The dual lidar scheme of concentration has aroused heated discussion. So, where exactly should lidar be installed? How do different locations affect their performance?
Wen 丨 wisdom driving network Huang Huadan
As soon as the dual lidar scheme of Jidu Automobile Robot was announced, it triggered a heated discussion.
Where exactly should lidar be installed? This seemingly trivial question has attracted the big guys to personally go down, and Li Xiang, He Xiaopeng and Jidu CEO Xia Yiping have expressed their opinions.
Before the set, most of the on-board lidar was installed on the roof or front bumper. The installation of two retractable lidar on the front cover is arguably a groundbreaking solution.
And considering the practicality, what is this solution?
——01——
Ideal and set-degree schemes
Jidu's description of its dual lidar scheme is that not only is it distinctive and has a very good appearance, but its dual lidar configuration also shows safety advantages.
First of all, the point cloud field of view of dual lidar is wider and safer, and the frontal dual radar can achieve horizontal 180 degree FOV coverage compared to the 120-degree FOV of a single radar design.
In driving scenes such as "ghost probes" and left and right obstructions, the ability to recognize pedestrians or obstacles traversing left and right is stronger.
Secondly, the identification of the key area of the vehicle is more accurate, in the area of 60 degrees FOV directly in front of the vehicle, the dual lidar can be doubled and overlapped, and the point cloud data on the target is more, and the recognition accuracy is higher.
Third, in terms of the redundancy safety of high-level automatic driving, dual lidar can be mutually safe and redundant, which is more reliable than the single lidar solution.
Li wanted to comment almost at the first time:
"Putting one on the roof and two on the cover or bumper makes no difference in performance, and even a single one on the top of the head will perform better." However, in terms of pedestrian collisions, maintenance costs, and vibration control (linking the main body), the roof is optimal. The only problem is that the shape of the roof lidar will need to be adapted, because it is too much like a mobile suit - Gundam. ”
Of course, we know that Li wants his ideal L9 to use the roof lidar solution.
The next day, Xia Yiping also responded immediately:
"There is still a difference, 120 degrees OFV and 180 degrees of FOV are still not the same, the solution of the corner case is not the same, so there is a difference in the ability and experience of the product and even the safety."
For these advantages, Li Xiang probably also recognizes them. But at the same time, he also believes that Jidu should not put lidar on the front cover of the car during mass production, because it will not pass the latest pedestrian collision regulations.
According to Zhang Jiahao, head of marketing growth in Jidu, at the media communication meeting, the currently announced lidar scheme is to install two lidar symmetrically on the left and right of the front cover, and it can be lifted and lowered, and can be contracted when not in use.
This is the scheme of the Jidu Concept Car. In other words, the possibility of changing the installation method during subsequent mass production is not excluded.
——02——
The impact of different mounting locations on coverage
Is it a plan with two cars on the front cover or a plan with one roof?
At present, both schemes have advantages and disadvantages.
Intelligent Driving Network consulted The LiDAR System Mass Production Solution Provider Liangdao Intelligence, which has tested a number of different routes of lidar at home and abroad, and has a deep understanding of the mass production of lidar.
Liangdao Intelligence believes that the difference in installation height is differentiated for target detection, and the higher the ground line, the greater the blind spot. But at the same time, its vision will be better, for example, it can cross the front car to detect the front car.
Generally speaking, the roof needs to take into account the lower edge of the field of view (FOV) and the position of the roof cover, so there will usually be a few degrees of downward adaptation according to the different models. If it is installed in the hood position, the general hood is relatively flat, and the lidar is needed to lean upwards, sacrificing a part of the LIDAR FOV.
The main influence here is the vertical FOV of lidar. Generally, the vertical FOV is small, taking the ideal and set degree of use of Hesai AT128 as an example, its horizontal FOV and vertical FOV are 120 degrees and 25.4 degrees, respectively.
It is worth mentioning that because mechanical lidar uses a rotary mirror mode, its horizontal FOV can reach 360 degrees.
But let's just consider vertical FOV for the time being. SmartDriver borrowed a legend from Sagitar Juchuang to show the impact of lidar on the vertical field of view when installed in different positions.
It can be seen that in the vertical field of view, the higher the lidar installation position, the farther its field of view, but the blind spot near it will be relatively large.
Therefore, from the perspective of coverage, if the scheme of installing a forward-facing lidar on the roof is adopted, it is safer to add 2-4 short-range lidars in the four corners of the vehicle. This is also a more reasonable configuration that Liangdao Intelligence thinks is more reasonable.
Of course, this also depends on the needs of car companies to install lidar. Under the premise of considering the cost performance, if more attention is paid to the identification of nearby obstacles, the choice to install lidar in a lower position can minimize the blind spot in the vicinity.
For example, Mercedes-Benz's EQS with L3 level automatic driving assistance function. Since the L3 level of automatic driving ability to be achieved is automatic driving at high speed congestion and the speed of less than 60 km/h, the Valeo second-generation SCALA lidar equipped with it can be well achieved in the middle of the front bumper.
However, when the installation position is low, it is also necessary to consider the problem of being easily obscured by the front, so it also requires the cooperation of other sensors.
The scheme of set degree mounting on the front cover of the car belongs to the more central position. Under the premise that the AT128 lidar itself has a detection distance of 200 meters at 10% reflectivity, a moderate field of view can be obtained.
If it is in a high-speed scene, there are generally fewer obstacles nearby, and the roof lidar can have a better view of the distance. Adopters of this program include NIO ET7, including the Ideal L9.
Of course, if you are a local tycoon, all-round coverage is naturally the best.
The advantages of the set degree dual lidar scheme are mainly reflected in the horizontal FOV.
First of all, because the lidar currently on the mass production car is basically semi-solid, it cannot reach the mechanical 360-degree level FOV. As for why not use the mechanical type, on the one hand, it is expensive, on the other hand, it is ugly, and then it is also delicate, for details, please refer to the "LiDAR Blowout On the Car" previously published by the intelligent driving network, what happened this year? 》。
The ideal L9 and set degrees use the Hesai AT128 lidar level FOV of 120 degrees.
At this point, the advantages of using two lidars are obvious. On horizontal FOV, a single lidar can only achieve 120-degree coverage, while two can achieve 180-degree coverage. In the overlapping area of 60 degrees directly in front, due to the high density of point clouds, its recognition ability is also stronger and the accuracy is higher.
Of course, what is being discussed here is simply considering the impact of installation in different locations on FOV when all other variables are the same. In terms of practical effects, it is naturally affected by the performance of lidar itself.
In terms of horizontal FOV, Xiaopeng said that he had also considered installing two lidars on the roof. "We initially wanted to put two on the roof, but no matter how designed, they resemble rabbit rake ears, but then we gave up."
——03——
Appearance, engineering and other aspects of the impact
This involves other considerations when choosing the installation location, such as appearance.
Lee wanted to say that the only problem with mounting on the roof of the car was that it was too much like a Gundam warrior and needed to get used to it.
I have to say that the roof lidar shape of the ideal L9 is indeed a bit difficult to say, and Weilai's treatment is still quite pleasing.
But no matter how it is designed, it is inevitable that there will be an extra drum bag on the roof of the car. This not only affects the appearance, but also affects the wind resistance performance of the car.
In the end, Xiaopeng chose to install it at the headlights of the car on both sides to do hidden treatment.
Like the Audi A8 and Mercedes-Benz EQS, which were the first to carry lidar, their lidar hardware is also integrated on the bumper, which has almost no impact on the appearance.
In addition, many details such as engineering issues need to be considered when choosing the installation location.
For example, Liangdao Intelligence believes that in terms of engineering, lidar is installed on the roof of the car, and the impact of mud and gravel impact is relatively small.
However, it is installed on the roof of the car and is difficult to control the use of the cleaning device. In addition, the roof may be too hot due to sun exposure in the summer, which will also increase the rate of product aging.
The main challenge with its pop-up installation scheme is the reliability of the engineering. For example, due to mechanical aging, vibration and other reasons during use, the installation angle is offset, and the requirements for online misalignment detection and correction are higher.
In addition, as Li xiang proposed, installing lidar on the front cover of the car has hidden dangers in pedestrian protection and cannot pass the latest pedestrian collision regulations. The front cover of the car on the market is generally designed to be softer and more elastic, in order to minimize damage when colliding with pedestrians, but it is obvious that this requirement cannot be met after installing lidar.
At the same time, the position of the front cover is also easy to deform in daily small collisions, resulting in easy damage to the lidar, which in turn pushes up the maintenance cost of minor accidents.
In general, where to put lidar is not a one-line thinking question, but a balance and trade-off after comprehensively considering various factors such as perception performance, safety, cost, appearance and engineering.
——04——
Multi-lidar solution
As mentioned earlier, if the cost is not considered, it is more reasonable and safe to install a forward long-range lidar on the roof and 2-4 medium- and short-range angle lidar on the body. Let's take stock of a few schemes that are not bad for money.
The WM M7 is equipped with three lidars, located on both sides of the roof and fenders, using M1 from Sagitar Juchuang, achieving a horizontal detection range of 330 degrees.
The salon car, which high-profile declares that "don't talk below 4", is equipped with 4 lidars for its "mech dragon". Mecha Dragon uses Huawei's 96-line lidar, from the official website map, the position of the 4 should be placed on the roof of the car, one on each side of the front, and one on the rear of the car.
Also using the four-lidar scheme is the Lotus ELETRE released in March, which carries four radars, including two retractable 128-line lidars, also from Hesai. Its layout uses two front wheels and one front and one at the front and one on the roof.
The multi-lidar scheme is basically the scheme of roof forward lidar plus four-week blindness as we said earlier, and it should be said that the safety at the sensing end is worth affirming.
Of course, considering the cost of lidar, the price of these cars is not cheap.
——05——
epilogue
2022 is known as the first year of lidar on board. The so-called first year, that is, there is no experience of predecessors to refer to.
In the process of mass production of lidar on the car, what kind of effect to achieve, what kind of technical route to use, how to use several lidar, how to install, are still being explored.
Just as there is no conclusion as to what technical route of lidar is better, there is no conclusion on where it is installed, and it needs to be determined according to the different needs of the main engine plant.
Liangdao Intelligence said that the mass production of lidar is a long process, and there is still a long way to go from hardware landing to the real mass production on the car.
When it cooperates with foreign OEMs to produce lidar on the car, the other party will provide several thick books of information, which lists the engineering requirements in detail. The consideration of the installation location is only a very small part.
At present, domestic OEMs have not yet formed such a specification. What technology each family adopts and how to install it are still in a state of blooming. Because of this, there are many possibilities for the mass production of lidar.
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