A robot lawn mower cuts a little grass every day with a small spinning blade disc, tracks its position with a boundary wire, satellites, LiDAR or a camera, and drives itself back to a charging dock when the battery runs low. The clippings are so fine that they stay on the lawn, so there is no bag to empty. I come at these machines as an agricultural engineer: I want to know what the machine senses, what it decides and what it leaves behind. Below I cover the cutter, the ways a mower finds its way, a typical day, the safety sensors and the yard checks that decide whether it works for you.
How Does a Robot Lawn Mower Work in Four Jobs
Every robot mower, whatever the brand, repeats four jobs in a loop. Models differ most in the second job, and also in cutting system, drive layout and charging.
- Cut: a small blade disc trims a thin layer of grass, so the clippings fall back into the lawn.
- Locate: the mower tracks its position against a wire, a satellite map, a laser scan or a camera view.
- Avoid trouble: sensors stop the blades when the mower is lifted or tilted, and it turns away when it meets an obstacle.
- Recharge: when the battery runs low it drives to the dock, charges, then goes back to work on its schedule.
According to Husqvarna, its Automower 305, 310 and 315 Mark II alternate between mowing and charging all the time, with an average mowing time of 60 minutes and an average charging time of 60 minutes. That is one maker’s figure for three wire models, so read it as an example of the rhythm and not as a promise for every mower.
When a lawn looks wrong, I ask which of the four jobs failed before I blame the machine.
The Cutting System and Its Small Blade Disc
A robot mower has no big deck blade under it. Its cutter is a disc with a few small blades on the rim, and it takes off only the tip of the grass on each pass.
Pivoting Blades and Cutting Width
Robot lawn mower blades are often small razor blades that swing freely on the disc, so they can fold away from a stone or a root. Not every model uses them, so check the blade description for the model you are looking at. According to Husqvarna, the Automower 305, 310 and 315 Mark II carry three pivoted cutting blades, spin them at 2,200 to 2,300 rpm and cut a swath 8.7 inches (22 cm) wide. The manual says to replace all three blades and their screws together, so the disc stays balanced.
Next to the width of my orchard alleys, a 22 cm swath tells me at once that this is a lawn tool. A long alley would be a job of many hours at that width. For acreage that wide, my guide to a robot or zero turn mower shows where size and slope tip the choice.
Why Short, Frequent Cuts Work
Because the mower runs most days, it never removes much leaf at once. According to Husqvarna, this frequent cutting technique improves grass quality, and collecting the grass is not necessary. In an Italian field trial on tall fescue, an autonomous mulching mower gave denser turf than a gasoline walk-behind mulching mower, 3.2 shoots per square centimeter against 2.1, and a higher turf quality score (1). I also explain how a mulching mower works and when it suits a lawn.
The same research group found a limit. In a trial with transplanted weeds, four weed species grew larger under the autonomous mower, probably because a constant cutting height let creeping weeds spread sideways (2). That denser turf came from one tall fescue trial, and a robot mower does not make a lawn weed-free.
On my own lawn I pull clover and daisy runners by hand whatever mower I use, and a robot’s fixed daily height is a reason to start earlier in the season.
What It Leaves Behind
Wherever the mower stops short of a wall, a curb or a bed, a strip of grass remains. In a study of seven greenspaces managed by autonomous mowers, manual finishing along curbs and walls was needed in all seven (3). Plan a trimmer pass along those borders, and check the exact mower’s documented edge capability to see how much work remains. If you would rather hand that edge work to someone, my guide to a robot against a lawn care service shows which jobs stay yours.
How a Robot Lawn Mower Finds Its Way
Navigation is the part that differs most between models. It decides how much setup you do and where the mower gets confused, and some models combine two or three of the methods below.
| Method | What it uses | What you set up |
|---|---|---|
| Boundary wire | A low-voltage wire loop that the mower senses at the lawn edge | You lay the loop and a guide wire to the dock |
| Satellite positioning (RTK) | A satellite receiver, corrected by a base station or a network service | You drive the mower round the edge in the app to draw the map |
| LiDAR | A laser scanner that measures distance to nearby objects | You map the lawn in the app, as the maker describes |
| Camera vision | An AI camera that tells lawn from non-lawn | You follow the maker’s setup for tricky boundaries |
Boundary Wire
The wire is the oldest method and the simplest to understand. According to Husqvarna, sensors in the mower tell when it nears the wire, the front of the mower always passes the wire by a set distance before it turns, and the movement pattern is random, so the lawn is mowed evenly with less wear. That set distance is why a strip stays uncut along a wired border. My answer on whether robot mowers need a boundary wire goes through each type.
The wire has rules. The Husqvarna 305, 310 and 315 manual allows up to 800 meters (2,600 feet) of boundary wire, asks for a physical barrier at least 6 inches (15 cm) high between the wire and water, slopes or roads, and says not to let the mower operate on gravel. A break in the wire stops the loop signal, and the manual has a whole section on finding breaks. A wire free robot lawn mower swaps this loop for a map you draw in the app.
Satellite Positioning (RTK)
A GPS robot lawn mower, as the satellite models are often called, carries a receiver that reads satellite signals. Real-Time Kinematic (RTK) positioning corrects the usual satellite errors with data from a fixed reference point, either a base station you place or a network service. That correction is what lets a mower follow a map edge. My explainer on what is RTK on a robot lawn mower goes through the base station and what it needs.
The weak point is the sky. Mammotion’s 2023 guidance for its LUBA asks for an open sky view of at least 90 degrees at the lawn and at the base station, so check the installation requirements of the model you are considering. Research on forest machines agrees with the direction: under mature spruce canopy, RTK on a moving harvester reached 8 mm precision for 86 percent of observations, but canopy cover increased inaccurate positions (4). A smartphone-class receiver under canopy showed about 1.5 meters of error, but in static, post-processed observations, which is not the same as a moving mower using real-time corrections (5).
That is why my first check on any satellite model is the sky over my house lawn, which has two or three shade trees, and over the orchard rows, which are in leaf for most of the season.
LiDAR and Camera Vision
LiDAR measures distance with a laser, so the mower sees the shape of walls, fences and trees around it. Some makers pair it with satellite correction and vision in one model: Segway lists LiDAR, Network RTK and vision together for the Navimow H2. Camera vision works the other way round: the mower looks at the lawn and decides what is grass. My guide to what is LiDAR on a robot lawn mower shows how the laser scanner builds its picture.
The Worx Landroid Vision manual shows what that means in practice. Its camera steers around non-grass objects such as a tree stump, a water pipe or a ball, it reads leaves and wildflowers on the lawn as obstacles and leaves them uncut, and without the optional light it can only work during the day. For the camera method, my guide to robot mower vision navigation shows the limits.
Random or Planned Paths
Some mowers wander in a random pattern, and others drive straight lines or a grid. In a test of three navigation patterns on one mower with custom tracking software, the random pattern made the most passes and left the lowest average green cover, 64 percent, against 80 percent for a chessboard pattern and 81 percent for vertical lines (6). That was a test mower, so it ranks patterns and not retail models. I compare the two patterns in my random or systematic robot mower guide.
How Do Robotic Lawn Mowers Work Through a Typical Day?
The Husqvarna wire models in the manual do not run until the lawn is finished. They follow a schedule you set, and across the hours you allow they alternate between mowing and charging. Other models handle completion and restarts differently.
When the battery state of charge is low, the mower heads for the dock. On a wire model a guide wire runs from the dock to a far corner of the lawn or through a narrow passage, so the mower finds its way back faster. According to the Husqvarna manual, the mower starts mowing again once the battery is full if the schedule allows it, and otherwise it waits for the next permitted window.
Where the Dock Goes
The dock needs level ground and a clear approach. Worx asks for 2 meters (6.6 feet) of straight path in front of its base, with no bare or sparse grass and no sprinklers nearby. Husqvarna asks for a guide wire at least 2 meters in front of its station. Power comes from an outdoor socket, and the maker’s power supply is the only one to use.
The shed and the workshop on my farm already have outlets, so the dock would go within reach of one, in shade and on flat ground.
Rain, Wet Grass and Sprinklers
Rain behavior belongs to the model, so read its manual. The Worx Landroid Vision has a rain sensor: it stops mowing, returns to its base and restarts when the grass is no longer wet, with a default rain delay of 180 minutes. Husqvarna tells owners that a mower slipping on wet grass should wait until the lawn has dried.
Do not run the mower at the same time as a pop-up sprinkler, as the Husqvarna manual says. I run my drip irrigation on timers, so I know how easily two automatic jobs collide, and I give a mower its own clear window.
Safety Sensors and Rules That Matter
A robot mower works alone on a lawn where people live, so its safety features are part of how it works. The sensors help, and the rules in the manual do the rest.
Before You Touch the Blades
Stop the mower, then switch it off the way the maker’s manual says, then wait for the blades to stop, then put on protective gloves. On the Husqvarna 305, 310 and 315 that means pressing STOP and holding ON/OFF for 3 seconds until the keypad lamp is out. Never lift a mower that is running or sitting in its dock.
Lift, Tilt and Collision Sensors
According to Husqvarna, a lift sensor at the front switches the blades off when the mower leaves the ground, a tilt sensor does the same when the body is tipped, and collision sensors make the mower stop, back up and change direction. The 305, 310 and 315 manual also has a PIN code and an alarm that sounds if the PIN is not entered within 10 seconds after STOP is pressed. Never disable a lift or tilt sensor or the PIN.
People and Pets
The manual is plain: do not use the product when persons, especially children, or animals are in the work area. A sensor never replaces keeping people and pets off the lawn while it runs, and a child must never ride on it or play with it.
Hedgehogs and Night Mowing
The Husqvarna manual warns that the mower can injure animals at night, for example hedgehogs. In collision tests of 18 robotic mower models with hedgehog cadavers, none detected juvenile hedgehogs under 200 grams, and every model had to touch the animal to detect it. Pivoting blades, skid plates and front wheel drive significantly raised the safety index (7). The test used dead animals of a European species, but its authors say running mowers by day might largely solve the problem.
My rule for any robot mower is daylight hours only, with the lawn checked for animals first.
Preparing the Yard and Keeping the Mower Running
A robot mower is only as good as the lawn it is given. Clearing the lawn before a run helps prevent blade damage and some stuck-mower faults.
Clear the Lawn Before a Run
- Stones, branches, tools and toys: the Husqvarna manual says to make sure none are on the lawn, because the blades can be damaged if they hit an object.
- Hoses, drip lines and cables: anything lying on the grass can be caught, so lift it or fence it off with a no-go zone or a wire island.
- Fallen fruit and dog waste: pick them up, as you would any loose object.
- Holes and shallow roots: in the seven-site study some mowers got stuck on shallow tree roots, so mark them before the first run.
From June the plums drop on my lawn, and that is the first thing I sweep off before a mower goes out.
Read the Spec Sheet Like an Engineer
Spec sheets give ratings with conditions. Take the Husqvarna Automower 310 Mark II: the manual lists an area capacity of 1,000 square meters (0.25 acre), plus or minus 20 percent. That is a real range of about 800 to 1,200 square meters, or 0.20 to 0.30 acre. For a lawn near that size, I compare nine wire-free options in my robot mower for 1/4 acre roundup.
| Spec | What it means | The 310 Mark II manual |
|---|---|---|
| Area capacity | The coverage the maker rates, with a tolerance | 1,000 square meters (0.25 acre), plus or minus 20 percent |
| Slope, work area | The steepest slope inside the lawn | 40 percent, about 22 degrees |
| Slope, boundary wire | The steepest slope where the wire runs | 15 percent, about 8.5 degrees |
| Cutting height | The range the disc can be set to | 0.8 to 2.0 inches (2 to 5 cm) |
Percent is rise over run times 100, so 40 percent means 40 centimeters of vertical rise over 100 centimeters of horizontal distance. Always check whether a slope figure is for the lawn or for the edge, because the same mower can have two very different numbers. If slope is your worry, my guide to AWD vs RWD robot lawn mower drive layouts compares how each climbs.
Blades, Battery and Winter
Husqvarna says to examine the blade disc and blades weekly at first, and gives the normal life of a set as 3 to 6 weeks under favorable conditions. Another maker may differ. A blunt robot lawn mower blade gives a poorer cut, so a ragged tip on the grass is the sign to change the set. First stop the mower and switch it off the way your manual says, wait until the blades have fully stopped, and put on gloves.
The battery is lithium-ion and charges only in the maker’s station, within the charging temperature range in your manual. Never charge or use a damaged or swollen battery. For winter, the Husqvarna manual asks for a full charge, a clean mower and a dry, frost-free place within its storage temperature range, with the power to the station disconnected if the station is indoors.
What to Remember Before You Choose One
Three points carry over to any model. The cutter is a small disc that trims a little every day, so the lawn improves while the borders stay yours to trim. The navigation method sets your workload: a wire to lay, a sky to check, or a laser or camera view to suit your yard. Check the exact model’s installation requirements before you buy. The dock and the schedule decide how much of the lawn actually gets cut. If you still weigh this against a push mower, my comparison of a robot versus traditional lawn mower lays the work side by side.
My tip is to stand on your lawn at midday and look up before you read a spec sheet, because a wire model is the one that does not depend on the sky at all. Every robot is a small blade disc, a way to know where it is and a dock, and every model deserves to be judged on those three. My roundup of robot lawn mowers ranks nine of them by lawn size and slope.
Frequently Asked Questions
Where does the grass go with a robotic lawn mower?
The grass stays on the lawn, because a robotic lawn mower cuts such a thin layer that the fine clippings fall back into the turf. According to Husqvarna, its frequent cutting technique means collecting the grass is not necessary, and Worx says daily mowing leaves clippings short enough that they need no raking. Robot mowers have no bag to empty.
Do you need internet for a robot lawn mower?
You do not need home internet for every robot lawn mower, because the answer depends on the model. A Husqvarna Automower 305, 310 or 315 Mark II takes settings from its keypad and reaches the app over Bluetooth within range, while Worx uses Wi-Fi for firmware updates and cellular connections handle long-range app control on models that have them.
How do robot mowers deal with dog poo?
Robot mowers deal with dog poo only if you pick it up before the run, the same as the stones, sticks and toys the manuals tell you to clear. A camera model steers around objects it reads as non-grass, but I would not rely on it to recognize waste.
What are the disadvantages of a robotic mower?
The main disadvantages of a robotic mower are the uncut strip along walls and curbs, the setup it needs and the limits of its navigation. Wire models need a loop laid and checked for breaks, satellite models need open sky, and every model needs a clear lawn, a dock with power and daylight scheduling to protect wildlife.
Do robot lawn mowers do a good job?
Robot lawn mowers do a good job on the grass itself and a poorer job on the borders. In an Italian trial an autonomous mower gave denser, higher quality turf than a gasoline mulching mower, while edges and walls still needed manual finishing at every site in a seven-site study. Expect an even, tidy lawn and keep a trimmer for the edges.
References
- Grossi N, Fontanelli M, Garramone E, et al. Autonomous Mower Saves Energy and Improves Quality of Tall Fescue Lawn. HortTechnology. 2016;26(6):825-830. doi:10.21273/horttech03483-16
- Pirchio M, Fontanelli M, Frasconi C, et al. Autonomous Mower vs. Rotary Mower: Effects on Turf Quality and Weed Control in Tall Fescue Lawn. Agronomy. 2018;8(2):15. doi:10.3390/agronomy8020015
- Sportelli M, Martelloni L, Orlandi A, et al. Autonomous Mower Management Systems Efficiency Improvement: Analysis of Greenspace Features and Planning Suggestions. Agriculture. 2019;9(6):115. doi:10.3390/agriculture9060115
- Lopatin E, Väätäinen K, Kukko A, et al. Unlocking Digitalization in Forest Operations with Viewshed Analysis to Improve GNSS Positioning Accuracy. Forests. 2023;14(4):689. doi:10.3390/f14040689
- Tomaštík J, Everett T. Static Positioning under Tree Canopy Using Low-Cost GNSS Receivers and Adapted RTKLIB Software. Sensors. 2023;23(6):3136. doi:10.3390/s23063136
- Luglio SM, Frasconi C, Gagliardi L, et al. Modeling the Relationship Between Autonomous Mower Trampling Activity and Turfgrass Green Cover Percentage. Agronomy. 2025;15(12):2890. doi:10.3390/agronomy15122890
- Rasmussen SL, Schrøder A, Mathiesen R, Nielsen JL, Pertoldi C, Macdonald DW. Wildlife Conservation at a Garden Level: The Effect of Robotic Lawn Mowers on European Hedgehogs (Erinaceus europaeus). Animals. 2021;11(5):1191. doi:10.3390/ani11051191
Safety Note: A robot mower has sharp blades. Keep hands and feet away from them. Do not run it with children, other people or animals on the lawn; stop it and park it or switch it off if they come onto the lawn. Never ride on it or let children play with it. Clear toys, hoses, sticks, stones and fallen fruit before a run, and do not mow while sprinklers run. Never lift or tip it while it runs or while it sits in its charging station. Before you lift it, clean it or touch the blades, press STOP, switch it off exactly as your manual says, wait until every blade has stopped, and wear protective gloves. Daytime schedules reduce encounters with animals that come out at night, though animals can be on the lawn by day too. Plug the power supply into a covered outdoor GFCI outlet, keep its cable out of the mowing area, and follow your manual for installation, slopes, charging and storage.