Subject:
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rotation sensors and input limitations
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Newsgroups:
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lugnet.robotics
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Date:
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Wed, 10 Feb 1999 22:35:47 GMT
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Original-From:
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John A. Tamplin <jat@traveller.com#AvoidSpam#>
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Viewed:
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1303 times
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It seems that in all the designs I think of, I wind up needing two
rotation sensors. Since I need one input for 4 touch sensors (muxed as
previously discussed on this list) and 1 for a light sensor, I have a
problem. I have been trying to come up with a way of muxing two rotation
sensors on a given input, but the problem there is the resistances vary
widely for the 4 states.
Finally I think I have the solution. What I am doing is using one motor's
reverse motion (separated from the forward motion by a differential and a
couple of ratchets) to change gearing for the third motor. I need to be
able to tell where the shifting mechanism is to make sure I consistently
get the proper gear, yet I also need to count the output of the "shifted"
motor (since it is doing things like moving arms etc, and if I rely on
timing it eventually gets off and I have no touch sensors to spare to detect
end-of-travel).
The solution I have come up with is to take the axle for shifting gears
and connected with the axle for the "shifted" motor through a differential,
and put the rotation counter off that differential. As long as both axles
aren't running at the same time, I can precisely count both of them. Since
I shut down the shifted motor while I am changing its output gearing with
the other motor, I already meet this requirement.
Here is how everything is being used:
Motor A steers a "synchro drive" platform
Motor B forward provides drive power to the wheels
Motor B reverse shifts gears for motor C
Motor C is connected to one of the following:
ball kicker
main drive transmission (high gear to outrun the opponents, low gear to
push them out of the way)
additional auxilliary things I may add later :) (such as arm & gripper
control)
Input 1 is 4 muxed touch switches (not Lego touch sensors)
Input 2 is a light sensor for reading lines on the playing field (think
optical mouse pad)
Input 3 is the rotation sensor, which counts Motor B reverse and Motor C.
I think this is about as much as can be packed into an RCX-based
mobile robot :).
I haven't finished it yet, but I think I now have the last design issue
solved.
John A. Tamplin Traveller Information Services
jat@Traveller.COM 2104 West Ferry Way
256/705-7007 - FAX 256/705-7100 Huntsville, AL 35801
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | Re: rotation sensors and input limitations
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| (...) You've come up with an admirable solution to the problem! Here's another idea, one that works on a general class of problems and doesn't require any sensor input for controlling motor positioning: The general problem class is one where you're (...) (26 years ago, 12-Feb-99, to lugnet.robotics)
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