Ever Wonder How a Robot Lawn Mower Works?
June 2, 2024
As we’re now in full-on lawn mowing season I thought I’d follow up with more on robot lawn mowers. I’ve covered the topic in the past in previous posts:
However, I never really did the deep dive on how they actually know how to mow just your yard and not everything in the neighborhood. I posted a similar article earlier this year about home robot vacuums operate in your home — How do Robot Vacuums Know How to Clean Your Smart Home? — so I thought it was time to post the same on robot lawn mowers.
It’s probably not a surprise that robot lawn mowers operate much like a robot vacuums. Obviously a different setting — outdoors, spinning blades — you can see where this could go badly really fast. If a robot vacuum runs over your foot it might bother you a little bit. But if a robot lawn mower does the same thing that’s serious business. Not to mention the damage to other objects left in the lawn by pets or children. And then there’s all the carefully planned and manicured landscaping at risk.
Robot lawn mowers are equipped with sensors, like the ones in robot vacuums, to help them avoid such issues. But without the advantage of walls to establish a perimeter that helps them navigate and map the spaces they’re working in, less-expensive robot lawn mowers rely on the homeowner to lay down a boundary wire that serves the same purpose. More recent, and more expensive models use more sophisticated technology and don’t have to rely on those wires.
Most robot lawn mowers are equipped with sensors that can identify and avoid obstacles in front of them. Like their vacuum cousins, the typical robot lawn mower is equipped with an array of sensors to help them operate autonomously, safely, and effectively.
Grass Sensors
These sensors detect the presence of grass below the mower. The sensors on more sophisticated mowers can also detect the height of the grass they’re cutting.
Rain Sensors
Robot lawn mowers are built for outdoor use but they shouldn’t be exposed to the elements unnecessarily. Anyone who’s mowed wet grass has found out it can clog the mower and or leave clumps of grass than can impact the health of your lawn. A rain sensor can prevent the mower from operating, or have it return to its charging base if it starts raining during a mowing job.
Ultrasonic, Infrared, and Bump Sensors
Robot mowers use a combination of these sensors to detect obstructions. The bump sensor is the simplest, similar to robot vacuums, where the mower taps an obstruction and sensor data instructs the mower how best to work around it. Ultrasonics and infrared detect the obstruction before the mower hits it, allowing it to miss it completely.
Lift and Tilt Sensors
During operation, lift sensors alert the mower that it’s caught on an object, while tilt sensors detect if the mower is operating at an unsafe angle. They also detect when the mower is picked up, which is particularly useful as an anti-theft mechanism.
Boundary Wire Sensors
Some robot mowers rely on you to lay down a boundary wire marking the edge of your lawn. Sensors on the bottom of the mower detect this current and keep the mower inside the perimeter.
With robot lawnmowers that rely on a boundary wire, you connect a wire to their charging station and then pull the wire in a loop around your lawn’s outer edges. The wire will either be secured to the ground with stakes or buried just below the surface. Sensors on the mower detect the current flowing through the wire and keep within that perimeter while it’s operating. Some boundary wire mowers are also outfitted with GPS and/or cellular radios, not for the purposes of navigation but to help you locate the mower.
While some boundary wire-free use grass sensors to detect the edges of your yard, most use GPS technology to establish their location in the world. They also use other sensors to detect their surroundings, identifying obstructions and fine-tuning how they mow around them. In most cases, you’ll need to do an initial walk around your property, using the mower’s mobile app to “teach” the robot mower the unique layout of your yard.
Boundary wire-free mowers are typically equipped with these additional sensors:
Vision Sensors
Without a boundary wire, a robot mower needs some way to find its way around. The most common technology I’ve seen is a camera mounted to the front of the mower.
Advanced Grass Sensors
While all robot mowers have some type of grass sensor, they have a more important role on boundary wire-free mowers. They detect the transitions between your sidewalk or driveway and the grass, keeping the mower where it should be.
Additional Radios
Unless the mower is completely self-reliant for navigation, boundary wire-free mowers will have additional radios that connect to either a base station or an antenna.
Artificial Intelligence
We’re not talking about SkyNet here but certainly a more advanced way for robot lawn mowers to navigate. While most boundary wire-free mowers will need an initial walk-around of your yard, onboard AI takes over after that and your robot mower will navigate your yard more efficiently over time as it ‘learns’ your yard, making slight changes to its layout.
Boundary Wire-Free Robot Mower Navigation Types
Boundary wire-free mowers generally fall into three types of navigation methods. There are no industry-standard definitions for these terms, and each type has its pros can cons.
- Antenna Dependent — You’ll set up an antenna at a location on your property that’s within the line of site of all areas that the mower will operate. While it might be able to operate for brief periods out of sight of the antenna, the antenna serves as its primary source for positioning. The mower’s charging station might provide a second reference point.
- Mower Dependent — This type of robot mower geolocates on its own, without any antenna and its charging station simply charges. These mowers often include cellular backup when WiFi reception is poor, either as standard equipment or as an option.
- Hybrid — This class of mowers uses a combination of the methods above, either to make positioning more precise or for backup. These mowers are a great (and potentially cheaper) option for more complex yards that have varied terrain and/or where a larger portion of the line of sight is obstructed.
Boundary wire-free robot lawnmowers are equipped with sensors that can discern between your lawn and your sidewalks. They also deliver the most benefits to larger suburban and rural properties, because boundary wire circuits are typically limited to around 2,600 feet, and many base stations can’t power more than 1,000 feet of wire. Very large properties could very well require a fleet of boundary wire robot mowers.
If you ever decide to change your landscape design it’s a relatively simple task to retrain a boundary wire-free mower. And with AI it might even be able to teach itself. With a mower that depends on a boundary wire, you’d obviously need to pull up the existing wire and redeploy or replace it if it’s damaged or not long enough to complete the perimeter loop.
Boundary wire-free mowers generally cost considerably more than their boundary wire counterparts. To keep their price tags down, some manufacturers leave out things like all-wheel drive, which means they’re not good candidates for uneven lawns or steeper slopes.
This type of mower, and its antenna, relies on GPS satellites, so it needs a clear view of the sky, so not every yard will be compatible. Should the GPS signal degrade or fail, whether it be due to equipment failure, plant growth, a storm knocking your antenna down, or extreme solar storm activity, a boundary wire-free mower simply won’t be able to operate.
Although boundary wire-free robot lawnmowers have been around for several years now, the technology overall is still relatively new. If you’re willing to deal with challenges here and there and have patience, a robot lawn mower might be a great solution for you.
Simple yards with smooth slopes and few obstructions are best unless, you opt for one of the more expensive all-wheel drive models. The more complex the yard, however, the more you may want to consider the traditional boundary wire-style models. While more expensive boundary wire-free models will likely do just fine, you’ll be able to get a similar boundary wire robot mower for a lot less.
Personally, I love the idea of robot lawn mowers because of the success Debbie and I have had with our robot vacuums. But I think they have a narrower use case. Regardless of the type or model you buy, they tend to be significantly more expensive than a traditional lawn mower. Obviously if you calculate your time savings over the life of the mower it might make sense. But I do have concerns over battery life especially when taking the size lot we’ll build our house on. I’m just not seeing mowers that would be able to effectively tackle our yard without practically mowing every day. I just don’t like the idea of never having a completely mowed lawn as it seems that by the time it started at one end by the time it got to the other it’d probably be time to start over again.
If I had a smaller yard I’m pretty sure I’d be ordering a robot lawn mower though, regardless of cost. Because despite how much I love mowing those straight, uniform lines in my lawn it might look just as nice if a robot did it. What are your thoughts around this? If you already own a robot lawn mower how do you like it? Was it worth the investment? How easy was it to set up?
Let Debbie and I know what you think in the comments, DMs and emails as we really enjoy hearing from you. Thanks again to all those following Debbie and I through our home building journey. It’s great to hear your success stories and suggestions as we move through the process. And if you like the content I’m posting each week, don’t forget to ‘Like’ and ‘Follow.’
SmartHomeOnTheRange.com
In full disclosure, I’m not an affiliate marketer with links to any online retailer on my website. When people read what I’ve written about a particular product and then click on those links and buy something from the retailer, I earn nothing from the retailer. The links are strictly a convenience for my readers.
