Lidar, which Musk once called "something that fools will use", has 13 models of self-driving cars that will be mass-produced in 2022, ranging from one to four.
Not long ago, Jidu's front cover lidar caused a space-to-air discussion between Li Xiang and Xia Yiping, and the hot discussion also reflected the trend of lidar being widely used. So what kind of lidar is there, and where to put it? Today we will take a look at this amazing lidar.
What is LiDAR?
Vehicle-mounted lidar, also known as vehicle-mounted 3D laser scanner, is a mobile 3D laser scanning system and one of the most effective tools for urban modeling. It is mainly composed of three parts: transmitting system, receiving system and information processing, and the basic principle is to install the three-dimensional laser scanner + POS system on the car, which can carry out a larger range of 3D modeling.
It has the advantages of high resolution and high precision, fast reaction speed, and small working environment. Compared with the commonly used millimeter-wave radar, it can be seen that the modeling and imaging ability of lidar is superior, and the left side of the figure below is lidar.
At this stage, there are three main types of lidar: mechanical lidar, semi-solid-state lidar and all-solid-state lidar.
1. Mechanical rotary lidar
It belongs to the earliest and most mature radar technology, but there are problems such as large volume and assembly difficulties, and it is impossible to achieve vehicle specification level verification in vehicle applications.
It achieves a coverage of 360° horizontally by rotating, and a vertical coverage by the internal lenses. Compared with other types of lidar, mechanical lidar has more durable and stable characteristics, so the general test vehicle uses mechanical lidar for scanning work.
2. Semi-solid-state lidar
This is the mainstream product of the current vehicle radar, which is classified according to the scanning method: silicon-based MEMS, rotor, galvanometer + rotor and rotary transmission prism.
Semi-solid-state lidar can achieve 120 ° swing, which can achieve scanning at a lower cost and higher accuracy, which is relatively mature at present, and is a technical solution that quickly passes the certification of vehicle regulations, and is currently more suitable for loading needs.
3. All-solid-state lidar
At present, the all-solid-state lidar technology is not very mature, belongs to the experimental stage, and it is difficult to mass-produce for the time being. This lidar does not have any mechanical oscillating structure, so it is smaller and performs better.
In summary, the history of the development of lidar can also be likened to the history of the development of computer hard disks - from bulky and complex mechanical hard disks to lightweight and high-performance solid-state drives. Step by step to improve the development, perhaps soon the solid-state mechanical radar will also be popularized in our daily life.
Where exactly is lidar going to be placed?
There are currently two main schemes regarding where to place lidar. One is to place it on the roof like the Ideal L9, NIO ET7 and Zhiji L7, raising a "small horn" like a watchtower. Another option is to place it near the front bumper, and the Xiaopeng P5 and Polar Fox Alpha S Huawei HI Edition all use this installation scheme. So where is it more reasonable to install?
At present, although a bag on the top of the head has been criticized by many people, it is more appropriate to place it on the roof of the car after comprehensive consideration, mainly for the following reasons.
First, minimize maintenance costs, if placed in the front part of the car, it is inevitable to encounter problems such as rear-end collisions. Referring to the price of lidar, Velodyne's initial 64-line lidar for Google's self-driving car cost 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. Therefore, placing it on the roof of the car avoids increasing maintenance costs.
Second, anti-occlusion. Lidar and millimeter-wave radar are similar in principle, using echo imaging to outline the detected object, if placed in a lower position near the bumper, there may be a situation of being obscured by sludge and the like. Although RoboSense demonstrated at CES last year, the M1 lidar was designed with an automatic cleaning function. But now the models equipped with lidar on the market have not yet been equipped with this function. So for now, lidar may be better placed on the roof of the car.
Third, the detection effect is better. As the saying goes, standing high and looking far, higher lidar positions can bring better detection field of view, help us predict obstacles in front of us in advance, and detect more comprehensively. At present, the farthest detection distance of lidar is generally 100 meters to 150 meters, and the vertical direction can get a greater field of view when placed on the roof, which can make up for the lack of vertical width of some lidar.
Fourth, play a role in protecting pedestrians. According to the pedestrian collision regulations, the front of the car is properly made softer to act as a buffer to avoid injuring pedestrian legs. Because in the event of a collision between a car and a pedestrian, the lower limbs of the pedestrian are the "hardest hit areas" of the injury, although generally not life-threatening, but it is easy to cause disability, bringing a heavy burden to the life of the injured person.
If lidar is installed in the front part of the car, it is bound to increase the rigidity of the front of the car, which will increase the risk of pedestrian injury, so from this point of view, the solution of placing lidar on the roof of the car will be better.
At the same time, the lidar placed on the roof of the car also has some disadvantages. For example, the most controversial styling design issues, such as waterproofing, wiring harness arrangement, etc., as well as the inevitable blind spot problem.
Lidar will have a certain blind spot for low obstacles in the near field. If the lidar is placed in the bumper position, its recognition of low-field obstacles in the near field will be better, such as the Mercedes-Benz EQS, which chooses to integrate 1 lidar in front of the bumper.
Is the more radar the better?
After analyzing the advantages and disadvantages of each location above, some people may say, "That's easy to do, it's better to add a few more lidars." "It is true that the more lidar the better, but considering the current level of software processing, the method of blindly increasing the number of radars is actually not advisable." Because lidar has a very large transmission volume and fast detection time, so its requirements for the controller are very high, too many radars may lead to the current chip overload situation, there will be heat, serious power consumption and other issues.
Assisted driving ability is a system, not just look at which parameter can be determined, the need for further deep integration calculations, that is to say, the number of lidar is no more, without a more advanced automatic driving software platform is also futile.
Therefore, with the current technology, the more the better, but in the case of technology can be achieved, the more the better.
Other integration locations
In addition to the two mainstream integrated positions above, there is also a design that is placed on the front cover and windshield.
In the front part of the first car robot concept released by Jidu, the design scheme of the lidar was adopted, and the founder of Ideal Car, Li Xiang, did not agree with this design, believing that the design of placing lidar on the engine cover could not pass the latest pedestrian collision regulations, and the scheme placed on the roof was better than placing two lidar on the cover.
In addition, Apple filed a patent application for an on-board lidar device in March 2020, designing it to be installed behind the vehicle's windshield.
This does solve the problems of modeling and wind resistance placed outside the car, but the problem of signal attenuation caused by glass cannot be solved for a while and a half.
Compared to cameras, the windshield of the curved structure causes the lidar electromagnetic wave signal to attenuate. Moreover, the light transmittance of the windshield under the provisions of the "Automotive Safety Glass" is only not less than 70%, which is not a highly transmittable glass that meets the needs of lidar, and the transmittance of high-transmittance glass is required to reach more than 90%, which will bring about an increase in cost. At present, it is still difficult.
Write at the end
In the current situation where the technical level is limited and the number of lidar is limited, the layout of the roof lidar is the optimal solution at present. At the same time, in improving automatic driving, it is necessary to carry out data training, develop high-precision maps and mature software, and comprehensively improve the accuracy of automatic driving.
With the advancement of science and technology, lidar technology is becoming more and more mature, and the demand for lidar in the automotive industry is becoming more and more strong, and we believe that it will have a very grand development space in the future.