.com/lego-robotics
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message is in Reply To:
 | | Re: Adder/Subtractor revisited
|
| (...) 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 (...) (25 years ago, 4-Feb-99, to lugnet.robotics)
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