How does a robot vacuum know a wall is there?

Have you ever seen a robot vacuum at work? It rolls across the floor with a soft hum, picking up crumbs. It goes all around the room by itself. Maybe you heard a gentle thump when it reached the wall.

A robot vacuum has no eyes like yours. It cannot look at the wall the way you do. You can spot a wall from across the room. So how does a robot vacuum notice a wall?

Look at the front of the robot. There is a bumper, which means a curved strip that can slide in a bit. It wraps around the front like a shield. The bumper is there to touch things before the rest of the robot does.

The robot rolls forward until its bumper touches the wall. The wall does not move out of the way. So the wall pushes back, and the bumper slides in a tiny bit. Now the robot cannot roll any farther forward.

Tucked behind the bumper sits a small switch, much like a button. The switch is so small that you would hardly see it. When the bumper slides in, it presses that switch. What do you think the switch does next?

The switch sends a quick message along a thin wire. That message hurries to the robot's computer. It travels much faster than you can blink. The computer is the part that does the robot's thinking.

Now the computer gets the message. It knows something is right in front of the robot. That one small bump on the bumper is how the robot notices the wall.

Let's remember our special word: bumper. The robot bumps the wall, the wall pushes its bumper in, and the switch tells the robot.

Next time you hear that soft thump, you will know just what the robot found. Sweet dreams, clever little explorer.