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15861Re: SRF08 beam angle

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  • dan michaels
    Dec 2, 2003
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      --- 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
      >
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