Subject:
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Re: Motor Speed value interpretation?
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Newsgroups:
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lugnet.robotics.rcx.legos
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Date:
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Tue, 23 Jan 2001 10:46:38 GMT
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Viewed:
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1322 times
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In lugnet.robotics.rcx.legos, Ross Hennessy writes:
> Hi all,
Greetings! Another Ross!! That's three hangin' around here now!! Well, OK ones
a Rossz, but it's close enough!
> sorry if this question has been asked before but i was just wondering what
> the speed values for the motors represent? i have a robot with two motor • driven
> wheels which i would like to be able to make drive in an arc. To do this i • have
> to set the motors at different speeds so that the angular velocities of the • two
> wheel shafts are at the right ratio for the arc. My problem is that the
> relationship between the speed value eg 0 - 255, isn't in linear proportion to
> the angular velocity of the motors drive shaft (which seems resonable since • you
> can only really specify a force for the motor since the angular velocity will
> rely upon the weight of the robot). Does anyone know a formula for this
> relationship so that i can work out the exact figures for the speeds of the
> motors rather than put rotation sensors on the wheel shafts, since this is
> providing to be quite difficult (not the actual watching of the rotation
> sensors, but rather adjusting the speeds acording to what values you are
> getting back, not difficult to do slowly, but difficult to get the robot to • hit
> the right arc quickly).
>
> any help would be greatly appreciated.
Well, you could work it out really carefully, but then you've gotta take into
account the varying characteristics of the motors, ie 200 on one may be the
same speed as 190 on the other. And this may change according to ambient
temperature, battery level, the terrain, etc.
Your two best options are:
1. Use rotation sensors. A lot of programming required, and they're not
cheap...at least not here in Australia. YMMV.
2. Use an adder-subtractor, with one motor controlling speed, the other
controlling direction. There's a few people have done these - I have
info about this on my Lugnet page, www.lugnet.com/~469/projects/addsub
Hope this helps
ROSCO
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Message is in Reply To:
 | | Motor Speed value interpretation?
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| Hi all, sorry if this question has been asked before but i was just wondering what the speed values for the motors represent? i have a robot with two motor driven wheels which i would like to be able to make drive in an arc. To do this i have to set (...) (24 years ago, 23-Jan-01, to lugnet.robotics.rcx.legos)
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