This article is from the WeChat public account: TopMove (ID: topmove2020) , author: Verification of Zhao Xiao, from the cover: Oriental IC

The car parked in front is not a real car, it is a “balloon car”. This is the AEB (Automatic emergency braking function) / span> Test the nickname of the item.

Although it looks like an inflatable block disguised as the back of a car, there is something else in it. There is a triangular cone in the middle of the interior, and there is an aluminum plate on the top and bottom. Even the materials wrapped on the outside have requirements: they must be absorbing materials so that the rear car can recognize it as “a car” instead of An iron plate hanging in front of the balloon cart.

When the Chery Tiggo 8 riding in Geek Park was traveling at a speed of 40km / h, when it was about 2 meters away from the balloon car, the inside of the vehicle issued a sirens sound and took an emergency The brake measures finally stopped at about 50cm from the balloon car.

The vehicle stopped automatically in front of the balloon car | live shooting

This is the complete car-to-car AEB test process. As a very important function in the L2 level automatic assisted driving system, it can guarantee active safety. When the conditions are met, the driver does not take any measures in the face of a crisis situation, and the machine can make emergency actions autonomously. Because of this, AEB has even been called the “light of assisted driving” by some people.

Will AEB deserve this title?

The superior of AEB——PEBS

If you want to ask, first look at why. To talk about today’s protagonist AEB, let’s start with PEBS.

Predictive Emergency Braking System, (Assistance) system, referred to as PEBS, belongs to the active safety of L2 level automatic assisted driving system system. You can think of it as a collection of safety features, including PCW (predictive collision alarm) , AEB (Automatic Emergency Braking) , and EBA (Emergency Brake Assistance) .

When the vehicle is potentially dangerous, it is when PEBS let go. However, the criteria for “potential danger” must be determined by the machine itself. Supplier of Automated Assistance System at L2 levelAccording to Bosch, there are roughly four stages in the machine’s judgment of potential dangers. For example, when the distance is relatively long and the speed is fast, the vehicle will issue an audible warning and the brake system will be pre-charged at the same time. In the event of a crash, the system automatically adopts emergency braking, and if equipped with a seat belt tightening function.

Of course, this is only a rough standard. In actual situations, the judgment of the machine will change due to various factors, such as the speed of the vehicle and the vehicle in front, whether the driver takes corresponding measures, etc. Determine if it is necessary or not, and how to remind the driver.

Several stages triggered by AEB function | Bosch

In terms of equipment, the L2 level automatic driver assistance system requires millimeter-wave radar and cameras in front of the vehicle to implement the predictive emergency braking function.

The working principle of millimeter-wave radar is also easy to understand. Simply put, the radar will capture the electromagnetic waves of the target object, process it into a signal, and then render it as a graph through an algorithm, so that the machine can depict the shape of the object, which is convenient for performing various functional operations afterwards.

The camera is easier to understand, because the information received by the radar does not fully help the machine “recognize” the target object, and after the camera collects the image, it uses the image information processing unit (ISP) Analyze images to detect vehicles and their lights, pedestrians, lane lines, and other targets in the picture. The camera is divided into monocular, binocular, etc. At this stage, most of the L2 level auto-assisted driving systems are still completed by the millimeter-wave radar + monocular camera, which will not be repeated here.

Automatic driver assistance system with L2 level can be achieved through sensors and cameras on the body | Bosch

Bosch revealed that its L2 auto-assisted driving system is also being gradually installed in the vehicle. Weimar EX5, MG ZS, Geely Borui and other models are all equipped. In 2019, Bosch is expected to land 40 models in China. Currently, dozens of models are equipped, and the specific digital Bosch has not explained.

Because both the millimeter-wave radar and the camera have unique advantages and disadvantages, the two need to be complementary to jointly increase the safety factor of the system, which will be explained in detail later. It is worth noting that to combine these two sensors with completely different properties is not as simple as 1 + 1 = 2.

What are the key points for assisted driving?

Unlike balloon cars, AEB functional tests for pedestrian crossings seem more complicated.

(at a speed of about 30km / h) in the case of low speed driving, a simulated person passes by the front of the vehicle in the driving lane. When the vehicle was about to crash, the vehicle suddenly braked and stopped when a pedestrian passed. At this time, the distance between the person and the vehicle was only about 20cm.

Although the distance is very close, the vehicle has done a good job in AEB testing. If it is difficult, the detection of pedestrians ahead tests the response of the assisted driving system more than the detection of vehicles in front.

AEB functional test for pedestrian crossing | live shooting

Why is this happening? If the real situation, can the safety of pedestrians be guaranteed?

Humans are much smaller than cars. This is a fact that is visible to the naked eye. For the detection of millimeter-wave radars, the reflection intensity of humans on radars is also much weaker. This makes millimeter-wave radar difficult to detect pedestrians ahead.

Mr. Du Yu, manager of the engineering department of the driver assistance system business unit of Bosch Chassis China, told media including Geek Park that the advantage of millimeter-wave radar is its relative to the longitudinal direction when detecting objects ahead Speed, distance and other attribute detection are very accurate. The camera has inherent advantages in judging the characteristics of the object, such as what type of object, and at the same time, the vision-based algorithm is more accurate in determining the displacement of the object in the lateral direction than the radar.

With the double judgment, the system can determine the road ahead, and then decide whether to perform other operations. This is the so-called “data fusion”, the key point of the assisted driving system. When building the system, the data fusion of the two is basically something that must be considered.

AEB functional test for pedestrian cycling scenes | Bosch

As mentioned above, this is a result of 1 + 1> 2. More importantly, data fusion will increase the credibility of the existence probability of the detection target. Data fusion superimposes the existence probability of the same attribute target detected by different types of sensors. Especially when a certain sensor is affected by internal or external factors, such as the camera is affected by strong light, extreme weather, etc., it can avoid the system performance degradation caused by it and ensure the reliable operation of the system.

Examples of data fusion can be found everywhere in the L2 automated driving assistance system. E.g. radar and cameraThe integration can realize the traffic congestion assistance and intelligent cruise assistance functions of L2 level automatic assisted driving. By introducing more sensors (such as four corner radars), automatic lane changes under driver monitoring can also be achieved.

In the driver assistance system, data fusion is the key point | Bosch

Back to the beginning, can the car-to-pedestrian AEB function prevent a car accident?

The answer is no. In the international strictest European new car safety test system Euro NCAP, the AEB function is clearly defined: the brakes that are automatically applied when a vehicle detects a collision is likely to reduce the speed of the vehicle and avoid collisions as much as possible happened.

Decrease the speed of the vehicle instead of stopping it; “avoid as much as possible” rather than completely avoid it. These words all point to one thing: machines really can’t replace humans today.

The staff at the test site told Geek Park that, generally, when a pedestrian is detected and the AEB function is triggered, the vehicle ’s speed reduction by 40km / h is in line with the standard. After the AEB function drops to 20km / h in a short time, it can be regarded as qualified.

In addition, even triggering the AEB function requires certain conditions.

Like a computer phone, if we want to achieve a certain purpose on the device, we must trigger that condition to achieve the goal. The same is true in cars. Even if the device has artificial intelligence, even if its detection distance can reach hundreds of meters ahead, the triggering conditions of the AEB function have many restrictions.

Even with active security features, there are many restrictions | Bosch

The staff at the site told Geek Park that vehicles can only turn on the AEB function at speeds above 4km / h. If the speed is below that level, the sensor’s judgment is inaccurate, so it will not be turned on by default; the vehicle in front encounters an emergency system 2 seconds after activating the AEB function, if the driver still does nothing, the vehicle will restart for idling, because the active safety function will stop after the vehicle is stationary, there is no AEB function; the vehicle needs the AEB function when the vehicle is running smoothly It is likely that the machine will turn on. If the driver constantly adjusts the direction, or the driving speed is very uneven, the machine will not work … There are many similar restrictions.

In September 2019, the American Automobile Association (AAA) conducted a series of tests for AEB and pedestrian detection warning. The results show that these systems, which claim to detect pedestrians and automatically brake, are far from meeting the standards. (at a speed of about 32km / h) when driving at low speeds, there is only a 40% probability that four vehicles equipped with L2 level automatic driver assistance Collisions can be avoided, and if the speed is increased, or if pedestrians are replaced by children, the probability of accidents will greatly increase.

Four cars are testing automatic emergency braking system | American Automobile Association

It is conceivable that only automatic brakes are availablePeople with car assistance (AEB ) people at the L2 level of automatic driver assistance system dare to spread the steering wheel on the road and use a bottle of water to deceive the machine. What a dangerous thing. For car companies or suppliers, while ensuring safety, they must also take into account the driving experience. For consumers, knowing the reality is the biggest responsibility for personal safety.

This article is from the WeChat public account: TopMove (ID: topmove2020) , author: Zhao Zi Xiao