Airbags

9.3.1 Description of airbags

Airbags are components of the passive safety system.

This system has saved hundreds of human lives. The essence of this system is to smoothly stop the body, which, we can say, flies towards the front of the car in case of frontal collision.

Note
Let's make a reservation at the very beginning: the maximum effect when the airbag deploys can be achieved only in case if the driver is fastened with seat belts.

Initially, there was only one airbag - for the driver. It was located in the steering wheel hub (it's right in the center). But over time, the number of airbags reached seven in order to prevent the negative effects of the collision.

9.3.2 Types of airbags

At the moment there are the following types of airbags (in Figure 9.3 they are presented in a deployed form): frontal (or front) airbag, side airbags, side curtain airbags and knee airbag.

Figure 9.3 Example of location of airbags in the car.

9.3.2.a Frontal airbag

• Frontal (or front) airbag, can be driver's or passenger's. These airbags are installed inside the hub of the steering wheel and the dashboard on the passenger side, respectively. They are triggered in case of a frontal collision of the car.

9.3.2.b Side airbags 

• Side airbags. Modules of these airbags are most often installed in the sides of the seat backs. They are triggered in case of a side impact.
• Side curtain airbags are installed along the edge of the passenger compartment ceiling on each side. They are designed for avoiding hitting the head on the side windows in case of a collision.

9.3.2.с Knee airbag

• Knee airbag. They are designed for dampening the driver's knee impact on the dashboard in case of a frontal collision. The need for installing this airbag is because that the legroom on the driver's side is quite limited. Due to this, in case of a strong frontal collision, a person can move a considerable distance, which will lead to an impact on the elements of the dashboard and the stiffness bar of the steering column. 

Airbags that are built into seat belts for softening the impact in case of a sudden stop are a promising direction in the development of passive safety system.

9.3.3 Airbag system operation

In case of a frontal collision, the impact sensors that are installed on the front of the car body send a signal to the electronic passive safety control unit. From this unit the signal enters the propellant charge, which, when triggered, emits a large amount of gas, thereby inflating the airbag.

Note
Propellant charge (short for "pyrotechnic cartridge") is a device, which is very similar to the most common shotgun cartridge, only without a capsule and warhead. It is filled with a special flammable substance, which is ignited by electric discharge.

Two- and then multi-stage airbag deployments were introduced in the process of improving the airbag system. The fact is that before the airbag was inflated at the same speed, regardless of the speed of the car. There were cases when drivers have received quite serious injuries due to the deployment of airbags in seemingly minor collisions. Therefore, at present the electronic control unit of this system also receives data on speed of the car, and depending on this parameter "decides", with what speed the airbag will work.