Subject:
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Re: Ideal Tank Platform Was: adder-subtractor ????
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 23 Jan 2001 04:45:44 GMT
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Original-From:
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Steve Baker <SJBAKER1@AIRMAIL.nomorespamNET>
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Reply-To:
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sjbaker1@SPAMCAKEairmail.net
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Viewed:
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516 times
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Chris 'Xenon' Hanson wrote:
>
> Steve Baker wrote:
>
> > Chris 'Xenon' Hanson wrote:
> > > Both motors should be driven in 'forward' direction so if one
> > > had a matched set of motors, you could perhaps achieve lateral
> > > speed balance.
> > Well, if you read my *long* post from a week or so ago, you'll know
> > that motor mismatch makes up at least 11% of performance, motor
> > direction perhaps 1% or at most 2%, and HOW YOU BUILD YOUR MODEL
> > accounts for at least 7% ... even when you are being careful not
> > to trap axles.
> > Compared to those things, motor direction is almost irrelevent - and
> > certainly not worth much extra complexity.
>
> Yeah, I saw that. nice work, that. I figured I'd throw
> it in anyway on the principle that eliminating error of any
> source is always a noble cause. I like to use worm drives to
> 'turn the corner' anyway to get the extra torque so it's not
> a design problem for me.
I guess - but surely - having an asymmetry in the robot's construction
is more likely to cause it not to drive straight than the 1% to 2% due
to the motor rotation direction.
You may be a 'better' builder than I am - and perhaps be able to
pinch those axle collars *just* tight enough so they don't bind
but also prevent the gears from slopping back and forth. If you
don't have the 'magic fingers' needed to get that *identical* on
both sides of the tank, that 7% that I measured due to build variance
will surely bite you.
Now, if you have a DIFFERENT gearing on the two sides of the
tank so that the motors can rotate the same way, the odds of your
being able to eliminate that 7% error get **WAY** higher...and if you
have to put the motors in different places on the two sides, your
weight distribution will be different - which is probably another
cause of asymmetric driving.
So, does anyone set their collars onto the axles using feeler-gauges
to space them at just the *ideal* distance from the beams? That
may be the *best* thing you could do to make your models go
straight!
> If one we using the adder-subtractor drive that started this
> thread, it'd all be irrelevant anyway.
That's true. It's an elegant solution.
--
Steve Baker HomeEmail: <sjbaker1@airmail.net>
WorkEmail: <sjbaker@link.com>
HomePage : http://web2.airmail.net/sjbaker1
Projects : http://plib.sourceforge.net
http://tuxaqfh.sourceforge.net
http://tuxkart.sourceforge.net
http://prettypoly.sourceforge.net
http://freeglut.sourceforge.net
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Message has 1 Reply:
 | | RE: Was (Tank Platform)
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| I know this isn't scientific or anything but this is what I have observed. If I have a bot with a "crazy" wheel, the direction that that wheel is pointing when the bot starts moving forward controls the bots direction more than anything else. And it (...) (23 years ago, 23-Jan-01, to lugnet.robotics)
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Message is in Reply To:
| | Re: Ideal Tank Platform Was: adder-subtractor ????
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| (...) Yeah, I saw that. nice work, that. I figured I'd throw it in anyway on the principle that eliminating error of any source is always a noble cause. I like to use worm drives to 'turn the corner' anyway to get the extra torque so it's not a (...) (23 years ago, 23-Jan-01, to lugnet.robotics)
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