🚀 go-pugleaf

James Ryan Miller <jmce+@andrew.cmu.edu> writes:
>    I am curious if anyone has programmed a 6811 to find distances with
>one of those polaroid sonar things.  
>    Here is how I'm envisioning it ... The 6811 could pulse a trigger
>line which has the transducer xmit a "ping".  When the ping was
>received, it would pulse a line that the 6811 would time, and calculate
>distance.  With the great Input Capture features of the 6811, the
>software should be easy, but how much circuitry is needed to have these
>two nice digital lines at the computer to actually driving the
>transducer.

       All you need is a Texas Instruments type SN28827 Sonar Ranging
Module, which is a board about 1.5" square.  The application note
(D2780, October 1983) explains how to use it.  Runs on +5, but you need
a big external capacitor for filtering, because it draws about an amp
for a few milliseconds when it "pings".  This unit drives the round,
electrostatic Polaroid transducer.  There's a similar unit for the
rectangular pizeoelectric transducer.

       Control is simple; you raise INIT, and it pings; when you get
an echo, the board returns ECHO.  INIT and ECHO can be connected
directly to the appropriate pins of a 68HC11.  Works fine.

       I did this back in 1987, and you may have trouble finding the
modules.  But contact TI headquarters in Dallas, and bug them until
they tell you how to order.  Price runs around $30-50 each.  TI built
some vast number of these things for some camera application, and they're
still around.  I've seen them in a surplus catalog, but don't have the
reference.

       I have FORTH code to drive these things, if anyone needs it.

					John Nagle

What about a differential sonar, has anyone done it? I envision 
a set of three receivers with the center one as the only transmitter.
Any ideas?

As I am not current in my physics, what would be the difficulties in
making a phased array? (wavelength too long?)

Mark Epperson

epperson@adobe.com (Mark Epperson) writes:
>What about a differential sonar, has anyone done it? I envision 
>a set of three receivers with the center one as the only transmitter.
>Any ideas?
>As I am not current in my physics, what would be the difficulties in
>making a phased array? (wavelength too long?)

      It's really time for somebody to start developing smarter sonar
systems for robots.  We've been using those dumb Polaroid sensors for a
decade now, and enough is known about bat, dophin, and submarine sonar
to do a much better job.  The DSP chips are available and cheap.  
Somebody with audio, DSP, or sonar experience needs to do this one.

      A reasonable way to start would be to use a machine with stereo
audio inputs and outputs, and try to do bat-type FM sonar, operating
around 10-20KHz.  

					John Nagle

nagle@netcom.com (John Nagle) writes:

>epperson@adobe.com (Mark Epperson) writes:
>>What about a differential sonar, has anyone done it? I envision 
>>a set of three receivers with the center one as the only transmitter.
*deleted lines*
>      It's really time for somebody to start developing smarter sonar
>systems for robots.
*deleted lines*

When I searched in the library computer, I came across following record:

"Title: Mobile robot map making using sonar.
 Author: Zelinsky, A.
 Corporate Source: Univ of Wollongong, Wollongong, Aust
 Source: Journal of Robotic Systems v 8 n 5 Oct 1991 p 557-577
 CODEN: JRSYDB  ISSN: 0741-2223"

The abstract describes that the article deals with a method of producing high-
resolution maps of an indoor environment. The method is based on investigating
straight line segments extracted from the sonar range data describing obstacles
near the robot. The mobile robot then moves parallel to the straight line sonar
segments, in close proximity to the obstacles, continually applying sonar
barrier test. This determines whether or not a sonar line segment is a true 
obstacle edge or a false reflection.

Sounds interesting, doesn't it? Unfortunately I don't have access to this
publication myself. Would anyone who has, like to reply to me?

Henrik Bohre

  @>-+-- 

In article <1993Jan24.183226.10455@netcom.com> nagle@netcom.com (John Nagle) 
writes:

>       It's really time for somebody to start developing smarter sonar
> systems for robots.  We've been using those dumb Polaroid sensors for a
> decade now, and enough is known about bat, dophin, and submarine sonar
> to do a much better job.  The DSP chips are available and cheap.  
> Somebody with audio, DSP, or sonar experience needs to do this one.
> 
>       A reasonable way to start would be to use a machine with stereo
> audio inputs and outputs, and try to do bat-type FM sonar, operating
> around 10-20KHz.  
>
>					John Nagle
=================

About fifteen years ago I saw a movie made by --I believe-- Doctor
Leslie Keyes of the University of Canterbury in New Zealand.  It
showed blind children playing a block-stacking game while wearing
baseball caps fitted with Keye's phased-array sonar transducers above
the bills.  The transducers had about a dozen emitter/receivers
arranged horizontally to produce a narrow vertical beam that the kids
could sweep side-to-side by turning and tilting their heads to locate
objects precisely.  The kids listened to signals from the arrays using
stereo earphones (whether they heard the signals heterodyned down to
the audio range, or whether they heard beat frequencies from the
different transducers, I forget).  Anyway, the kids rapidly learned to
interpret the wideband, binaural acoustic signals to "see" the blocks
on the table in front of them, and were able to take turns adding a
block to the stack.  They could stack up about six blocks before the
stack fell over.  They placed the blocks on top of the stack
one-handed, without feeling their way up the stack.  This demonstrated
that they really were "seeing" the objects on the table with the sonar
arrays.  Other experiments showed that the kids could distinguish
different materials based on frequency-dependent scattering from
different surface textures, acoustic absorption characteristics, etc.
E.g., they could distinguish coarse from fine sandpaper, drapes from
walls, people from other objects.

Keyes had had a long and productive career developing secret military
underwater sonar systems, then decided to try to help blind children
with his skills after he retired.  In those days, the idea of even
approximating electronically the acoustic signal processing that the
kids learned to do with their ears was out of the question--and not
what Keyes was trying to do, anyway.  These days, inexpensive DSP
chips and neural network chips would make practical a great deal of
sophisticated processing of signals from such transducers.  There
would be plenty of applications for such technology in industrial
process control and inspection, robot guidance, and perhaps medical
applications as well.

I've mentioned Keyes' work repeatedly in different forums over the
years since then, but I've never heard of anyone's taking the
slightest interest in it.  If someone knows different, I'd like to
hear about it.  I think there's a lot of amazing technology like this
withering on the vine out there because the right person has simply
never heard about it.

Bill Park
=========

-- 
Grandpaw Bill's High Technology Consulting & Live Bait, Inc.