Academic journal article Science and Children

Q: How Do Self-Driving Cars Work?

Academic journal article Science and Children

Q: How Do Self-Driving Cars Work?

Article excerpt

A: For my own peace of mind, no matter how they work, I hope they work really well! Maybe my wife and I are just getting too old for all these newfangled contraptions, but neither one of us is anxious to have a bunch of driverless cars roaming the highways, even though it seems that many cars with humans behind the wheel already don't have a driver.

Anyway, to understand how driverless cars work, it will help to consider how a car with a driver works. What are the essential components of a car successfully negotiating roads with a human driver? Let's consider the driver components. As a first step, the driver has to be able to see the surroundings. You have to know the location of all the other cars on the road and know what they're doing. This includes how fast other cars are moving, whether they're slowing down or speeding up, and whether they're moving toward you, away from you, or in some other direction. You have to be able to stay in your lane, you have to know which roads you want to take, you have to know which exits and entrances on the freeway to take, and you have to be able to anticipate any changes you need to make in your route.

Included in your surroundings are road signs such as stop signs and speed limit signs; signal lights and whether they're green, yellow, or red; warning lights for construction sites; those flashing colored lights on emergency vehicles; and that cop that wants you to pull to the side of the road. There are more things to know, but that will do for starters. Plus, listing all those items makes it quite logical why I spend most of my driving time watching for other drivers who are lacking in their awareness of one or more of the items.


To understand how a self-driving car takes care of some of these tasks, I'm going to have you do a mental activity that I've used in a number of my columns. Imagine you're sitting on a chair in a completely dark room and you want to find out where the walls are without moving from your chair. You have a bag of tennis balls. One way to figure out where the walls are is to throw tennis balls away from you in different directions. You can listen for when a ball hits a wall, and then, knowing how hard you threw the ball, you can guess how far away the wall is. Do this a lot, and you can get an idea of how far away the walls are. In fact, seeing where the walls are in a lit room isn't much different from that process. Light from the lightbulbs in the room bounces off the walls, and we gather that reflected light in our eyes.

So, one way for a car to determine where other cars and objects are around it is for the car to shoot tennis balls out in all directions, record the sound the balls make when they hit objects, and thus determine where the objects are. Not a practical solution, because your car would run out of tennis balls in no time, and the people in the other cars wouldn't like it much. Instead of throwing out tennis balls, self-driving cars throw out electromagnetic waves in the form of radio waves and laser beams, and they also emit sounds and record the reflection of the sound waves off of objects. Using radio waves is known as RADAR (RAdio Detection and Ranging), using laser beams is known as LIDAR (Laser Illumination Detection and Ranging), and using sound waves is known as SONAR (Sound Navigation and Ranging). Each method is used for a different purpose. Lasers are quite good at figuring out where objects are, so self-driving cars emit many laser beams continuously. The laser light reflects off surrounding objects and returns to the self-driving car, allowing the car to figure out where everything is. These laser beams also sweep across various sections of the car's "field of view," allowing the car to map out its surroundings. This sweeping action is so rapid that the lasers can help the car's computer tell the difference between a car, a truck, a bicycle, a pedestrian, and a building. …

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