[Robotgroup] Control systems

[Gray Mack]

I have heard of people using tubes or apertures around
the emitter and/or detector to further restrict the
focus. That technique might work with the AX-S1 if you
found it to be too wide a field of view at the sensor
distance, or might be used to allow the sensor to be
closer to the surface without overflowing to 0xff.
Experimentation might be only way to determine the
reflectivity of the line made from a particular brand
of tape. Most of the line followers I have seen seem
to locate the sensors within 1/2 inch or less of the
surface, pointed straight down with external light
shielding. One notable exception being CMU-Cam camera
based line followers, which use a real time 2d camera
image to figure the line location and curves.

-Gray

--- Acy Stapp <acy.stapp at gmail.com> wrote:

> Thanks for the input, Edwin. I'm surprised I didn't
> remember the incidence
> angle term. Maybe I could calculate some sort of
> correction factor lookup
> that compensates for the range and angle attenuation
> (assuming a fixed head
> angle and distance and a flat floor plane), giving
> me a more linear input
> model.
> 
> The sensor is the AX-S1 forward IR sensor. I believe
> it has an IR
> illuminator LED with a 40khz carrier. A bandpass at
> 40khz reports the active
> illumination in one register and the remaining
> non-modulated IR is reported
> in another register. The reported value seems to go
> down with the square of
> the distance, from 0xFF at about 3 or 4 inches to
> 0x80 at about a 9-12
> inches and 0x00 at a few feet. The passive IR sensor
> typically reports 0x03
> or 0x04 seeing a human or 0x07 or 0x08 seeing a
> relatively warm surface. I'm
> not sure whether the active sensor is including the
> energy from the passive
> sensor but for a line-following robot it shouldn't
> make much difference.
> 
> Most of the precision is concentrated in the front
> of the view volume as
> well but it clamps the result at 0xFF so I'm limited
> in to really about a 3
> to 6 inch range of good precision. The eye seems to
> read a fairly narrow
> cone, but probably wider than the tape at the
> distances I'll be reading.
> 
> Acy


       
____________________________________________________________________________________
Be a better Globetrotter. Get better travel answers from someone who knows. Yahoo! Answers - Check it out.
http://answers.yahoo.com/dir/?link=list&sid=396545469