## 15861Re: SRF08 beam angle

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• Dec 2, 2003
--- In SeattleRobotics@yahoogroups.com, "Alejandro Alonso Puig"
<alejandro.alonso@m...> wrote:

You might also check out the following page, which shows a sweep
using such a sonar. The "image" shows extended widths of objects in
azimuth.

http://www.hazmat.com/~mjb/projects/picsonar/

I had often wondered about the idea of doing an inverse spatial
convolution on such an image in order to try and remove the beam
width characteristic. This might be a lot of processing for a small
microcontroller.

- dan michaels
======================

> Really interesting answers. Thanks. Dan, the graph from Acroname is
really
> clear. I'll make some tests during this weekend but it seems that
the tests
> I performed more or less agree with the graph. The measures were
taken at 1
> meter from the transducer. That is 3,28 feet and as from the
graph, the
> width at such distance is of about 80 degrees (not so far from the
100
> degrees I measured, considering I'm not testing in an ideal
environment).
>
> In any case I think it is very wide if we really want to have some
clear
> information on the surroundings. As per trigonometry
> (Arc=angleº(pi/180)Distance), the chord (arc) detected at 1 meter
from the
> transducer is Arc=80º(pi/180)1= 1,4 meters. That means 0,7m to the
right,
> 0,7m to the left, 0,7m to the top and 0,7m to the bottom. If I'm not
> mistaken, this means that if you want to detect something at a
distance of 1
> meter from your robot, the transducer should be either installed at
least
> 0,7m from the floor and in 90º position, or install it in a lower
position
> but with a vertical inclination greater than 90º, so you will not
detect the
> floor (kind of reflecting floor), but you will detect things over
the robot
> (may be a problem in some cases)
>
> If I am right with this assertions, the SRF08 is good because of
the I2C
> interface, but not so good because of the beam width.
>
> I read something about putting some kind of foam around the
transducer to
> force a reduction on the detection cone. I'm not sure if it will
work, but
> I'll try it during the weekend. I'll tell you.
>
> By the way, I raised the question to Devantech Company and the
> was: "Beam width on the SRF04/8 is a function of the transducers
and is
> fixed. For the transducers used on the SRF04/8 this is 55 degrees at
>
> Best regards
>
> Alejandro Alonso Puig
> http://mundobot.com
> alejandro.alonso@m...
>
>
>
>
> -----Original Message-----
> From: dan michaels [mailto:dan@o...]
> Sent: martes, 02 de diciembre de 2003 3:48
> To: SeattleRobotics@yahoogroups.com
> Subject: [SeattleRobotics] Re: SRF08 beam angle
>
>
> --- In SeattleRobotics@yahoogroups.com, "Phil" <phil1960us@y...>
> wrote:
> > what about some sort of tuning "pipe" that you slip over the
> reciever
> > to decrease the field of view that the receiver actually sees?
> sort
> > of like blinders for a horse...
>
>
> I was thinking about the same sort of thing, but I really haven't
> much idea how to do it. Sound works differently from light. Sound
can
> go around corners, etc. Something to try might be tubes of rolled
> cardboard/plastic/etc around the transmitter with lengths at "odd"
> multiples of "quarter" wavelength. At even multiples, I think the
> stuff at all. Or possibly a megaphone/conical horn - but again it
> probably needs the correct length and end aperture size for best
> results. Good area for experimentation - plus some preliminary
> legwork into acoustics. Tell us how it goes ;-).
>
>
> - dan michaels
> www.oricomtech.com
> ============================
>
>
>
> Visit the SRS Website at http://www.seattlerobotics.org
>
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