It’s Not Just Rain
Hard sunlight, extreme temperatures and dust need to be considered. Extreme weather conditions not only make it harder to interpret any information provided by vehicle sensors but also cause practical challenges to the sensor equipment.
Extreme Weather Tests the Limits of Sensor Technology
Cameras and radars are quite easy to place inside the vehicle body, safe from the environment. However, camera optics in particular require good visibility out of the vehicle, so in bad weather when dust, sand and water keep blocking the sensors they should be equipped with washers and wipers. In freezing temperatures the frost needs to be removed by heaters.
LiDAR, like any other electronics, does not function well in elevated temperatures. The powerful lasers in the sensors produce excess heat, which can be a challenge when combined with high outside temperatures and a scorching sun. The cooling and casing of sensor devices is a key challenge in enabling autonomous vehicles to operate in all types of weather in warm regions.
On the other hand, arctic cold is rarely an issue for autonomous driving technology. In some cases snow may melt on top of the sensor, creating a freezing drain of water to the surface of LiDAR-scanner. This sort of icing needs to be tackled with special surface materials and heaters. In general, sensor heating is easier to arrange than cooling.
When temperatures drop significantly below zero, snowfall no longer melts on the car and sensor surfaces but is simply carried away.
Considering the weather, radars are the easiest sensor to manage. By nature, radars don’t mind if there’s water, dust, or ice on the surface of the sensor and they also see well through plastic or glass shielding. But just like LiDAR’s, radars are electronic devices with requirements regarding operational temperatures. Especially in warm areas they may require cooling.
LiDAR scanner is the most challenging sensor in terms of weather. Since it scans a full 360 degree image of its surroundings by design, it often needs to be placed on top of the vehicle with an unobstructed view.
It may be a bit surprising, but rain and drops of water on the surface of LiDAR-scanner are rarely an issue for the sensor to do its job. But temperatures may be.
