Emergency braking systems
Content
One of the key devices that prevent accidents or reduce their consequences is the emergency braking system. It is necessary for the effective operation of the braking system in a critical situation: on average, the braking distance of a car is reduced by twenty percent. Literally BAS or Brake assistant can be translated as “brake assistant”. The auxiliary emergency braking system (depending on the type) either assists the driver in emergency braking (by “pressing” the brake pedal), or automatically brakes the car without the driver's participation until it comes to a complete stop. In the article, we will consider the device, principle of operation and types of each of these two systems.
Varieties of auxiliary emergency braking systems
There are two groups of emergency braking assist systems:
- emergency braking assistance;
- automatic emergency braking.
The first creates the maximum braking pressure resulting from the driver pressing the brake pedal. In fact, it “brakes” for the driver. The second one performs the same function, but without the participation of the driver. This process happens automatically.
Emergency braking assistance system
Based on the principle of creating maximum braking pressure, this type of system is divided into pneumatic and hydraulic.
Pneumatic Emergency Brake Assist
The pneumatic system ensures maximum efficiency of the vacuum brake booster. It consists of the following elements:
- a sensor located inside the vacuum amplifier and measuring the speed of movement of the amplifier rod;
- electromagnetic rod drive;
- electronic control unit (ECU).
The pneumatic version is mainly installed on vehicles equipped with anti-lock braking systems (ABS).
The principle of the system is based on the recognition of the nature of emergency braking by the speed at which the driver presses the brake pedal. This speed is recorded by the sensor, which transmits the result to the electronic control system. If the signal is greater than the set value, the ECU activates the rod actuator solenoid. The vacuum brake booster presses the brake pedal against the stop. Even before the ABS is triggered, emergency braking takes place.
Pneumatic emergency braking assistance systems include:
- BA (Brake Assist);
- BAS (Brake Assist System);
- EBA (Emergency Brake Assist) - installed on Volvo, Toyota, Mercedes, BMW cars;
- AFU - for Citroen, Renault, Peugeot.
Hydraulic Emergency Brake Assist
The hydraulic version of the "break assist" system creates maximum fluid pressure in the brake system due to the elements of the ESC (Vehicle Stability Control).
Structurally, the system consists of:
- brake pressure sensor;
- a wheel speed sensor or a vacuum sensor in a vacuum amplifier;
- brake light switch;
- ECU.
The system also has several types:
- HBA (Hydraulic Braking Assistance) is installed on Volkswagen, Audi;
- HBB (Hydraulic Brake Booster) is also installed on Audi and Volkswagen;
- SBC (Sensotronic Brake Control) - designed for Mercedes;
- DBC (Dynamic Brake Control) - put on a BMW;
- BA Plus (Brake Assist Plus) - Mercedes.
Based on the signals from the sensors, the ECU turns on the hydraulic pump of the ESC system and increases the pressure in the brake system to the maximum value.
In addition to the speed at which the brake pedal is depressed, the SBC system takes into account the pressure on the pedal, the road surface, the direction of travel, and other factors. Depending on the specific conditions, the ECU generates the optimal braking force for each wheel.
The BA Plus variation takes into account the distance to the vehicle ahead. In case of danger, she warns the driver, or brakes for him.
Automatic emergency braking system
The emergency braking system of this type is more advanced. It detects a vehicle in front or an obstacle using radar and a video camera. The complex independently calculates the distance to the vehicle and, in the event of a possible accident, reduces the speed. Even with a possible collision, the consequences will not be so serious.
In addition to automatic emergency braking, the device is equipped with other functions. Such as: warning the driver of the danger of a collision by means of sound and light signaling. Also, some passive safety devices are activated, due to which the complex has a different name - “preventive safety system”.
Structurally, this type of emergency braking system is based on other active safety systems:
- adaptive cruise control (distance control);
- exchange rate stability (automatic braking).
The following types of emergency automatic braking systems are known:
- Pre-Safe Brake - for Mercedes;
- Collision Mitigation Braking System, CMBS are applicable for Honda vehicle;
- City Brake Control - Fiat;
- Active City Stop and Forward Alert - installed on Ford;
- Forward Collision Mitigation, FCM- Mitsubishi;
- City Emergency Brake - Volkswagen;
- City Safety is applicable to Volvo.
