Subject:
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Re: PID implementation
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 13 Aug 1998 23:18:39 GMT
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Original-From:
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David Kott <DAKOTT@ALPHA.ihatespamDELTA.EDU>
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Viewed:
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3819 times
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On Wed, 12 Aug 1998, Darkman wrote:
> Problem:
>
> I have built a small robot with differential drive using 3+ACI- diam whee
> ls turning at 66 RPM +AEA- full power PWM no load.
>
> Each wheel has a 16 pulses per rev. reflective type shaft encoder.
> the robot is controlled by the Handy Board running IC 3.2.
>
> I'm fairly new to the robotics field and looking for some info or Tips on
> how to accomplish some sort of PID control for this robot.
>
> I toyed around with different timing ideas to move the robot 1 rev but I
> soon found out it's very unreliable type of control due to the fact that
> each surface has a different drag coefficient and battery voltage also
> makes a big difference.
It seems that you have a feedback system here. How does battery voltage
and surface resistance add error to your system when you have a feedback
loop to correct your error signal?
>
> Another problem I'm facing is that with the L293D IC's have no brake
> capabilities , so once the power to the motor is removed the momentum of
> the robot moves the robot past it's target.
No braking? We solved that problem by effecting reverse current through
the DC motors we were using for propulsion. A 70ms pulse worked great.
We didn't even use any feedback.
Any book on modern control systems would detail the basics of a feedback
system. Unless you are truly desperate for a very fast system, you
wouldn't really have to do any calculations. I would just write up a
simple program and experimentally much with the coefficients until you
found a stable system that does what you want. A full PID controller
might be overkill. Just a simple linear feedback system, in all
likelyhood, would suffice.
-d
The box said "Requires Windows 95/NT or better"...
So I got Unix.
Free the Source. Free your Computer... http://www.FreeBSD.org
http://www.NetBSD.org
http://www.OpenBSD.org
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Message is in Reply To:
 | | PID implementation
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| Problem: I have built a small robot with differential drive using 3+ACI- diam whee ls turning at 66 RPM +AEA- full power PWM no load. Each wheel has a 16 pulses per rev. reflective type shaft encoder. the robot is controlled by the Handy Board (...) (28 years ago, 12-Aug-98, to lugnet.robotics.handyboard)
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