Building A Homebrew Robotic Lawnmower? 486
mmonkey writes "With the seemingly small amount of summer we get here in the UK, the last thing I want to be doing on a sunny day is mow the lawn. So I started thinking "surely a light-ish lawnmower could 'gain' a couple of motors, and suddenly be computer-controlled?". Then I started thinking about stuff like obstacle avoidance, optimum path planning, guidance system, how to get pretty-looking stripes, and I realised that it's actually a potentially complex (read: fun) thing to do. So, have any Slashdotters done this before? Did you modify an existing lawnmower or build a whole new one from scratch? What motors work best? For that matter, what type of mower works best? I know you can already get these, but that detracts from both my geek-drive and my wallet, both of which I'd prefer to keep as full as possible."
Uhhhh (Score:4, Insightful)
another way (Score:2, Insightful)
not very popular over there but many people do that over here in n.america
even in the long-run would be cheaper than a robot solution (unless this is a personal interest i wouldn't go ahead with it)
so let me get this straight... (Score:1, Insightful)
Enjoy your summer.
Kill Switch (Score:1, Insightful)
Personally I dont think this thing would ever be considered safe enough to operate unsupervised. It might save you some work, but if it went out of control or some passerby tried to tamper with it you could end up with a very expensive lawsuit. (IANAL)
Can I scan pictures of neighbor kids? (Score:1, Insightful)
I've had old folks bitch at me for going through their lawns when I was a kid...now it's my turn! As a geek, though, I bet we can do a whole lot more than yell "get off my lawn you good-fer-nuthin..."
Watch your bits (Score:5, Insightful)
Think safety and just make it an RC vehicle first (Score:4, Insightful)
Re:Just for you? (Score:5, Insightful)
Those big trak programmable toys really didn't do all that good a job of making ninety degree turns. They worked best on floors and poorly on everything else - my cousins had one and I got to play with it like once but it didn't do what it was supposed to do. It was still neat, though.
There are other problems with your plan, such as the fact that most lawns are not perfect, empty rectangles. Even if you can accurately track how far you are traveling and how far you have rotated, it's going to be a little more complex than just making a couple of right angle turns. If the problem were that simple, meaning you had a level, flat, even rectangular yard with nothing in it but grass which had already been carefully mowed not more than a day before, you wouldn't even need robotics :P
Re:so let me get this straight... (Score:4, Insightful)
Re:Uhhhh (Score:5, Insightful)
I suspect that if this worked, lawnmower manufacturers would have already done it for liability reasons. One thing about a grill is that it would probably clog for any non-trivial amount of wet grass.
The simple way (Score:1, Insightful)
electric "invisible" dog fence (Score:2, Insightful)
So, you start with one of them. That will keep your mower inside the designated area wherever you bury the wire. The mower part is an electric self propelled mower, They make them, you buy one of them. You'll have to make all 4 wheels drive so they can be individually activated for steering. Take the steel blade off, replace it with a string trimmer head, they are lighter, work about as good, and safer somewhat, and give you longer range on a battery charge. Now how to make it bounce off the obstacles and go in another random direction you got me, but I've seen several different cheap toys do it, so that tech has to be out there as well. You would have to add that into in the signal from the invisible fence to activate the turning mechanism, so you would get both kinds of turning, planned turning at the fence line, and random off of odd obstacles, like you sitting in your chair with a brewski or whatnot.. You turn the thing on, aim it out to the yard, let er go, it will randomly go around and trim, and being all electric, won't be all that loud, so you can run it a lot. If it consistently misses an area or two, just hand cut that part. Seems like the cheapest easiest way to go, but I am talking out my nether regions as well, might be a bear to make, no idea. I mow all day long mostly, or trim, or cut, or some other various chew up the jungle action, so I have thought of this many times, and can't think of anything heavy duty enough to do it on a big scale that wouldn't be dangerous as all get out for my purposes (one of the mowers I use will cut to almost 20 feet high and has about an 8 foot blade, so no way that could be a autonomous robot), so I've never tried to build one. But man, when it's 90+ F and near-equal humidity like it's been recently, I SURE HAVE thought about it...
Now a big female amazon warrior robot that you could task to drive the mower-among other things-now you're talking! And flyin cars!
%^)
Good Idea, But No. (Score:3, Insightful)
RFID Perhaps? (Score:2, Insightful)
Then again, a video camera with "grass recognition software" might be more fun.
Mike Scanlon
Re:Just for you? (Score:3, Insightful)
How much do you think it would cost to build one of these? The pride of building one yourself can't be measured, but there would be a cost of developing your own. Either via your upfront costs, maintenance, or time involved. Buying a ready made product does have some advantages.
While many homebrew projects are better than commercial products, you have to be pretty handy to build a product more efficiently than a team of engineers. This company probably had a higher R&D budget and worked out lots of kinks before releasing this lawn mower through multiple iterations of development cycles.
--
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Electric sheep (Score:5, Insightful)
The underlying problem is the amount of kinetic energy you have in a spinning blade. The less kinetic energy, the safer. A spinning fishline is going to be safer than what amounts to a giant spinning knife.
Of course the reason you need the kinetic energy is so you can cut a lot of grass very quickly. With a conventional lawn mower, you can probably mow about a square meter or more per second. It cuts down on the drudgery time. But since the author is building a robot, drudgery is not an issue. So why not go slow?
I am imagining something that is very, very slow. Something that moves slowly from place to place gently cropping a tiny amount of grass at a time. In other words, an electric sheep (with apologies to Phillip K Dick). You'd calibrate the jaw strength so that it is enough to rip up a mouthful of grass easily, but not so strong it would sever a finger. You could get a nasty robot bite, but it wouldn't require a trip to the neurosurgeon.
I like the sheep idea because it leads off in more interesting directions. I'd think you'd run out of ideas for a robotized conventional mower. With the electric sheep, you can set a number of more interesting goals than having it walk a predetermined path. For starters, you could give your robot sheep a simple vision system so it could perceive the edge of your walk and touch up the edges. What would be interesting is to train it to visually recognize certain objects: it perhaps could recognize common lawn pests like dandelions or plantains and give them an extra close crop. Maybe it could retrieve the paper the paper boy threw onto the lawn and put it on your front porch. Maybe you could teach it to recognize beer cans and throw them in a recycling bin. You could make several of them and have a flock and begin to program them to interact in interesting ways.
Re:Just for you? (Score:5, Insightful)
Since you are talking about your own lawn only (I assume), you actually have pretty good control over the environment. I would take a page from Rodney Brooks and from toy manufacturers:
First, as other posters have suggested, go for a weed-whacker or other smaller, less dangerous cutting design. Compensate by planning to have it running for long periods of time, like an hour daily, essentially making it a "touch-up" design, relying on manual mowing if you let the grass get away from you.
Second, basically forget about complicated, error-prone sensor packages. Use the minimal amount of sensorics you can get away with, and tailor them specifically for the task at hand. I would use one single front-and-sides bumper, set at exactly the level you want the grass to be cut.
Third, tune the environment. If you have a fence, that will work fine. For flowerbeds, ponds, cobra pits and other garden features that you don't want it to run into, set evenly spaced (rounded!) wooden pegs at the edges, so the bumper has something to run into. If you think pegs will be ugly, be creative: rocks, small fencing, whatever. It needs to be only as high as the bumper - which we alreadey set at the level of the grass.
For control, start out easy. "If we hit something, back up a few centimeters, turn a random amount and go." This can work surprisingly well if the lawn isn't too big. You can even figure out approximately how long you need to run the robot to get reasonable coverage. An added benefit of this Brownian Walk algorithm is that you really need minimal sensors - the bumper is it. You can experiment with some fancier algorithms as well - initiating a turn after some time whether you hit anything or not, for instance, or turning off altogether if you've been going forward for a very long time without hitting anything.
If you want to add some more sensorics, like shaft encoders for the wheels, you can start to play with dead reckoning and do dynaimc map generation and other funs stuff. Even with lousy precision, you can still figure out an approximate average on how much time you've been using to cut a given area, and compensate for it by going (approximately) there for some extra random walking.
As long as you can keep the unit simple, it will tend to be robust, and perhaps inexpensive enough that you can build two or three and cut the time (sorry) by quite a bit.
One important thing: make sure you have a safe, convenient way to turn the thing off. Big red button on top should do it. Have the red top be translucent and add a couple of blinking LEDs inside for that "heavy industry" look that will make you the envy of your neighbours.
And yes, BTW, I am a robot scientist, so I sort of know what I'm talking about
don't (Score:1, Insightful)
No matter how safe you think it will be; the debug phase is deadly dangerous, and maintaining it in the face of entropy and growth in neighbor's use of devices that send signals (that could affect the behavior of your running lawnmower) spells danger.
Automate OTHER stuff !
Re:Electric sheep (Score:3, Insightful)
Re:Just for you? (Score:2, Insightful)
Why not use a constellation of transponders (RFID tags would actually be ideal - cheap and each is unique) and a two antenna setup to locate the robot's position relative to the transponders via interferometry? If you had a map (or could build one) and the transponders were in known positions in that map, then knowing where you are relative to the transponders would mean that the bot knows where it is. No need for unreliable image processing or bumpers that need to be manually trimmed.
Re:Uhhhh (Score:2, Insightful)
Noise?
Don't use a sharp spinning blade.
Scissors, tweezers, propane torch, laser beam, acid or caustic brush.
Or program the robot to select for grass which only grows two inches high, and let it evolve the lawn. In several decades it might not be necessary to cut the grass -- although in the meantime we don't know how the robot will do the "selection".
Re:Uhhhh (Score:2, Insightful)
What is up with making *every* fucking thing safe for kids per default? This is really asking for trouble, it makes parents *and* kids more careless than appropriat.
and what the hell is a child doing on a lawn that is getting mowed (by a human or otherwise) in the first place? Evolution - Stupidity 1:0
Re:Uhhhh (Score:2, Insightful)
You'd probably need to set up some sort of suspension and stabilizing system to keep it from tipping over, though.