Thursday, April 11, 2013

Robotic Lawn Mowers

[Note: this post needs cleaning but a friend wanted to have a quick look to it so...]

I looked at this market back in the 2005, when I was leaving my job to go study (play with?) robotics. After all these many years, I have not seen many (none) of these and I wonder what is the issue. Maybe because I seldom go around on residential neighborhoods? Yeah, that could be the case, because now that I am thinking, I seldom see anybody mowing their lawn, period. The article in Wikipedia says that actually the market is booming.

Long story short, looks like there is actually a lot of activity on this area. Read mostly this and this (with prices). Robots are on the $2k range, they navigate/recharge by themselves, set the perimeter with a wire. Other things to take into account:
Safety

"All of the mowers keep safety as their first priority. The designs above all but totally eliminate the possibility of objects being thrown from beneath the mowers. Projectiles like rocks, sticks and balls launched by traditional mowers result in a large number of serious injuries each year. As of the date of this page being created, there are no recorded emergency room visits at all related to robotic lawn mowers."

Many (all?) robots have also tilt sensors.

Definition of covered area

All of the mowers presently in production use a thin wire placed around the perimeter of the lawn to contain the mower. I think you don't need to bury it but just place it around with sticks. The lawn mowers follow it to provide an edge trim. Self charging models also follow the same wire to locate their docking station." They usually use some kind of dummy algorithm to cover that area...

Notice that the example below from a university uses GPS, IMU and magnetometer for the navigation.

Autonomy/worry free

How autonomous they really are. This includes things like getting avoid getting stuck in corners, walls, trees, water hoses, toys, tree branches, rocks, sprinkler systems, water faucets, poo...Some complains in that area, but in general, they seem to be doing ok.

Also self recharging...

Getting stolen

This has been addressed in general by alarms, lock pin and sheer weight (not so easy to pick it up and run with it).

Price

They are affordable when compared to what you save, but still pricy ($1k-$4k for consumer type), which probably holds people up.

Reliability/Maintenance

Stuff like blade breaking because it hits a rock or... Haven't seen negative comments about that but there is some estimates on the web on estimated maintenance costs per year.

Finish

This would cover the individual cut of the blade or the overall look of the grass. But overall, only saw one negative comment on this.

Noise

Speed

I think this is more a safety issue. Standard travel speed is about 60 feet/minute.

Do they need to collect the grass they cut?

Many do, but no need!!   It is actually better. But make it mulch.

Stop under the elements

Avoid mowing after heavy rains, as this will make mowing more difficult and cause clippings and mulch to bunch.



Then, we just had a look to what is out there:

Traditional mowers: electric weed trimmer and reel mower (~$100). Didn't check the motorized ones. Note: check out the video on sheep getting trained to eat only a given type of grass...

Robotic manufacturers:

Wolf-garten
Honda, http://www.engadget.com/2012/08/21/honda-miimo-robotic-lawn-mower/
Husqvarna
Lawnbotts


There is a robotic lawn mower competition. Found this paper from one of the participants. Also this and this

Overall, feels that the products out there are pretty good. Below a "negative" feedback from customer, but in general, not sure why we are not seeing more...

Feedback:
"again with the buried line crap...   There was a GREAT system available about 5 years ago that used a series of positional sensors outside the home, and software on a PC to manage the mowing process.  Why it this not in use?  Buried lines create dumb mowers, the system I was about to buy (I aborted when my company informed me i was being relocated, and i have not got back looking) not only mowed, it reported back issues in the yard where fill dirt was needed, grass height information (which could indicate water or fertilizer changes are needed in some areas), etc.  Whole thing installed was about $2500, including a secure outdoor charging station and all the sensors.  It needed 1 sensor on the center of each facing wall of the house, and 1 on each corner, and the robot used positional triangulation for movement, which was accurate to the inch.  It also included an edger attachment, and would not just mow, but left clean edges where you told it to. 
These things are glorified roombas still requiring me to manually interrvene weekly in the maintenance of my lawn.  They provide no real value."

A quick thought about using a laser to cut the grass:
http://www.candlepowerforums.com/vb/showthread.php?279367-Laser-lawnmower
http://articles.chicagotribune.com/2001-07-21/news/0107210078_1_clippings-grass-laser
http://grounds-mag.com/news/grounds_maintenance_youve_seen_mower/


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