The concept of the self-driving car is a decades-old dream of the science fiction. But when you have bought a new car recently, you must have made a big leap into that future. This is called the technology that fills the gap between full manual driving and full autonomy, which is known as Advanced Driver Assistance Systems or ADAS.
ADAS can be described as a combination of electronic technologies, which are used to guide drivers in their driving and parking tasks. Instead of becoming a full-fledged controller, ADAS performs the role of a co-pilot, which is to make driving vehicles safer and more enjoyable by automating, adjusting and refining vehicle systems to be safe and drive better. The very end purpose of ADAS is not convenience but a dramatic minimization of human error, a contributor in an overwhelming majority of road accidents.
The Building Blocks: The ADAS Vision of the World.
To be useful, an ADAS should be able to sense the environment in a manner that is both accurate and reliable enough to compete, and in other cases exceed, the human senses. This is by the way of an advanced system of cameras and sensors which serve as the eyes and ears of the car. Such systems are not independent, and they integrate information about various sources into a holistic, 360-degree view of the environment around a vehicle. The key components include:
Radar (Radio Detection and Ranging): Radar sensors are the ADAS workhorse, especially in distance and relative speed functions. They send out radio waves which reflect back on the objects and timing how long the signal takes to come back, the system is able to determine the distance of the object, speed and angle of the object. Radar is very useful during weather conditions that are unfavorable such as rain, fog, or snow where cameras may fail. Long-range radar in the front grille is usually used to provide adaptive cruise control and automatic emergency braking, and short-range radar in the corners of the car to track the blind spots.
Cameras: Cameras give images that give abundant visual information just like the human eye. They are essential when information about images needs to be recognized, e.g. road signs, road lane markings, picking out pedestrians and bicycles, and offering a video display of a parking area. These can be attached at the back of the windshield, close to the rear view mirror. Poor lighting or glare or dirty lenses may however degrade their performance.
LiDAR (Light Detection and Ranging): LiDAR is a more developed technology that produces a high-resolution, three dimensional map of the surrounding by firing millions of laser pulses per second and recording the time they take to bounce back. It also provides very accurate depth perception and is believed by most to be what is needed to advance automation further. LiDAR is now found in high-end models, though it was too expensive to be used in consumer vehicles in the past.
Ultrasonic Sensors: It is the short range heroes of the ADAS mostly meant to be used in low speed maneuvers such as parking. They operate under a similar principle as radar except that they operate with sound waves. They are generally in the form of a small, round disc on the front and the rear bumpers. They send a sound wave with high frequency and wait to get the echo back to identify the curbs, other cars, and any other obstacles in the parking space.
Central Computer and Sensor Fusion: The basic data of individual sensors is meaningless in itself. Magic actually occurs in the powerful central computer in the vehicle. The computer then takes the information of all these sources, radar, the visual identification offered by the camera and the 3D map offered by LiDAR, and uses a process known as sensor fusion to produce an accurate, reliable and single model of the surrounding world of the car. Such redundancy is essential to safety, and is necessary in case one sensor is not functioning or is impaired in some way, the others will make up.
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