Exploring future autonomous driving technology: 4D millimeter wave radar

The current realization of self-driving car perception is inseparable from sensing equipment such as lidar, on-board cameras, and millimeter-wave radar installed on the vehicle. By collecting data on the traffic environment around the vehicle, self-driving cars can surpass or even surpass humans. eyes to perceive the surrounding world and provide more accurate and rich environmental information for the decision-making and planning module, so that self-driving cars can drive safely.

The stacking of sensor hardware allows self-driving cars to drive more safely on the road, but on the other hand, a single hardware device cannot obtain all required data. , and in many extreme environments, hardware equipment will also have problems. For example, in extreme weather such as heavy fog and heavy rain, the measured data of lidar will have large deviations; millimeter-wave radar does not have the ability to measure altitude, and it is difficult to judge the stationary position ahead. Whether the object is on the ground or in the air; on-board cameras can only capture 2D plane images. Even with the assistance of deep learning, they still cannot accurately measure the distance between surrounding objects and self-driving cars. Therefore, self-driving cars require different hardware equipment. Working simultaneously, autonomous vehicles can achieve perception accuracy and capabilities that are no less than those of humans under any circumstances. The emergence of 4D millimeter wave radar will bring revolutionary changes to autonomous driving.

What is 4D millimeter wave radar

In autonomous driving perception, millimeter wave radar, as one of the most important sensors in autonomous driving, is a crucial one. ring. However, because it does not have the ability to measure height, it is difficult to determine whether the stationary object ahead is on the ground or in the air. When encountering ground or air objects such as manhole covers, speed bumps, overpasses, traffic signs, etc., it is impossible to accurately measure the height data of the object. . The emergence of 4D millimeter wave radar will make up for this problem. 4D millimeter wave radar is also called imaging radar. Based on the original distance, speed, and direction data, it adds a high degree of analysis of the target, and the fourth Dimensions are integrated into traditional millimeter wave radar to better understand and map the environment, making the measured traffic data more accurate.

As early as 2020, Tesla announced that it would add a 4D sensor technology to Tesla cars. Through 4D sensor technology, existing work The range is tripled for more traffic information. 4D millimeter wave radar can effectively analyze the contours, behaviors and categories of measured targets. It can adapt to more complex roads and identify more small objects, blocked objects and monitoring of stationary or horizontal objects, so that it can accurately understand the needs of vehicles. Under what circumstances should you brake? Compared with 3D millimeter wave radar, which can only measure three data: azimuth angle, elevation angle and speed, 4D millimeter wave radar can obtain more data, thus providing more reliable information for decision-making and planning.

Solution of 4D millimeter wave radar

4D millimeter wave radar was first proposed by an Israeli company in 2019. In early 2020, Waymo announced its fifth-generation autonomous driving 4D millimeter wave radar is launched in the perception suite. In the same year, Continental launched the first 4D millimeter wave radar mass production solution and stated that BMW would be the first car company to implement it. At 2021CES, 4D millimeter wave radar is also gaining momentum. Many manufacturers have unveiled their products. Texas Instruments, Mobileye and other companies have successively launched or updated 4D millimeter wave radar solutions.

Last year, Aptiv unveiled its next-generation L1~L3 autonomous driving platform, claiming that its sensor suite included 4D millimeter wave radar; ZF said it had obtained a production order for 4D millimeter wave radar from SAIC Group , will be officially supplied in 2022; Bosch launches the 5th generation radar extreme version, namely 4D millimeter wave radar, for the first time in the Chinese market.

4D millimeter wave radar, like traditional radar, will not experience great deviations when working under extreme weather conditions, and after increasing the elevation angle, it can form point cloud images, which means that 4D millimeter wave radar The radar can not only detect the distance, relative speed and azimuth of the object, but also detect the vertical height of the object in front as well as stationary and laterally moving objects in front, which will make up for the shortcomings of traditional radar in detecting static targets. At present, there are two main technical solutions for 4D millimeter wave radar:

• One is for 4D millimeter wave radar companies to independently develop multi-channel array radio frequency chipsets, radar processor chips and post-processing software algorithms based on artificial intelligence.
• The other is a solution based on traditional radar chip suppliers, which uses multi-chip extreme connection or software algorithms to achieve dense point cloud output and recognition. ​

The main feature of 4D millimeter wave radar is that the angular resolution is very high. The angular resolution of the front 4D millimeter wave radar can reach 1 degree in azimuth and 2 degrees in elevation. , when a self-driving car equipped with 4D millimeter wave radar detects road information, it can directly detect the outline of objects around the vehicle. For example, when road information is relatively rich, such as when pedestrians and vehicles are mixed together, 4D millimeter wave radar can directly identify pedestrians and vehicles, and can determine the movement of the corresponding objects (whether they are moving and the direction of movement).

4D millimeter wave radar can also detect geometric shapes, such as the length and width of tunnels in tunnel scenes. The emergence of 4D millimeter wave radar has made up for the performance shortcomings of traditional millimeter wave radar in a targeted manner. It not only increases the dimension of 3D, but also brings about comprehensive upgrades in detection accuracy, sensitivity, resolution and performance, giving autonomous driving more capabilities. High safety is expected to make millimeter wave radar one of the core sensors in autonomous driving systems.

The future development trend of 4D millimeter wave radar

According to analysis by industry insiders, the large-scale implementation of 4D millimeter wave radar is coming soon. In terms of marketization, the current technology is becoming mature, and there are many innovative algorithms in the process of productization. Many car manufacturers already have requirements for equipping new vehicles. Among them, automatic parking and L3 and above level autonomous driving require 4D imaging. In fact, since last year, many 4D millimeter wave radar products have been installed in vehicles for road testing. and prepare for mass production.

For example, NXP announced that the industry’s first dedicated 16nm millimeter wave radar processor S32R45 will be used for customer mass production for the first time starting in the first half of the year. Mobileye, a subsidiary of Intel, is also actively promoting the development and application of 4D millimeter wave radar. Mobileye CEO Amnon Shashua emphasized the application scenarios of 4D imaging millimeter wave radar in automobiles in this year's CES speech.

He said: "By 2025, except for the front of the car, we only want millimeter-wave radar, not lidar." In Mobileye's plan, millimeter-wave radar-based radar will be launched by 2025 /Lidar's consumer-grade autonomous vehicle solution, the car is equipped with a radar-LiDAR subsystem, and the vehicle only needs to be equipped with a forward-facing lidar and a 360-degree fully-covered millimeter-wave radar to achieve autonomous driving tasks.

Autonomous driving technology cannot rely on a single sensor to dominate the world and become an industry consensus. According to the current market understanding of autonomous driving, there is no one-size-fits-all sensor, because the market has many segments and different levels of autonomous driving. In the end, it is very likely that cameras and radars will coexist because their advantages and disadvantages are very complementary. What is special is lidar. The author believes that there is a great possibility that 4D millimeter wave radar solutions can reduce or replace the use of lidar. 4D millimeter wave radar is still in the early stages of development, but the author believes that its performance will be greatly improved in the future, and under ideal circumstances, it can eventually replace lidar. ”

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