bridon@auto-trol.com (Brian Donahue) (06/21/91)
yo. i have this (maybe ridiculous) idea for a 'automatic' lawn mower. The idea would be to mount a mulching lawn mower on a 'computer-guided' platform of sorts. You could then do a(n accurate) drafting/CAD layout of your lawn (including trees, flower gardens (ie. places you dont want mowed)), figure out a start point, use an NC-type algorithm to guide your mower and then sit back with a beer while your PC does all the work. Being a robotics neophyte, i have no idea how to approach this problem or what complications may make the problem harder than it sounds. For example, would i need some sort of tracking system? or can i assume that for every turn of the wheel the lawn mower goes a certain distance? (how accurate can i get w/ no tracking system?) Are there suppliers of rs232-driven 'wheels'?? or is this totally ridiculous & not worth pursuing? thanks for any advice, bd bridon@auto-trol.com
cphoenix@csli.Stanford.EDU (Chris Phoenix) (06/21/91)
In <1991Jun20.192334.24623@auto-trol.com> bridon@auto-trol.com (Brian Donahue) writes: >i have this (maybe ridiculous) idea for a 'automatic' lawn mower. >The idea would be to mount a mulching lawn mower on a 'computer-guided' >platform of sorts. ... use an NC-type algorithm to guide your mower and Maybe I'm just brain-dead today... what's an NC-type algorithm? >Being a robotics neophyte, i have no idea how to approach this problem >or what complications may make the problem harder than it sounds. >For example, would i need some sort of tracking system? or can i assume >that for every turn of the wheel the lawn mower goes a certain distance? >(how accurate can i get w/ no tracking system?) You definitely need some kind of tracking system. Consider: 1) Wet grass is slippery. 2) The yard is bumpy, so the wheels actually travel slightly different distances. I doubt anyone could build an unguided system that would hit a 1-meter target across a 10-meter yard, without some massive sensing/feedback. Maybe a walking-type system would work, but I don't think it can be done with wheels. (If I'm wrong, someone please tell me, but we had problems making a synchronous-drive base roll straight on carpet, and this seems like a much harder problem.) >or is this totally ridiculous & not worth pursuing? It's not totally ridiculous. It'll be a great learning experience. :-) Seriously, it depends on how much time you want to spend on it, and how general you want the solution to be. My first inclination was to advise you to build some sort of position-and-orientation sensor, that could tell the platform where it was well enough to use a general path-planning algorithm. I've been in school too long. So, I'd advise building a really simple sensing system, consisting of reflectors all around the yard and a machine that only knows enough to head for a reflector and turn when the PC tells it to. Mark off the yard with a grid, making each "strip" (crossing strips form the grid) the width of the mower's blade. Where each strip intersects the edge of the yard, put a reflector. If there is an obstacle in the middle of a strip that obscures the strip's reflector, put a reflector on each side of the obstacle as well. Now sit down with graph paper and draw your yard, and then draw a path that covers each square of graph paper without an obstacle in it. Put hardware on your mower to do two things: 1) Move toward a reflector that is in front of it. 2) Turn 90 degrees. 3) Sense when it rolls past a reflector to the side of it. Program your PC to count the reflectors it passes and turn at the appropriate points to follow your path. Another possibility: Bury a wire under the yard, and make your machine follow the wire. This is simplest--you don't even need a computer. But it takes a lot of wire for a big yard, and you have to worry about something breaking the wire. (Of course, you have to worry about something removing the reflector, too.) I don't know what kind of circuitry you need to make this work--I would guess an RF generator you hook up to the wire, two antennas on the machine, compare the signal strength from the antennas to decide where to turn. If anyone has any feedback on anything I've said, please tell me, either in e-mail or on the net. Thanks! -- Chris Phoenix cphoenix@csli.stanford.edu #insert <funnyquote.t> #insert <graphic.t> #insert <stddisclaimer.t> bomb detonate assasinate Libya Bush nuclear PCP <- Just to waste the CIA's time
klaus@captain-crunch.ai.mit.edu (Klaus B. Biggers) (06/22/91)
In article <20073@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU (Chris Phoenix) writes: >Another possibility: Bury a wire under the yard, and make your machine follow >the wire. This is simplest--you don't even need a computer. But it takes a >lot of wire for a big yard, and you have to worry about something breaking the >wire. (Of course, you have to worry about something removing the reflector, >too.) I don't know what kind of circuitry you need to make this work--I would >guess an RF generator you hook up to the wire, two antennas on the machine, >compare the signal strength from the antennas to decide where to turn. > >If anyone has any feedback on anything I've said, please tell me, either in >e-mail or on the net. Thanks! > I like that idea best... I saw an add the other day by a company called invisible fence. You bury a wire around the perimeter of your yard and then put a special collar on your dog. When the dog gets close to the wire, his collar beeps, and if he continues on, it then gives the dog a mild shock. It seems you could use this type of approach to tell the mower to turn around but not completely. It may be possible to just let the mower make a random pattern over your yard.. It would eventually cover all of it unless it got into some sort of limit cycle. You could probably increase the efficiency by making the mower take a curved path or arc. You could also bury wires around flower beds, swimming pools, etc. and you could put some sort of bumper on it to get it to turn around when it hits a tree. I've seen automagic pool sweepers that work on this random traversal principle and they seem to work quite well with respect to covering the entire pool. You may want to add a grass level sensor to determine if the grass you are passing over has already been cut and if so, alter your path. Then again you could get an expert system... a son or daughter... they could even get you your beer out of the fridge and if they refuse you could always dig out that old dog collar and activate the fence again :). (just joking). -klaus klaus@.ced.utah.edu _______________________________________________________________________________
hollombe@ttidca.TTI.COM (The Polymath) (06/22/91)
In article <20073@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU (Chris Phoenix) writes: }Another possibility: Bury a wire under the yard, and make your machine follow }the wire. This is simplest--you don't even need a computer. But it takes a }lot of wire for a big yard, and you have to worry about something breaking the }wire. ... This is a very old idea. I first saw it in Popular Electronics about thirty mumble years ago. I can think of other disadvantages: The yard must be clear of all obstacles (anything not accounted for in the wire's path and/or mower's ground clearance). The yard better be guaranteed clear of small children and pets. If the mower hits a bump and takes off at a sharp enough angle, it will lose the wire and get lost. Remember, you're dealing with a massive blade driven by a gasoline powered engine. The potential for damage is serious. (Now you know why there aren't any commercial versions on the market). -- The Polymath (aka: Jerry Hollombe, M.A., CDP, aka: hollombe@ttidca.tti.com) Head Robot Wrangler at Citicorp Illegitimis non 3100 Ocean Park Blvd. (213) 450-9111, x2483 Carborundum Santa Monica, CA 90405 {rutgers|pyramid|philabs|psivax}!ttidca!hollombe
gcary@SRC.Honeywell.COM (Greg Cary) (06/22/91)
The June 1990 issue of Radio Electronics has a feature article on "The Lawn Ranger", an automatic lawn mower robot. Greg Cary MN65-2500 Honeywell, Inc. Systems & Research Center gcary@src.honeywell.com 3660 Technology Drive office: (612)782-7683 Minneapolis, MN 55418 FAX: (612)782-7438
carter@mcs.anl.gov (Richard Carter) (06/22/91)
In article <16607@life.ai.mit.edu>, klaus@captain-crunch.ai.mit.edu (Klaus B. Biggers) writes: > ... You may want to add a grass level sensor to determine >if the grass you are passing over has already been cut and if so, >alter your path. > You mean, kind of like the screen termite program on my sun ? :-) -- Richard Carter | Dicisne mihi maculas in sole mercatum MCS Division | labi fecisse???? Argonne National Lab | Argonne IL 60439 |
hm02+@andrew.cmu.edu (Hans P. Moravec) (06/22/91)
klaus@captain-crunch.ai.mit.edu (Klaus B. Biggers) writes > In article <20073@csli.Stanford.EDU> cphoenix@csli.Stanford.EDU > (Chris Phoenix) writes: >>Another possibility: Bury a wire under the yard, and make your machine follow >>the wire. This is simplest--you don't even need a computer. But it takes a >>lot of wire for a big yard, and you have to worry about something breaking the >>wire. (Of course, you have to worry about something removing the reflector, >>too.) I don't know what kind of circuitry you need to make this work--I would >>guess an RF generator you hook up to the wire, two antennas on the machine, >>compare the signal strength from the antennas to decide where to turn. >> >>If anyone has any feedback on anything I've said, please tell me, either in >>e-mail or on the net. Thanks! > > >I like that idea best... I saw an add the other day by a company >called invisible fence. You bury a wire around the perimeter of your >yard and then put a special collar on your dog. When the dog gets >close to the wire, his collar beeps, and if he continues on, it then >gives the dog a mild shock. It seems you could use this type of >approach to tell the mower to turn around but not completely. It may >be possible to just let the mower make a random pattern over your >yard.. It would eventually cover all of it ... Around 1964 (that's right, almost 30 years ago) there was a construction article in Radio Electronics describing a mower built on the wire follower principle suggested by Chris. It described how to convert a conventional power mower by adding drive motors and control electronics. A year or so later a commercial product, called the "Mowbot", appeared, costing about $2000, that used the "boundary bounce" principle suggested by Klaus. Trees were put off limits by running the (buried) boundary wire from the property periphery to the tree, around it, and then back to the periphery by the same route. The colinear wires between the periphery and the tree were invisible to the mower because the opposite directions cancelled the signal. The turtle-like car-battery-powered Mowbot had small, safe, cutter blades, and depended on persistence to get all the grass. It was too heavy to move around by hand, but had a plug-in manual control "leash" that let one drive it to its recharger. There did not seem to be a great market for a $2000 lawnmower, and I never heard of it again. Hans Moravec <hpm@cs.cmu.edu>
mikef@IASTATE.EDU (Fahrion Michael J) (06/24/91)
Funny, I was just discussing this the other day with an M.E. colleage. Our idea was more commercial application, businesses with large, mostly obstacle-free lawns. The idea was to replace the $4k-10k lawn tractors used by these companies. We were thinking electric, very small path, and very slow. The system would run at night, until it ran out of charge. Then hopefully have a solar charge cycle during the day. The buried boundary idea was favored, also with a cut grass/uncut grass sensor system and some intelligence (microprocessor) to keep it running straight (relative to the last path), reverse directions at the end of each pass, and to sense simple obstacles. Theres some definate problems, and it sounds like similar attempts have already been made, but I'd say there's still something to it. mikef
smith@sctc.com (Rick Smith) (06/24/91)
bridon@auto-trol.com (Brian Donahue) writes: >i have this (maybe ridiculous) idea for a 'automatic' lawn mower. >For example, would i need some sort of tracking system? or can i assume >that for every turn of the wheel the lawn mower goes a certain distance? >(how accurate can i get w/ no tracking system?) Well, put it this way. People doing the same thing in large rooms with slip-resistant rubber wheels on nice, flat floors _can't_ get by without alternative positioning information. If you get off by a little bit, then the mowing will be uneven. If you get off by a lot, then you might find yourself living an unwritten Stephen King novel. Since you proposed using a mulching mower, you could start from the middle of the lawn and work outwards. If you can find some way of detecting the grass height, then you can use this information to guide the mower. It could just go back and forth as long as it finds long grass. Once it runs out of long grass, it stops. Then you come along and drag it over to some more long grass and start it up again. You'll want to incorporate some collision avoidance behavior that coordinates with the grass-cutting behavior. If I were you I'd take a look at the the stuff that Rod Brooks et al are doing at the MIT AI lab. >or is this totally ridiculous & not worth pursuing? It depends on your goal. Sounds like a fun project even if you fail, so long as the mower doesn't chase you down the street, or mulch any small living things, like children. Rick. smith@sctc.com Arden Hills, Minnesota
cwpjr@cbnewse.cb.att.com (clyde.w.jr.phillips) (06/27/91)
In article <1991Jun20.192334.24623@auto-trol.com>, bridon@auto-trol.com (Brian Donahue) writes: > > yo. > > i have this (maybe ridiculous) idea for a 'automatic' lawn mower. > The idea would be to mount a mulching lawn mower on a 'computer-guided' > platform of sorts. You could then do a(n accurate) drafting/CAD > layout of your lawn (including trees, flower gardens (ie. places > you dont want mowed)), figure out a start point, use an NC-type > algorithm to guide your mower and then sit back > with a beer while your PC does all the work. > > Being a robotics neophyte, i have no idea how to approach this problem > or what complications may make the problem harder than it sounds. > For example, would i need some sort of tracking system? or can i assume > that for every turn of the wheel the lawn mower goes a certain distance? > (how accurate can i get w/ no tracking system?) > Are there suppliers of rs232-driven 'wheels'?? > > or is this totally ridiculous & not worth pursuing? > > thanks for any advice, > bd bridon@auto-trol.com A multi-part series on this project ran last year... Clyde
ckeele@oregon.uoregon.edu (06/27/91)
For safety, I think that Jacobson or some such company made a lawn mower that used a rubber or plastic blade. This was about 10 - 15 years ago, but you may still be able to find blades, or mowers. If I remember right, it had a solid plastic center section about 15" in diameter, and 3 or 4 replacable rubber blades attached to it. I think that you were supposed to be able to put your foot into the blade and not get hurt, although I never tried it. It probably would hurt some. I don't think that it worked very well, but it probably would be a necessary safety feature of the CALM system. Clifford Keele ckeele@donald.uoregon.edu Well, at least I think I remember seeing one of the above described beasts, but it was a long time ago when I was about 10, so it is hard to be sure.
abg@mars.ornl.gov (Alex L. Bangs) (06/29/91)
One method for tracking that you can use is watching the already mowed area, which should be relatively easy to sense. This works nicely for rectangular areas with no obstacles. Alex L. Bangs ---> bangsal@ornl.gov Of course, my opinions are Oak Ridge National Laboratory/CESAR my own darned business... Autonomous Robotic Systems Group