Like most of us, to do their job well sensors such as lidars and cameras need more than just "smarts." They need to be given the best possible chance of perceiving the greatest amount of information in the driving environment.
Two factors are critical to achieving this: the sensor must be in the right position on the vehicle, and it must have the right operating conditions.
There are two primary locations for autonomous vehicle sensors -- on the roof, or on the grille -- and both are intersections between other forces in the vehicle and in the industry.
Roof placement
Sensors placed on the roof have the best chance of maximizing the range and field of view, thanks to their height and central position. This placement is also farther from the road, reducing the extent to which the sensor needs to contend with contaminants such as mud and spray splash, lowering its risk for misalignment, and keeping it cooler overall.
On the other hand, the front of the roof (where sensors are usually located) is both the crest of the vehicle silhouette and key to the vehicle's aesthetics, as well as a critical location for vehicle aerodynamics.
When a Lidar is placed at that crucial point, it not only has the potential to ruin the vehicle's design lines, but can also disrupt the continuity of the airflow, causing noise, increasing vibrations, and reducing fuel/energy efficiency.
Grille placement
The grille, or front bumper, is another popular placement for automotive sensors and offers inverse pros and cons to roof placement. Its proximity to the road makes it less likely to interfere with aerodynamics, and less likely to significantly impact the vehicle's aesthetics.
However, it is not ideal for maximizing optic range and makes the sensor more susceptible to harsh contaminants like mud and snow, misalignment due to bumps and hits, and overheating due to its proximity to the engine.
These advantages and disadvantages come into play in different ways for different driving scenarios. For example, the long range that roof placement provides is especially important for high speeds and long distances of highway driving.
On the other hand, for electric vehicle adoption, the issue of aerodynamics and its impact on energy efficiency is central: every bit of energy used fighting against drag is energy that doesn't go toward maximizing the vehicle's range.
Because range anxiety continues to be a very real obstacle to consumer EV adoption, the drawbacks associated with roof placement cannot be dismissed.
Supportive conditions
The physical conditions under which a sensor operates, which are impacted to a great extent by the sensor placement, can also significantly affect the sensor's effectiveness overall.
Obstructions, thermal imbalances, and misalignments can cause sensors to falter or fail -- rendering even the most advanced technologies useless and threatening the safety of all road users.
Successful sensor cleansing and thermal management can mitigate these threats, but only if they offer continuous, real-time, instantaneous detection and immediate correction.
In high-speed, high-stakes driving scenarios, every millisecond counts. Aerodynamics plays a factor here as well: with strong streams of air coming rapidly across the roof-mounted sensor, for example, the cleaning system needs to work with the laws of aerodynamics, not against them.
Finally, the system needs to be able to contend with both the common contaminants for roof-mounted sensors, including a wide range of water droplet sizes, and with the harsher contaminants more often seen on grille-mounted sensors, such as snow, mud and ice.
Looking ahead
The autonomous driving revolution will begin on the highway. Ensuring that automotive sensors such as lidar have a clean, unobstructed view of the road from the roof provides the best hope for the longest range and the greatest perception capabilities.
How the industry contends with the design and aerodynamics challenges, as well as the auxiliary cooling, cleaning, and health maintenance components, will be a determining factor in how quickly and safely the revolution is realized.
