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Lawn-Mowing Robots? Now That's a Fertile Idea

October 26, 2000|ASHLEY DUNN | Times staff writer Ashley Dunn covers technology.

Mowing the lawn is one of those backbreaking chores left strangely untouched by technology.

The kitchen has seen the arrival of the microwave oven, the living room has benefited from Tivo television recorders. In my bathroom is an electric toothbrush that manages a remarkable 31,000 brush strokes per minute.

Enter the robotic lawn mower.

You probably want to laugh. I have to admit that before setting up the machines, I had visions of rogue robots chasing pets down the street or butchering my lawn.

I am happy to report that after several weeks of work, no small children or dogs were harmed. The Husqvarna Auto Mower and the Friendly Robotics RL500 are real workhorses--and understanding their basic operating principles makes you wonder why robotic lawn mowers didn't appear earlier.

The machines work by sensing a wire set a few inches in from the lawn's edge. A small electric current passes through the wire, which gives off a very low-power radio signal. Sensors on the battery-powered mowers detect the signal and command the mower to turn away.

The mower travels in a more-or-less random pattern, meaning that it is about as efficient as sending a monkey out. But given enough time the robotic lawn mowers eventually cut every spot on a lawn.

One side benefit to this random movement is that the mowers don't leave the usual tracks in a lawn. Instead, the grass takes on a very even appearance, although it is not as smooth as a machine-cut.

The mowers also have collision sensors, making them relatively safe.

The biggest problem with these devices is their outrageous prices.

The RL500 sells for $795, which makes it three or four times more expensive than a regular gas mower. The Husqvarna Auto Mower costs an insane $2,000--about the cost of a lawn tractor--and you are required to have a Husqvarna dealer install the system for an extra $200 to $400.

Are the mowers worth it? Neither machine is an easy choice, but they give a glimpse of what will surely become a standard home tool in the future.

Husqvarna Auto Mower

The Husqvarna Auto Mower is a deceptively revolutionary device.

Instead of seeing lawn mowing as a weekly chore, the Auto Mower is designed to cut the lawn for a few hours every day. It has a recharging station and is programmed to park itself when the power is low.

These two features make the Auto Mower a completely automated device that moves lawn mowing out of the "chore" category.

The mower, which looks like a sea turtle with wheels, is very quiet; you can program it to run at night and never hear it.

The hardest part of the installation is laying the boundary wire into the grass. The wire doesn't have to be buried, but set into the dirt for a very neat installation.

The easiest way is just to lay the wire in the grass and then use a stick to clear the grass underneath so the wire sits lower in the lawn. In a few weeks, the grass will grow over the wire.

The wires connect to a charging station that plugs into a wall socket.

The only complicated step is programming the mower with a security code and the cutting schedule. Once set, the mower automatically leaves its charging station at the right time and cuts.

It is actually a bit smarter than that. The Auto Mower has a sensor that detects the resistance on its cutting motor. When it hits a spot with high resistance, indicating tall grass, the mower reverts to a pattern that concentrates on that area until the resistance is low again.

One of the beauties of the Auto Mower is it's exceptionally light--just 16 pounds, which allows it to cover a wide range of terrain without getting stuck.

Because the machine knows to recharge itself, it can cut about half an acre of lawn in 24 hours.

One bad point about the mower is that it tends to pitch at every little irregularity in a lawn, creating a cut that, while very even, seems a bit coarse and clumpy. And the Auto Mower does not work very well on steep slopes.

The key issue with the Auto Mower--besides its price--is security.

Husqvarna has included a variety of security measures, including a loud alarm that sounds whenever the mower is moved without first entering a code. Without the code, the machine won't work.

I'm still uncomfortable with these measures. What's to prevent someone from stealing it just to make mischief? Nothing. For this reason the machine is better used in the backyard or a gated yard.

Husqvarna has priced the Auto Mower to compete with riding lawn tractors, which sell for about $1,000 and up.

While the Auto Mower is a better deal because it entirely removes the whole idea of mowing a lawn, there still just aren't enough parts in this machine to justify even half its $2,000 price.

Friendly Robotics RL500

The Friendly Robotics RL500 is the simpler of the two machines, essentially designed as a replacement for a regular lawn mower. You have to wheel it out onto the lawn to start mowing and manually charge the mower by plugging it into a wall.

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