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Subject: [DPRG] CMUcam
From: Tommy Raz tr at tommyraz.com
Date: Tue Feb 8 10:29:46 CST 2005

Sure that makes perfect sense.  Another thing I didn't consider is that a small
wide anomally will only look like a line for a short distance and be gone
before there is much change in the heading.

Quoting "Randy M. Dumse" <rmd at newmicros.com>:

> > I'm not an expert at image analysis, but am wondering
> > about your idea.
> I appreciate the reply, none the less. It's an interesting item
> to discuss.
> > Do you
> > think limiting your view to a few scan lines is as
> > robust?  What if the course
> > is not very clean?
> You know, I'm more worried about reflections on the surface of
> the course looking like white out areas. Those big plate glass
> windows at the Science Place have tricked many robots into very
> strange behavior!
> > Would a random scuff mark or
> > patch of dirt be more likely
> > to trick analysis of a few scan lines?  Would
> > analysis of the whole quadrant
> > help average out the noise in such a scenario?
> I plan on putting Ultra Bright white LED's  shining down on the
> camera's field of view to try to even out lighting.
> The thing about quadrants is you get "bang bang" outputs. That
> is, you cant tell left right, up down (if I am understanding the
> suggestion correctly).
> The thing about using thin horizontal windows is you get center
> of mass of the color along a continuum. This should give me up
> to 80 positional "outputs" with a horizontal resolution of 80
> (Or is it 143?. The X output seems to be 1 to 80 pixels in
> width. 80 I think.) So, I hope to use this as a rather fine
> error signal, and use a PID loop to compensate, keeping the line
> in the middle. The further the MM of the line shows up, left or
> right, the greater the need for correction in the steering.
> Now my thinking is, if I use, say, half the lines (the upper
> half of the picture) rather than just a few scan lines, the MM
> will be spread out over a larger area, and so the resolution of
> the offset would be decreased. For instance. Let's say I'm right
> on top of the line, and its running staright ahead. I'm getting
> a MM with an Mx value of 40.
> Now a near right angle turn ahead just comes into view, call it
> to the left (decreasing pixel positions). If I'm only looking at
> the top lines, the Mx value there jumps out left to 20. However
> if I'm using 77 lines, top half of all vertical lines, and most
> of them are still at 40, and only the top couple are at 20, the
> average Mx value will come out like 38. Not much signal change
> to know I have to make a radical turn ahead.
> Well, that's my thinking, right, wrong, or otherwise. Without
> more experimentation, it's just thinking. I did use a white LED
> to see if I could track all over the screen, and am pretty
> pleased as it looks to capture a tiny dot of the right color
> very precisely. So I'm thinking a few line will do.
> Randy
> www.newmicros.com
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