"Inflatable" protection: how do airbags work and what are they? How do car airbags work? New impact recognition systems

Hello dear guests and readers of the blog Autoguid.ru Today in the article we will learn how the airbags of our cars work. The crown of the evolution of car safety systems is the airbag. Hundreds of thousands of accidents and tens of thousands of lives saved are a prime example of the effectiveness of the use of airbags in modern cars.

Any driver who gets behind the wheel of a vehicle is automatically at risk of getting into a traffic accident. Often the cause of an accident can be your own carelessness or the mistakes of other road users. Even low speed is fraught with danger to the driver and his passengers. Car collisions at speeds of 60 km/h can be fatal. Airbags were invented to protect the driver and passengers in the event of an accident.

The increase in the number of motor vehicles on the roads led to a rapid increase in accidents. The rules at the dawn of the automotive industry were still in their infancy and control by law enforcement agencies was not sufficiently established. The first traffic police units, which had no experience, were just appearing.

Due to design flaws and a significant mass of vehicles, many accidents ended in death or severe disability of the participants in the collision. According to statistics, the number of victims on the roads has increased every year due to the increase in the use of road transport.

The first design element designed to reduce the number of victims of road accidents was the appearance of a seat belt. Its use allowed to reduce sad statistics by 30%. Until the 90s of the last century, due to the peculiarities of the development of technological progress, it was not possible for engineers of automobile companies to introduce new security systems into cars. The seat belt remained the only chance for the driver and passengers to minimize the harmful consequences of an accident.

The advent of airbags in cars was a turning point in improving the safety of road users. In the late 90s of the last century in the United States, at the legislative level, the mandatory equipment of a car with airbags was fixed. In frontal collisions, airbags reduce the risk of death of the driver and passengers by 30-40%. The main task of the airbag is to minimize the possible damage to the human body in a collision with another moving vehicle or an immovable object.

The airbag is designed to deploy in the event of a severe impact. After a collision with another movable or immovable object, sensors located in the front of the car transmit a signal to the squib, which activates the airbag.

The order of deployment of the airbag is as follows:

The reaction of body sensors to a strong impact.

The shock sensor itself is a glass tube with a hole. Inside it is a small ball of mercury. When a car collides, the mercury ball moves and activates the sensor. He, in turn, sends an electrical impulse to the squib with gunpowder.

Igniter.

The explosion of the squib activates the seat belt tensioners. The belt tightly presses the human body to the car seat and securely fixes it for a few seconds.

The explosion of gunpowder in the squib activates the airbags. They fill up in a very short time with the gas formed by mixing sodium azide and potassium nitrate. The pressurization system is responsible for mixing them, which pumps the gas formed almost instantly into the airbags of the car.

Airbag.

Mixing the two chemicals results in the formation of nitrogen gas. As a result of the reaction, a mini-explosion occurs, almost instantly filling the pillows with gas. Very convenient and practically trouble-free system.

It is the deploying airbag that instantly fills the space between the driver and the instrument panel, thereby eliminating their contact, which often leads to serious injuries.

The main task of the airbag is to reduce the speed of the passenger or driver to zero. At the same time, all actions must take seconds to really provide a high level of protection for people.

Today, there are fewer and fewer cars on the roads of the country that are not equipped with airbags. It is impossible to see a new car that does not use this important element of active protection for the driver and passengers.

The device of a modern airbag

The airbag design of a modern car is simple and effective in use. It must be remembered that it can be used only once and then the system requires restoration and installation of new components. After the airbags are deployed, almost all the main elements require a complete replacement.

In total, 3 components of the airbag can be distinguished:

Bag.

Represented by a strong nylon fabric that can withstand very serious short-term loads. It is stored until triggered in a special tire closed with a plastic or cloth lining.

Impact sensor.

The main task of the impact sensor is to timely activate the airbag at the initial stage of the collision. Not every impact causes the airbags to deploy, and the sensor necessarily takes into account the force with which the collision occurs.

Additionally, accelerometers are installed with the sensors, which determine the position of the car in real time. The driver and passenger protection system is configured to deploy airbags in seconds. Human life largely depends on this.

Inflating system.

Serves for the rapid filling of airbags with gas in order to instantly increase its volume. Everything about everything takes a fraction of a second.

In principle, there were no cases when the system failed. A prerequisite for the deployment of airbags is the use of a seat belt. If the driver or passenger is not wearing seat belts, the airbags may not deploy.

Rules for the use of airbags

It is not enough to know the principle of operation of airbags, you also need to interact with them in the right way in order to avoid harm from their operation during an accident. The risk of injury when the airbag is activated is minimal, but it still exists. Often, individual drivers were seriously injured precisely because they did not know the rules for using airbags.

Baby car seat.

Many parents often incorrectly install a child car seat in the passenger seat next to the driver and thereby put their child in serious danger. They install the chair not back to front, but vice versa. The face of the child is right in front of the opening airbag. Doing this is strictly prohibited. A fired airbag can break the cervical vertebrae of a fragile young organism.

Stickers.

The use of stickers in places of deployment of airbags is unacceptable. Sealing the firing elements of the cabin can lead to a violation of the airbag deployment order. The effectiveness of protection in this case is significantly reduced.

Safety belt.

The airbag serves to slow the passenger forward in a collision in a matter of seconds. It is made of nylon fabric and is stowed in the dashboard, steering wheel, seat or door. A device sensor is installed there, which tells the pillow when it needs to be inflated. About what gas is filled with an airbag, the principle of its operation, as well as precautions when using airbags, this publication will tell.

Inflation starts at collision force equivalent to a collision with a wall at a speed of 16-24 km / h. Upon impact, a massive shift occurs that closes the electrical contact, after which the mechanical switch is activated. This informs the sensors about the accident.

The airbag pressurization system mixes potassium nitrate and sodium azide. Eventually gas is released, which inflates the airbag with an explosion .

Pressurization system similar to a rocket booster. It ignites solid fuel, which burns quickly, creates large volumes of gas, and they inflate the pillow. The pillow bursts out of its place in the blink of an eye, at a speed of 322 km/h. The gas is then dispersed through small holes in the chamber, deflating the cushion so that you can move.

The entire process takes 1/25th of a second, but extra time is required to prevent serious injury. The powdery substance that is released from the pillow is talc or cornstarch. It is used to keep the pillow flexible and to lubricate when the pillow is in its storage.

The main precautions that are associated with airbags.

From the first use of airbags, they were warned that airbags should be used in conjunction with seat belts. Seat belts were necessary because the airbags only worked in the event of a frontal match. In a side crash or skid, only seat belts will help. Although side airbags are now common, they are much more effective when used in conjunction with seat belts.

The strength of the pillow can hurt someone close to it. The most dangerous are 5-8 cm of airbag inflation. It should be located 25 cm from the pillow. If the distance from the center of the steering wheel to the chest is less than 25 cm, the driver's seat must be adjusted. Lower the seatback slightly. Move the driver's seat back so that you can comfortably reach the pedals. You also need to make sure that the pillow is "aimed" at the chest, and not at the neck or head.

For children, the rules for using airbags are different.

If a child is not wearing a seat belt, or is sitting close to an airbag, the airbag could injure or kill the child.

Conditions necessary for the safety of the child:

• Children under the age of 12 need to ride in special child seats that are appropriate for the child's age.

• Infants under 1 year of age who are in a child seat should not ride in the front seat of a vehicle where there is an airbag on the passenger side.

• A child over 1 year old who is forced to ride in the front seat must be seated in a forward-facing child seat or booster cushion, or using a shoulder or knee belt. The seat should be reclined as far as possible.

For many years, the seat belt has protected passengers and the driver in the event of an accident. But modern technology and the automotive industry are developing, there is a need for more effective protection. With the advent of airbags, we can say about the reliable protection of people in the car. The airbag inflates in just a fraction of a second in an accident. It is able to protect the body and head from injury.

Airbag Reliability

Crash tests show how safe modern car models are. If there are no pillows in the car, then the driver and passengers risk their health and life. More reliable protection is provided by the presence of at least two pillows in front. In this regard, there were cases when a driver was injured from a blow with a pillow, and not in an accident. This arose as a result of incorrect adjustment. The airbag is fired at a speed of over 300 km/h. This is a powerful blow. If it did not work correctly, then the driver may have head injuries. And yet, during their existence, they saved many people and cases of failures in work are rare.

How does an airbag work

The airbag has a far from simple device and is divided into main elements: a sensitive sensor, a system that inflates the airbag and, accordingly, the airbag. It is made of nylon and inflates with a sharp push with air. It is installed in the car under the plastic lining. The sensor is sensitive, it is he who releases the pillow. It is usually set up to fire the airbag at low speed in a crash. A complex device is responsible for a quick shot of the pillow and its inflation with a special composition. This is a pillow inflation system that includes electronic and chemical components. We will not consider electronics here, but the chemistry in the airbag is the subject of our interest.

When designing an airbag, the inventors had to solve the following problem. If the car crashes at low speed into any object, then the sensor reacts in connection with the load. The launcher detects this and gives a signal for instant take-off and airbag inflation.

At first, they tried to install gas cylinders in the passenger compartment, which, upon impact, mechanically sent their contents into the airbag. But such solutions were too unsafe, cumbersome and slow. Inventors had to try many options before chemistry came to the rescue in 1970, which made it possible to turn the airbag into a safe and reliable means of protection!

In the inflation system there are tanks with sodium azide (NaN 3) with potassium nitrate (KNO 3). In the event of an accident, electronic impact sensors initiate the ignition of a solid propellant charge, which starts a chemical reaction that produces a large amount of nitrogen. The reaction is so rapid (the total time from the start of the ignition to the completion of the reaction is about 50 milliseconds) that the pillow breaks out of its seat at a speed of 300 km / h! After filling the pillow with gas, it instantly bleeds through special holes. This is done for safety reasons, because if you do not blow off the pillow, then a person can be tightly clamped to it in the cabin! During the blowing of the pillows, you can observe a slight “smoke” in the cabin - this is nitrogen coming out.

Types of airbags

The standard option is two front airbags, which are equipped with most cars. But at present, models with six different pillows are being made.

There are two front airbags. They protect the driver and front passenger. There are also side airbags that can protect not only the body of passengers, but also the legs. Together with them, special curtains do not allow injuring the head in a side impact. Manufacturers also took care of the protection of the legs and created a pillow that proved itself in crash tests and minimized injuries.

The latest development is a pillow located in the center. It protects passengers from impacts in the cabin. Another pillow is installed on the belt, which can protect the chest area. Some modern models are equipped with such innovations. But this is not yet widespread.

To sum it up: an airbag saves lives in an accident. But at the same time, you must not forget to fasten your seat belts.

Airbag (airbag) is one of the passive safety elements in modern cars. Their presence is an important factor ensuring the safety of the driver and passengers. Airbag in translation from English means "airbag", hence the Russian name arose - an airbag, which we are all used to using.

Airbags have saved thousands of lives since they were mass-installed in vehicles. The idea of ​​the Airbag system is simple: the airbags inflate quickly enough to protect the human body in the event of an accident. But how do they do it so fast?

The content of the article:

The device and principle of operation of airbags

The secret of instantaneous filling of airbags actually lies not so much in the pillows themselves, but in a special device - a gas generator. This is the most technically complex part in the entire Airbag system.

The gas generators used in airbags can inflate it about three times faster than you can blink. At the end of the article watch the video about how the airbag is arranged, and what stages of production it has to go through before being installed on a car.

The principle of operation of airbags is quite simple. They are activated on impact when the vehicle speed exceeds 20 km/h.

• In the event of a collision with an obstacle, one or more special sensors are triggered. These sensors can be installed at the front, rear and sides of the vehicle.
• The signals from the sensors are processed by an electronic control unit (ECU) that controls the operation of the Airbag system. Under certain conditions (for example, a strong frontal or oblique impact, running into a high curb, a hard fall after a jump, etc.), the ECU commands the airbags to deploy.
• Based on the programmed algorithm, the control unit decides on the need to deploy the airbags and transmits an electrical signal for execution.
• This signal enters the airbag gas generator, and a pyrotechnic charge is triggered in it (the squib fires).
• As a result of the triggering of the squib, the sodium acid contained in the gas generator burns out, releasing a significant amount of gas (nitrogen), which enters the Airbag and instantly opens it.

Airbags are made from nylon fabric similar to parachute fabric. It has holes through which the gas after inflating the pillow leaves it in just 0.3 seconds. Rapid deflation is necessary because as air is released from the air bag, it becomes softer.

A gas generator is attached to each airbag during the manufacturing process, after which it is rolled up into a compact package (small enough to fit in the steering wheel or in the passenger side dash panel). In this case, the gas generator for the driver's airbag is additionally placed in a rubber ring, in which it plays the role of a balancing weight.

Airbag Inflator Device

Since drivers and passengers come in different sizes, engineers at one time wanted to come up with an Airbag generator that could regulate the amount of gas. Early airbags could not change their inflation rate in relation to the size and position of a person, or the force of a vehicle collision.

Therefore, the designers came up with a "smart" generator - it has two squibs instead of one. One of them releases gas only by 80 percent (this is enough for a “soft landing”). But if that's not enough, a second squib triggers a refill, and the remaining gas fills the Airbag and makes it stiffer.

A typical driver's airbag inflator consists of the following main parts (refer to the illustration above):

1. Housing with combustion chambers;
2. Charges #1 and #2 from sodium acid tablets;
3. Auxiliary charge to ignite charge #1;
4. Two pyrotechnic cartridges for igniting charges;
5. Metal filter.

So what happens in the gas generator when the Airbag is triggered?

• The igniters installed in the airbag inflator contain a material similar to gunpowder. When they receive a signal from the electronic control unit, they work, generating heat and high pressure.
• From the operation of a pyrotechnic cartridge in the gas generator housing, special sodium acid tablets (charge) located there light up. These pellets, when burned, release a hot but harmless nitrogen-based gas that deforms the alternator case and leaves it filling the Airbag.
• Before entering the airbag, nitrogen passes through a special metal filter that removes particulate matter formed during the combustion of the charge and cools the gas.
• When electricity is applied to the squib #2, it ignites the second charge. The gas generated during the combustion of the charge lifts the cap of the chamber of the stage #2 and inflates the airbag through the combustion chamber of the first stage.

From the moment the car gets into an accident until the airbag is fully inflated, no more than 30 milliseconds pass.

Types of car airbags

There are three main types of airbags most commonly used in cars:

1. Front airbags- are installed in the steering wheel for the driver, and on the right side of the front panel of the car for the passenger. Such airbags are found in almost all foreign-made cars and in some domestic cars.
2. Side airbags- in case of an accident, they protect the human chest, abdominal cavity and pelvic bones. These airbags are most often built into the backs of the front car seats.
3. Curtain pillows(head airbags) - designed to prevent head injuries due to side impacts. Automakers install these airbags in the roof area, either front or rear, or between the B-pillars.

Also on some car models you can find knee airbags and even a central airbag (between driver and passenger). But these types of airbags are much less common than the first three, and mainly on premium car brands.

Since airbags have become such an important part of the design of a modern car, engineers are constantly looking into the possibility of testing their operation. German specialists, for example, have developed and systematized a number of tests that take into account climatic factors and vibration, extreme temperature changes and various conditions for device operation.

Manufacturers guarantee the perfect operation of airbags, because, compared to the environment they create in the laboratories, the real situations in which the car is operated can be called very gentle.

Airbags serve for a long time and reliably, not only thanks to the tests that precede their serial introduction, but also due to the perfection of the design, which itself monitors the maintenance of the Airbag system and eliminates the possibility of aging and wear of the fabric.

This is the author's translation of the article " Air Bag Deployment Criteria published in 2014 by Kenneth Solomon and Jesse Kendall in The Forensic Examiner®, the official peer-reviewed scientific journal of the American College of Forensic Science Institute, which has gained popularity and recognition as the world's leading forensic journal.

And since our people don’t read such magazines to the bakery by taxi, this article on Pravorub will be useful to both accident lawyers and auto experts who read. Lawyers - as information for interrogation in court of non-reading auto experts in order to explain their empty conclusions to them, and reading auto experts - in order not to give conclusions based on shamanic rites.

Introduction

Airbag control modules use sophisticated algorithms to make deployment decisions based on an assessment of the severity of an accident involving a change in vehicle speed or deceleration over time. Due to the fact that the control algorithms are manufacturer know-how, their actual speed, acceleration, or deformation (path) threshold values ​​for airbag deployment in a collision are not known. Car manufacturers do not disclose the values ​​of these parameters and algorithms, limiting themselves to the declarative “strong blow” or “strike of sufficient force” in the owner’s manuals, and dealers simply do not know them, while playing performances for customers with testing instrument control modules.

Indeed, such vague non-technical criteria create deadlock in litigation by car owners whose airbags did not deploy in an accident, or deployed arbitrarily for no apparent reason. This also creates fertile ground for fraudulent staging of accidents, which consists in “transferring” panels with deployed airbags to a practically undeformed car.

However, the technical parameters required for the deployment of an airbag can be determined by examining the results of laboratory crash tests of vehicles of specific manufacturers.

Article objectives

1. Obtaining information and understanding the operation of the airbag control system and its components.
2. Getting information and understanding when airbags should or should not deploy. The article contains an introduction to airbag control systems and their deployment processes, a brief history of impact sensors. The variables used in airbag deployment algorithms are described and comparative examples are given using several proprietary control systems. A method is shown for estimating a range of speed, deceleration, or strain (path) that is a threshold for airbag deployment.

Airbag Deployment Process

The purpose of an airbag is to provide a resilient, cushioned cushion between the occupants and the car's interior. To achieve this goal, the airbags must be fully inflated in a short amount of time and before passengers come into contact with them. The rapid deployment of an airbag has the potential to cause fatal injury to persons if they are already in contact with the airbag at the time of its deployment. Therefore, airbags must have a control system that can correctly recognize that a collision is occurring. At the same time, recognize it early enough so that the airbag has time to deploy safely.

The airbag deploys after an electrical signal to deploy is sent to the detonator from the airbag control module. This signal initiates a chemical reaction that rapidly inflates the nylon fabric air bag with gas. The gas contains dust particles from the material used to lubricate the bag (typically talc and cornstarch). Once the bag is fully deployed, the gas escapes through small vents. The holes are sized and positioned to reduce the volume of the bag at different rates, depending on the type of vehicle.

History of shock sensors

Early airbag deployment systems used mechanical sensors to detect impact, which were then phased out in the US market around 1994. Sensors such as, for example, rolamite", contained metal rollers stabilized in the standby position by means of a spring or a magnet.

When struck beyond the intended threshold, the spring or magnet could no longer hold the metal mass in place. The mass moved and pressed against the contact, sending an electrical signal to the airbag control module. Systems with mechanical sensors tend to be inaccurate in interpreting small collisions. There may not be enough movement in mechanical sensors in frontal collisions, which may cause delayed response. Modern shock sensors are now based on microelectromechanical systems (MEMS).

New impact recognition systems

New MEMS impact sensors measure acceleration with an accelerometer, which sends a continuous stream of data to the airbag control module. Accelerometers are usually piezoelectric or variable capacitance sensors. The most common MEMS accelerometer in use today is the ADXL-50 manufactured by Analog Devices.

The author had to meet the conclusions of complete idio "non-reading" auto experts, in which they, by visual inspection or by the organoleptic method, establish a malfunction of the shock sensor. Their logic is limited to a primitive chain "there was a blow - the pillows did not work - it means that the shock sensor is not working." In fact, the testing procedures for such sensors are based (on not approved by the Ministry of Justice, and, therefore, not recognized by state experts as scientific) algorithms such as Gauss-Newton, require special software and equipment. Examples of numerous tests can be viewed on YouTube, and if necessary, you can find the official regulations for testing and calibrating a specific sensor model on the manufacturer's website.

https://youtu.be/ycThnu3k_vc

As the masses aimed at the elastic elements move relative to the sensor housing due to acceleration, special plates attached to the masses approach other fixed plates. Changing the distance between the plates affects the capacitance of the sensor, or the ability to hold an electrical charge. This change in capacitance is easily measured and then converted into a change in voltage. The change in voltage is directly related to the force of inertia due to acceleration, and the reading is interpreted by the airbag control module as acceleration. The control module algorithm can determine whether the deployment of the airbag is necessary based on its mathematical model of acceleration pulses over time.

Decision making process

The airbag control module (ACM) receives a continuous signal from each MEMS sensor and records the data for a certain period after a specific event. With the help of the central processing unit (CPU), it performs algorithmic calculations and gives or does not give a command to deploy the airbag. Algorithms for determining the severity of an impact work by evaluating one or more kinematic parameters (acceleration, its derivatives or integrals), a list of which is given in Table 1 below. Examples of block diagrams of decision making algorithms are shown in the following figures.

Table 1.

Block diagram of an algorithm using parameters: change in speed, path and energy density.

Block diagram of the algorithm using the parameters: deceleration and jerk (push).

Block diagram of an algorithm using the parameters: acceleration and change in speed.

Algorithm Options
Impact recognition systems vary greatly between patents. Most systems patented after 1995 use delta-V, acceleration, or jerk as the parameters to activate the wake-up system and deploy the airbags. The latest systems also include systems for analyzing the presence of passengers and analyzing the distance to the passenger. In the approaches used between 1995 and 2008 by several inventors, the differences are quite significant. However, the command to deploy the airbags depends on one or more of the set of basic kinematic parameters described above.

When the airbags deploy

In accordance with the position of the National Traffic Safety Administration of the United States Department of Transportation ( enshrined in the relevant US standard, which is followed by a number of well-known foreign car manufacturers), "Airbags are generally designed to deploy in frontal and near-frontal collisions, which are comparable to hitting an immovable rigid barrier at about 8 to 14 miles per hour." Certain thresholds are calibrated by each manufacturer according to the size of the vehicle and the rigidity of its structure. The control system is activated to distinguish between events such as hitting a pothole or colliding with another vehicle. This typically occurs when two successive acceleration pulses of less than (about) -1g for small vehicles or less than (about) -2g for large vehicles occur within 10 milliseconds. Upon awakening, the decision is made to either deploy the airbags or return to normal.

Due to the know-how status, the control algorithms and the values ​​of the kinematic parameters for the deployment of the airbag in the event of a collision are not known. However, using the NHTSA directive for airbags, in terms of their deployment during a frontal impact into a barrier at a speed of 8 to 14 mph, the range of threshold values ​​of the kinematic parameters can be estimated using known values ​​​​of vehicle stiffness and their mass.

Threshold evaluation

Collision deformation amount FROM(in inches) at a given impact velocity V(in miles per hour) is related to the stiffness ratio of the vehicle k(in lb/in) and its weight w(in pounds) using the following equation:

The time from the beginning of the impact to the moment of reaching the maximum impulse upon impact:
Replacing the relation in the first expression C/V from the second expression, we get:
Vehicle stiffness k can be determined from the results of crash tests, taking into account the mass of the car m, deformation C, and impact speed V. Vehicle stiffness is calculated by the formula:

Table 2 shows the corresponding spectrum of decelerations and deformations (movements) in frontal crash tests, for vehicles equipped with airbags, considering the estimated time for maximum impact momentum and for various vehicles in terms of stiffness and mass.

table 2


It can be seen that there is no significant correlation between the weight of the car and its stiffness. Two cars of similar weight can have very different stiffness values, as can be seen from a comparison between a 2010 Ford Fusion and a 2010 Toyota Prius. Both vehicles have roughly the same car weight, but the front end rigidity of the Toyota Prius is significantly greater than that of the Ford Fusion. Since the amount of deformation and duration of impact on the Ford Fusion is greater, the Ford Fusion's airbag will need to deploy within a deceleration value less than that required by the Toyota Prius.

Value Comparison

The conditions of real collisions often do not coincide with a blow to a rigid immovable barrier, and this must be taken into account when comparing the ranges of actual (from crash tests) and calculated parameter values. The duration of the impact does not change significantly with the speed of the impact, but depends largely on the type of collision. The airbags may not deploy if there is a hard impact, like hitting a pole, where only one part of the car is deformed. Airbags sometimes fail to deploy when the impact is gradual over a long period of time, such as when a vehicle is driven under or over another object. Airbags may not deploy in collisions in which the relative stiffness of the colliding vehicles is very different. For example, a collision between the front of one car and the side of another car. In addition, collisions that occur at sharp corners do not always lead to the deployment of airbags, since there is no significant deceleration in the direction of the longitudinal axes of the vehicles (in the direction measured by the impact sensor).

Example: airbags did not deploy

An example of an impact where there was a significant change in speed but the front airbags did not deploy was a crash involving a 2007 Chevrolet Equinox with an oncoming Harley-Davidson motorcycle. The airbag control module in the Equinox recorded a maximum speed change of 9.27 mph. This value is within the 8.0 to 14.0 mph range in which the airbags are expected to deploy (as in the case of a frontal impact into a rigid immovable barrier). However, the maximum slowdown was 3.27g. This deceleration was well below the calculated value over the deployment range from 7.5g to 13.2g, as shown in the table above. Thus, the frontal airbags should not have deployed.

Example: airbags deployed

An example of an impact that did not result in a significant change in speed, but the airbags deployed, was an accident involving a 2007 Chevrolet Corvette that knocked out several traffic signs, trees, and road posts at very high speeds. The vehicle hit the first object at over 60 mph and the airbag control module recorded a maximum speed change of 4.96 mph, well below the 8.0 to 14.0 mph range in which airbags are expected to deploy (as in the case of a frontal hitting a rigid, immovable barrier). Fortunately for the passenger and driver, the recorded maximum deceleration during impact was 11.3g, which is above the calculated threshold range of 6.1g to 10.6g from the table above. As a result, the airbags deployed and saved the lives of the passenger and driver.

Conclusion

Airbags must have a control system that can recognize impacts correctly and early enough to deploy the airbags safely. Deployment systems typically use electronic sensors that continuously report the vehicle's acceleration to the airbag control module. The modules use complex algorithms to make airbag deployment decisions based on one or more kinematic variables. Due to the "know-how" status of deployment algorithms, the speed, acceleration or strain values ​​used in these algorithms are not known. Instead, ranges of impact velocities, decelerations, or deformations can be calculated from crash test data and then used to judge whether airbags should have deployed in a particular crash.

Linkson thesources

1 Collision Safety Institute. (2011). Bosch Crash Data Retrieval System - Crash Data Retrieval. Data Analyst Course Manual.
2. Huang, Mathew. (2002). Vehicle Crash Mechanics. C.R.C. Press.
3. US Department of Transportation National Highway Traffic Safety Administration. (2003). What You Need to Know About Air Bags - DOT HS 809 575.

About authors

Jesse Kendall received his Bachelor of Science in Civil Engineering from the University of Vermont in Burlington, Vermont. He completed his engineering internship in Denver, Colorado working for construction consulting firms before becoming a six-state licensed professional engineer. With over fifteen years of experience in civil engineering, Jesse Kendall now lives and works in California at the Institute for Risk and Safety Analysis, specializing in forensic engineering and accident reconstruction.

Dr. Solomon received his B.S., M.S., and Ph.D. in mechanical engineering from Los Angeles. Dr. Solomon also holds professional engineering licenses. Dr. Solomon has been conducting research in the field of accident reconstruction and biomechanics for over 40 years, has more than 200 scientific publications in international publications, reports and presentations. He and co-authored 13 books. He has served as a Senior Fellow with the RAND Corporation and has taught on the faculty at the RAND High School, the University of California, the University of Southern California, the Naval Postgraduate School, George Mason University, and the Orange County Sheriff's Academy.