Airbag Restraint Systems Research Articles

Injury Severity for Hazard & Risk Analyses:Calculation of ISO 26262 S-parameter Values from Real-World Crash Data

Our goal was the development of a robust and data-driven approach to ISO 26262 injury severity (S-parameter) estimation, replacing the current heuristic methods. The situations investigated as part of an ISO 26262 hazard & risk analysis are broken down into crash configurations. These crashes are analyzed from the perspective of the ADAS-equipped vehicle with the failing system as well as from the crash opponent's point of view. Mainly due to sample size limitations, we focus on belted front-row vehicle occupants.We cluster the crash data into traffic domains (TD) based on the speed limit, i.e., residential streets, city roads, arterial thoroughfares, rural roads, and intercity highways and calculate the crash speed distribution for each domain. The injury severity clustering is based on the ISS injury aggregator with cut-offs at 4, 9, and 16 for S1, S2, and S3, respectively. We estimated the 90th-percentiles of the S-parameter cut-offs with a 95% confidence level using the GIDAS accident database. The percentiles were calculated for the ADAS-equipped vehicle as well as for the crash opponent, stratified for crash type (front, oblique, side). The stratification had to be detailed further for side crashes as impact direction (near-side vs. far-side) and availability of a curtain airbag restraint system have a significant impact on injury severity. The application of the results towards the assessment of a crossing scenario is detailed in the discussion.

A novel contact-enhanced low-g inertial switch with low-stiffness fixed electrode

A novel contact-enhanced low-g inertial switch with low-stiffness fixed electrode was designed, fabricated and tested for airbag restraint systems in this paper. Its sensitive direction is vertical of the switch. By adopting a novel low-stiffness arc structure as the fixed electrode and using Archimedean spiral beams to support center proof mass, the flexibility of the system increased and the contact duration extended. In order to restrict the radial displacement of the proof mass and keep it at the central zone of the switch, a circular limited post was installed at the center of the proof mass. The dynamic response of the switch was simulated and analyzed by ANSYS software. The simulation results indicate that the novel arc electrodes have low stiffness and the switch with this kind of new structure has long contact time. Six-layer photolithography and electroplating technology were used to fabricate the micro-switch and the overall dimension of the switch is 3850 μm × 3850 μm × 240 μm. Ultimately, the fabricated prototypes were tested by dropping hammer system. The contact times of the prototypes can be up to 260 μs under the acceleration with 26 g.

Injuries in Full-Scale Vehicle Side Impact Moving Deformable Barrier and Pole Tests Using Postmortem Human Subjects

Objective: To conduct near-side moving deformable barrier (MDB) and pole tests with postmortem human subjects (PMHS) in full-scale modern vehicles, document and score injuries, and examine the potential for angled chest loading in these tests to serve as a data set for dummy biofidelity evaluations and computational modeling.Methods: Two PMHS (outboard left front and rear seat occupants) for MDB and one PMHS (outboard left front seat occupant) for pole tests were used. Both tests used sedan-type vehicles from same manufacturer with side airbags. Pretest x-ray and computed tomography (CT) images were obtained. Three-point belt-restrained surrogates were positioned in respective outboard seats. Accelerometers were secured to T1, T6, and T12 spines; sternum and pelvis; seat tracks; floor; center of gravity; and MDB. Load cells were used on the pole. Biomechanical data were gathered at 20 kHz. Outboard and inboard high-speed cameras were used for kinematics. X-rays and CT images were taken and autopsy was done following the test. The Abbreviated Injury Scale (AIS) 2005 scoring scheme was used to score injuries.Results: MDB test: male (front seat) and female (rear seat) PMHS occupant demographics: 52 and 57 years, 177 and 166 cm stature, 78 and 65 kg total body mass. Demographics of the PMHS occupant in the pole test: male, 26 years, 179 cm stature, and 84 kg total body mass. Front seat PMHS in MDB test: 6 near-side rib fractures (AIS = 3): 160–265 mm vertically from suprasternal notch and 40–80 mm circumferentially from center of sternum. Left rear seat PMHS responded with multiple bilateral rib fractures: 9 on the near side and 5 on the contralateral side (AIS = 3). One rib fractured twice. On the near and contralateral sides, fractures were 30–210 and 20–105 mm vertically from the suprasternal notch and 90–200 and 55–135 mm circumferentially from the center of sternum. A fracture of the left intertrochanteric crest occurred (AIS = 3). Pole test PMHS had one near-side third rib fracture. Thoracic accelerations of the 2 occupants were different in the MDB test. Though both occupants sustained positive and negative x-accelerations to the sternum, peak magnitudes and relative changes were greater for the rear than the front seat occupant. Magnitudes of the thoracic and sternum accelerations were lower in the pole test.Conclusions: This is the first study to use PMHS occupants in MDB and pole tests in the same recent model year vehicles with side airbag and head curtain restraints. Injuries to the unilateral thorax for the front seat PMHS in contrast to the bilateral thorax and hip for the rear seat occupant in the MDB test indicate the effects of impact on the seating location and restraint system. Posterolateral locations of fractures to the front seat PMHS are attributed to constrained kinematics of occupant interaction with torso side airbag restraint system. Angled loading to the rear seat occupant from coupled sagittal and coronal accelerations of the sternum representing anterior thorax loading contributed to bilateral fractures. Inward bending initiated by the distal femur complex resulting in adduction of ipsilateral lower extremity resulted in intertrochanteric fracture to the rear seat occupant. These results serve as a data set for evaluating the biofidelity of the WorldSID and federalized side impact dummies and assist in validating human body computational models, which are increasingly used in crashworthiness studies.

Deformable Carbon Nanotube-Contact Pads for Inertial Microswitch to Extend Contact Time

We have demonstrated a batch-fabricated inertial microswitch with extended contact time using carbon nanotube (CNT)-contact pads. Self-assembled and aligned CNT bundles, as deformable electromechanical contact pads are selectively synthesized on fully fabricated single crystal silicon microstructures. Outstanding mechanical flexibility and resilience, as well as electrical conductivity of CNTs, make them suitable as an electromechanical contact material. It is experimentally verified that the elastic deformation of CNTs dramatically enhances the contact time of the inertial microswitch from 7.5 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{s}$</tex></formula> to 114 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{s}$</tex></formula> . Due to the prolonged contact time, the presented inertial microswitch provides reliable and easy detection of threshold acceleration, which is crucial in diverse commercial applications such as airbag restraint systems in vehicles or geriatric healthcare systems.

Occupant and Crash Characteristics for Case Occupants With Cervical Spine Injuries Sustained in Motor Vehicle Collisions

Motor vehicle collisions (MVCs) are the leading cause of spine and spinal cord injuries in the United States. Traumatic cervical spine injuries (CSIs) result in significant morbidity and mortality. This study was designed to evaluate both the epidemiologic and biomechanical risk factors associated with CSI in MVCs by using a population-based database and to describe occupant and crashes characteristics for a subset of severe crashes in which a CSI was sustained as represented by the Crash Injury Research Engineering Network (CIREN) database. Prospectively collected CIREN data from the eight centers were used to identify all case occupants between 1996 and November 2009. Case occupants older than 14 years and case vehicles of the four most common vehicle types were included. The National Automotive Sampling System's Crashworthiness Data System, a probability sample of all police-reported MVCs in the United States, was queried using the same inclusion criteria between 1997 and 2008. Cervical spinal cord and spinal column injuries were identified using Abbreviated Injury Scale (AIS) score codes. Data were abstracted on all case occupants, biomechanical crash characteristics, and injuries sustained. Univariate analysis was performed using a χ analysis. Logistic regression was used to identify significant risk factors in a multivariate analysis to control for confounding associations. CSIs were identified in 11.5% of CIREN case occupants. Case occupants aged 65 years or older and those occupants involved in rollover crashes were more likely to sustain a CSI. In univariate analysis of the subset of severe crashes represented by CIREN, the use of airbag and seat belt together (reference) were more protective than seat belt alone (odds ratio [OR]=1.73, 95% confidence interval [CI]=1.32-2.27) or the use of neither restraint system (OR=1.45, 95% CI=1.02-2.07). The most frequent injury sources in CIREN crashes were roof and its components (24.8%) and noncontact sources (15.5%). In multivariate analysis, age, rollover impact, and airbag-only restraint systems were associated with an increased odds of CSI. Using the population-based National Automotive Sampling System's Crashworthiness Data System data, 0.35% of occupants sustained a CSI. In univariate analysis, older age was noted to be a significant risk factor for CSI. Airbag-only restraint systems and both rollover and lateral crashes were also identified as risk factors for CSI. In addition, increasing delta v was highly associated with CSIs. In multivariate analysis, similar risk factors were noted. Of all the restraint systems, seat belt use without airbag deployment was found to be the most protective restraint system (OR=0.29, 95% CI=0.16-0.50), whereas airbag-only restraint was associated with the highest risk of CSI (OR=3.54, 95% CI=2.29-5.46). Despite advances in automotive safety, CSIs sustained in MVC continue to occur too often. Older case occupants are at an increased risk of CSI. Rollover crashes and severe crashes led to a much higher risk of CSI than other types and severity of MVCs. Seat belt use is very effective in preventing CSI, whereas airbag deployment may increase the risk of occupants sustaining a CSI. More protection for older occupants is needed and protection in both rollover and lateral crashes should remain a focus of the automotive industry. The design of airbag restraint systems should be evaluated so that they are not causative of serious injury. In addition, engineers should continue to focus on improving automotive design to minimize the risk of spinal injury to occupants in high severity crashes.

Protecting Performance Analysis and Structural Optimization of a Sandwiched Tube-type Airbag

It is well known that airbag restraint system is a kind of effective and important passive safety equipment; it can reduce the impact force of the second collision during a crash. However, airbag not only provides protection but also may cause injuries to the occupants especially to the out-of-position occupants. So it is quite necessary to proceed with further researches on its related techniques to minimize the possible side-effects. A further research on the sandwiched tube-type airbag invented by the author is made. The sled tests and virtual testing technique are used together, first the collision accelerations are collected from sled tests and treated as baseline. The baseline curves are synthesized with the white noise generated by the computer to form the collision curves for the virtual tests. By using the finite element modeling technology and MADYMO virtual testing technique, the static initiation characteristics and protection effect of the sandwiched tube-type airbag are analyzed, and the simulation results indicate that the tube-type airbag deploys steadily and the deploying mode is well controllable, so it can reduce the injury risk and provide better protections to the out-of-position occupants. The structural optimization is performed to work out the potential instability problem.

A Novel Threshold Accelerometer With Postbuckling Structures for Airbag Restraint Systems

Based on the postbuckling theory of large deflection beams, the nonlinear stiffness of a postbuckling beam is deduced and in agreement with the results of buckling experiments. Then, a novel post machined threshold accelerometer is designed, which consists of eight oblique post beams with an inertial mass in the middle to ensure its single moving direction and an electrical contact part fabricated on the bottom of the inertial mass. The threshold accelerometer is an integration of a threshold sensor and an inertial driven actuator used in airbag restraint systems. When the acceleration reaches the threshold, the beams buckle and close the threshold accelerometer, and when it gets down to be a certain value, the accelerometer opens quickly under the effect of the elastic force developed by the postbuckling beams. Compared with the design models of other threshold accelerometers with linear beam structures, the nonlinear postbuckling beams are introduced as threshold sensing elements. A number of design factors such as the air film damping and the contact force are taken into full consideration, thus establishing the dynamic equation of the accelerometer under coupled forces. The dynamical simulation for the strong nonlinear system with elliptic integrals indicates its good threshold characteristic and high contact reliability. The threshold accelerometer responds within 4 ms when it is triggered by a threshold acceleration ac = 20 g, and cuts off quickly when the cutoff acceleration is under ad = 5 g. Meanwhile, the unstable contact time is only 0.02 ms for the contact force to reach 50 mN, which guarantees the contact resistance to be less than 20 mOmega. With the results of the dynamic simulation, supported by previous buckling experiments, the accelerometer can provide accurate threshold sensing without false actuations under interferences outside, especially electromagnetic and vibration interferences, and hence their wide applications in safe-arming systems.

Microelectrical Mechanical Systems in Surgery and Medicine

It is apparent that in the year 2001, the methods by which one negotiates the world are becoming more efficient and more powerful. This phenomenon is encountered when checking email or reviewing the latest journal articles on a desktop computer. The trend in microcomputing is evident in surgery, which is certainly at the forefront of miniaturization technology. To take advantage of next generation tools, physicians must first be aware of the current trends in technology, and then understand them well. The need for such an understanding serves as the impetus for this discussion of microelectromechanical systems (MEMSs). MEMS comprise a technology that most use without realizing it. A car with an airbag restraint system, for example, is likely to use a micromechanical system in the form of an accelerometer, which deploys a life-saving airbag (Fig. 1). Other common examples include the nozzle in an inkjet printer, the fuel injection system in a car, and the sensor in a vehicle’s antitheft system. Surgeons, internists, and researchers have always tried to interact directly with the physical domain of the diseases that are fought every day. Surgeons have long used loupes to reapproximate tissues on the microscopic level. Oncology, transplant surgery, and cardiology researchers have tried to approach diseases microscopically. MEMS technology allows us to do this. Most MEMS devices are less than the size of a 50m human hair and can be used singly or in vast groups of millions. Such miniaturization might seem at the outset to be advantageous in all circumstances, but this is not universally true. Some of these devices can be outsized and overpowered by the organic and physiologic processes they encounter, reducing their effectiveness. Because a microscopic dimension is not always efficient, intense planning for the scaling of these devices is imperative. As the medical community continues to rely on computers to enhance treatment, physicians require an instrument that does not only function to compute, but one that also performs actual tasks. MEMS fill this need. MEMS involve integrated circuits, which can actuate, sense, and modify the outside world, on the micrometer scale. One must begin by reviewing the theory of micromechanical devices. These devices are made largely of silicon, the same material used in producing the central processor of a personal computer. They perform on the micron level, having sizes of approximately 10 to hundreds of micrometers. Some are smaller than the width of a human hair. MEMS are generated using a unique fabrication method called micromachining. Each micromachined device will have a particular capability that will interact with the world on the macro scale. Specifically, there are three main advantages to MEMS: size, reliability, and inexpensive production cost. All MEMS fabrication methods share particular common features, which will be discussed in the following sections. There are advantages and disadvantages that are inherent to MEMS technology. To understand these points, it will be useful to have at least a cursory understanding of the MEMS “toolbox.” This article provides insight into the toolbox by dissecting the fabrication process involved in the manufacture of integrated circuits, and will touch on many of the aspects that are involved in the fabrication of micromechanical devices in a manner intended to be useful to the nonengineer physician. The goal is to outfit the reader with a meaningful understanding of the basic science behind each of the real-world applications discussed in Section II of the article. In Section III, there are descriptions of a number of important, existing medical applications of MEMS technology, with a succinct discussion of the advantages and disadvantages of each. Section IV reviews some disadvantages of the technology as an overall field, and No competing interests declared.

The air bag system: What went wrong with the systems engineering?

The air bag restraint system in automobiles has received a great deal of attention since the summer of 1996. The purpose of this paper is to review the successes and failures of the air bag from its introduction in 1988–1996 and to relate these successes and failures to the requirements that led to the current air bag design. The issue addressed in this paper is whether the systems engineering development process that led to the first generation air bag system could be considered reasonably successful. This question is not the same as whether the first generation air bag was better than no air bag system for the spectrum of drivers and passengers in automobiles and light trucks. Rather the issue is whether the first generation air bag system addresses the spectrum of requirements one could expect from such a system. Finally suggestions are made about how the requirements development process can be improved for all systems, considering the obvious and not-so-obvious mistakes that were made during the development of the air bag. © 1998 John Wiley & Sons, Inc. Syst Eng 1: 90-94, 1998

The Air Bag System: What Went Wrong with the Systems Engineering?

ABSTRACTThe air bag restraint system in automobiles has received a great deal of attention since the summer of 1996. The purpose of this paper is to review the successes and failures of the air bag since its introduction in 1988 and to relate these successes and failures to the requirements that led to the current air bag design. Finally suggestions are made about how the requirements development process can be improved for all systems, considering the obvious and not‐so‐obvious mistakes that were made during the development of the air bag.

Airbag safety: Deployment in an automobile crash with a fall from height

Airbag restraint systems have demonstrated a significant reduction in mortality in motor vehicle crashes (MVCs). While airbag devices are effective primarily in frontal or near-frontal impacts, little is known about the efficacy of these devices in nonfrontal types of collisions. Moreover, there are reports of injuries specific to airbag deployment that have led some investigators to question the benefit of such devices. This article reports a rollover MVC with a considerable fall from height in which lap/shoulder belts were used in addition to airbag deployment that resulted in protection of the driver from injury. The outcome of this case continues to support the combination of belt and airbag restraint systems as the most effective occupant protection in both frontal and nonfrontal types of MVCs.

PATTERNS OF FRACTURE AFTER AIR BAG DEPLOYMENT

The airbag restraint system has been described as a means of reducing fatalities in frontal crashes. This conclusion is based on crash investigations and statistical extrapolation, but few data exist to document specific fracture patterns and injuries after airbag deployment. Seven cases of driver's side airbag deployment after motor vehicle crashes were studied for extent of injury. Unrestrained (non-seatbelted) drivers demonstrated flexion injuries of the cervical and thoracic spine and direct impaction fractures of the face and sternum. One restrained (lap-shoulder belt) driver demonstrated an extension injury of the upper cervical spine. What may emerge from further study is a decrease in fatalities, but also a pattern of fractures specific to airbag use.

Air bags: Lifesaving with toxic potential?

Federal Motor Vehicle Safety Standard No. 208, “Occupant Crash Protection”, requires that all passanger cars manufactured after September 1, 1989 be equipped with automatic crash protection. Car manufacturers met this requirement by installing automatic safety belts or air bags. No chemical injuries have been reported as a result of airbag deployment in motor vehicle accidents (MVA). A 6-month retrospective study was conducted to evaluate the toxic effects of the white powdery residue from air bags, a combination of talc and sodium hydroxide, found in the driver compartment after an MVA. The study reviewed time to onset of symptoms, symptomatology, and treatment. The study included seven patients exposed to deployed air bags after an MVA. Four cases resulted in dermal burns and three patients were diagnosed with unrelated injuries. Three patients presented to an emergency department within 48 hours of the exposure complaining of burns to the skin. Two patients attempted home therapy but became concerned when the symptoms did not subside. One patient was discharged with the diagnosis of first degree burns of the chin and left hand. Another patient experienced bilateral hand erythema and blisters. Standard burn therapy was instituted in both instances. A third patient arrived 1 hour post-exposure to the emergency department complaining of a burning sensation to the hands, but the skin appeared normal. Thorough irrigation was initiated and Silvadene (Marion, Kansas City, MO) applied. One patient notified the poison center 1 hour post-exposure complaining of erythema and burning to his hands after an MVA. Vehicle air bag restraint systems are a new phenomenon that can result in dermal injury due to the presence of sodium hydroxide. All cases were treated symptomatically and recovered without significant effect. Although automobile safety air bags are a reliable, proven method of occupant protection against severe injury in an MVA, they are associated with at least minor corrosive toxicity. We recommend that all patients exposed to deployed air bags have thorough skin irrigation to decrease the potential for dermal irritation or burns.

Primary Components of Simulated Air Bag Noise and Their Relative Effects on Human Hearing

Air bag inflation noise contains a positive pressure pulse caused by the air bag volume displacement and a high-frequency noise burst associated with bag unfolding, air turbulence, and the like. Auditory temporary threshold shift (TTS) was measured for 12 discrete frequencies (125-12-kHz range) for volunteers exposed to (1) a positive pressure pulse of 165 dBpk, (2) a high-frequency noise burst of 153 dBrms, and (3) (1) and (2) presented simultaneously. Results indicated that (a) the high-frequency noise burst produced the greatest amount of TTS, (b) the positive pressure pulse produced no measurable TTS, and (c) the two components occurring simultaneously produced less TTS than the high-frequency noise burst alone. TTS associated with air bag inflation noise is primarily the product of the high-frequency noise. It is indicated that the positive pressure pulse reduces the effectiveness of the high-frequency noise in producing TTS. Some implications of these observations relative to the use of air bag restraint systems are discussed.