An airbag is a vehicle safety Automobile safety is the study and practice of vehicle design, construction, and equipment to minimize the occurrence and consequences of automobile accidents device. It is an occupant restraint consisting of a flexible envelope designed to inflate rapidly in an automobile collision A collision is an isolated event in which two or more bodies exert relatively strong forces on each other for a relatively short time. The g-force can be very large during a short time, to prevent vehicle occupants from striking interior objects such as the steering wheel or window.

Terminology

Because no action by the vehicle occupant is required to activate or use the airbag, it is considered a passive device. This is in contrast to seat belts A seat belt, sometimes called safety belts, is a safety harness designed to secure the occupant of a vehicle against harmful movement that may result from a collision or a sudden stop. As part of an overall automobile passive safety system, seat belts are intended to reduce injuries by stopping the wearer from hitting hard interior elements of the, which are considered active devices because the vehicle occupant must act to enable them.^{[1][2][3][4][5]} Note that this is not related to active and passive safety Automobile safety is the study and practice of vehicle design, construction, and equipment to minimize the occurrence and consequences of automobile accidents, which are, respectively, systems designed to prevent accidents in the first place and systems designed to minimize accidents once they occur. For example, the car's Anti-lock Braking System An anti-lock braking system, or ABS is a safety system which prevents the wheels on a motor vehicle from locking up while braking will qualify as an active-safety device while both its seatbelts and airbags will qualify as passive-safety devices. Further terminological confusion can arise from the fact that passive devices and systems — those requiring no input or action by the vehicle occupant — can themselves operate in an active manner; an airbag is one such device. Vehicle safety professionals are generally careful in their use of language to avoid this sort of confusion, though advertising Advertising is a form of communication intended to persuade an audience to purchase or take some action upon products, ideals, or services. It includes the name of a product or service and how that product or service could benefit the consumer, to persuade a target market to purchase or to consume that particular brand. These brands are usually principles sometimes prevent such syntactic In linguistics, syntax is the study of the principles and rules for constructing sentences in natural languages caution in the consumer marketing of safety features.

Various manufacturers have over time used different terms for airbags. General Motors' General Motors Company, also known as GM, is a United States-based automaker with headquarters in Detroit, Michigan. GM manufactures cars and trucks in 34 countries, recently employed 244,500 people around the world, and sells and services vehicles in some 140 countries. By sales, GM ranked as the largest US automaker and the world's second first bags, in the 1970s, were marketed as the Air Cushion Restraint System (ACRS). Common terms in North America include Supplemental Restraint System (SRS) and Supplemental Inflatable Restraint (SIR); these terms reflect the airbag system's nominal role as a supplement to active restraints, i.e., seat belts.

History

Invention

An American inventor, John W. Hetrick,a retired industrial engineer, designed the original safety cushion for automotive use in 1952 at his kitchen table. His patent lasted only 17 years - long before mainstream automotive usage. Dr. David S. Breed, invented and developed a key component for automotive use: the ball-in-tube inertial sensor for crash detection. Breed Corporation then marketed this innovation first in 1967 to Chrysler Chrysler Group LLC is a U.S.-based automobile manufacturer headquartered in the Detroit suburb of Auburn Hills, Michigan. Chrysler was first organized as the Chrysler Corporation in 1925. From 1998 to 2007, Chrysler and its subsidiaries were part of the German based DaimlerChrysler AG (now Daimler AG). Prior to 1998, Chrysler Corporation traded. A similar "Auto-Ceptor" crash-restraint, developed by Eaton, Yale & Towne Inc. for Ford was soon offered as an automatic safety system in the USA,^[6][7] while the Italian Eaton-Livia company offered a variant with localized air cushions.^[8]

As a supplement to seat belts

Airbags for passenger cars were introduced in the United States ^ b. English is the de facto language of American government and the sole language spoken at home by 80% of Americans age five and older. Spanish is the second most commonly spoken language in the mid-1970s, when seat belt A seat belt, sometimes called safety belts, is a safety harness designed to secure the occupant of a vehicle against harmful movement that may result from a collision or a sudden stop. As part of an overall automobile passive safety system, seat belts are intended to reduce injuries by stopping the wearer from hitting hard interior elements of the usage rates in the country were quite low. Ford The Ford Motor Company is an American multinational corporation based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford, Lincoln, and Mercury brands, Ford also owns Volvo Cars in Sweden, and a small stake in Mazda in Japan and Aston Martin in the UK. Ford' built an experimental fleet of cars with airbags in 1971, followed by General Motors General Motors Company, also known as GM, is a United States-based automaker with headquarters in Detroit, Michigan. GM manufactures cars and trucks in 34 countries, recently employed 244,500 people around the world, and sells and services vehicles in some 140 countries. By sales, GM ranked as the largest US automaker and the world's second in 1973 on Chevrolet vehicles. The early fleet of experimental GM vehicles equipped with airbags experienced seven fatalities, one of which was later suspected to have been caused by the airbag.^[9]

In 1974, GM made the ACRS or "Air Cushion Restraint System" available as a regular production option (RPO code AR3) in some full-size Buick, Cadillac and Oldsmobile models. The GM cars from the 1970s equipped with ACRS have a driver side airbag, a driver side knee restraint (which consists of a padded lower dashboard) and a passenger side airbag. The passenger side airbag, protects both front passengers and unlike most newer ones, it integrates a knee cushion, a torso cushion and it also has dual stage deployment which varies depending on the force of the impact. The cars equipped with ACRS have lap belts for all seating positions but they do not have shoulder belts. These were already mandatory equipment in the United States on closed cars without airbags for the driver and outer front passenger seating positions.

The automotive industry's first passenger side knee airbag (not separate) was already used on the 1970s General Motors cars, it was integrated in the passenger airbag that had a knee cushion and a torso cushion.^{[citation needed]}

The development of airbags coincided with an international interest in automobile safety Automobile safety is the study and practice of vehicle design, construction, and equipment to minimize the occurrence and consequences of automobile accidents legislation. Some safety experts advocated a performance-based occupant protection standard rather than a standard mandating a particular technical solution, which could rapidly become outdated and might not be a cost-effective approach. As countries successively mandated seat belt restraints, there was less emphasis placed on other designs for several decades.^[8]

Manufacturers emphasize that an airbag is not, and can not be an alternative to seatbelts. They emphasize that they are only supplemental to a seatbelt. Hence the commonly used term "Supplemental Restraint System" or SRS. It is vitally important that drivers and passengers are aware of this. In the majority of cases of death caused by air bags, seat belts were not worn.^{[citation needed]}

As a supplemental restraint

Frontal airbag

The auto industry and research and regulatory communities have moved away from their initial view of the airbag as a seat belt replacement, and the bags are now nominally designated as Supplemental Restraint System (SRS) or Supplemental Inflatable Restraints.

In 1980, Mercedes-Benz Mercedes-Benz is a German manufacturer of luxury automobiles, buses, coaches, and trucks. It is currently a division of the parent company, Daimler AG (formerly DaimlerChrysler AG), after previously being owned by Daimler-Benz. Mercedes-Benz has its origins in Karl Benz's creation of the first petrol-powered car, the Benz Patent Motorwagen, introduced the airbag in Germany as an option on its high-end S-Class (W126). In the Mercedes system, the sensors would automatically pre-tension the seat belts to reduce occupant's motion on impact (now a common feature), and then deploy the airbag on impact. This integrated the seat belts and airbag into a restraint system, rather than the airbag being considered an alternative to the seat belt.

In 1987, the Porsche Porsche Automobil Holding SE, usually shortened to Porsche SE , a Societas Europaea or European Public Company, is a German automotive manufacturer of luxury high performance automobiles, which is majority-owned by the Piëch and Porsche families. Porsche SE is headquartered in Zuffenhausen, a city district of Stuttgart, Baden-Württemberg 944 turbo became the first car in the world to have driver and passenger airbags as standard equipment. The Porsche 944 The 944 is a sports car built by Porsche between 1982 to 1991. It was built on the same platform as the 924, although 924 production continued through 1988. The 944 was intended to last into the 1990s, but major revisions planned for a 944 S3 model were eventually rolled into the 968 instead, which replaced the 944. The 944 was a successful model and 944S had this as an available option. The same year also saw the first airbag in a Japanese car, the Honda Legend The Honda Legend is a Full-size luxury car made by the Japanese automaker Honda. It was originally developed as part of Project XX, a joint venture with the Austin Rover Group of Great Britain and was a twin of the Rover 800 series.^[10]

Airbags became common in the 1980s, with Chrysler Chrysler Group LLC is a U.S.-based automobile manufacturer headquartered in the Detroit suburb of Auburn Hills, Michigan. Chrysler was first organized as the Chrysler Corporation in 1925. From 1998 to 2007, Chrysler and its subsidiaries were part of the German based DaimlerChrysler AG (now Daimler AG). Prior to 1998, Chrysler Corporation traded and Ford The Ford Motor Company is an American multinational corporation based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford, Lincoln, and Mercury brands, Ford also owns Volvo Cars in Sweden, and a small stake in Mazda in Japan and Aston Martin in the UK. Ford' introducing them in the mid-1980s; it was Chrysler that made them standard equipment across its entire line in 1990 (except for trucks until 1995).^{[citation needed]}

Audi Audi AG is a German manufacturer of automobiles marketed under the Audi brand, German pronunciation: [ˈaʊdi] was relatively late to offer airbag systems on a broader scale; until the 1994 model year, for example, the 80/90 The Audi 80 is a compact executive car produced by the German car manufacturer Audi, from 1966 to 1996. It initially shared its platform with the Volkswagen Passat, and was available as a saloon car/sedan, and an Avant . The coupé and convertible models were not badged as members of the range but shared the same platform and many parts, by far Audi's 'bread-and-butter' model, as well as the 100/200 The Audi 100 and Audi 200 are mid-sized automobiles from Audi , made between 1968 and 1994. The C3 model of the Audi 100 was sold in the United States as the Audi 5000 until 1988, did not have airbags in their standard versions. Instead, the German automaker until then relied solely on its proprietary procon-ten restraint system.

In Europe Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus region (Specification of borders) and the Black Sea to the southeast. Europe is bordered by the, airbags were almost entirely absent from family cars until the early 1990s, except for Saab Saab Automobile AB, better known as Saab, is a Swedish car manufacturer owned by General Motors. It was the exclusive automobile royal warrant holder as appointed by H.M., the King of Sweden. Since its inception, Saab had been known for its innovation; as it evolved and adopted ever more advancements to its turbocharging, safety, and green, who made them standard on the 900 Turbo The 900 is a car that was made by Saab Automobile from 1978 until 1998 in two generations. The first generation from 1978 to 1993 is known as the "classic"; the generation from 1994 to 1998 is known as the "new generation" in 1989 and on all models in 1990. The first European Ford The Ford Motor Company is an American multinational corporation based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford, Lincoln, and Mercury brands, Ford also owns Volvo Cars in Sweden, and a small stake in Mazda in Japan and Aston Martin in the UK. Ford' to feature an airbag was the facelifted Escort MK5b in 1992; within a year, the entire Ford range had at least one airbag as standard. By the mid 1990s, European market leaders such as Vauxhall Vauxhall Motors is a British automobile company owned by Magna International and General Motors. Most current Vauxhall models are right-hand drive derivatives of Magna's Opel brand; however, production of left hand vehicles also takes place for export to other parts of Europe and certain marginal markets. There are also several performance/Opel Adam Opel GmbH is a German automobile company founded by Adam Opel in 1863. It has been a subsidiary of General Motors 1929–present. The company was an AG (German plc) up to 2005, Rover Rover Group plc was the name that was given by the British government, in 1986, to the state-owned vehicle manufacturer British Leyland or BL, Peugeot Peugeot is a major French car brand, part of PSA Peugeot Citroën, the second largest carmaker based in Europe, Renault Renault S.A. is a French automaker producing cars, vans, buses, tractors, and trucks, and, in the past, autorail vehicles. Due to its alliance with Nissan, it is currently the world's fourth largest automaker. Headquartered in Boulogne-Billancourt, Renault owns the Romanian automaker Automobile Dacia and the Korean automaker Renault Samsung Motors and Fiat Fiat S.p.A., an acronym for Fabbrica Italiana Automobili Torino , is an Italian automobile manufacturer, engine manufacturer, financial and industrial group based in Turin in the Piedmont region. Fiat was founded in 1899 by a group of investors including Giovanni Agnelli. Fiat has also manufactured railroad vehicles, tanks and aircraft. As of 2009, had included airbags as at least optional equipment across their model ranges. By the end of the decade, it was very rare to find a mass market car without an airbag, and some late 1990s products, such as the Volkswagen Golf Mk4 Launched in 1997, the Volkswagen Golf Mk4 was the best selling car in Europe in 2001 (though it slipped to second place, behind the Peugeot 206, in 2002). The Mk4 was a deliberate attempt to take the Volkswagen Golf series further upmarket, with a high-quality interior and higher equipment levels. Overall the level of maturity of the design and also featured side airbags. The Peugeot 306 was a classical example of how commonplace airbags became on mass market cars during the 1990s. On its launch in early 1993 most of the range did not even have driver airbags as an option. By 1999 however, side airbags were available on several variants.

During the 2000s side airbags were commonplace on even budget cars, such as the smaller-engined versions of the Ford Fiesta The Ford Fiesta is a small front wheel drive supermini car designed by the Ford Motor Company and built in Europe, Brazil, Argentina, Mexico, Venezuela, China, India and South Africa. The model is marketed worldwide, including Japan, Australasia and the Americas and Peugeot 206 The Peugeot 206 is a supermini , manufactured by the French automaker Peugeot since 1998, in addition to licensed manufacturing by Iran Khodro since 2005, and curtain airbags were also becoming regular features on mass market cars. The Toyota Avensis The Toyota Avensis is a large family car built in Derbyshire, United Kingdom by Japanese automaker Toyota since the 1998 model year. It is the successor of the Carina E and is available as a four-door saloon, five-door liftback and estate. A large MPV called the Toyota Avensis Verso is built in Japan on a separate platform. The Avensis is the, launched in 1998, was the first mass market car to be sold in Europe with a total of nine airbags. Although in some countries, such as Russia Russia (pronounced /ˈrʌʃə/ ; Russian: Россия, tr. Rossiya, pronounced [rɐˈsʲijə] ( listen)), also officially known as the Russian Federation (Russian: Российская Федерация, tr. Rossiyskaya Federatsiya, pronounced [rɐˈsʲijskəjə fʲɪdʲɪˈraʦəjə] ( listen)), is a country in northern Eurasia. It is a federal, airbags are still not standard equipment on all cars, such as those from Lada Lada is the trademark of AvtoVAZ, a Russian car manufacturer in Togliatti, Samara Oblast. All AvtoVAZ vehicles sold currently are of the Lada brand but this has not always been so. Ladas were AvtoVAZ's export vehicles, the same models being sold under the Zhiguli brand on the domestic Soviet market since 1970.

Variable force deployment front airbags were developed to help minimize injury from the airbag itself.

Shaped airbags

The Citroën C4 provides the first "shaped" driver airbag, made possible by this car's unusual fixed hub steering wheel.^[11]

Side airbag

There are essentially two types of side airbags commonly used today, the side torso airbag and the side curtain airbag.

Most vehicles equipped with side curtain airbags also include side torso airbags. However some exceptions such as the Chevrolet Cobalt,^[12] 2007-09 model Chevrolet Silverado/GMC Sierra The Chevrolet Silverado , is the latest line of full-size pickup trucks from General Motors, and 2009-10 Dodge Ram The Dodge Ram is a full-size pickup truck from Chrysler LLC's Dodge brand. The name was first used in 1981 on the redesigned Ram and Power Ram, though it came from the hood ornament used on 1930s and '40s Dodge vehicles^[13] do not feature the side torso airbag.

Side torso airbag

Side-impact airbags or side torso airbags are a category of airbag usually located in the seat, and inflate between the seat occupant and the door. These airbags are designed to reduce the risk of injury to the pelvic and lower abdomen regions. Some vehicles are now being equipped with different types of designs, to help reduce injury and ejection from the vehicle in rollover crashes.

The Swedish company Autoliv AB Autoliv is a Swedish-American company with headquarters in Stockholm, Sweden, that in 1997 sprung from the merger of the Swedish company Autoliv AB and Morton Automotive Safety Products, Inc., a division of the American firm Morton International, was granted a patent on side airbags, and they were first offered as an option in 1994 on the 1995 model year Volvo 850 The Volvo 850 is a compact executive car produced by Volvo Cars from 1992 to 1997 and designed by Jan Wilsgaard. Available in sedan/saloon and station wagon/estate body styles, the Volvo 850 was notable as the first front-wheel drive vehicle from this Swedish manufacturer to be exported to North America. It is often considered the vehicle that, and as standard equipment on all Volvo cars made after 1995.

Side tubular or curtain airbag

In late 1997 the 1998 model year BMW 7-series and E39 5-series were fitted with a tubular shaped head side airbags, the "Head Protection System (HPS)" as standard equipment. This is an industry's first in offering head protection in side impact collisions.^[14] This airbag also maintained inflation for up to seven seconds for rollover protection. However, this tubular shaped airbag design has been quickly replaced by an inflatable 'curtain' airbag for superior protection.

In May 1998 Toyota began offering a side curtain airbag deploying from the roof on the Progrés.^[15] In 1998 the Volvo S80 The Volvo S80 is an executive sedan from Swedish automaker Volvo and was introduced in 1998 as a replacement for the rear-wheel drive Volvo 960/S90 sedan. The Volvo S80 was built at the Torslanda Plant in Gothenburg, Sweden. Unlike most Volvo models, it did not have a station wagon version for its first generation. Now, the third generation V70 was given seat-mounted curtain airbags to protect both front and rear passengers later made standard equipment on all new Volvo cars from 1998 and while initially seat-mounted later versions deployed from the roof.

Roll-sensing side curtain airbags found on vehicles more prone to rollovers such as SUV's and pickups will deploy when a rollover is detected instead of just when an actual collision takes place. Often there is a switch to disable the feature in case the driver wants to take the vehicle offroad.

Curtain airbags have been said to reduce brain injury or fatalities by up to 45% in a side impact with an SUV. These airbags come in various forms (e.g., tubular, curtain, door-mounted) depending on the needs of the application.^[16] Many recent SUVs A sport utility vehicle is a generic marketing term for a vehicle similar to a station wagon, but built on a light-truck chassis. Usually equipped with four-wheel drive for on- or off-road ability, and with some pretension or ability to be used as an off-road vehicle, some SUVs include the towing capacity of a pickup truck with the passenger- and MPVs A minivan, multi-purpose vehicle , people-carrier, people-mover or multi-utility vehicle (shortened MUV) is a type of automobile similar in shape to a van that is designed for personal use. Minivans are taller than a sedan, hatchback or a station wagon, and are designed for maximum interior room have a long inflatable curtain airbag that protects all 3 rows of seats.

Knee airbag

The first driver's side and separate knee airbag was used in the 1996 model Kia Sportage The Kia Sportage is a compact crossover SUV built by the Korean automaker Kia Motors since 1995. Originally, it was a mini SUV, but the second generation Sportage has grown in size to become a compact crossover SUV vehicle and has been standard equipment since then. The airbag is located beneath the steering wheel.^[17] The Toyota Avensis The Toyota Avensis is a large family car built in Derbyshire, United Kingdom by Japanese automaker Toyota since the 1998 model year. It is the successor of the Carina E and is available as a four-door saloon, five-door liftback and estate. A large MPV called the Toyota Avensis Verso is built in Japan on a separate platform. The Avensis is the became the first vehicle sold in Europe equipped with a driver's knee airbag.^[18][19] The EuroNCAP reported on the 2003 Avensis, "There has been much effort to protect the driver's knees and legs and a knee airbag worked well."^[20] Since then certain models have also included front passenger knee airbags, which deploy near or over the glove compartment in a crash. Knee airbags are designed to reduce leg injury. The knee airbag has become increasingly common in the 2000s, with a large minority of cars featuring them on the driver side by 2010. Passenger knee airbags remain extremely rare.

Rear curtain airbag

In 2008, the Toyota iQ launched featuring the first production rear curtain shield airbag to protect the rear occupants' heads in the event of a rear end impact.^[21]

Center airbag

In 2009, Toyota developed the first production rear-seat center airbag designed to reduce the severity of secondary injuries to rear passengers in a side collision. This system deploys from the rear center console first appearing in on the redesigned Crown Majesta.^[22]

Seat belt airbag

In 2009, the S-class ESF safety concept car showcased seatbelt airbags. They will be included standard on the production Lexus LFA in late 2010, and the 2011 Ford Explorer will offer rear seatbelt airbags as an option. Cessna Aircraft also now feature seatbelt airbags. They are now standard on the 172, 182, and 206.

On motorcycles

Various types of airbags were tested on motorcycles by the UK Transport Research Laboratory in the mid 1970s. In 2006 Honda introduced the first production motorcycle airbag safety system on its Gold Wing motorcycle. Honda claims that sensors in the front forks can detect a severe frontal collision and decide when to deploy the airbag, absorbing some of the forward energy of the rider and reducing the velocity at which the rider may be thrown from the motorcycle.^[23]

Airbag suits have also been developed for use by Motorcycle Grand Prix riders. They are connected to the motorcycle by a cable and deploy when the cable becomes detached from its mounting clip, inflating to protect the back.^[24]

How airbags work

The design is conceptually simple; a central "Airbag control unit"^[25] (ACU) (a specific type of ECU) monitors a number of related sensors within the vehicle, including accelerometers, impact sensors, side (door) pressure sensors,^[26] wheel speed sensors, gyroscopes, brake pressure sensors, and seat occupancy sensors. When the requisite 'threshold' has been reached or exceeded, the airbag control unit will trigger the ignition of a gas generator propellant to rapidly inflate a nylon fabric bag. As the vehicle occupant collides with and squeezes the bag, the gas escapes in a controlled manner through small vent holes. The airbag's volume and the size of the vents in the bag are tailored to each vehicle type, to spread out the deceleration of (and thus force experienced by) the occupant over time and over the occupant's body, compared to a seat belt alone.

The signals from the various sensors are fed into the Airbag control unit, which determines from them the angle of impact, the severity, or force of the crash, along with other variables. Depending on the result of these calculations, the ACU may also deploy various additional restraint devices, such as seat belt pre-tensioners, and/or airbags (including frontal bags for driver and front passenger, along with seat-mounted side bags, and "curtain" airbags which cover the side glass). Each restraint device is typically activated with one or more pyrotechnic devices, commonly called an initiator or electric match. The electric match, which consists of an electrical conductor wrapped in a combustible material, activates with a current pulse between 1 to 3 amperes in less than 2 milliseconds. When the conductor becomes hot enough, it ignites the combustible material, which initiates the gas generator. In a seat belt pre-tensioner, this hot gas is used to drive a piston that pulls the slack out of the seat belt. In an airbag, the initiator is used to ignite solid propellant inside the airbag inflator. The burning propellant generates inert gas which rapidly inflates the airbag in approximately 20 to 30 milliseconds. An airbag must inflate quickly in order to be fully inflated by the time the forward-traveling occupant reaches its outer surface. Typically, the decision to deploy an airbag in a frontal crash is made within 15 to 30 milliseconds after the onset of the crash, and both the driver and passenger airbags are fully inflated within approximately 60-80 milliseconds after the first moment of vehicle contact. If an airbag deploys too late or too slowly, the risk of occupant injury from contact with the inflating airbag may increase. Since more distance typically exists between the passenger and the instrument panel, the passenger airbag is larger and requires more gas to fill it.

Front airbags normally do not protect the occupants during side, rear, or rollover accidents.^[27] Since airbags deploy only once and deflate quickly after the initial impact, they will not be beneficial during a subsequent collision. Safety belts help reduce the risk of injury in many types of crashes. They help to properly position occupants to maximize the airbag's benefits and they help restrain occupants during the initial and any following collisions.

In vehicles equipped with a rollover sensing system, accelerometers and gyroscopes are used to sense the onset of a rollover event. If a rollover event is determined to be imminent, side-curtain airbags are deployed to help protect the occupant from contact with the side of the vehicle interior, and also to help prevent occupant ejection as the vehicle rolls over.

Triggering conditions

Airbags are designed to deploy in frontal and near-frontal collisions more severe than a threshold defined by the regulations governing vehicle construction in whatever particular market the vehicle is intended for: U.S. regulations require deployment in crashes at least equivalent in deceleration to a 23 km/h (14 mph) barrier collision, or similarly, striking a parked car of similar size across the full front of each vehicle at about twice the speed.^[28] International regulations are performance based, rather than technology-based, so airbag deployment threshold is a function of overall vehicle design.

Unlike crash tests into barriers, real-world crashes typically occur at angles other than directly into the front of the vehicle, and the crash forces usually are not evenly distributed across the front of the vehicle. Consequently, the relative speed between a striking and struck vehicle required to deploy the airbag in a real-world crash can be much higher than an equivalent barrier crash. Because airbag sensors measure deceleration, vehicle speed is not a good indicator of whether an airbag should have deployed. Airbags can deploy due to the vehicle's undercarriage striking a low object protruding above the roadway due to the resulting deceleration.

The airbag sensor is a MEMS accelerometer, which is a small integrated circuit with integrated micro mechanical elements. The microscopic mechanical element moves in response to rapid deceleration, and this motion causes a change in capacitance, which is detected by the electronics on the chip that then sends a signal to fire the airbag. The most common MEMS accelerometer in use is the ADXL-50 by Analog Devices, but there are other MEMS manufacturers as well.

Initial attempts using mercury switches did not work well. Before MEMS, the primary system used to deploy airbags was called a "rolamite". A rolamite is a mechanical device, consisting of a roller suspended within a tensioned band. As a result of the particular geometry and material properties used, the roller is free to translate with little friction or hysteresis. This device was developed at Sandia National Laboratories. The rolamite, and similar macro-mechanical devices were used in airbags until the mid-1990s when they were universally replaced with MEMS.

Nearly all airbags are designed to automatically deploy in the event of a vehicle fire when temperatures reach 150-200 °C (300-400 °F).^[29] This safety feature, often termed auto-ignition, helps to ensure that such temperatures do not cause an explosion of the entire airbag module.

Today, airbag triggering algorithms are becoming much more complex. They try to reduce unnecessary deployments and to adapt the deployment speed to the crash conditions. The algorithms are considered valuable intellectual property. Experimental algorithms may take into account such factors as the weight of the occupant, the seat location, seatbelt use, and even attempt to determine if a baby seat is present.

Inflation

When the frontal airbags are to deploy, a signal is sent to the inflator unit within the airbag control unit. An igniter starts a rapid chemical reaction generating primarily nitrogen gas (N₂) to fill the airbag making it deploy through the module cover. Some airbag technologies use compressed nitrogen or argon gas with a pyrotechnic operated valve ("hybrid gas generator"), while other technologies use various energetic propellants. Propellants containing the highly toxic sodium azide (NaN₃) were common in early inflator designs. However, propellants containing sodium azide were widely phased out during the 1990s in pursuit of more efficient, less expensive and less toxic alternatives.^{[citation needed]}

The azide-containing pyrotechnic gas generators contain a substantial amount of the propellant. The driver-side airbag would contain a canister containing about 50 grams of sodium azide. The passenger side container holds about 200 grams of sodium azide.^[30]

The alternative propellants may incorporate, for example, a combination of nitroguanidine, phase-stabilized ammonium nitrate (NH₄NO₃) or other nonmetallic oxidizer, and a nitrogen-rich fuel different than azide (e.g. tetrazoles, triazoles, and their salts). The burn rate modifiers in the mixture may be an alkaline metal nitrate (NO₃-) or nitrite (NO₂-), dicyanamide or its salts, sodium borohydride (NaBH₄), etc. The coolants and slag formers may be e.g. clay, silica, alumina, glass, etc.^[31] Other alternatives are e.g. nitrocellulose based propellants (which have high gas yield but bad storage stability, and their oxygen balance requires secondary oxidation of the reaction products to avoid buildup of carbon monoxide), or high-oxygen nitrogen-free organic compounds with inorganic oxidizers (e.g., di or tricarboxylic acids with chlorates (ClO₃-) or perchlorates (HClO₄) and eventually metallic oxides; the nitrogen-free formulation avoids formation of toxic nitrogen oxides).

From the onset of the crash, the entire deployment and inflation process is about 0.04 seconds. Because vehicles change speed so quickly in a crash, airbags must inflate rapidly to reduce the risk of the occupant hitting the vehicle's interior.

Variable-force deployment

Advanced airbag technologies are being developed to tailor airbag deployment to the severity of the crash, the size and posture of the vehicle occupant, belt usage, and how close that person is to the actual airbag. Many of these systems use multi-stage inflators that deploy less forcefully in stages in moderate crashes than in very severe crashes. Occupant sensing devices let the airbag control unit know if someone is occupying a seat adjacent to an airbag, the mass/weight of the person, whether a seat belt or child restraint is being used, and whether the person is forward in the seat and close to the airbag. Based on this information and crash severity information, the airbag is deployed at either a high force level, a less forceful level, or not at all.

Adaptive airbag systems may utilize multi-stage airbags to adjust the pressure within the airbag. The greater the pressure within the airbag, the more force the airbag will exert on the occupants as they come in contact with it. These adjustments allow the system to deploy the airbag with a moderate force for most collisions; reserving the maximum force airbag only for the severest of collisions. Additional sensors to determine the location, weight or relative size of the occupants may also be used. Information regarding the occupants and the severity of the crash are used by the airbag control unit, to determine whether airbags should be suppressed or deployed, and if so, at various output levels.

Post-deployment

A chemical reaction produces a burst of nitrogen to inflate the bag. Once an airbag deploys, deflation begins immediately as the gas escapes through vent(s) in the fabric (or, as it's sometimes called, the cushion) and cools. Deployment is frequently accompanied by the release of dust-like particles, and gases in the vehicle's interior (called effluent). Most of this dust consists of cornstarch, french chalk, or talcum powder, which are used to lubricate the airbag during deployment. Newer designs produce effluent primarily consisting of harmless talcum powder/cornstarch and nitrogen gas. In older designs using an azide-based propellant (usually NaN₃), varying amounts of sodium hydroxide nearly always are initially present. In small amounts this chemical can cause minor irritation to the eyes and/or open wounds; however, with exposure to air, it quickly turns into sodium bicarbonate (baking soda). However, this transformation is not 100% complete, and invariably leaves residual amounts of hydroxide ion from NaOH. Depending on the type of airbag system, potassium chloride (often used as a table salt substitute) may also be present.

For most people, the only effect the dust may produce is some minor irritation of the throat and eyes. Generally, minor irritations only occur when the occupant remains in the vehicle for many minutes with the windows closed and no ventilation. However, some people with asthma may develop a potentially lethal asthmatic attack from inhaling the dust.

Regulatory specifications

United States

On 11 July 1984, the U.S. government amended Federal Motor Vehicle Safety Standard 208 (FMVSS 208) to require cars produced after 1 April 1989 to be equipped with a passive restraint for the driver. An airbag or an automatic seat belt would meet the requirements of the standard. Airbag introduction was stimulated by the U.S. National Highway Traffic Safety Administration.^[32] However, airbags were not mandatory on light trucks until 1995.^{[citation needed]}

In 1998, FMVSS 208 was amended to require dual front airbags, and de-powered, or second-generation airbags were also mandated. This was due to the injuries caused by first-generation airbags, though FMVSS 208 continues to require that bags be engineered and calibrated to be able to "save" the life of an unbelted 50th-percentile size and weight "male" crash test dummy.

Outside the U.S.A.

Most countries^[who?] outside North America adhere to internationalized European ECE vehicle and equipment regulations rather than the U.S. Federal Motor Vehicle Safety Standards. ECE airbags are generally smaller and inflate less forcefully than U.S. airbags, because the ECE specifications are based on belted crash test dummies. In the United Kingdom, and most other developed countries there is no direct legal requirement for new cars to feature airbags. Instead, the Euro NCAP vehicle safety rating encourages manufacturers to take a comprehensive approach to occupant safety; a good rating can only be achieved by combining airbags with other safety features.^[33] Thus almost all new cars now come with at least two airbags as standard.

Maintenance

Inadvertent airbag deployment while the vehicle is being serviced can result in severe injury, and an improperly installed or defective airbag unit may not operate or perform as intended. Some countries impose restrictions on the sale, transport, handling, and service of airbags and system components. In Germany, airbags are regulated as harmful explosives; only mechanics with special training are allowed to service airbag systems. Under German Federal Law, used but intact airbags are to be detonated under secure conditions, must not be passed on to third parties in any way, and no untrained person is permitted to handle airbags. Purchase is restricted to buying a new replacement unit for immediate installation by the seller's qualified personnel.^{[citation needed]}

Some automakers (such as Mercedes-Benz) call for the replacement of undeployed airbags after a certain period of time to ensure their reliability in an accident. One example is the 1992 S500 which has an expiry date sticker attached to the door pillar. Škoda vehicles say 14 years from the date of manufacture. In this case replacement would be uneconomic as the car would have negligible value at 14 years old, far less than the cost of fitting new airbags. Volvo, on the other hand, has stated "airbags do not require replacement during the lifetime of the vehicle," though this cannot be taken as a guarantee on the device.^[34]

Injuries and fatalities

Airbags can injure or kill vehicle occupants. To provide crash protection for occupants not wearing seat belts, U.S. airbag designs trigger much more forcefully than airbags designed to the international ECE standards used in most other countries. Recent airbag controllers can recognize if a belt is used, and alter the bag deployment parameters accordingly.^[35]

Injuries such as abrasion of the skin, hearing damage from the extremely loud 165-175 dB deployment explosion, head injuries, eye damage, and broken nose, fingers, hands or arms can occur as the airbag deploys.^{[citation needed]} Most vehicle airbags are inflated using hot gas generated by a chemical process. Using hot gas allows the required pressure to be obtained with a smaller mass of gas than would be the case using lower temperatures. However, the hot gas can pose a risk of thermal burns if it comes in contact with the skin during deployment and occupant interaction. Burns are most common to the arms, face and chest. These burns are often deep dermal or second-degree burns that take longer to heal and risk scarring.^{[citation needed]}

In 1990, the first automotive fatality attributed to an airbag was reported,^[36] with deaths peaking in 1997 at 53 in the United States.^{[citation needed]} TRW produced the first gas-inflated airbag in 1994, with sensors and low-inflation-force bags becoming common soon afterwards. Dual-depth (also known as dual-stage) airbags appeared on passenger cars in 1998. By 2005, deaths related to airbags had declined, with no adult deaths and two child deaths attributed to airbags that year. Injuries remain fairly common in accidents with an airbag deployment.

Serious injuries are less common, but severe or fatal injuries can occur to vehicle occupants very near an airbag or in direct contact when it deploys. Such injuries may be sustained by unconscious drivers slumped over the steering wheel, unrestrained or improperly restrained occupants who slide forward in the seat during pre-crash braking, and properly belted drivers sitting very close to the steering wheel.

The increasing use of airbags may actually make rescue work for firefighters, emergency medical service and police officers more dangerous,^{[citation needed]} because of the risk of deployment while the emergency responder is assisting or extracting vehicle occupants.

Improvements in sensing and gas generator technology have allowed the development of third generation airbag systems that can adjust their deployment parameters to size, weight, position and restraint status of the occupant. These improvements have demonstrated a reduced injury risk factor for small adults and children who had an increased risk of injury with first generation airbag systems.^[37]

Airbag fatality statistics

From 1990 to 2008, the U.S. National Highway Traffic Safety Administration identified 175 fatalities caused by air bags. Most of these (104) have been children, while the rest are adults. About 3.3 million air bag deployments have occurred and the agency estimates more than 6,377 lives saved and countless injuries prevented.^[36][38]

A rear-facing infant restraint put in the front seat of a vehicle places an infant's head close to the airbag, which can cause severe head injuries, or death if the airbag deploys. Some modern cars include a switch to disable the front passenger airbag (although not in Australia, where rear-facing child seats are prohibited in the front where an airbag is fitted), in case a child-supporting seat is used there.

In vehicles with side airbags, it is dangerous for occupants to lean against the windows, doors, and pillars, or to place objects between themselves and the side of the vehicle. Articles hung from a vehicle's clothes hanger hooks can be hazardous if the vehicle's side curtain airbags deploy.^[39] A seat-mounted airbag may also cause internal injury if the occupant leans against the door.^[40]

Aerospace and military applications

The aerospace industry and the US Government have applied airbag technologies for many years. NASA, and US DoD have incorporated airbag systems in various aircraft and spacecraft applications as early as the 1960s.

Airbag landing systems

The first use of airbags for landing were Luna 9 and Luna 13, which landed on the Moon in 1966 and returned panoramic images. The Mars Pathfinder lander employed an innovative airbag landing system, supplemented with aerobraking, parachute, and solid rocket landing thrusters. This prototype successfully tested the concept, and the two Mars Exploration Rover Mission landers employed similar landing systems. The Beagle 2 Mars lander also tried to use airbags for landing, but the landing was unsuccessful for reasons which are not entirely known.

Airbags have also been used on military fixed wing aircraft such at the Escape Crew Capsule of the F-111 Aardvark.

Occupant protection

The US Army has incorporated airbags in its UH-60A/L^[41][42] Black Hawk and OH-58D Kiowa Warrior^[43] helicopter fleets. The Cockpit Air Bag System (CABS)^[44] consists of forward and lateral airbags with an Electronic Crash Sensor Unit (ECSU). The CABS system was conceived and developed by the US Army Aviation Applied Technology Directorate, Fort Eustis, Va.^[45] It is the first conventional airbag system for occupant injury prevention designed and developed specifically for helicopter applications.^[46][47]

See also

• Airplane airbags
• Automobile safety
• Safety standards
• Precrash system
• Airbag dermatitis

References

1. ^ Bags, Buckles, and Belts: The Debate over Mandatory Passive Restraints in Automobiles
2. ^ U.S. air bag history
3. ^ U.S. patent 6272412 - Passive restraint control system for vehicles
4. ^ Passive Seatbelt Systems and the 65 MPH Speed Limit: A Cause for Concern
5. ^ New York State memo re insurance discounts for passive restraints
6. ^ Popular Science May, 1968
7. ^ "Inventor of the Week: Archive". Web.mit.edu. http://web.mit.edu/invent/iow/breed.html. Retrieved 2010-02-27.
8. ^ ^{a b} Safety Design, John Fenton, The Times Jan 24 1969
9. ^ GM's ACRS
10. ^ "240 Landmarks of Japanese Automotive Technology - Subaru Legend airbag system". Jsae.or.jp. http://www.jsae.or.jp/autotech/data_e/7-3e.html. Retrieved 2009-12-08.
11. ^ Wilson, Robert (3 August 2005). "Citroen C4". The Australian. http://www.theaustralian.news.com.au/story/0,20867,16128857-13232,00.html. Retrieved 3 November 2009.
12. ^ "IIHS-HLDI: Chevrolet Cobalt 4-door". Iihs.org. http://www.iihs.org/ratings/ratingsbyseries.aspx?id=527. Retrieved 2010-02-27.
13. ^ "IIHS-HLDI: Dodge Ram 1500". Iihs.org. 2009-11-18. http://www.iihs.org/ratings/rating.aspx?id=1087. Retrieved 2010-02-27.
14. ^ BMW Head Protection System Sets New Standard in Side-Impact Protection in Latest IIHS Crash Test
15. ^ "Toyota to Make Side Airbags and Curtain Shield Airbags Standard on All New Passenger Vehicle Models in Japan". Theautochannel.com. 2007-07-23. http://www.theautochannel.com/news/2007/07/23/055878.html. Retrieved 2009-12-08.
16. ^ NHTSA Side-Impact Airbags
17. ^ "Kia Motors' Knee Airbag System | Firehouse.com". Cms.firehouse.com. http://cms.firehouse.com/web/online/University-of-Extrication/Kia-Motors-Knee-Airbag-System/19$708. Retrieved 2009-12-08.
18. ^ [1]
19. ^ "Toyoda Gosei". Toyoda Gosei. 2003-06-30. http://www.toyoda-gosei.com/news/2003/030630.html. Retrieved 2009-12-08.
20. ^ "For safer cars | Toyota Avensis". Euro NCAP. http://www.euroncap.com/tests/toyota_avensis_2003/172.aspx. Retrieved 2009-12-08.
21. ^ Abuelsamid, Sam (2009-03-23). "Toyota develops rear curtain airbag for tiny iQ — Autoblog Green". Autobloggreen.com. http://www.autobloggreen.com/2008/09/30/toyota-develops-rear-curtain-airbag-for-tiny-iq/. Retrieved 2009-12-08.
22. ^ Hellwig, Ed (2009-03-11). "Toyota Unveils First Rear Seat Center Airbag". Blogs.edmunds.com. http://blogs.edmunds.com/straightline/2009/03/toyota-unveils-first-rear-seat-center-airbag.html. Retrieved 2009-12-08.
23. ^ Motorcycle News '06 Wing gets airbag 2 September 2005
24. ^ Motorcycle News Dainese airbag suit in action 21 November 2007
25. ^ Airbag control unit at Audi.com Glossary
26. ^ at Continental.com
27. ^ Safercar.gov
28. ^ http://www.nhtsa.gov/people/injury/airbags/airbags03/page3.html
29. ^ "What You Need to Know About Air Bags, DOT HS 809 575". Nhtsa.dot.gov. http://www.nhtsa.dot.gov/people/injury/airbags/airbags03/page3.html. Retrieved 2009-12-08.
30. ^ ET 08/00: Sodium azide in car airbags poses a growing environmental hazard
31. ^ Thermally stable nonazide automotive airbag propellants - Patent 6306232
32. ^ http://www-nrd.nhtsa.dot.gov/pdf/nrd-01/Esv/esv16/98S8P12.PDF
33. ^ Frontal impact test description Euro NCAP website
34. ^ Bohr, Peter (July/August 2010), "Air Time", AAA World 12 (4): 24
35. ^ NHTSA 49 CFR Parts 552, 571, 585, and 595, Docket Notice
36. ^ ^{a b} National Highway Traffic Safety Administration Air Bag Fatalities
37. ^ American Journal of Epidemiology, Association of First- and Second-Generation Airbags with Front Occupant Death in Car Crashes: A Matched Cohort Study, October 4, 2005.
38. ^ The statement "...they've saved some 26,000 lives, according to estimates from the ... (NHTSA)" has been published. Bohr, Peter (July/August 2010), "Air Time", AAA World 12 (4): 24
39. ^ Toyota Aurion: User Manual 2006 model - Australia
40. ^ http://www.ncbi.nlm.nih.gov/pubmed/20184829
41. ^ Defenselink article
42. ^ US Army Demonstrates Simula's Cockpit Air Bag System at Helios.com
43. ^ FAS OH-58D article
44. ^ Simula CABS brochure
45. ^ Air Defense concept papers
46. ^ BNET News Release on AHS Annual Forum award
47. ^ Simula Receives Orders for its Cockpit Air Bag Systems at All Business.com

External links

• Airbag Information and Airbag Deployment video in slow motion
• Chemistry behind airbags
• Internals of airbag module (enclosure removed)
• Pictures and details about the 1970s GM Air Cushion Restraint System

Categories: Automotive safety technologies | American inventions | Aerospace

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