Subject:
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Re: Encoder Implemenation questions
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 11 Jan 2001 16:02:44 GMT
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Viewed:
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816 times
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At 05:32 PM 1/11/2001 +0000, James Munro wrote:
> It certainly helps. I guess I'll stick to my kludge... it's easier. ;)
> So in order to do effective rotation sensors I need to monitor not only
> the rotations, but the power applied to the motor as well? That seems
> fairly complex but I guess what I want to do is fairly sophisticated.
> (My methods are usually otherwise. ;))
No, your conclusion is too broad, simply stated if you don't monitor motor
current (and to some extent model the inertia of the motor) in software,
then your damping algorithm (which is effectively a constant based on your
description) won't always be optimal. As you mention below, that isn't
necessarily one of your design constraints.
> I'm really not concerned with mm accuracy, since my resolution isn't that
> high it am defenitely for sacrificing accuracy for speed, within reason.
> This robot is an entry into the Firefighting competition so speed is
> important, but so is not bashing into walls when I turn. ;)
If your high order design goal is "not bash into walls" then perhaps a
sensor that detects walls and imparts a higher control authority on the
drive mechanism is in order? In the subsumption work there is a great
discussion of robots the "know" by virtue of their lower level interrupt
routines not to run into walls. It works by injecting a "motor back" into
the motor control subroutine ahead of the top level control program (thus
it has a higher control authority for the motors). The IR detectors like my
Cougar's "eyes" and the IRPD from LynxMotion and others is suitable for
feed into such a system. If you connect it to the input capture pins you
can generate an interrupt when the sensor detects the wall and reverse the
motors. This forces the motors to back up, even as your higher level
control program was saying to go forward.
Interestingly, the top level program then can 'detect walls' by noting that
motors are refusing to go where its telling them. This is analogous to you
realizing your stuck in the snow because pushing on the accelerator has no
effect on your forward motion.
--Chuck
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Message has 1 Reply:
 | | Re: Encoder Implemenation questions
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| (...) Actually I was simplifying too much here. My goal is to be able to execute a relatively accurate 90 deg. turn to "round the curve" in a narrow hallway and to be able to spin on axis (robot is circular) a full 180 so I actually can count on (...) (23 years ago, 11-Jan-01, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Re: Encoder Implemenation questions
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| You step into the morass that separates reality from theory :-) The "right" way to do this is to measure the current on the servos, ramp their accelleration up and then down again as you approach your final endpoint. Read up on feedback systems and (...) (23 years ago, 11-Jan-01, to lugnet.robotics.handyboard)
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