The fierce discussion around "where and how many lidar should be placed" by the three "factory directors" has aroused widespread concern in the industry, and the origin of the matter is the design details of the front part of the first car robot concept of Jidu Automobile on April 18, which for the first time exposed the automatic driving technology scheme from the front cover of the car to the dual lidar. The media forwarded the publicity of Jidu, Li wanted to discuss with Jidu under Weibo, and then He Xiaopeng also posted his own opinions in the circle of friends. The three "factory directors" have their own opinions, so let me analyze what are the advantages and disadvantages of each of these three schemes.
The lidar scheme adopted by these three "factory directors" is also the three most representative schemes used by car manufacturers at present: the ideal use of a single lidar in the front of the roof; the set of two lidars on the front cover of the symmetrical arrangement; Xiaopeng adopts the symmetrical arrangement of two lidars in the position of the bumper under the headlight group.
Roof arrangement, is the current optimal solution?
The ideal way to arrange a single lidar in the front of the roof is a more popular way on the market, not only ideal, like THE NEW ARCHITECTURE OF NIO's ET5, ET7, ES7, Lotus's Eletre, and xiaomi cars exposed by patents, all of which have adopted this method. The above vehicles are arranged on the roof of a lidar, sensing the redundancy, that is, if this one is broken, then there is no spare, which is indisputably inferior to multiple lidar models. But Li Xiang said: There is no difference between putting one and putting two, just put one.
The advantages of this method are well reflected: first of all, the so-called "standing higher, seeing farther", the roof layout of lidar can bring better detection effects, especially SUV models, not easy to be obscured by objects or dirt, its perspective tends to be the driver's visual position, can better start from the driver's line of sight; secondly, the front collision of the vehicle will hardly damage it, the possibility of damage is small, reduce the cost of vehicle maintenance, if the accident collision has endangered the roof, Then the severity of the accident should probably threaten the overall safety of the vehicle, it is not only considering repairing lidar, considering total loss scrapping and replacing the car; moreover, because it is not arranged in the front encirclement or bumper part, it can leave space for cameras, ultrasonic radar and millimeter wave radar, the roof space is relatively large, if necessary, optimize the automatic driving program, increase redundancy, and there is also space to arrange multiple lidars.
There are disadvantages to this method, but I think it is not so important: mainly reflected in the aesthetics of the vehicle, the overall look and feel of the vehicle is somewhat affected, it will feel like lidar is forced to install, which may bring some wind noise problems. At the same time, the roof temperature in the summer may exceed 70 degrees, although the lidar can work within 80 degrees, but the long-term critical to the limit of the working temperature of the working conditions, is bound to affect the life and effect of the lidar.
The sword goes sideways, and the flip lamp design
Set degree using the front cover symmetrical arrangement of two lidar way, this is a very novel way, some similar to the design of the old car in the past, and the set degree confirms that these two lidar can be lifted and lowered, and the flip light is really the same magic, there is no mass production car to use this way, the lidar of the mass production car is bare, can not be put away.
The advantages of this way are: First of all, two lidar can do stronger redundancy, even if one is broken, the other can still work, this advantage is beyond reproach for a single lidar, I think the number of two or more lidar is very important for autonomous vehicles, as an important perception hardware, it relies on lidar in the automatic driving scheme, irreplaceable, can be seen as as important as the walking mechanism of the autonomous vehicle. Just like a large aircraft is designed with a single engine, at least 2, more than 8, even if you lose an engine, you can also ensure a normal aircraft or forced landing, multi-cylinder car, lack of cylinders can also open. At the same time, as Jidu CEO Xia Yiping himself said: "The 120-degree FOV and the 180-degree FOV are still not the same, and the corner case solved is not the same, so there is still a difference in the ability and experience of the product and even the security." "Dual lidar level 180 degree FOV coverage."
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. It can also strengthen the identification of the key area of the vehicle, in the area of 60 degrees FOV directly in front of the vehicle, the dual lidar can be doubled and overlapped, which can greatly increase the point cloud density in this area, and it takes a certain amount of time to form a dense point cloud, but the dual lidar works together to shorten the time, improve safety, and leave more time for the algorithm platform to process data. Set the degree of this lifting design of the lidar, you can take it back when parking, to avoid lidar has been in contact with the outside world, to avoid long-term parking of the wind and sun, so that the lidar has a longer service life, of course, a liter and a drop can also bring a certain sense of science and technology to the vehicle, to the owner of some sense of ceremony.
There are also some shortcomings in this arrangement, and Li wants to point out the problem: First of all, the layout on the cover is not very friendly to the safety of pedestrian collisions, and the edge position of the lidar shell may become a very sharp "weapon" during the collision process Once the collision may bring additional damage to pedestrians, which can actually be optimized, and the lidar can be immediately put in at the moment of collision, protecting pedestrians and avoiding damage to lidar. I think there is a point to pay extra attention to, that is, the pedestrian protection device of the cover, once the pedestrian protection is triggered, the cover bounces up, this light pedestrian protection device is a lot of maintenance costs, and if the lidar is damaged in the process of the cover bouncing up, the owner will really cry. There is also a point to note, that is, the vibration problem, because the set degree is the use of Hesai AT128 hybrid solid-state lidar, laser emitter vertical arrangement, the formation of a laser line, and then through a 1-dimensional rotor, the line into a surface, the internal presence of a fixed rotor bearing, the cover and the body of the vibration frequency is not necessarily consistent, may affect the rotation frequency of the bearing, and then affect the accuracy of the lidar work.
Traditional manufacturers design platforms for this purpose, the most cost-effective for car companies?
But when it came to the discussion between Li Xiang and Xia Yiping, He Xiaopeng said bluntly: "Two lidars are definitely far better than one in terms of performance, and the difference can be seen in the future in the urban NGP and robustness." In fact, the hardware configuration simply represents a possibility of potential, ultimately a balance of safety, cost, scenario and capability, still the barrel effect rather than sprint logic. He Xiaopeng also revealed: "We first wanted to put two on the roof, but no matter how designed, they are similar to the rake ears of rabbits, and then we gave up." "The Xiaopeng P5, which has already been listed, and the Xiaopeng G9, which will be released soon, both have two lidar symmetrically arranged on the bumper under the headlight group. A large number of models on the market have adopted this arrangement, the earliest mass production of L3 Audi A8, Mercedes-Benz S-Class, Polar Fox Alpha S, Salon...
This arrangement is more traditional, just like millimeter wave radar and ultrasonic radar, lidar is also a kind of radar, it is arranged with other radar, it is indeed very reasonable, everyone does this, there is indeed a reason to do so: without affecting the overall appearance of the vehicle, the lidar is tolerated, avoiding the "sense of abruptness". At the same time, it will not affect the collision safety as the concentration degree, the front position of the vehicle is relatively "empty", no longer need to find a place for the lidar, save costs, and can also use a lower-cost double wedge prism lidar.
The disadvantages are: First of all, the bumpers on today's models are mostly made of plastic, quite soft, and can reduce the damage to pedestrians as much as possible in the event of a pedestrian collision, but this also suffers from expensive lidar on the front of the car, the bumper may not protect the lidar, and a small collision may also require high maintenance costs. Secondly, the lidar arrangement position is low, easy to be obscured, for the detection of long distances in front, may not achieve the expected effect, but also easy to be obscured by dirt, affecting the detection effect.
There will also be new solutions, focusing on cooperation
Above, we analyzed the advantages and disadvantages of the three common lidar arrangements, where the lidar is placed, depending on how the car company balances the relationship between the perception effect, the degree of appearance and aesthetics, the hardware cost, the collision safety and the maintenance cost. In fact, these ways we see now are relatively conservative, since each has advantages and disadvantages, it is also possible to have a way to integrate the strengths of each family in the future, such as in the front of the car, the cover, the roof are arranged, and the redundancy is increased in an all-round way.
At the same time, it should be emphasized that lidar is only one of the automatic driving perception hardware, no matter where it is placed, the number is large, it must be coordinated with other sensors and algorithm platforms, and the specific energy consumption of each program is to be considered, this article only makes an objective analysis of the advantages and disadvantages of the lidar layout in different places, as for its specific effect, but also the specific analysis of specific problems, you can look at the previous article, and the detailed analysis of each automatic driving program.