LIDAR, cameras, and radars, oh my!
The main event of Google's and Lexus' self-driving cars is the whirling metal LIDAR unit that sits atop the vehicles' roofs. LIDAR, which stands for Light Detection and Ranging, is a laser range-finder that spins in a circle and creates a 3D picture of the world around it using 64 layers of laser beams. According to Toyota, the LIDAR unit atop its self-driving Lexus can detect objects (both metallic, such as cars, and nonmetallic, such as people and trees) within a 230-foot radius.
Of course, the 3D picture that the LIDAR unit paints is just the first step in the process of determining what's around the car and how the car can proceed. The self-driving Lexus has an array of sensing equipment to ensure that it knows everything: what obstacles are around the car, how fast (and in which direction) those obstacles are traveling, how fast (and in which direction) the car is traveling, and which direction the car is facing.
The Lexus features three high-definition color cameras (one forward-facing, two side-facing), each of which has a range of about 500 feet. These cameras let the car detect colored objects, such as traffic lights and signs, other cars, and lane lines. The Lexus also has radars dotted around the front and sides of the car. These radars can measure the location and speed of objects around the car--so, for example, they can tell if the car is keeping up with traffic or not.
The car has built-in GPS (two GPS antennas allow the car to determine its orientation), as well as an inertial measurement unit (IMU), which is sort of like a "super GPS," according to Brian Lyons, Toyota's manager of safety and quality communications. The IMU is capable of working when GPS cannot (such as inside a tunnel), and it also has accelerometers and gyroscopes to measure the yaw, pitch, and roll of the vehicle--convenient if the car happens to be at a weird angle on a hill. Not surprisingly, IMUs are typically found on unmanned aircraft. "The tech is basically here," says Lyons. "Everything has to get smaller and cheaper, but the tech is here."
A central computer ties it all together
Of course all of these sensors, lasers, and cameras aren't there simply to look good. They tie into a central computer, which also talks to the ABS and electric power steering. Basically, once the car figures out where it is, what it's doing, what's around it, and what those surrounding objects are doing, it can start to drive itself.
Driving is not really the issue. Think about it: thanks to cruise control, ABS, and electric power steering, your car is already capable of moving, stopping, and steering on its own. It's the "knowing what's going on" part that's difficult.
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