Tesla spy photos are expected to be equipped with 4D millimeter wave radar.
I think many friends already know about it. Tesla's upcoming HW 4.0 smart driving plan is expected to include 4D millimeter-wave radar. As soon as the news came out, the stocks of major related companies soared. Let the stock market fluctuate and make Musk "really fragrant". What is the capability of 4D millimeter wave radar?
millimeter-wave radar
Before answering this question, we need to know something about the vehicle-mounted millimeter-wave radar.
Working model diagram of vehicle-mounted millimeter wave radar
If we describe the vehicle-mounted millimeter-wave radar in one sentence, I can only say that it has opened the era of intelligent assisted driving-1999 Mercedes-Benz S-class model applied the adaptive cruise function based on millimeter-wave radar for the first time, and this system was named Distronic (Distance Control System).
Mercedes-Benz S-Class with Distronic System
Even if we see that car companies are more willing to use lidar as a facade to promote their intelligent assisted driving ability, in fact, the characteristics of millimeter-wave radar are irreplaceable by lidar.
Millimeter-wave radar is a radar working in millimeter-wave frequency band. Generally, the wavelength of millimeter wave is 1- 10mm, and the frequency is 30-300GHz. After transmitting and receiving electromagnetic wave signals, various parameters of the target (such as distance measurement, speed measurement and angle measurement) are calculated by using Doppler effect.
Doppler effect
Waves with different lengths will be hindered and absorbed in different degrees when propagating in the atmosphere, while the wavelength of millimeter wave is between microwave and infrared wave, so it has the advantages of both. Compared with microwave, millimeter wave has good directivity, high resolution, strong anti-interference ability and better detection performance.
Compared with infrared waves, millimeter waves have less attenuation when propagating in the atmosphere, and can better penetrate smoke and dust, and are less affected by weather. These characteristics determine that millimeter-wave radar has all-weather working ability (except rainstorm).
Because radar involves military use, the frequency bands opened by the state to civilian use are regulated. At present, the mainstream vehicle-borne millimeter-wave radar frequencies in the world are 24GHz (also considered as millimeter-wave frequency), 77GHz and 79GHz, and a few countries, such as Japan, open 60GHz frequency.
The open frequencies of China's vehicle-mounted millimeter-wave radar are 24GHz and 77GHz, so at present, China's vehicle-mounted millimeter-wave radar is divided into 24GHz and 77GHz.
Haila 24GHz millimeter wave radar
Just as sounds with different decibels can reach different distances, millimeter-wave radars with different frequencies can detect different distances. The detection distance of 24GHz is usually 30- 120 m, and the detection distance of 77 GHz is usually more than 200 m.
radio frequency
Seeing that there may be friends with better physics here who want to question me: according to wave propagation theory, the higher the frequency, the higher the resolution and the stronger the penetration ability, but the greater the transmission loss and the shorter the transmission distance; Relatively speaking, the lower the frequency, the longer the wavelength, the stronger the diffraction ability and the farther the transmission distance.
Then why do I say that the detection range of 77GHz millimeter wave radar is farther than that of 24GHz millimeter wave radar? This is related to the structure and technology of millimeter wave radar.
The hardware of millimeter wave radar accounts for about 50%, which is mainly composed of radio frequency front end (MMIC), digital signal processor, antenna and control circuit, and the other 50% is composed of software algorithms.
In the process of building millimeter wave radar
The size of radar antenna is proportional to the wavelength. The 24GHz radar has a longer wavelength, so the antenna is larger, while the 77GHz radar antenna is smaller (the size is about 1/3 of the 24GHz radar antenna), so more antenna elements can be arranged in the same volume.
Generally, the antenna of 24 GHz millimeter wave radar can only transmit 1 and receive 2, while the antenna of 77GHz millimeter wave radar can transmit 4 and receive 4. The gain of the whole antenna array is one of the reasons for the longer detection range of the 77GHz millimeter wave radar.
In addition, the millimeter wave diffraction ability of 24GHz is stronger, just like the game of "playing cards". At the end, there has been a serious information deviation, so the detection information at close range is more reliable.
There are also differences in resolution between them: the minimum resolution distance of 77GHz millimeter wave radar is 3.75cm, while that of 24GHz millimeter wave radar is 60cm.
Domestic 77GHz millimeter wave radar
This means that when the distance between two target objects is 60cm, only 77GHz millimeter wave radar can successfully distinguish, and 24GHz millimeter wave radar will be regarded as only one target object.
Although it seems that the frequencies are different, in fact, their performance is very different, so the usage scenarios are different. At present, the common collocation method of millimeter-wave radar in the industry is 1 forward direction +4 lateral directions (left front, left rear, right front and right rear), which are arranged as follows:
At present, the mainstream millimeter wave radar has the functions of angle measurement, distance measurement and speed measurement, that is, measuring the orientation, distance and speed of the target object. We call it 3D millimeter wave radar. But it has a huge defect, that is, it can't identify static objects.
Due to the lack of altitude information, for 3D millimeter wave radar, ground speed bumps or other static obstacles that do not produce speed information are no different from the overpass above.
If it is detected that the overpass will immediately affect the brakes, it will be too outrageous. Therefore, the algorithm of three-dimensional millimeter wave radar directly ignores the information of these static objects. Even if there is a meteorite in front, the 3D millimeter wave radar will not trigger the brakes.
This may be the reason why a Tesla crashed directly into the stationary car in front in 2020. Millimeter-wave radar chose to close its eyes, and Tesla's vision scheme was not as good as it is now.
Tesla is about to hit a truck in assisted driving mode.
This defect makes millimeter-wave radar deadlocked in the increasingly demanding intelligent driving market until the first 4D millimeter-wave radar was born in 2020.
4D Millimeter Wave Radar and Lidar
4D millimeter-wave radar adds altitude information to 3D millimeter-wave radar, which directly affects the imaging of 4D millimeter-wave radar.
When the wave hits the surface of an object, the reflected wave will carry information such as orientation and distance, and it will appear in the form of point cloud data after coordinate transformation. The images converted by two millimeter-wave radars through software algorithms are as follows:
For example, a person with a body width of 80 cm and a height of 1.7m is running fast. 3D millimeter wave radar will recognize that a horizontal 80 cm dashed line composed of points moves in a certain direction at a certain distance, while 4D millimeter wave radar will recognize that a person with a body width of 80 cm and a height of 1.7m moves in a certain direction at a certain distance.
There is a height-limiting pole 2m long in front and 3m off the ground, and there is a speed bump with the same length below. 3D millimeter-wave radar will recognize it as two almost overlapping dashed lines with a length of 2m, while 4D millimeter-wave radar will recognize it as the barrier-free distance between the two dashed lines with a length of 2m is 3m.
4D millimeter wave radar no longer has the defect that it can't identify static objects. In addition, the price is only 10%-20% of that of laser radar, and its own millimeter-wave radar has the characteristics of long detection distance, strong anti-interference ability, rain and fog unimpeded and so on. 4D millimeter-wave radar is considered as a strong opponent of lidar.
laser radar
Is it feasible to replace lidar with 4D millimeter wave radar? At present, the answer is no.
The essence of 4D millimeter-wave radar and laser radar is to actively detect transmitted signals. The wavelength of 4D millimeter wave radar is 3.9mm, while that of laser radar is usually 905 or 1550nm. Because of the wave propagation characteristics, lidar is almost helpless in the face of rain, fog, sandstorm and other weather, while millimeter wave radar can play a role.
Although both can be imaged, lidar has the advantage of crushing 4D millimeter-wave radar, that is, resolution. The 4D millimeter wave radar on the market can generate about 65438+ million point clouds per second, while the 128 line laser radar can generate 1.4 million point clouds per second.
Imaging effect of lidar
The portrait drawn at 654.38+0.4 million is naturally more accurate than the portrait drawn at 654.38+0.4 million. Not only is the definition of portrait contour different, but the more direct influence is the gap of angular resolution.
The angular resolution of lidar is 0. 1, while that of 4D millimeter-wave radar is 1. That is to say, when the angle difference between two target objects is 1, only lidar can distinguish it.
In the final analysis, in terms of imaging, the resolution of lidar is incomparable to that of 4D millimeter wave radar. At present, 4D millimeter wave radar is more suitable to supplement visual algorithms and help cameras in rainy and snowy weather.
In this way, 4D millimeter wave radar is more suitable for Tesla than lidar.
In addition to the cost, the imaging advantages of lidar are repeated for Tesla's vision scheme. The same disadvantage of camera and lidar is limited by the weather with low visibility, which can only be solved by millimeter wave radar for Tesla.
Millimeter wave radar history
Back to the question at the beginning, maybe many friends will choose China. After all, our current smart driving market is in full swing, but the actual answer is Germans.
1904, Qin Si hoels Meyer, a German, developed the first ship anti-collision radar by using the radio wave bounce detection device on the basis of previous electromagnetic theory and electromagnetic wave experiments, which is the first radar in the world.
1935, British Robert Watson Watt successfully developed a practical radar system, which was deployed by the British Air Force on a large scale. By detecting German aircraft in advance, this system helped Britain resist Nazi Germany's attack and won the "British air war".
Robert Watson Watt
The radar invented by the Germans was used by the British to defeat Germany? It is said that the Germans are very dissatisfied and go back to study hard. Later, the prosperity of automobile industry and 1986 "European Efficient and Safe Transportation System Plan" catalyzed the vigorous development of vehicle-borne radar.
In 20 12, Infineon, a German semiconductor giant, introduced a 24GHz monolithic radar solution, which lowered the technical threshold and manufacturing cost of millimeter-wave radar and promoted its application in various fields.
The research time of millimeter wave radar in China is not long. The products of 24GHz millimeter wave radar only entered China in 20 13 years, while the technology of 77GHz millimeter wave radar in China was blocked abroad.
20 14-20 16 domestic millimeter-wave start-ups were established, among which Huayu automobile, a subsidiary of SAIC, took the lead in researching millimeter-wave radar. 20 16-20 17, domestic 24GHz millimeter-wave radar began mass production, and 77GHz millimeter-wave radar began to appear samples.
Huayu automobile office
Although the global millimeter-wave radar market is still dominated by leading foreign manufacturers such as Bosch, China and Hella. The development of domestic industry is also in a state of vigorous development. Domestic 77GHz millimeter-wave radar has appeared, and leading domestic enterprises such as Desai Siwei, Senstek and Chu Hang Science and Technology already have mass production capacity.
Continental group logo
Finally, I want to say one-sided why foreign countries have better core sensor technology for intelligent assisted driving, while domestic countries have become the core battlefield for intelligent assisted driving.
20 18 Continental Group, a German manufacturer, investigated the acceptance of self-driving cars. Up to 89% of the respondents in China support autonomous driving technology, while 53% in Germany and 50% in the United States.
Deloitte Consulting also conducted a survey. By 20 19, the proportion of consumers in China who feel "dangerous" about self-driving cars is 25%, which is the lowest among the six countries and regions surveyed in Asia.
In 2022, Beijing Daily conducted a survey on China people's acceptance of autonomous driving. The results show that more than 80% of China people accept autonomous driving, which is much higher than other countries.
Saying this is not to let everyone ignore the immaturity of the current intelligent assisted driving technology. On the contrary, we need to accept the limitations of the existing intelligent assisted driving technology more realistically. But these data show that we have a more inclusive and positive attitude towards science and technology, even if we start a little late.
This article comes from AutoLab, the author of Easy Car Number, and the copyright belongs to the author. Please contact the author for any form of reprint. The content only represents the author's point of view and has nothing to do with the car reform.