I'm looking for a wire guidance transmitter and sensor system (similar to an invisible dog fence) to control the route of a  robot lawnmower.  A transmitter puts a RF signal on the buried wire and sensors on the robot pick up the signal and follow it.  This type of equipment is used a lot in industry but industrial grade electronics is very expensive.  I am looking for a low-priced transmitter and sensors.  I have googled and found nothing.  Please don't suggest I paint a white line all over my lawn and use photo sensors.  A GPS system is only good for plus or minus 5 meters, I want plus or minus a few centimeters.  Any other suggestions?  Maybe I will buy a used invisible dog fence and open up the dog collar and see if I could get a signal from it.

Anyone know where I might buy hobby robot wire guidance controls?

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Warren,

Why not painting the white line?? Just kidding!!! Hehehehe....

I have never seen this sensors available, probably you have to develop by yourself, what could give a nice product to sell.

The most difficult part, IMHO is to align the robot movement to the signal sent by the wire. It probably will be difficult to know how far from the wire the robot is. You can try to make corrections using the maximum strength of the signal, or use 2 sensors and try to measure the diference of the signal between then. Both cases sounds hard to develop.

This project is a nice chalenge.

Good luck!

check this out - it may give you some ideas.

http://www.philohome.com/sensors/filoguide.htm


I don't know about finding the signal if the wire is buried (would the dirt shield it?) but maybe if you increase the power?

Dave

Or, If the math doesn't throw you, how about homebrew MPS (Mower Positioning System)?  Devise some sort of beacon - could be ultrasonic, Infrared, something that can be detected and not normally occurring in your yard.  Then build a scanning detector that rides on the mower.  Put a number (3, at least) of the beacons around the periphery of your yard and the detector can determine where they are and calculate where it is, relative to the beacons, and plot a course.

Crazy, but it may work.

Or, even simpler - my neighbor has a mower that works like a "Roomba" vacuum cleaner.  That is, no guidance at all, just go until you hit something, then turn.  The randomness assures that, eventually, the whole yard is covered.


His is electric, pretty quiet, and gets the job done.  Because it is so quiet, he can turn it loose 2-3 times per week so that the grass does not get so tall as too bog it down.

Dave

Thanks for the replies.  I can't just depend on hitting something since we have no fences around our yards between neighbors.

My solution was to buy a pet invisible fence (http://www.hisgadget.com/waterproof-electronic-fencing-system-trans...) and hack into the collar unit to get a 0 - 5 VDC signal for how close to the wire (edge) the mower was getting.  It was easy and works well.  The perimeter wire is buried or out of sight.   Sometimes the mower follows the edge wire, sometimes it does random patterns, sometimes it does spirals.  It also has a IR receiver for remote manual control from an old TV remote,  ultrasonic ping sensor for object (people) avoidance and three bump switches if it hits something.  I used an old $100 power wheel chair (on Craigslist) base for the chassis, battery and charger (the owner had just bought new batteries before he died), wheels, drives, gears, and powerful motors included.  All I had to do was remove the chair part, add the cutters in front, add brains (Arduino Uno) and sensors.  The wheel chair maker said it goes 18 miles between charges.

Ah - I misunderstood and didn't consider your ultimate solution.  I thought you wanted it to actually follow the buried wire which would involve a lot of wire and a lot of digging to bury it!

So, you DO have something for it to bump into like a Roomba.  Just that yours is an invisible radio wall.

Well played.

Dave

How about going RFID?  You could bury the tags in a grid, then create a map for where to mow and where not to.  The signal strength for all of the tags within range would tell the mower precisely where it is.  You could push it around manually to delineate boundaries.  You could even mount tags on things that are movable, like lawn furniture/etc., and the mower would automatically avoid them.  Mounting two tags would be enough to define a shaped boundary, for closer trimming.

BTW

Use your dog fence and dead reckoning, just measuring where you go and plotting position. stop when you cross the fence.

Using a COTS dog fence is probably the easiest way to do the job. the hard part is all done.

Or you could use sonar to do triangulation. Mount 3 transmitters in the corners of your yard and have the mower listen to them and calculate position from there. Oh yea just like david said

still need to avoid things like said above tho

My company sells commercially available robot lawn mowers.  There is a reason most robot mowers go in a random fashion; it's really hard to make them go straight.

Bosch made one that only works in a fenced area.  It is available in Switzerland.  The robot learns the fenced area and then goes in straight lines within the fence.  This will not meet market requirements in the US because front yards are not fenced.

I also know of a research team in France that made it work on a BigMow commercial mower but they tried to sell it for **a lot** of money and nobody bought it so far (as far as I know).  They used a beacon, perimeter wire and lots of math.

The third thing I know of is a University competition that takes place once per year, but they gave up.   Here is the link:

http://robomow.ion.org/

You will probably learn the most from the competition documents.

If you find a solution, I **really** want to hear about it.

Kathy

I had another idea: place 3 high-output IR beacons on the mower, then mount an IR filtered webcam (..or 2 or 3 or...) on your roof/etc.  VERY low cost, and provides both position and orientation for the lawn mower.

I have put a snow plow (24" x 12" board with some rubber across the bottom) on the front of my robot mower and, with the help of a magnetometer compass ( $4.35 from China with free shipping), have programmed it to go back and forth across my driveway to keep the snow plowed to the sides as the snow is falling.  The magnetometer must be kept level so I float it in a bath of oil.  I will add an IR reflectance sensor to sense when snow starts to build up on my blacktop to start the robot snow plow operating (could start snowing overnight when I'm in bed).  It can't plow a foot of snow at one time, but if it keeps plowing as the snow is falling it should keep up with the snow accumulation.  Now I'm just waiting for the snow. 

Here is my "RoBoMo" in action: 
http://youtu.be/bmf7OF1B-lo  and  http://youtu.be/T9WiJkRTDTo

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