The obstacle detection unit includes sonar, stereo cameras, a localization camera, a laser, and a radar detection unit that helps the car computer to make driving strategy.
In one of our past posts, we discussed computer, display, and map & navigation system of driverless car of Google that it carries under its hood.
We are studying patents filed by Google to write these articles so that we can give you a holistic view of the driverless car before anyone else. You can access the full series from here.
Today’s post is about the obstacle detection unit of driverless car by Google that includes sonar, stereo cameras, a localization camera, a laser, and a radar detection unit.
These sensors help robotic chauffeur (driverless car computer) to identify, track and predict the movements of pedestrians, bicycles, and other vehicles on the roadway. And based on the data provided by these sensors, the robotic chauffeur makes driving strategies.
We will talk about the field of view and ranges of these sensors later in today’s post. Let’s first find out which sensor is located where and how it helps in self driving.
Position and Use of Various Obstacle Detection Units in Driverless Car
According to Chris Urmson (tech lead of driverless car project), the laser range finder of the car is “heart of the system”.
The car carries a Velodyne 64-beam laser on its roof. It measures the distance between the vehicle and the object surfaces facing the vehicle by spinning on its axis and changing its pitch, in other words by rotating.
The radar detection unit is used for adaptive cruise control systems that are located on the front and back of the car as well as on either side of the front bumper. For the same purpose Sonar will also be used.
Varieties of cameras are mounted on the car separated from each other by a small distance. The parallax from different images, which are captured from multiple cameras, is used to compute the distance to various objects.
The purpose behind using different units of different field of view and range is that they provide superb situational awareness and works in all type of weather.
For example, on a foggy day, chances are that the camera may provide wrong inputs, however, radar will work efficiently in such a weather condition.
Range of Obstacle Detection Units of Driverless Car:
The sonar has a horizontal field of view of approximately 60 degrees for a maximum distance of approximately 6 meters.
The stereo cameras have an overlapping region with a horizontal field of view of approximately 50 degrees, a vertical field of view of approximately 10 degrees, and a maximum distance of approximately 30 meters.
The localization camera has a horizontal field of view of approximately 75 degrees, a vertical field of view of approximately 90 degrees and a maximum distance of approximately 10 meters.
The laser has a horizontal field of view of approximately 360 degrees, a vertical field of view of approximately 30 degrees, and a maximum distance of 100 meters.
The radar has a horizontal field of view of 60 degrees for the near beam, 30 degrees for the far beam, and a maximum distance of 200 meters.
This is all about the various detection units their location in the car and their ranges. Now you may be wondering that how car uses the obstacle detection unit on road. And to find that out, I would further recommend you to read this– How Driverless Car Predicts Movement of Vehicles on Road
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