Air Bag Deployment

Presented By

Dr.K.Manivannan, VIT,Vellore

HISTORY

For years, the trusty seat belt provided the sole form of passive

restraint in our cars.

Debates about their safety, especially relating to children, but over

time most of the country adopted mandatory seat-belt laws.

The first patent on an inflatable crash-landing device for airplanes

was filed during World War II.

Statistics show that air bags reduce the risk of dying in a direct

frontal crash by about 30 percent.

FUNDA’S

Laws of motion:

Moving objects have momentum, Unless an outside force acts

on an object, the object will continue to move at its present speed and

direction.

Suppose objects inside a car are not restrained, they will continue

moving at speed the car is traveling at, even if the car is stopped by

collision.

Basic Function

Detecting when a crash occurs that is essentially based

on deceleration along the longitudinal car axis.

Normal Condition: Deceleration order of 1 g (acceleration due to gravity).

Collision Condition: Deceleration order of 10’s g (acceleration due to gravity).

Reaction Time: 30 msec ( to inflate)

COMPONENTS INVOLVED:

Bag:

It is made of a thin, nylon fabric, which is folded into the steering

wheel or dashboard or, more recently, the seat or door.

Sensor:

It is the device that tells the bag to inflate. Inflation happens when

there is a collision force equal to running into a brick wall at 10 to 15

miles per hour (16 to 24 km per hour).

Inflation System:

In this system, sodium azide (NaN3) with potassium nitrate

(KNO3) to produce nitrogen gas. Hot blasts of the nitrogen inflate the

air bag.

CONSTRUCTION

:

Passenger

Possibility of Air bags in the automobile:

Door Air Bag

Driver Air Bag

Generation Stages:

First Generation:

The ball and tube type.

Second Generation:

The switch type triggers.

Third Generation:

Accelerometer type triggers.

C

SW1 SW2Air Bag Squib

Second Generation System:

Back up even during battery failure

Third Generation System:

A1

A2

Signal Processing

Threshold Detector

Driver Circuit

Acts like Comparator

Widely Used in recent day cars.

OPERATION:

Accelerometer output signal is proportional to

acceleration or deceleration of the car along it’s axis.

Delay period must be minimized in the signal processor.

Signal compared with threshold value.

Driver circuit trigger’s the Air Bag Squib.

The air bag system ignites a solid propellant, which

burns rapidly to create a large volume of gas to inflate the bag.

The bag then literally bursts from its storage site at up to 200 mph.

Seconds later, the gas quickly dissipates through tiny holes

in the bag, thus deflating the bag so you can move.

Air Bag Inflation:

Inflator Construction:

Accelerometer Used in Air Bag Deployment:

DAS systemaccelerometer

Future of Air Bags

Statistics says:

40 percent of all serious injuries from accidents are the result of

side impacts, and 30 percent of all accidents are side-impact collisions.

Designing effective side air bags is much more difficult than

designing front air bags.

Inflatable tubular structure BMW

Science of air bags is still new and under rapid development.

THANK YOU