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15917Re: [SeattleRobotics] Re: SRF08 beam angle

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  • Paul R. Lundgren
    Dec 9, 2003
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      You might want to read chapter 10 :Sound Field Characteristics in Relation to Ultrasonic Transducers" of Yoshimitsu Kikuchi's book "Ultrasonic Transducers", published by
      Corona Publishing Co, Ltd, Tokyo, 1969. I found a English copy though my local (USA) library coop program.

      Hagar

      Alejandro Alonso Puig wrote:

      > As promised, here you have the results of my testing with the SRF08 sonar
      > ranger during the weekend (monday was also holiday at Madrid/Spain :-)
      >
      > 1) The SRF08 follow more or less the beam pattern at
      > http://acroname.com/robotics/parts/R145-SRF08.html
      > 2) The beam could be forced to be narrower by putting some foam around. I
      > have reduced it 20 degrees max. If it is used excessive foam surface or try
      > to narrow too much the beam, the results are unpredictable. Sometimes the
      > transducer detect the foam and sometimes it does not detect even the
      > obstacles just in front. In any case, by this trick it is possible to
      > prevent detecting the floor when we do not want it.
      >
      > I have finished a technical document on a sonar ranger to understand how
      > sonar rangers "see" the surroundings. Unfortunately it is in Spanish, but
      > there are several figures that could help understanding. Also there are
      > several links in English at the bottom of the page:
      > http://mundobot.com/tecnica/Sonar/Sonar.htm
      >
      > Whenever I have enough time I'll translate my webpage to English
      >
      > Best regards,
      > Alejandro Alonso Puig
      > http://mundobot.com
      > alejandro.alonso@...
      >
      > -----Original Message-----
      > From: Alejandro Alonso Puig [mailto:alejandro.alonso@...]
      > Sent: martes, 02 de diciembre de 2003 17:52
      > To: SeattleRobotics@yahoogroups.com
      > Subject: RE: [SeattleRobotics] Re: SRF08 beam angle
      >
      > Yes, I thought the same as you, eliminating the width in the image in order
      > to narrow the figures to its real form. I saw this article. In fact I'm
      > working in something similar. Look at my web page site. Its in Spanish yet,
      > but I'll treanslate to English soon. The page is not finished, but at least
      > you will find a figure that represents what I'm doing with the sonar
      > ranger(Hardware and Software): http://mundobot.com/tecnica/Sonar/Sonar.htm
      >
      > Best regards
      >
      > Alejandro Alonso Puig
      > http://mundobot.com
      > alejandro.alonso@...
      >
      > -----Original Message-----
      > From: dan michaels [mailto:dan@...]
      > Sent: martes, 02 de diciembre de 2003 17:24
      > To: SeattleRobotics@yahoogroups.com
      > Subject: [SeattleRobotics] Re: SRF08 beam angle
      >
      > --- 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
      > answer I got
      > > 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
      > > the -6db point". Not as interesting as your answers.
      > >
      > > 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
      > > sound pressure will be a minimum, but I'm not really sure about this
      > > 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
      > >
      > > To unsubscribe from this group, send an email to:
      > > SeattleRobotics-unsubscribe@yahoogroups.com
      > >
      > >
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      > http://docs.yahoo.com/info/terms/
      >
      > Visit the SRS Website at http://www.seattlerobotics.org
      >
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      >
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      >
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