Let’s talk about our views on AEB automatic emergency braking

Focus on automotive technology and analyze industry trends and waves of change

Today we will talk about the topic of automatic emergency braking system AEB - why does it generally feel that AEB has no sense of existence? Why can't we just rely on AEB?

Part 1. What is automatic emergency braking (AEB)?

Let’s start with the definition of AEB. AEB (Autonomous Emergency Braking) is not only the active safety design of the car, but also a function in the assisted driving design. Specifically, it automatically activates the car's brakes when a potential collision is detected; it can also increase braking force if the driver has applied the brakes but the braking force is not enough to prevent a collision.

The purpose of the AEB function is to reduce the probability and harm of accidents during the development stage of traditional automobiles. If the automatic driving assistance function of L3 and above is to help users drive, the basic function of AEB, L1, is to assist in braking when the user is about to collide, which is life-saving.

●Basic principles of AEB system (and key algorithms)

During the design process, the AEB function detects potential collisions, which introduces a concept of time to collision.

Collision time TTC (Time-To-Collision) refers to the time required for a moving vehicle to calculate that it may collide with the object in front. It is defined as the distance between the vehicle and the obstacle divided by the relative speed. Calculations take into account expected vehicle trajectories, road geometry, traffic control, and relative position and speed. This data can be used to evaluate the safety of the moving vehicle and road environment.

The key to AEB is the collision avoidance algorithm. The collision avoidance algorithm determines the timing and logic of early warning. Its core issue is to determine the appropriate intervention moment. What most users need is to intervene only when it is relatively dangerous, that is, when the TTC is small enough, AEB should take braking measures. Here are a few more principles:

◎ First, it cannot affect the user experience: the braking moment should be later than the driver’s latest braking moment and the driver’s latest steering moment; - translated into vernacular, if the driver has enough reaction time to operate the brakes by himself Or steering, AEB should not start prematurely.

◎ The second is to ensure braking efficiency: the braking time should be earlier than the latest braking time of the braking system to stop the vehicle to achieve the purpose of collision avoidance.

As the requirements of the AEB system expand, AEB perception needs to identify vehicles, pedestrians, and even more scenes that may be encountered: such as cyclists, children, etc.

● AEB trigger conditions

When the vehicle is driving, the AEB system algorithm calculates the current motion status of the vehicle and the vehicle in front in real time:

◎ When the TTC value is less than the threshold of the forward collision warning system FCW (Forward Collision Warning), the system uses visual, auditory or tactile alarms to alert the driver;

◎ When TTC is less than the AEB threshold, the system applies emergency braking at a certain deceleration rate.

Judging from the domestic test requirements, the test is mainly based on 20, 30 and 40 km/h, and the test is conducted at higher speeds of 50, 60, 70, and 80 km/h. During the test, the vehicle is at a plus or minus 50% offset from the vehicle in front. Set rate. Just like the daily scenarios mentioned earlier, due to differences in design, it is possible that AEB may not brake for you.

Part 2. Emergency Brake Assist (EBA)

Here we introduce a good partner of the AEB function, emergency braking assist (EBA) - in order to make the braking effect better, automobile companies have also designed this function.

Under normal circumstances, most drivers apply only a small amount of force when braking, and then increase or adjust the amount of braking force applied to the brake pedal depending on the situation. Many drivers are also unprepared for the need to apply relatively large braking force, or react too late. EBA understands its braking behavior through the rate at which the driver depresses the brake pedal. If it detects a panic increase in brake pressure on the brake pedal, EBA will initiate full braking force within a few milliseconds, which is faster than most The driver moves his feet much faster and EBA significantly shortens emergency braking distances.

Therefore, whether AEB helps users brake or users themselves see forward warning, automobile companies hope that users will be responsible for this process.

Part 3. Looking forward to the future of assisted driving

With the improvement of autonomous driving assistance systems above L3, the vehicle's perception capabilities will continue to expand during the process of avoiding collisions. The goal is to be able to choose whether to brake or use emergency avoidance to avoid a collision like a human being. Unified motion planning of autonomous vehicles to avoid moving obstacles provides steering correction for collision avoidance purposes, an emergency avoidance function. Especially with the enhancement of perception and computing capabilities, automatic assisted driving systems will decelerate or be specially configured for vehicles.

With the changes in the automatic assisted driving architecture, the improvement of stronger sensors and controller computing power, and even if a large number of V2X Internet of Vehicles functions are deployed in the future, the AEB function will be integrated into the entire automatic assisted driving function as a basic function of the system.

Of course, there will also be L3 automatic assisted driving systems that will leave the final decision to the driver, so until L4 automatic assisted driving, we still have to be responsible for the entire driving process.

Summarize:

The AEB function was originally designed to help users brake in emergency situations. It was introduced as a fundamental feature of vehicle safety as regulators saw the impact this feature had on reducing road fatalities. With the introduction of continuously enhanced functions of automatic assisted driving, AEB will be used in conjunction with automatic lane avoidance of steering. Before manufacturers commit to L4 autonomous assisted driving, it is always the users themselves who ultimately ensure road safety.