Sensors Overview

The sensors on our vehicles act as eyes, providing the input needed to create a model of the world around the vehicle. Unlike the human eye (the main sensor in human-driven vehicles), our sensors operate on a variety of wavelengths, providing much more information than even the most experienced driver. Our vehicles will have LIDAR, RADAR, stereo vision, GPS, and an INU.

LIDAR

Our team will use multiple forward-looking, and one rear-facing LIDAR units.  The LIDAR works on a simple principle: it sends a beam of light out and measures exactly how long it takes to send the light, hit an object, and reflect back to the sensor.  By knowing the speed of the beam, we can tell how far it traveled, and thus how far away the object is. The LIDAR scans a 90-degree field of view and measures 181 points across that field (about 1 measurement every half-degree), and it scans the entire line 75 times per second (that’s 13,575 measurements every single second). These powerful sensors are provided at-cost by SICK. The LIDAR is very precise, but also limited in it’s use because it doesn’t provide 3-dimensional distance ranging, it only places distances on a left-to-right plane and doesn’t tell us anything about how tall an object is.

RADAR

We are using an Epsilon Lambda RADAR system that provides 3-dimensional object detection and tracking. The RADAR sends out a radio wave that bounces off obstacles, providing an accurate 3D location of the obstacle. The RADAR works in the event of a rain or sand storm during the race, and it’s also the only sensor that can tell the difference between a metal fence-post and a really narrow tree (which we could just drive right through).

Stereo Vision

Stereo vision works exactly on the same principle as human eyes: it uses 2 cameras (hence “stereo”) placed a known difference apart from each other and compares the images taken from each camera to develop an idea of where objects are and how far away they are. More information on this sensor is on the left side of this page.

GPS/INU

The racecourse is defined using GPS waypoints, so an accurate GPS receiver is incredibly important. Most commercial GPS units have 20 feet accuracy, which is to say that you are somewhere in a 40-by-40 foot box (20 feet off in either direction). While that type of accuracy is suitable for most uses (hiking in the woods, or giving directions in a car), we need much more accuracy to guide our vehicle. The GPS receiver and antenna was donated by Trimble, and has an accuracy of 10-centimeters. Instead of a 40x40 foot box, we have a box that is 8 inches by 8 inches! The GPS receiver uses a signal from a subscription service called OmniSTAR that provides corrections to the standard GPS signal to improve accuracy. When the GPS service goes out or gets less accurate (for instance in a valley or other time the sky is obstructed, the antenna can only use 3 satellites instead of the preferred 8), we use an inertial navigation unit to pinpoint our position on the map. The INU was donated by Northrop Grumman, and uses fiber-optic gyroscopes and accelerometers to measure precisely how far the vehicle has traveled, in what direction, and at what heading. This allows us to tell not only where the vehicle is, but if it is going up a hill, down a hill, rolling sideways. This information also helps us determine the best driving commands to use in order to stay on course.