Pondering a Robotic Lawn Mower

Published on Sept. 13, 2008, 10:23 a.m.

Last weekend my gasoline powered lawn mower died. This prompted a search for a new mower, during which I stumbled upon some of Friendly Robotics' Robomow; a line of battery-powered robotic lawn mowers. Now, I have to admit that for the past 15 years or so, every time I've mowed a lawn, I've thought about the possibilities of a robotic lawn mower, and I'm not at all surprised that there's a company producing these. At first the Robomow seems like a really nice product, but it does a have a couple of major drawbacks that would prevent me from purchasing one:
  1. Cost: it's at least $2500. I just can't afford that
  2. It requires a low-voltage perimeter wire.
  3. It takes a huge, heavy-looking battery.
The first problem is a big one for me (i'm broke), though it's a completely uninteresting problem.

The second problem is the one that really irks me though. The Robomow requires that you install a low-voltage perimeter wire around your yard. Now... if you have a rectangular yard with nothing it it, this may not be that big a deal, but if you have trees or any other obstacles (flowers, gazebos, tool sheds, playground equipment, etc), laying that wire is going to be a lot of work. It just seems like there's enough technology out there that would allow a robotic lawn mower to navigate a yard in a much smarter fashion. If I were to build a robotic mower it just seems that there are a number of options that would allow it to navigate a lawn without the perimeter wire. Now I'm just thinking out loud here, and putting this all into one machine may be cost-prohibitive, but if I were to build my own robotic lawn mower, these are the things I would consider:
  • GPS: your lawn mower is probably outside. Couldn't a robot "know" its position and stay inside some predefined boundary?
  • Touch Sensors: why not just let the robot (gently) bump into stuff. Using touch sensors it might be possible to just back up and mow around stuff. This may be especially useful for fenced-in yards.
  • Light or IR sensors: if for some reason boundary problems could not be solved using GPS, couldn't lasers or IR LEDs be deployed (I'm thinking stakes with battery-powered LEDS on two sides at each corners of the yard) yard)
There's got to be a compination of these that would allow a robot to navigate obstacles without using a perimeter wire.


I don't have a solution for the third problem. I like the idea of a quiet electric motor, but batteries are heavy, and (in my opinion) just aren't ideal for a piece of lawn equipment. For now, a small, efficient gasoline engine (small like those in a hand-held weed-eater... I'm not sure how efficient those are, though) might be the best way to go. Solar power may also be a possbility.

I'm also thinking a reel mower might be a better way to actually cut the grass. Could a small motor attached to each wheel provide enough control/power/propulsion to make this work?

(I just bought a Craftsman Reel mower, so I'm curious to see how well it works...)

I guess there's also a number of other significant questions that may need to be addressed when considering robotic lawn care. How do we take care of sticks and leaves? I have lots of trees, so these a big problem for me.

I'm beginning to think we're a number of years away from completely robotic lawn care...

This is a completely unorganized, incompletely thought-out post, but I just wanted to get some ideas out in the open...
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