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Markov Chain-based Reliability Analysis for Automotive Fail-Operational Systems

SAE International Journal of Connected and Automated Vehicles

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SAE International Journal of Transportation Safety

AUDI AG-Andre Kohn, Rolf Schneider
Infineon Technologies AG-Antonio Vilela, Udo Dannebaum
  • Journal Article
  • 2017-01-0052
Published 2017-03-28 by SAE International in United States
A main challenge when developing next generation architectures for automated driving ECUs is to guarantee reliable functionality. Today’s fail safe systems will not be able to handle electronic failures due to the missing “mechanical” fallback or the intervening driver. This means, fail operational based on redundancy is an essential part for improving the functional safety, especially in safety-related braking and steering systems. The 2-out-of-2 Diagnostic Fail Safe (2oo2DFS) system is a promising approach to realize redundancy with manageable costs. In this contribution, we evaluate the reliability of this concept for a symmetric and an asymmetric Electronic Power Steering (EPS) ECU. For this, we use a Markov chain model as a typical method for analyzing the reliability and Mean Time To Failure (MTTF) in majority redundancy approaches. As a basis, the failure rates of the used components and the microcontroller are considered. The comparison to a non-redundant system shows a significantly higher reliability and MTTF of the redundant approaches.
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The Effect of Age on Fat and Bone Properties along the Vertebral Spine

SAE International Journal of Transportation Safety

University of Michigan-Chantal Parenteau, Sven Holcombe, Peng Zhang, Carla Kohoyda-Inglis, Stewart Wang
  • Journal Article
  • 2013-01-1244
Published 2013-04-08 by SAE International in United States
The human body changes as it becomes older. The automotive safety community has been interested in understanding the effect of aging on restraint performance. Recent research has been focused on assessing the structural and material changes associated with age. In this study, structural tissue distribution was determined using the computed tomography (CT) scan data of more than 19,000 patients, aged 16 and up. The data consisted of subcutaneous fat cross-sectional area, visceral fat cross-sectional area, and trabecular bone density taken at each vertebral level. The data was quantified as a function of five age groups with the youngest group defined as 16-29 years old and the oldest group as 75 and up. An additional analysis stratified on gender was carried out.Overall, visceral fat increased with age. Compared to the 16-29 group, the visceral fat measured at the L1 level was 1.97 in the 30-44 group, 2.55 in the 45-59 group, 3.33 in the 60-74 group and 3.21 times greater in the 75+ group. Subcutaneous fat also increased with age up to the 60-74-year-old group. The…
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Numerical Prediction of Dynamic Progressive Buckling Behaviors of Single-Hat and Double-Hat Steel Components under Axial Loading

SAE International Journal of Transportation Safety

Clifford Chou
Indian Institute Of Science-Bisheshwar Haorongbam, Anindya Deb
  • Journal Article
  • 2013-01-0458
Published 2013-04-08 by SAE International in United States
Hat sections, single and double, made of steel are frequently encountered in automotive body structural components such as front rails, B-Pillar, and rockers of unitized-body cars. These components can play a significant role in terms of impact energy absorption during collisions thereby protecting occupants of vehicles from severe injury. Modern vehicle safety design relies heavily on computer-aided engineering particularly in the form of explicit finite element analysis tools such as LS-DYNA for virtual assessment of crash performance of a vehicle body structure. There is a great need for the analysis-based predictions to yield close correlation with test results which in turn requires well-proven modeling procedures for nonlinear material modeling with strain rate dependence, effective representation of spot welds, sufficiently refined finite element mesh, etc. Although hat sections subject to axial loading have been studied widely in published literature, it is difficult to come across detailed information on modeling that can lead to sound correlation of CAE predictions with experimental results even for quasi-static conditions. In the current study, both single-hat and double-hat components made of…
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Front Rail Crashworthiness Design for Front Oblique Impact Using a Magic Cube Approach

SAE International Journal of Transportation Safety

Beijing Automotive Technology Center-Yi Ding
Beijing Automotive Technology Center/Dalian Univ. of Tech.-Sibo Hu
  • Journal Article
  • 2013-01-0651
Published 2013-04-08 by SAE International in United States
The front rail, as one main energy absorption component of vehicle front structures, should present steady progressive collapse along its axis and avoid bending collapse during the front oblique impact, but when the angle of loading direction is larger than some critical angle, it will appear bending collapse causing reduced capability of crash energy absorption. This paper is concerned with crashworthiness design of the front rail on a vehicle chassis frame structure considering uncertain crash directions. The objective is to improve the crash direction adaptability of the front rail, without deteriorating the vehicle's crashworthiness performance. Magic Cube (MQ) approach, a systematic design approach, is conducted to analyze the design problem. By applying Space Decomposition of MQ, an equivalent model of the vehicle chassis frame is generated, which simplifies the design problem. Based on this model, a two-layered front rail is proposed using a multi-step multi-domain topology optimization method and a response surface method. Numerical simulations are carried out with Altair/Hypermesh and LS-DYNA to compare the crashworthiness performances of the original front rail and the proposed…
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Analysis of Seat Belt Positioning in Recent NCAP Crash Tests

SAE International Journal of Transportation Safety

Automotive Safety Analysis Corporation-David Biss
National Crash Analysis Center-Randa Radwan Samaha
  • Journal Article
  • 2013-01-0460
Published 2013-04-08 by SAE International in United States
The objective of this study was to analyze the position of the shoulder belt and adjustable upper anchorage (AUA) relative to the occupant in recent (2011-2012) NHTSA NCAP frontal crash tests. Since 2011, certain changes have been made in the NCAP test procedure. These changes include different Hybrid III occupant sizes as well as variations in the methods for calculating injury risk. One of the most significant changes has to do with thoracic injury risk calculation which was previously associated with chest acceleration and is now based on chest deflection as the measurable parameter. Using the NHTSA NCAP database, as well as other crash test data sources, a comparison was made between the designated upper anchorage position prior to a crash test and the actual position of the belt webbing with respect to the chest deflection measurement potentiometer sub-assembly of the Hybrid III. It was found that virtually all of the recent NCAP tests reported a disparity between the position of the shoulder belt webbing and the location of the chest deflection measurement sub-assembly. Furthermore,…
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The Front Center Airbag

SAE International Journal of Transportation Safety

General Motors Company-Scott D. Thomas, Jacqueline E. Brown
Takata-Richard A. Wiik
  • Journal Article
  • 2013-01-1156
Published 2013-04-08 by SAE International in United States
General Motors and the Takata Corporation have worked together to bring to production a new, industry first technology called the Front Center Airbag which is being implemented on General Motors' 2013 Midsize Crossover Vehicles. This paper reviews field data, describes the hardware, and presents occupant test data to demonstrate in-position performance in far side impacts.The Front Center Airbag is an airbag that mounts to the inboard side of the driver front seat. It has a tubular cushion structure, and it deploys between the front seating positions in far side impacts, near side impacts and rollovers, with the cushion positioning itself adjacent the driver occupant's head and torso. This paper includes pictures of the technology along with a basic description of the design.In-position occupant performance is also described and illustrated with several examples. Single occupant and two front occupant far side impact test data are included, both with and without the airbag present. Resulting performance differences are discussed leading to the following test observations: a) In a far side impact with a single driver occupant present,…
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Full-Scale Burn Test of a 1992 Compact Pick-up Truck

SAE International Journal of Transportation Safety

Exponent-Jeff D. Colwell, Michael E. Cundy
  • Journal Article
  • 2013-01-0209
Published 2013-04-08 by SAE International in United States
A full-scale burn test of a 1992 compact pick-up truck was conducted to evaluate how temperature distributions changed over time, the manner in which the fire spread, and how burn patterns produced during the fire correlated with important characteristics of the fire such as the area of origin. After the fire was initiated on the lower portion of the dashboard of the test vehicle, it spread locally to nearby dashboard material and, at the same time, developed a strong temperature gradient from the ceiling to the floor. Once the ceiling temperature reached about 600°C, the rate of fire spread increased and, within 1 minute, the passenger compartment was fully involved. Initiation of the engine compartment fire, which occurred about 4 minutes after the passenger compartment was fully involved, was consistent with fire spread through the heating, ventilation, and air conditioning (HVAC) duct that passed through the passenger's side of the bulkhead. Instead of spreading to nearby combustibles on the passenger's side of the engine compartment, the fire spread to the driver's side of the engine…
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Flex-PLI Application to High-Bumper Vehicles - Optimization of Supplemental Weight

SAE International Journal of Transportation Safety

Nissan Motor Company, Ltd.-Yoshiko Kawabe, Chinmoy Pal, Hiroyuki Okuyama, Tomosaburo Okabe
  • Journal Article
  • 2013-01-0215
Published 2013-04-08 by SAE International in United States
The Flexible Pedestrian Legform Impactor (Flex-PLI) was developed to evaluate the risk of pedestrian lower extremity injuries. However, it has been pointed out that the post-crash kinematics of the Flex-PLI differs from those of a human body when it is hit by high-bumper vehicles. This paper describes the feasibility of applying the Flex-PLI to a wide range of vehicle types by adding a supplemental weight. The following aspects are discussed in this regard: A human body finite element (FE) model analysis shows that the upper body of the Flex-PLI is not involved in tibia and knee ligament injury indexes in the first contact with a high-bumper vehicle.A rigid bar model is introduced and its rotational energy ratio is formulated. The rotational energy ratio is employed to evaluate the post-crash kinematics of the Flex-PLI and a human leg model.The feasibility of adding a supplemental weight to the Flex-PLI with regard to the bumper height is discussed.
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The Accuracy and Sensitivity of 2005 to 2008 Toyota Corolla Event Data Recorders in Low-Speed Collisions

SAE International Journal of Transportation Safety

MEA Forensic Engineers & Scientists-Craig Wilkinson, Jonathan Lawrence, Tim Nelson, James Bowler
  • Journal Article
  • 2013-01-1268
Published 2013-04-08 by SAE International in United States
Collision related data stored in the airbag control modules (ACM's) of Toyota vehicles can provide useful information to collision investigators, including both front and rear collision severity. Previous studies of ACM's from other manufacturers found that the devices underestimated the actual speed change in low speed frontal collisions. To quantify the accuracy and sensitivity of select 2005 to 2008 Toyota ACM's, in-vehicle crash tests and linear sled tests were performed in both front and rear impact orientations. A 2005 Toyota Corolla with five extra ACM's mounted in the right front seat position underwent a series of vehicle-to-barrier collisions with speed changes of up to 10 km/h. Next, the same six Toyota ACMs underwent a range of crash pulses using a linear sled. In all in-vehicle tests, the speed change reported by the ACM underestimated the actual speed change for frontal collisions, and overestimated the actual speed change for rear-end collisions. The speed change underestimates ranged from 1.3 to 2.6 km/h and the speed change overestimates ranged from 0.6 to 2.2 km/h. The magnitude of the…
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Ballistic Testing of Motorsport Windshields

SAE International Journal of Transportation Safety

NASCAR-John Patalak, Thomas Gideon
  • Journal Article
  • 2013-01-0801
Published 2013-04-08 by SAE International in United States
Since its inception in 1948, NASCAR® (National Association for Stock Car Auto Racing, Inc.) has continually strived to promote and improve driver, crew and spectator safety. As the vehicles used in NASCAR have changed over the years, their windshields have evolved also. The 1948 NASCAR Rulebook specified that all cars must have safety glass. In 2013, the NASCAR Sprint cup Series will use a laminated polycarbonate windshield. This paper describes the ballistic testing of the latest polycarbonate laminated design as well as previous monolithic polycarbonate designs.
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