ADAS (Advanced Driver Assistance Systems) safety systems have to see what is happening around the car. They then collect that information (using machine learning algorithms that recognise the environment) and act to help the driver make safe decisions. Sensors have been evolving, with increasingly sophisticated cameras. These include: LiDAR sensors (Laser Imaging Detection and Ranging), which operate using laser technology.
Currently, only the most sophisticated vehicles are equipped with LiDAR sensors, but this technology will become more widespread. The reason is that they detect the vehicle’s surroundings more reliably. Over time, their costs will be reduced and they will become more compact systems that can be mounted on the windshield, next to other cameras and sensors. A location that offers advantages over the first models that are mounted on the vehicle’s roof.
How do LiDAR sensors work?
LiDAR technology is based on a laser emitter that emits infrared laser light beams that hit objects. When they bounce back, they are recorded by a receiver. The system is able to measure, thanks to laser scanning, the distance, position and height of that object. And with great precision in its range of up to 250 meters.
The great advantage of LiDAR over a camera is that the vehicle’s computer system forms a point cloud with which it creates a three-dimensional image of that object in real time. It is also more reliable, as it works both day and night and can generate reliable representations in adverse weather conditions.
In addition, the system updates in milliseconds the precise position of each point, which makes it possible to determine the movement and direction of the object being analysed. With LiDAR, vehicle computers perform many calculations per second and safety systems can make more appropriate decisions.
What do LIDAR sensors provide?
With the extra information provided by LiDAR, ADAS systems can work by recognizing their surroundings even better, with more data for decision-making. The LiDAR sensor complements cameras and radars, providing redundancy in the detection of objects around the vehicle.
This is very useful when cameras or radar may fail due to poor visibility conditions or interference from signals from other vehicles. With this extra information, you can develop functions for level 3 driver assistance Autonomous driving: LiDAR improves the ability to recognize objects, their distances, trajectories and movements. It also allows 3D mapping of the vehicle’s surroundings, including road geometry, lane markings or traffic signs.
Thanks to this, systems such as the autonomous driving assistant on highway (HDAA – Highway Driving Autonomous Assistant), which allows the driver to drive on certain motorways up to 130 km/h without having to keep their hands on the wheel, accelerate or brake. The driver, who is monitored, only has to pay attention to the traffic and take control of the vehicle again when the system asks them to. In Spain, the Mustang Mach-E already works like this on certain stretches of road.
LiDAR sensors on the roof or windshield
LiDAR technology has been used for years in development prototypes of autonomous cars. These cars use a LiDAR with 360-degree visionon the roof of the vehicle and rotates on its axis (up to 900 times per minute) to obtain a clear viewing angle of the entire environment.
LiDARs have evolved into more practical solutions that can be more easily implemented in production models. These sensors point towards the front of the vehicle, with a 120º angle of vision, collecting information on all objects. They are usually located at the front of the vehicle (behind a grille) or on the windshield.
Installing it behind the windscreen has the advantage of having an elevated viewing position, with sensors isolated and protected from the outside (water, dust, shocks, temperature). In addition, they do not affect the design or aerodynamic performance of the vehicle at all.
Its location on the windshield has presented some challenges. Modern windshields feature a film that absorbs infrared radiation to insulate the passenger compartment from heat and protect occupants… However, these treatments partially block the LiDAR sensor’s laser beams, both when they are emitted and when they are bounced back, reducing their range and accuracy (in tests carried out by Hesai and FUYAO, the LiDAR range was reduced from 250 to just 60 meters away).
This is why major manufacturers have developed windshields with anti-reflective coatingswhich help reduce heat and also allow the transmission of infrared laser beams with the specific wavelength of the LiDAR. Not the entire windshield needs this coating, only the part above the sensor module.
Recalibrating LiDAR sensors when replacing a windshield
When replacing a windscreen, the cameras must be removed from the broken glass and fitted to the new one. Once installed, these systems must be recalibrated to ensure that they operate with maximum precision and provide the correct information.
ADAS systems can take control of the car and the driver trusts them, and awaits their response to alert or assist in a risky situation. The LiDAR sensors used to date do not need to be recalibrated after a windscreen replacement, although some of them do need to be reset. The most common reason why ADAS systems can malfunction is because their cameras and sensors have not been recalibrated, or this operation has been done incorrectly.
