If we’re going to be talking and thinking about autonomous cars, self-driving cars, robo-cars, drive-o-droids (copyright pending) or whatever the hell we want to call these things, we should get a sense of exactly what they do and how they do it. How do they know what’s around them, and how can they potentially be better than human drivers?
Let’s just take a moment to break down what the act of driving actually is: controlling a moving object significantly larger than yourself through a complex environment full of other moving objects, and controlling the rate of motion, including entirely stopping the motion, the direction of that motion, and adjusting the manner by which speed and direction changes are effected based on environmental conditions like road surface friction and weather/visibility.
Really, the more you think about it, it’s pretty incredible we can drive at all. For one thing, we’re asking our bodies to act and react at far quicker intervals than we were ever designed for. Sure, many of the traits that make it possible for humans to drive at all come from millions of years of evolutions as predators and hunters, which gave us such handy-for-driving traits as forward-facing binocular vision, the ability to track moving objects while we’re in motion, handy for chucking spears at mammoths and bison, and the ability to anticipate the motion of other moving things.
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We can look at a pedestrian on a street corner and tell, thanks to an innate understanding of human behavior, if that person is paying attention to their surroundings or not, and we can adjust our focus on them accordingly. We can often tell if the person sees us, in the car, and can use that information to decide how to best approach them, or even to alert them to our presence by blowing the horn, which may or may not play a ridiculous version of Dixie.
We, as drivers, are able to compensate for gaps in what we see or expect thanks to our experiences. If we’re on a road that goes from having clearly marked lane divider lines to a section where none of the lines are visible, we can deal with that because we know roughly where the lanes should be and can continue based on what the last visible section of lane markings told us.
Machines don’t have many of the innate abilities that humans have that we use when driving, and as such making a car able to drive itself is pretty much starting from scratch. Machines have some pretty significant advantages to help them out, though, like the inability to feel fatigue, remarkable speed, the ability to be interfaced directly with the machinery of the car itself and receive data from other machines, among others.
Most modern autonomous vehicles rely on the same basic set of technologies and general procedures to work, so let’s walk through the basic toolkit that lets an a wildly advanced machine drive itself around just like your deadbeat cousin does every day.
The equipment on an autonomous vehicle that differs from a human-piloted vehicle primarily can be classified into two categories: sensory equipment and mechanical actuators. The actuators just convey the driving system’s decisions to the physical part of the car, and can be very tightly integrated with the car itself. Motors that are used to assist with steering for human drivers can also be used to turn the steering rack itself. With most modern cars being drive-by-wire— not requiring, say, a physical cable from the gas pedal to a butterfly valve in the fuel system and instead just sending electronic signals from the pedal to increase or decrease throttle—having something other than a human controlling the functions of a car are pretty straightforward. This part of the equation is by far the easy part.
The hard part is getting the car to perceive and understand the ever-changing, ever-moving world around it. That’s where the sensory equipment comes in. Here’s what that equipment usually consists of:
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Ultrasonic Sensors
You know those little round button-like things you see on some cars’ bumpers? Those are ultrasonic sensors, and they’re most often used as parking-assist sensors, since they’re good at telling what’s close to you, at low speeds. They bounce ultrasonic sound waves off objects to determine how close you are to them.
These actually don’t have much use in fully autonomous vehicle use, but they still do help a car understand its environment, so I thought they were worth a mention. Automatic parallel parking systems do use them, so there are someautonomous-driving/parking contexts where they’re used.
We can’t hear the pulses they make, since those pulses, while loud, tend to be between 40 kHz and 48 kHz (or higher, with newer sensors) or so. Human hearing stops at about 20 kHz. Dogs, cats, and bats, though, they should be able to hear them, which must be pretty annoying.
Cameras
Vision, is, of course, the most important sense we use when driving, so most self-driving machines will need a way to replicate it. Modern technology is capable of making some very small and high-resolution camera systems, and modern cars already are getting pretty laden with cameras, even if they don’t have any interest in driving themselves.
Cameras, usually mounted just above the inside rear-view mirror in the top-center of the windshield, are used for lane-departure systems, where computers run software that analyzes each frame of video to identify the lines painted on a highway, and makes sure the car stays inside them. These cameras may also be used for emergency braking systems and traffic sign identification. All of these examples would be for camera systems with some degree of artificial intelligence, since they’re actually attempting to make some sort of sense out of the images they capture.
“Sense” is a bit of an anthropomorphizing term, of course: they’re really just analyzing frames of video for a very specific set of criteria, and acting on that criteria in very defined ways.
Most autonomous vehicle camera systems with use two cameras to get binocular vision for real depth perception. While the cameras are good, they’re not usually as good as the one in, say, your phone. Most tend to be between 1 to 2 megapixels, which means they’re imaging the world at a resolution of about 1600 x 1200 pixels. Not bad, but much less than human vision. Still, this seems to be good enough to resolve what’s needed for driving, and is small enough to allow for image processing at the sorts of speeds required for driving.
Really, it’s not about image quality or color saturation or any of the sorts of criteria we normally use when we evaluate cameras for our use. For driving a car, you want fast image acquisition—the more frames per second you can capture and evaluate, the quicker the car’s reaction time will be.
When processing images from the camera, the car’s artificial vision system has to look out for and identify a number of things:
– Road markings
– Road Boundaries
– Other vehicles
– Cyclists, pedestrians, pets, discarded mattresses, and anything else in the road that is not a vehicle
– Street signs, traffic signs, traffic signals
– Other car’s signal lamps
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Source: Jalopnik