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PICList Thread
'[EE]: - Botboard'
2001\07\16@091722 by Lawrence Lile

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face
Dan,

Well, the botboard has worked out just great for me, met my needs exactly.
There's lots of stuff on the board I didn't need, which is just fine (future
expansion...)  It is just perfectly set up for someone doing most any kind
of small robot.

I am stalled on the mowbot project because of a pressing PAYING project that
is keeping me up late.  As soon as this stupid annoyance is over, and I get
my money, I'm back on the mowbot trail...

Meanwhile, the grass is getting long again.  Maybe it won't rain in July, so
the grass won't grow anymore...

-- Lawrence


{Original Message removed}

2001\07\25@131832 by Dan Michaels

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Hi Lawrence, I ran across this site - they have a robo
lawnmower kit that uses a Basic Stamp for brains. The
picture shows it about to mow down a bed of petunias.

http://www.lls.se/~mux/micro/robocut_kit.htm

Hopefully, you can do something more spectacular using
a regular PIC and your own code. ;-)

best regards,
- dan
http://www.oricomtech.com/robotics.htm
====================


Lawrence wrote:
{Quote hidden}

>{Original Message removed}


'[EE]: - Botboard'
2001\08\30@135526 by Lawrence Lile
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Hi, Dan,

I'm back on the Mowbot project with your BotBoard.  After letting the
project gather dust for a couple of months, I can't seem to find all the
documentation I thought I had.  (This always seems to happen)

I've scoured everything off your web page, but still seem to come up short
for a schematic.  If you have any additional docs beyond what;s on the page,
could you send them?  Thanks!

--Lawrence Lile

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2001\08\30@183818 by Dan Michaels

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Lawrence.L wrote:
>Hi, Dan,
>
>I'm back on the Mowbot project with your BotBoard.  After letting the
>project gather dust for a couple of months, I can't seem to find all the
>documentation I thought I had.  (This always seems to happen)
..........


Hi Lawrence, speaking of which, I am finally about broken loose
from other things, and gearing up to do some bot projects.

I picked up an R/C M1 tank at Radio shack this week. Marked down
to $29.95 from $49.95 regular - good deal for anyone interested
in a controllable bot platform. Should be lots easier to control
than those hi-speed R/C cars.

I did not get the battery packs & charger [another $40 or so] for
the tank - 6V NiCd - as I plan to use 6+ NiMH AA batteries to give
enough volts to compensate for the loss in the h-bridges. I
should have something to report soon - I hope [after months of
thinking about it :)].

BTW, interesting timing on your part - now that summer is over
and the grass will soon be covered with snow, you suddenly get
interested in your bot mower - [your wife will certainly pick
up on this].

- dan michaels
http://www.oricomtech.com
========================

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2001\08\30@222657 by Kathy Quinlan
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How about turning it into a bot snow plow ???

Regards,

Kat.

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{Original Message removed}

2001\08\30@224944 by Tom Handley

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  Dan, it must be that time of year! My robot has been in a box
all summer and I'm ready to get back to work on it. Where I left
off, I had a dual-deck chassis with dual Tamiya worm gear drives,
basic bumper switches, and IR sensors. I was having problems
with the Vector 2X compass and may just use the lower resolution
`heading' mode since I'm mainly using it to hold a heading. I had
also tested a few versions of ultrasonic detectors.

  One new thing I want to add is a low cost camera. I have a
wireless XCAM2 camera and I found a site with antenna hacks
for the camera. The main thing is replacing the directional
`paddle' antenna with a dipole or 1/4 wave ground plane. One
version uses 5 3cm stubs to make a 1/4 wave ground plane.
These were tested in R/C helicopters.

  Is that the same tank we talked about last winter? Keep us
up to date on all the `gory' details! ;-)

  - Tom

At 18:38 30-08-01 -0400, Dan Michaels wrote:
{Quote hidden}

------------------------------------------------------------------------
Tom Handley
New Age Communications
Since '75 before "New Age" and no one around here is waiting for UFOs ;-)

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2001\08\30@230126 by Jim

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bot *snow blower*?

Jim

----- Original Message -----
From: "Kathy Quinlan" <spam_OUTkatinkaTakeThisOuTspamMAGESTOWER.COM>
To: <.....PICLISTKILLspamspam@spam@MITVMA.MIT.EDU>
Sent: Thursday, August 30, 2001 9:27 PM
Subject: Re: [EE]: - Botboard


> How about turning it into a bot snow plow ???
>
> Regards,
>
> Kat.
>
>
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the
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2001\08\30@231513 by Dan Michaels

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Kat.Q wrote:
>How about turning it into a bot snow plow ???
>

Hopefully, he won't use mica to insulate the power transistors
from the metal chassis ;-)

however, a clever guy could have a mower for summertime and
snowblower for wintertime with a little morphing gizmo.

- dan
============

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2001\08\31@005327 by Dan Michaels

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Tom Handley wrote:
>   Dan, it must be that time of year! My robot has been in a box
>all summer and I'm ready to get back to work on it. Where I left
>off, I had a dual-deck chassis with dual Tamiya worm gear drives,
>basic bumper switches, and IR sensors. I was having problems
>with the Vector 2X compass and may just use the lower resolution
>`heading' mode since I'm mainly using it to hold a heading. I had
>also tested a few versions of ultrasonic detectors.
>


Hi Tom,

well it's been 7-8 months since we had the robot follies on piclist,
so maybe time to come round again :).

I've been "thinking" about bots a lot, but been bogged down in
other F&G. As I recall, Roman spent exactly 2 hours one evening
building and programming his bot, and then grabbed the PIC and
ran off to do something else. [geez, those motorcycle racers].
I've  spent lots more time than that just "thinking" about mine.
Saw the Radio Shack tank cheap and figured what the heck.

I did design my PIC74/77 botboard several months ago, and picked
up some $5 PIR sensors plus an ultrasonic movement detector
from Hostfelt last week, so now I am about ready to go.

Also "designed" [in concept] a whole pile of other bot-thingies
in the meantime. Originally I planned to have the tank terrorize
the neighbors' cat, but they moved away, so I designed a bot-cat
this week, among other things :).

My interest is not so much in the mechanical end of things, but
in the programming/behavioral stuff. What I am really itching
to do is play with subsumption techniques. Apparently you can
get some really cool emergent behavior out of this. "Mobile
Robots" by Jones & Flynn has a really good description - you
should take a look if you havena seen the book.
==============


>   One new thing I want to add is a low cost camera. I have a
>wireless XCAM2 camera and I found a site with antenna hacks
>for the camera. The main thing is replacing the directional
>`paddle' antenna with a dipole or 1/4 wave ground plane. One
>version uses 5 3cm stubs to make a 1/4 wave ground plane.
>These were tested in R/C helicopters.
>

If your bot is large enuf, 12" or so, you might consider
getting one of those off-the-shelf 900 mhz A-V transmitter-
receiver pairs - can probably be found for $70-80 at Ckt
City/etc, and will be FCC approved. And your bot will look
like a low-flying saucer.

I expect you are going to write some nice robust machine vision
code and not simply send the pics - yes ???? ;-)
==========


>   Is that the same tank we talked about last winter? Keep us
>up to date on all the `gory' details! ;-)
>

I imagine this must be the same tank, only now it is $20 cheaper
on sale.

Maybe we'll get to hear from a few others about their bot F&G
too. I've discovered there are very few PIC-botters around,
most use 68HCxx.

best regards,
- dan michaels
http://www.oricomtech.com
=============================

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2001\08\31@044316 by Alan B. Pearce

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>BTW, interesting timing on your part - now that summer is over
>and the grass will soon be covered with snow, you suddenly get
>interested in your bot mower - [your wife will certainly pick
>up on this].

Well is it not the ideal time to get it ready for next summer???  :)

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2001\08\31@054938 by John Walshe

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It must be something in the air, I've just done a deal with my dad to swap a
5HP petrol mower for his electric cylinder mower - just to start such a
project. Unfortunately in Ireland the grass stays growing in the Winter
also, albeit it does slow down a little - one cut a month as against every
weekend in the summer (3-4hrs on a tractor mower!)

Dan,
   Where can I get the details on the botboard?

John

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2001\08\31@071217 by Byron A Jeff

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On Fri, Aug 31, 2001 at 09:41:55AM +0100, Alan B. Pearce wrote:
> >BTW, interesting timing on your part - now that summer is over
> >and the grass will soon be covered with snow, you suddenly get
> >interested in your bot mower - [your wife will certainly pick
> >up on this].
>
> Well is it not the ideal time to get it ready for next summer???  :)

Grass grows here in the Atlanta area into November. I'm still planning to
prototype for this season.

James, if you're reading: Should be consider a ROBOT/MOBILE tag?

There's one mowbot behavior question I'd like to get on the table: How are you
planning the cutting path? I'm planning on using bumpers to keep the bot in
an enclosed area for now, but I'm wondering if edge sensing, random pattern,
planned path (and how to measure that the path is maintained), or some other
technique is viable. At this point power efficiency is secondary to getting
good cutting coverage.

Any thoughts?

BAJ

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2001\08\31@082550 by Jinx

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> How are you planning the cutting path ?

The most successful I've seen is tracking a buried wire. Not
sure what the signal is but the demo looked pretty good. If
you edged the area with white (painted bricks ? logs ?) you
could perhaps use optics. Industrial robots follow a white line
around their work area

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2001\08\31@095114 by Madhu Annapragada

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I have been toying with this idea for a while and I will throw it out there
to see if it even holds up to the piclist scrutiny. What do you think about
teaching the bot the first time? With heading information from a compass and
wheel rotation information from encoders, the bot would build a table of
heading changes vs wheel rotations the first time (starting from a home
position). One would use a joystick to mow the lawn the first time. The bot
records the wheel position every time the heading changes by a certain
amount. The second time around, the bot would head out in the first heading
direction until it reaches the wheel rotation figure for the next heading
change, change to the new heading and so on.
Of course, the problems I see right away are wheel slippage and  noise from
the compass. But for arguments sake, if I could solve those problems, do you
see any other potential pitfalls for this method. The merits of this method
are that you do not need to depend on any external markers. Teach it one
lawn ( even multiple lawns using a selector switch) and let it go from a
know position every time. One might have to re-teach it every so often if
the bot starts wandering into the flower patch....
Anyway, does the method seem feasible?...winter is coming and I need to go
into hibernation in my basement lab...
Madhu


{Original Message removed}

2001\08\31@101004 by Kathy Quinlan

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Start another war involving America, all the military satellites come online
and use GPS I think when all the satellites are operational the accuracy is
in the cm's (<10cm)

Regards,

Kat.

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----- Original Message -----
From: "Madhu Annapragada" <EraseMEmadhuspam_OUTspamTakeThisOuTCONECTIV.NET>
To: <PICLISTspamspam_OUTMITVMA.MIT.EDU>
Sent: Friday, August 31, 2001 9:51 PM
Subject: Re: [EE]: - Botboard


> I have been toying with this idea for a while and I will throw it out
there
> to see if it even holds up to the piclist scrutiny. What do you think
about
> teaching the bot the first time? With heading information from a compass
and
> wheel rotation information from encoders, the bot would build a table of
> heading changes vs wheel rotations the first time (starting from a home
> position). One would use a joystick to mow the lawn the first time. The
bot
> records the wheel position every time the heading changes by a certain
> amount. The second time around, the bot would head out in the first
heading
> direction until it reaches the wheel rotation figure for the next heading
> change, change to the new heading and so on.
> Of course, the problems I see right away are wheel slippage and  noise
from
> the compass. But for arguments sake, if I could solve those problems, do
you
> see any other potential pitfalls for this method. The merits of this
method
> are that you do not need to depend on any external markers. Teach it one
> lawn ( even multiple lawns using a selector switch) and let it go from a
> know position every time. One might have to re-teach it every so often if
> the bot starts wandering into the flower patch....
> Anyway, does the method seem feasible?...winter is coming and I need to go
> into hibernation in my basement lab...
> Madhu
>
>
> {Original Message removed}

2001\08\31@105319 by Michael Pont

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This is a nice solution: teach the robot once, and use GPS.  You may have to
use a 'strimmer' to do the edges of the grass, but that is a fairly easy
job.

I'd like to try this for a student project I'm involved in next year (not
cutting the grass, just mapping a lab).

We did a little work last year with a GPS sensor (easy to use, data was sent
down an 'RS-232' interface to an 8051: not too much data involved).
However, we had that GPS sensor on loan: I suspect the purchase cost of such
a device would blow my budget.

Michael.

{Original Message removed}

2001\08\31@110142 by Jim

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     "I think when all the satellites are operational the
      accuracy is in the cm's (<10cm)"

Do you have a source on that accuracy figure?

Is that using what is called 'P code' - Precision code,
using a 10.23 MHz chip rate and available -so far- only
to the US Military versus 'C/A code' - (Course/Acquisition
code - available for civil apps) which uses a 1.023 MHz
chip rate?

There are ways right now to gain increased accuracy - such
as DGPS - differential GPS - simplified explanation: a technique
wherein *the position error* in the GPS sugnal from the satellites
in a given geographical area is noted and transmitted for use as a
correction factor by user-segment GPS equipment.

One could *also* implement one's own localized "GPS"
system (as was done when test of the system was done at
Yuma Az) during development testing. One could use the
principles of the GPS system and implement a localized
position determining system using unlicensed gear in the
900 MHz ISM-band ... perfect app for a PIC ...


Jim  (a veteran of GPS/HDUE (High Dynamic User Equipment)
development at TI in the late seventies ...)


{Original Message removed}

2001\08\31@113552 by Alan B. Pearce

face picon face
>However, we had that GPS sensor on loan: I suspect the purchase cost of
such
>a device would blow my budget.

Check out the Garmin 25 series, these are complete uncased receivers without
antenna. I can get these in the UK for GBP99 from RS components, and they
are an expensive source in an expensive country. YMMV due to taxes etc, but
in the UK this is a good buy. Anyone have a cheaper source in the UK I would
like to know before committing to one of these, must have an accurate 1ppm
output.

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2001\08\31@121152 by Dan Michaels

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John Walshe wrote:
>It must be something in the air, I've just done a deal with my dad to swap a
>5HP petrol mower for his electric cylinder mower - just to start such a
>project. Unfortunately in Ireland the grass stays growing in the Winter
>also, albeit it does slow down a little - one cut a month as against every
>weekend in the summer (3-4hrs on a tractor mower!)
>
>Dan,
>    Where can I get the details on the botboard?


http://www.oricomtech.com/bot40.htm

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2001\08\31@121205 by Dan Michaels

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BAJ wrote:
.......
>There's one mowbot behavior question I'd like to get on the table: How are you
>planning the cutting path? I'm planning on using bumpers to keep the bot in
>an enclosed area for now, but I'm wondering if edge sensing, random pattern,
>planned path (and how to measure that the path is maintained), or some other
>technique is viable. At this point power efficiency is secondary to getting
>good cutting coverage.
>
>Any thoughts?
>

I have several links to commercial mowbots here - you might check
what they do.

http://www.oricomtech.com/robolnk1.htm#Mobo2

Some are quite stupid, and require a square mowing area
unhindered by trees, bushes. etc. Surely a picster could build
something more intelligent than that.

- dan
==============

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2001\08\31@122524 by Dan Michaels

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Madhu Annapragada wrote:
>I have been toying with this idea for a while and I will throw it out there
>to see if it even holds up to the piclist scrutiny. What do you think about
>teaching the bot the first time? With heading information from a compass and
>wheel rotation information from encoders, the bot would build a table of
>heading changes vs wheel rotations the first time (starting from a home
>position). One would use a joystick to mow the lawn the first time. The bot
>records the wheel position every time the heading changes by a certain
>amount. The second time around, the bot would head out in the first heading
>direction until it reaches the wheel rotation figure for the next heading
>change, change to the new heading and so on.
>Of course, the problems I see right away are wheel slippage and  noise from
>the compass. But for arguments sake, if I could solve those problems, do you
>see any other potential pitfalls for this method.
.........


Personally, I don't think that a dead reckoning system would work
at all well in this case. Yards are never perfectly flat, and the
moisture content - related to wheel slippage - is going to change
daily. However, if you were to add "some" kind of fixed markers, I
think a combination approach between marker sensing and dead
reckoning based upon an internal representation would put you in
business.

Possibly a wire around the outer perimeter, as Quiet Joe mentioned,
plus some low bricks at the edge of the flower beds, etc.

- dan
=============

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2001\08\31@124926 by Alan B. Pearce

face picon face
>However, if you were to add "some" kind of fixed markers, I
>think a combination approach between marker sensing and dead
>reckoning based upon an internal representation would put you in
>business.
>
>Possibly a wire around the outer perimeter, as Quiet Joe mentioned,
>plus some low bricks at the edge of the flower beds, etc.

For mowing a lawn it may well be possible to have some IR Led marker posts
at strategic points which the bot could sense. A scheme something like this
has been used on tractors to plough a field, but that was done with a laser
on the tractor sensing survey type corner reflectors I believe.

If the Leds were only about a foot above the ground it should be possible to
have a slit that the bot uses to view them which would keep incident
sunlight from overpowering the sensor. If each led was permanently implanted
in the garden border and operated at a different frequency then the bot
would always know where it was. The leds could even be mounted on the house
wall or fence some way back from the mowing limit. With enough leds it would
not matter if bushes sometimes obscured some of them, the bot may even be
able to learn how much the bush has grown by the shadow of a sensor :)

This would save burying a wire all round the perimeter of the mowing area.

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2001\08\31@125733 by Jim

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    "For mowing a lawn it may well be possible
     to have some IR Led marker posts at strategic
     points which the bot could sense."

What if these IR LED markers were 'swept' at known
intervals over the work area?

What I mean is, what if they were 'rotated' in place and
acted much like a VOR beacon.

By taking the angular bearing from 2 (or more of these
beacons) a very accurate position could be determined.
Perhaps this in combination with a perimiter wire to mark
the outer boundary?

Jim


{Original Message removed}

2001\08\31@132622 by David VanHorn

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face
At 11:57 AM 8/31/01 -0500, Jim wrote:
>      "For mowing a lawn it may well be possible
>       to have some IR Led marker posts at strategic
>       points which the bot could sense."
>
>What if these IR LED markers were 'swept' at known
>intervals over the work area?
>
>What I mean is, what if they were 'rotated' in place and
>acted much like a VOR beacon.
>
>By taking the angular bearing from 2 (or more of these
>beacons) a very accurate position could be determined.
>Perhaps this in combination with a perimiter wire to mark
>the outer boundary?

Why rotate?
The beacons could be solar powered, (no mowing at night of course) with
movable blinders to restrict their output to cover only the yard.
You look around, and if you don't see the beacons, you're out of the yard.
If you see one, you're still out of the yard.
If you see two, then you can triangulate.

There are some nice solar powered lights made that I could see modifying
into mowbot beacons.

Alternatively, the beacons could be set up the other way, so that as the
bot begins to get outside, it comes into view of the beacons, but I am more
comfortable with positive control.

How would you deal with missing beacons due to kids or damage?

One of these days, I want to launch on a mowbot.
I already have a B+D battery powered mower.
I have an irregular yard. The front is two rectangular sections, divided by
a concrete sidewalk, which is crossable, but only at certain points for a
mower. The back is one rectangular section, with two apple trees, and some
minor hazards.  They are joined by a side which is about 4' wide.


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2001\08\31@140807 by jamesnewton

face picon face
I think your beacon idea is great but I would use LEDs and modulate them to
ensure that reflections, etc.. don't confuse the robot.

Here is a way to scan for the beacons.
http://www.cyberg8t.com/pendragn/actlite.htm

Also, on the subject of safety, I really (REALLY) think that mowbots should
use the old multi-scissors clipper bar design operated very slowly (but all
the time) to avoid liability. The commercial mowbots do this.

P.S. Dave, let me know if you want another B+D battery lawn mower... with a
locked up motor... real cheap. Two weeks after the warranty ran out...

"Real men use push mowers."

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{Original Message removed}

2001\08\31@141230 by Lawrence Lile

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face
Phooey on all that complex programming.  I want my mowbot to be as stupid as
a cochroach.  Did you know, a cochroach is so stupid, it cannot even
individually address it's own legs?  They have about four modes - go slow
with six legs, go fast with six legs, go with the right legs only, go with
the left legs only.  Robot scientists puzzle over how they clamber over tall
obstacles with no finesse, they just scrabble until they get over it.  No
finesse at all.

Now, who would argue that cochroaches are not wildly successful?

My mower is going to stumble aimlessly across the yard until it bumps into
the barrier at the edge, back up, turn a random number of degrees, and
wander aimlessly until it bumps into something again.  You get good coverage
by randomness.  Stupid as a cochroach!

Also, I don't want any complex rocket science edge sensing.  A line of big
dumb bricks is what I'm considering.  I'd rather not find my Bot mowing the
nieghbor's flowers when the house-of-cards edge sensing scheme fails.  As
long as the edge is a barrier the bot cannot climb over, then bumpers are
all that I need.

Besides, I've got to finish this project by next summer.

--Lawrence Lile

> There's one mowbot behavior question I'd like to get on the table: How are
you
> planning the cutting path? I'm planning on using bumpers to keep the bot
in
> an enclosed area for now, but I'm wondering if edge sensing, random
pattern,
> planned path (and how to measure that the path is maintained), or some
other
> technique is viable. At this point power efficiency is secondary to
getting
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2001\08\31@141433 by Douglas Butler

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The "accumulation of error" problem will eat you alive.  People have
been trying to solve that for decades, maybe centuries.  If you could
add a few north/south and east/west buried wires, then occasionally the
mower would cross one and could correct its position.
Wheel turns are really bad for measuring position.  How about using an
optical mouse looking through an (un)magnifying glass at the ground.
That would measure distance better than wheel turns.

Sherpa Doug

> {Original Message removed}

2001\08\31@141641 by Lawrence Lile

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I can really recommend Dan's Botboard - it's crammed with every concievable
peripheral that a Bot designer might want - plus a prototyping area if you
think of something else.  Besides, I helped beta test it.

-- Lawrence Lile

{Original Message removed}

2001\08\31@141916 by Lawrence Lile

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After watching my bot crawl across the bumpy yard, sans brains at this
point, I can tell you that dead reconing will fail immediately.  The thing
doesn't even cut a straight path, kind of wanders back and forth, climbing
up and down the bumps and over cats, baseball bats molehills etc.

Standard GPS is not accurate enough for mowing control.  But it would be
accurate enough for theft control (see long thread March 2001)  to tell when
your bot had left the yard.  What's the cheapest GPS on the US side of the
water?

--Lawrence

{Original Message removed}

2001\08\31@144304 by Lawrence Lile

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part 1 4653 bytes content-type:text/plain; (decoded 7bit)

The scissors-clippers are great, but I've found a swinging blade type of
cutter to be very safe, and also very efficient.

Attached is a picture of the blade, next two emails are pictures of the
DAMAGE done to a tennis shoe held in the path of the blade for 1 minute.
You'll see its not too bad at all.  Even a bare foot would remain attached
(although a bit bloody).  Try that with a regular mower!

I attached razor knife blades to a standard swing blade cutter head
attachment for string trimmers.  I found it worked best at about 1700-2000
RPM.  Slower, and it would not cut grass.  Faster, and it started to move a
lot of air and the idling power started to climb.  At 4000 RPM it was
consuming many times the horsepower (air friction goes up as the square of
the fan RPM!)

--Lawrence

----- Original Message -----
From: "James Newton. Admin 3" <KILLspamjamesnewtonKILLspamspamPICLIST.COM>
To: <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU>
Sent: Friday, August 31, 2001 1:06 PM
Subject: Re: [EE]: - Botboard


> I think your beacon idea is great but I would use LEDs and modulate them
to
> ensure that reflections, etc.. don't confuse the robot.
>
> Here is a way to scan for the beacons.
> http://www.cyberg8t.com/pendragn/actlite.htm
>
> Also, on the subject of safety, I really (REALLY) think that mowbots
should
> use the old multi-scissors clipper bar design operated very slowly (but
all
{Quote hidden}

> {Original Message removed}
part 2 19065 bytes content-type:application/octet-stream; (decode)

part 3 144 bytes
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2001\08\31@144650 by Lawrence Lile

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part 1 130 bytes content-type:text/plain; (decoded 7bit)

Damage done to a tennis shoe when held in path of swing blades for 1 minute.

--Lawrence Lile


part 2 15482 bytes content-type:application/octet-stream; (decode)

part 3 144 bytes
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2001\08\31@144712 by Lawrence Lile

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part 1 96 bytes content-type:text/plain; (decoded 7bit)

Here's a picture of the (now brainless) mowbot.

--Lawrence


part 2 22964 bytes content-type:application/octet-stream; (decode)

part 3 144 bytes
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2001\08\31@145516 by David VanHorn

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>
>I attached razor knife blades to a standard swing blade cutter head
>attachment for string trimmers.  I found it worked best at about 1700-2000
>RPM.  Slower, and it would not cut grass.  Faster, and it started to move a
>lot of air and the idling power started to climb.  At 4000 RPM it was
>consuming many times the horsepower (air friction goes up as the square of
>the fan RPM!)

Air drag alone is KV^3.

For a start, I'm planning to make this an add-on to my existing mower.
I won't be letting it run unsupervised.

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2001\08\31@151918 by Dan Michaels

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Alan Pearce wrote:
>>However, if you were to add "some" kind of fixed markers, I
>>think a combination approach between marker sensing and dead
>>reckoning based upon an internal representation would put you in
>>business.
>>
>>Possibly a wire around the outer perimeter, as Quiet Joe mentioned,
>>plus some low bricks at the edge of the flower beds, etc.
>
>For mowing a lawn it may well be possible to have some IR Led marker posts
>at strategic points which the bot could sense.
......
If each led was permanently implanted
>in the garden border and operated at a different frequency then the bot
>would always know where it was.
.......


Alan, in fact this is precisely the scheme I plan to employ when
I get to the point of having my bots navigate around multiple rooms
inside the house.

Each room will have at least 1 permanent beacon, with that in each
room modulated at a different freq. Once the bot acquires a beacon,
it will know what room it is in, and then it can use other techniques
to map the room, but it will always have a fixed reference point to
prevent getting hopelessly lost. Also, if it does get lost inside
a room, it can go over to the beacon and start over.

$1 beacon or $120 GPS???

- dan
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2001\08\31@152623 by Dan Michaels

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Lawrence.L wrote:
>I can really recommend Dan's Botboard - it's crammed with every concievable
>peripheral that a Bot designer might want - plus a prototyping area if you
>think of something else.  Besides, I helped beta test it.
>

True, Lawrence, it is over-designed ;-).

Lacking a 100 Amp h-bridge, but you do have the capability to
parallel or remove the 8 on-board h-bridges [0.6-1A] and wire to
external cards.

- dna
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2001\08\31@153512 by Dan Michaels

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Lawrence.L wrote:
>Phooey on all that complex programming.  I want my mowbot to be as stupid as
>a cochroach.  Did you know, a cochroach is so stupid, it cannot even
>individually address it's own legs?
........


Of course, a cockroach doesn't have to worry about liability
insurance when it runs over your neighbor's kid either. Talking
about disconnected legs, after all ........

BTW, last week I picked up some PIR sensors from Hosfelt that
cost only $5.95 each. 180 deg of view. Look perfect for helping
to not run over a potential litigant.

- dan
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2001\08\31@154050 by Dan Michaels

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At 01:42 PM 8/31/01 -0500, you wrote:
>Damage done to a tennis shoe when held in path of swing blades for 1 minute.
>
>--Lawrence Lile
>
>Attachment Converted: C:\WIN31APP\EUDORA\ATTACH\S_shoe.JPG
>


Better than the fingers of your neighbor's 5 YO kid.

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2001\08\31@163302 by David VanHorn

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>
>P.S. Dave, let me know if you want another B+D battery lawn mower... with a
>locked up motor... real cheap. Two weeks after the warranty ran out...

Shipping might be problematic, but it would be a good start for a platform.
I'm in EC indiana.

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2001\08\31@170141 by Terry

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Maybe you could hire a roach to drive it instead? *grin*


It's been a really long time since i've had to cut grass since the
majority over here live in apartments. I probably won't get a chance to
try this out anytime soon but will there be an easily defined difference
between the uncut and freshly cut grass?


If there is, couldn't a simple pair of hand-formed wires attached to leaf
switches track the boundary between cut and uncut grass? Something like
how kids enjoy walking through a clothing store with their hand brushing
through every item of clothing hanging on a rack.


If so, the controller should navigate the mower so that the 1st wire is
constantly brushing against the uncut grass and the 2nd shorter wire does
not contact any grass. (Debris from the mower should be expelled as far
away from the tracking wires possible. Doesn't matter if it lands on the
cut or uncut side.)


This method should make a really simple "open field" concentric uncut
grass follower possible. Make the first cutting path manually (preferably
with a nice turning radius for the mower bot to track) and let it do the
rest. It should shut down after say 15 seconds of going round in circles
and unable to find anymore uncut grass.


Obsticle avoidance will require a controller with some smarts and i'd go
with at least a 2 bumper switch design. 3 may be better, front Left
corner, front center, front right corner. A bumper gets hit, reverse a
little, turn a little to the cut grass side and "feel" it's way around
the tree, bricked up flower bed, dead cat, etc till it finds the uncut
grass and starts tracking again.


Last note, install a huge red emergency stop button on the top of the
mower.


Cheers

Terry


Design Consultant

T3DESIGN

Innovative Product Development

<italic>Thinking out of the box.

</italic>


At 01:18 PM 8/31/01 -0500, you wrote:

>After watching my bot crawl across the bumpy yard, sans brains at this

>point, I can tell you that dead reconing will fail immediately.  The
thing

>doesn't even cut a straight path, kind of wanders back and forth,
climbing

>up and down the bumps and over cats, baseball bats molehills etc.

>

>Standard GPS is not accurate enough for mowing control.  But it would
be

>accurate enough for theft control (see long thread March 2001)  to tell
when

>your bot had left the yard.  What's the cheapest GPS on the US side of
the

>water?

>

>--Lawrence

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2001\08\31@202948 by Kathy Quinlan

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Jim,

All I can remember was an article stating that during the gulf war the
accuracy of the GPS system was increased dramatically, and after the war
finished, some of the satellites were turned off :o(

The accuracy could have been ,10 mm not cm as it has been a while since
reading the article.


Regards,

Kat.

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2001\08\31@205317 by Jim

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It was in the month of May just several years
back that Prez. Clinton ordered 'SA' (Selective
Availabilty) turned off - could that be what you
are making reference to?

SA caused readings/the reported position to drift
to and fro - it seemed to do it in a more or less
sinusoidal way - both position (lat/long) and altitude
varied. I *guess* this was done so that no hostile foreign
power could target the front doors of Cheyene Mt. with
an ICBM via the proper coordinates marking same.

Since SA has been turned off - there isn't near as much
'drift' as before. But there still is some 'drift'.

As it takes 24 some birds to cover the earth - I find it
*very* difficult to believe that these birds were actually
turned off. Although it is still possble - the entire GPS/NAVSTAR
system could/can as any time be made 'unavailable' at the behest
of those in charge in a moment with no notice whatsoever
(perhaps when NORAD views ICBMs coming over the
Pacific or over the N. pole they would 'turn down' GPS
for a short period 'til the ICBMs terminate somewhere).

Some of the better GPS OEM-class receivers will
actually output the bird numbers used for fix/or currently
in view as well as their 'signal stringth'. It is easy that way
to observe and perform an audit verfying those birds that
the NAVSTAR program office shows as 'active'.

The GPS/NAVSTAR program office still maintains a web
site where they post the health of the birds in service - years
back this used to be available via a dial-up BBS system. My
how times have changed ...

Jim


{Original Message removed}

2001\08\31@212306 by Kathy Quinlan

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Thanks for the clarification Jim :of)


Regards,

Kat.

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2001\08\31@220432 by Byron A Jeff

face picon face
On Fri, Aug 31, 2001 at 01:41:03PM -0500, Lawrence Lile wrote:
> The scissors-clippers are great, but I've found a swinging blade type of
> cutter to be very safe, and also very efficient.
>
> Attached is a picture of the blade, next two emails are pictures of the
> DAMAGE done to a tennis shoe held in the path of the blade for 1 minute.
> You'll see its not too bad at all.  Even a bare foot would remain attached
> (although a bit bloody).  Try that with a regular mower!
>
> I attached razor knife blades to a standard swing blade cutter head
> attachment for string trimmers.  I found it worked best at about 1700-2000
> RPM.  Slower, and it would not cut grass.  Faster, and it started to move a
> lot of air and the idling power started to climb.  At 4000 RPM it was
> consuming many times the horsepower (air friction goes up as the square of
> the fan RPM!)
>

I just wanted to let you know that your description of this the last go round
inspired me to implement a similar setup.

The only real problem I have is trying to keep the clippings from getting
caught in the works.

BAJ

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2001\08\31@221327 by Byron A Jeff

face picon face
On Fri, Aug 31, 2001 at 01:10:47PM -0500, Lawrence Lile wrote:
> Phooey on all that complex programming.  I want my mowbot to be as stupid as
> a cochroach.  Did you know, a cochroach is so stupid, it cannot even
> individually address it's own legs?  They have about four modes - go slow
> with six legs, go fast with six legs, go with the right legs only, go with
> the left legs only.  Robot scientists puzzle over how they clamber over tall
> obstacles with no finesse, they just scrabble until they get over it.  No
> finesse at all.
>
> Now, who would argue that cochroaches are not wildly successful?
>
> My mower is going to stumble aimlessly across the yard until it bumps into
> the barrier at the edge, back up, turn a random number of degrees, and
> wander aimlessly until it bumps into something again.  You get good coverage
> by randomness.  Stupid as a cochroach!

It still has an asthetic inelegance that I just can't shake. Between power
inefficiency, spot poor coverage, and the inability to navigate obsticles
or do planning the concept bothers me.

>
> Also, I don't want any complex rocket science edge sensing.  A line of big
> dumb bricks is what I'm considering.  I'd rather not find my Bot mowing the
> nieghbor's flowers when the house-of-cards edge sensing scheme fails.  As
> long as the edge is a barrier the bot cannot climb over, then bumpers are
> all that I need.

Sorry wrong edge. Not the edge of the property, the edge of the cut grass.
It could be a navigational tool (follow the cut grass edge) and even with
random wandering it can save power by only engaging the cutting motor if the
high grass sensors indicate that there's grass to cut.

I agree on the physical boundaries. I plan some type of low fencing along
with bumbers.

>
> Besides, I've got to finish this project by next summer.

I understand. Mine is two revisions and several years in the making.

BAJ

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'[EE]: - Botboard'
2001\09\01@135848 by Peter L. Peres
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> mowing neighbor's flowers

Maybe you could consider using a 433 MHz Tx/Rx pair as a beacon and have
the robot stop dead if the signal becomes too weak. You could also
consider two or more beacons and DF equipment on the robot for navigation.
It strikes me that RF is not disturbed by water, dirt, sunlight etc. The
position where you would mount the beacons would be indifferent (i.e. not
in the center, preferrably spaced out to give good angle resolution and
coverage). The multiplexed whip antenna (artificial doppler) would be
usable I think, using PIN diodes switched by a PIC, that would also
evaluate the standard 433MHz receiver output. The transmitters would be
sequenced (also using PICs) so they use the same frequency but different
IDs. Combined with a mechanical restrainig scheme (bricks on border or
cable on short tent stakes 10 cm above ground delimiting perimeter) this
would be reasonably safe I think.

Since the mower is already round putting the doppler whips on in a circle
on top will be esthetical ;-). Just be sure to put some english
inscription on it so nobody takes it to SETI by mistake.

This could work with the learning scheme. The robot could weave
deliberately to cover a swath slightly wider than the DF accuracy in each
pass, to avoid leaving uncut areas.

There is a firm called Friendly Robotics which makes robotic lawn mowers.
I know nothing of their system.

Peter

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2001\09\01@173944 by David VanHorn

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>
>Since the mower is already round putting the doppler whips on in a circle
>on top will be esthetical ;-). Just be sure to put some english
>inscription on it so nobody takes it to SETI by mistake.

The doppler bit is non-trivial, but I've done it in the AVR.

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2001\09\04@103702 by Lawrence Lile

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Right you are on power efficiency, an efficient mowing algorithm will beat
randomness.  But, in the long view, what else does this mower have to do
other than mow the lawn?  If it gets around to mowing in front of the walk
this week, or next week, what's the diff?  I plan on a solar cell for
autonomy eventually.   If it mows the lawn with an efficient algorithm, then
waits around for a week for the grass to grow again, there's not much
difference.

 Elegance is an arguable point, since perception of elegance is like
perception of beauty.  Even a trash heap, or a noisy cantankerous
smoke-belching push mower, might be seen as beautiful by some warped
individual.

The elegance of simple systems is in their simplicity.  (another circular
argument indeed.)


--Lawrence

{Original Message removed}

2001\09\04@133801 by Raymond Choat

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I once had an idea (bet I was one of the first 100,000) of a pulling box
that pulled a mower or seed spreader or automated weed sprayer or ....
You get the idea.  So there are other things an automated mower can do. So
if you save power by using an efficient mowing algorithm, the saved power
can be used for other things or the need for a smaller amount of solar
cells. Hope this sparks an idea. The automated weed sprayer would only spot
spray when it sees the weeds.
Wrong Way Ray (Raymond Choat)

{Original Message removed}

2001\09\04@135349 by Dan Michaels

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Raymond Choat wrote:

>I once had an idea (bet I was one of the first 100,000) of a pulling box
>that pulled a mower or seed spreader or automated weed sprayer or ....
>You get the idea.  So there are other things an automated mower can do. So
>if you save power by using an efficient mowing algorithm, the saved power
>can be used for other things or the need for a smaller amount of solar
>cells. Hope this sparks an idea. The automated weed sprayer would only spot
>spray when it sees the weeds.


Excellent idea, a puller is a puller is a puller, likewise for pushing.

As a possible way to keep the spouse/family happy, a general unit could
be built which could hook onto the [regular] mower, the snow blower,
AND the inhouse vacuum cleaner. With a broom attachment, it sweeps the
driveway/etc.

One drive unit and [basically] one algorithm serves all. Why limit to
the backyard only?


[also, weeds are easy to spot - as someone said, if you water it and
it dies, it's a flower; if you cut it and it regrows, it's a weed
- therefore .... easy to spot a weed :)].

- dan michaels
http://www.oricomtech.com
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2001\09\04@153130 by Byron A Jeff

face picon face
On Tue, Sep 04, 2001 at 09:36:23AM -0500, Lawrence Lile wrote:
> Right you are on power efficiency, an efficient mowing algorithm will beat
> randomness.  But, in the long view, what else does this mower have to do
> other than mow the lawn?  If it gets around to mowing in front of the walk
> this week, or next week, what's the diff?

That's the coverage issue that I referred to below. Lawn mowing is a wholly
aesthetic activity. If we didn't want the yard to look decent, there's be no
need to mow it.

So no matter the mechanism, a robotic lawnmower will have to guarantee even
coverage of the target area. This means that it needs to get all of the grass
in the area, and do it in a reasonable time.

I can even buy your "E-goat" type concept where it does nothing else but
wander around and munch grass all day. But there's a very strong desire to
get the whole coverage area right?

> I plan on a solar cell for
> autonomy eventually.   If it mows the lawn with an efficient algorithm, then
> waits around for a week for the grass to grow again, there's not much
> difference.

Except that the efficient algorithm will cover all of the are.

>
>   Elegance is an arguable point, since perception of elegance is like
> perception of beauty.  Even a trash heap, or a noisy cantankerous
> smoke-belching push mower, might be seen as beautiful by some warped
> individual.

;-) Agreed.

>
>  The elegance of simple systems is in their simplicity.  (another circular
> argument indeed.)

As long as they are not so simple as to not meet their intended objective.
That's my concern with the blind random method.

Of course once one starts with the sensors, one tends to go overboard!

BAJ
>
>
> --Lawrence
>
> {Original Message removed}

2001\09\04@164112 by Lawrence Lile

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I'm actually calling my 'bot the Robot Goat.

Maybe I should add a little milk dispenser on the bottom.

We actually had goats for a while when I lived in the country.  Cantankerous
little imps, we had 'em caged up in a little pen one night, the next morning
they were gone.  Nothing in the pen but a panther track and a little goat
hair.

Maybe the panther will leave this one alone.

--Lawrence Lile

{Original Message removed}

2001\09\05@061532 by Alan B. Pearce

face picon face
>[also, weeds are easy to spot - as someone said, if you water it and
>it dies, it's a flower; if you cut it and it regrows, it's a weed
>- therefore .... easy to spot a weed :)].

Right - out with the weedsprayer over the whole lawn - well every time I cut
it it regrows, so it must all be weed :)

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2001\09\05@061536 by Alan B. Pearce

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>   Elegance is an arguable point, since perception of elegance is like
> perception of beauty.  Even a trash heap, or a noisy cantankerous
> smoke-belching push mower, might be seen as beautiful by some warped
> individual.

It certainly is by those warped individuals who have lawn mower races - I am
not kidding :)

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2001\09\06@125342 by Raymond Choat

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Broad leaf plants would reflect different than narrow leaf grass. If wide,
spray weeder on it.
Wrong Way Ray (Raymond Choat)

{Original Message removed}

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