Robot lawnmowers - boundary wire detection
 

Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?

Robot lawnmowers - boundary wire detection
 

On 18/04/20 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?

Have a look at the article he
https://www.ardumower.de/index.php/en/induktion

In particular, see the section "Sender/receiver principle using polarity
change ("Perimeter v2")" which appears about two thirds of the way down.
Quote:
"While crossing the perimeter loop, something interesting happens:
signal changes polarity, that means negative and positive voltages
reverse each other. By using this principle, crossing the perimeter wire
will be detected. The robot knows its current perimeter state all the
time (inside/outside)."

I'm not sure if crossing the wire is the detection for inside/outside,
or simply being outside is different from being inside - it's a bit
ambiguous. To my way of reading it, however, it tends towards always
knowing where it is, whether it actually crosses the wire or not.

--

Jeff

Robot lawnmowers - boundary wire detection
 

On 18/04/2020 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works
really nicely

One thing I haven't got clear in my head is how it knows whether it
is inside or outside of the charged boundary wiring.

When inside the boundary loop it gets a slightly better signal and there
is a null and then a phase reversal as it crosses the boundary wire. It
isn't dissimilar technology to a current based hearing loop. Except that
the lawnmower can afford to use a fair sized loop antenna.

I can power down the whole system, move the robot to just outside the
boundary loop, and when it is all powered back up it instantly
detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that
is the boundary wire to allow the robot unit to detect where it is in
relation to being inside or outside?



--
Regards,
Martin Brown

Robot lawnmowers - boundary wire detection
 

"Martin Brown" wrote in message
...
On 18/04/2020 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works
really nicely

One thing I haven't got clear in my head is how it knows whether it
is inside or outside of the charged boundary wiring.

When inside the boundary loop it gets a slightly better signal and there
is a null and then a phase reversal as it crosses the boundary wire. It
isn't dissimilar technology to a current based hearing loop. Except that
the lawnmower can afford to use a fair sized loop antenna.

I can power down the whole system, move the robot to just outside the
boundary loop, and when it is all powered back up it instantly
detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that
is the boundary wire to allow the robot unit to detect where it is in
relation to being inside or outside?

I think the crucial part of the OP's question was what happens if the mower
is turned on outside the loop. IN this case, it has no phase-reversal event
to detect when it is going outside. If the mower can detect that it is
*already* outside (as opposed to having just *gone* outside) that suggests
that it knows what the normal phase of the signal is, to know that it is
receiving a 180 degree phase-shifted version of it.

Robot lawnmowers - boundary wire detection
 

On 19/04/2020 10:37, NY wrote:
"Martin Brown" wrote in message
...
On 18/04/2020 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works
really nicely

One thing I haven't got clear in my head is how it knows whether it
is inside or outside of the charged boundary wiring.

When inside the boundary loop it gets a slightly better signal and
there is a null and then a phase reversal as it crosses the boundary
wire. It isn't dissimilar technology to a current based hearing loop.
Except that the lawnmower can afford to use a fair sized loop antenna.

I can power down the whole system, move the robot to just outside the
boundary loop, and when it is all powered back up it instantly
detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that
is the boundary wire to allow the robot unit to detect where it is in
relation to being inside or outside?

I think the crucial part of the OP's question was what happens if the
mower is turned on outside the loop. IN this case, it has no
phase-reversal event to detect when it is going outside. If the mower
can detect that it is *already* outside (as opposed to having just
*gone* outside) that suggests that it knows what the normal phase of the
signal is, to know that it is receiving a 180 degree phase-shifted
version of it.

Depends if it also receives something else...a sort of synchronisation
clock via e.g. radio.

There are also algorithms which would allow it to determine where it is
by shuffling a bit.

Inside the loop field strength would be relatively constant but outside
it would be tailing away rapidly..

--
The theory of Communism may be summed up in one sentence: Abolish all
private property.

Karl Marx

Robot lawnmowers - boundary wire detection
 

On Sat, 18 Apr 2020 13:41:14 -0700 (PDT), larkim
wrote:

Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?

I know nothing about this, but I have a theory. If there was DC
current in the loop (of course there isn't), inside the loop might
look like a N pole and outside would look like a S pole.

If instead a +ve pulse is fed to the loop followed by a -ve pulse,
with a gap before the next pair, the robot mower knows what to expect
when inside the loop, but would get the opposite effect outside, so
knows which way to move.
--
Dave W

Robot lawnmowers - boundary wire detection
 

On 18/04/2020 21:41, larkim wrote:
Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?


Somewhere in the world of patents, you'll find the answer ...

Automated lawn mower - US5974347A
https://patents.google.com/patent/US5974347A/en

.... but you may be reading through that for weeks...

--
Adrian C

Robot lawnmowers - boundary wire detection
 

On 19/04/2020 20:34, Dave W wrote:
On Sat, 18 Apr 2020 13:41:14 -0700 (PDT), larkim
wrote:

Recently got a dose of laziness and bought a robot mower. Works really nicely

One thing I haven't got clear in my head is how it knows whether it is inside or outside of the charged boundary wiring.

I can power down the whole system, move the robot to just outside the boundary loop, and when it is all powered back up it instantly detected as being outside the wire.

Anyone know how this works? What goes down the low voltage cable that is the boundary wire to allow the robot unit to detect where it is in relation to being inside or outside?

I know nothing about this, but I have a theory. If there was DC
current in the loop (of course there isn't), inside the loop might
look like a N pole and outside would look like a S pole.

If instead a +ve pulse is fed to the loop followed by a -ve pulse,
with a gap before the next pair, the robot mower knows what to expect
when inside the loop, but would get the opposite effect outside, so
knows which way to move.

THAT is pretty cunning. I think you have nailed it.


--
Religion is regarded by the common people as true, by the wise as
foolish, and by the rulers as useful.

(Seneca the Younger, 65 AD)