Text | Number Seven - Song
This year, which car to have lidar, is definitely the most beautiful boy.
You might say, "That's not just something that's scarce." ”
Not really. Compared to flashy wearing luxuries, it really upgrades the driving ability of the car. We like to compare radar to the human eye, compared with the most commonly used millimeter-wave radar, if the lidar is 2.0 vision, millimeter-wave radar is 0.5 vision. If you look at the imaging comparison between lidar and millimeter-wave radar, is the former more clearly visible?
But although good things should be placed in the most eye-catching place, who likes to bite a bag on the head. If you look at the bangs screen of the Apple mobile phone, even if the split screen is powerful, the heart is still a knot. Therefore, it is not surprising that the recently released ideal L9, as well as the Weilai ET7 and Zhiji L7 released last year, were controversial by netizens.
Does lidar have to be placed on the roof of the car?
In fact, lidar is not mandatory to be placed on the roof of the car. For example, Xiaopeng P5 and Polar Fox Alpha S Huawei HI Version have chosen to put lidar on the front bumper.
Judging from the lidar properties, they all belong to solid-state lidar (the other is mechanical lidar).
Solid-state lidar can not be rotated, the detection angle is usually only 120 °, so the position must be uniform. The Xiaopeng P5 is two lidars, so it is chosen to be placed on both sides. The Polar Fox Alpha S Huawei HI Edition has three lidars and one on the left, center, and right front bumpers.
So obviously can be placed on the front of the car, some car companies still choose to put a bag on the head, is this their own "point of controversy"?
Whether it is self-seeking or some mystery, we should not rush to conclusions.
This matter, in fact, depends on how the car company weighs it.
From the perspective of the need for single lidar detection, placing it on the roof of the car is a common choice in the industry.
The red box in the following figure is a common layout of lidar, and Weilai ET7 and Ideal L9 use lidar to be arranged in the middle of the roof front. Or Waymo tests the Honeycomb mechanical lidar on the top of the car, because to meet the 360° rotation, mounting on the roof is also the most suitable.
The first reason why the industry generally chooses this way is to avoid increasing maintenance costs.
Velodyne initially offered 64-line lidar for Google's self-driving car for as much as $80,000. The solid-state lidar HAP used by Xiaopeng P5, because it is an upgrade of DJI's Livox based on the Horiz series of products, the unit price of HAP has finally been reduced to several thousand yuan, but it is still a wallet dripping blood.
If placed on the front of the car that is most prone to collision, I am afraid that the driver's mentality and driving skills must be honed
Placing lidar at a high altitude is also good for anti-occlusion.
From the perspective of working principle, lidar and millimeter-wave radar are similar in principle, and they all use echo imaging to construct the detected object, which is equivalent to the difference between human detection with both eyes and bats relying on ultrasonic detection.
If placed in a lower position, be careful not to be obscured by sludge, etc.
The lidar sensing method is to use light in the form of pulsed lasers to measure the range by analyzing the time-of-flight (ToF) of the returned signal
In order to avoid the impact of sludge, RoboSense designed the automatic cleaning function of the M1 lidar shown at CES last year. But now the models equipped with lidar on the market have not yet been equipped with this function.
In addition, the higher position of the lidar can also help improve the detection effect.
When lidar detects, the maximum value of measurement is a very important parameter, which can help us predict as early as possible. As the saying goes, standing high to see far, now the mass production of lidar detection distance is generally 100 meters ~ 150 meters (for 10% reflectivity target), the position is slightly higher, more conducive to the realization of long detection distance.
When it comes to parameters, the vertical detection of lidar is also critical. For example, the SCALA Gen.1 (the first generation of products in 2017) can only see lower positions due to the small vertical field of view angle (see red in the figure below). Therefore, the high position can also make up for the lack of vertical test width of some lidar.
Of course, it does not have to be solved by the elevation position, SCALA Gen.2 (the second generation of the 2021 product) will increase the vertical viewing angle by 3 times, but obviously it takes more effort and time to do it, and the time span of these two products is as long as 4 years.
Finally, there is the reason for pedestrian protection.
Recently, Li wanted to comment on the design of the SET DEGREE SIMUCar is very interesting, he believes that lidar is not suitable for the bonnet, because this model can not pass the latest pedestrian collision regulations. Indeed, affected by pedestrian protection regulations, even if the wind is like jumping lights and setting up signs, it is not obediently withdrawn from the historical stage.
It's just interesting that Lee would think that the LIDAR of jiduSIMUCar would be placed on bumpers and fenders. But why doesn't its ideal L9 do that? Of course, this may be the reason for the context, and we don't need to cut the words. Plus, as mentioned above, there are other benefits to being placed on the roof of the car.
And the best pedestrian protection design is not to put lidar on bumpers and fenders. This is because the front of the car is properly soft can effectively avoid hurting the legs of pedestrians, if the lidar is placed on the front of the car, it is obvious to increase the rigidity, and the two requirements are contradictory.
In fact, in order to protect pedestrians, there is now a "pedestrian protection leg type test", this long strip of experimental blocks, can even simulate the rupture of the cruciate ligament of the knee. Friends who like to watch the NBA must know that the sharpshooter and defensive gate Klay Thompson was unable to play for two years because of this injury, and his athletic ability was seriously weakened after his comeback.
The main standard for this test (GB24550-XXXX Car Crash Protection Standard for Pedestrians) will also become a mandatory national standard on July 1, 2024. The most taboo thing for car companies is the drastic adjustment of technology, so instead of changing it at that time, it is better to fix a model at the beginning.
Why isn't lidar designed at the windshield?
It must be admitted that lidar placed on the roof of the car not only affects the appearance value, but also increases the wind resistance. Although the roof plan can convince everyone from the engineering principle, this "straight male thinking" still makes everyone a little uncomfortable.
It's like you're reasoning with your girlfriend, the problem is: she understands the reason, but she'll certainly say you don't understand her.
Don't rush.
How to reconcile this problem, there is indeed another idea, that is, to integrate lidar on the windshield. This can not only meet the technical needs, but also has a high appearance. You see, Tesla installed the trinocular camera behind the windshield. So wouldn't it be nice to simply replace the camera with lidar?
This integrated camera includes a front-view wide-field, main-view, and narrow-vision camera
Apple filed a patent application in March 2020 for an in-vehicle lidar device designed to be mounted behind a vehicle's windshield to provide real-time 3D vision for self-driving cars.
However, this technology cannot be so simple to complete the port.
Above, we mentioned that lidar is to emit a laser beam layer outward, receive reflected back wave imaging, compared to the camera, the curved structure of the windshield will cause the lidar electromagnetic wave signal to attenuate. Moreover, the light transmittance of the windshield under the provisions of the national standard GB 9656-2016 "Automotive Safety Glass" is only not less than 70%, and it is not a high transmittance glass that meets the needs of lidar (the transmittance requirement is more than 90%).
To solve this problem, a special windshield of optical grade is required. It has controlled refraction and can be used in sensor applications to avoid signal attenuation.
We also ignore some rumors about Apple's dissolution of the car-making team, according to the revealed goal of ensuring the realization of mass production by 2025, according to this schedule, whether Apple's first model can use lidar, and whether lidar can use the scheme described in the patent, I think there is a great difficulty.
But Apple is speeding up work on the project, with the goal of building an electric car with fully autonomous driving capabilities, but without the lidar blessing, there will be great difficulties. Apple also knew that it would be difficult to do it alone, and found a partner with the European company XenomatiX and the windshield manufacturer AGC. How to develop in the future, we will continue to pay attention.
summary
From millimeter-wave thunder to lidar, automotive technology has improved expectations. But in terms of specific implementations, there is still a lot to discuss. In the existing situation, lidar on the roof is the most cost-effective solution, although it is not beautiful enough, it also needs to optimize the roof design and minimize wind resistance.
Of course, perhaps in the future, this program will gradually be replaced, but a special windshield is not cheap, if you can achieve mass production is good, otherwise the price may be very high.