Book 15, Question 78
Why Does a Robot Lawn Mower Stay Inside the Yard?
A robot lawn mower stays in the yard by sensing an invisible boundary! Usually a thin wire is buried at the edge of the lawn. The wire carries a weak signal that the mower can feel.
More fun facts
- Many robot mowers use a boundary wire laid or buried around the edge of the lawn and around things to avoid.
- A sensor coil inside the mower detects the magnetic signal from the wire.
- The wire carries a coded signal. If the code looks flipped, the mower knows it is outside the loop.
- Some newer mowers skip the wire and use precise satellite signals to make virtual boundaries.
- Collision sensors help the mower slow down and steer away from objects in its path.
- If someone lifts the mower or it tips over, its blades shut off right away.
Sources: patents.google.com, husqvarna.com
Questions kids ask
What happens to the grass clippings?
The small clippings fall back into the lawn and work as a natural fertilizer.