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Machine Learning considerations in the context of Automotive Functional Safety Requirements for Autonomous Vehicles

General Motors LLC-Vijai K Gopalakrishnan
  • Technical Paper
  • 2019-28-2519
Published 2019-11-21 by SAE International in United States
We are currently in the age of developing Autonomous Vehicles (AV). Never before in history, the environment has been as conducive as today for these developments to come together to deliver a mass produced autonomous car for use by general public on the roads. Several enhancements in hardware, software, standards and even business models are paving the way for rapid development of AVs, bringing them closer to production reality. Safety is an indispensable consideration when it comes to transportation products, and ground vehicle development is no different. We have several established standards. When it comes to Autonomous Vehicle development, an important consideration is ISO 26262 for, Automotive Functional Safety. Going from generic frameworks such as Failure Mode and Effects Analyses (FMEA) and Hazard and operability study (HAZOP) to Functional Safety, Safety of Intended Functionality, and Automotive Safety Integrity Levels specific is a natural progression. This, in specific to AV development context with a renewed perspective is the need of the hour. The fundamental assumption of a human driver being part of the vehicle, considered in…
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Changes in user experiences of electric vehicles

General Motors LLC-Pandurang Baliga, Tulasi KL
General Motors Technical Center India-Rudrappa Madagunki
  • Technical Paper
  • 2019-28-2489
Published 2019-11-21 by SAE International in United States
Research Objective The objective of the paper is to research what are the changes in experiences being brought about due to the advent of Electric Vehicles (EVs). EVs are silent, have less complex propulsion system, and have free space under the hood, amongst other things. Each change brings about both good and bad experiences across the spectrum of users. Some of the bad experiences can be safety incidents leading to death as well. Researching the areas that are harmful to end users, including pedestrians, will be our focus area. Methodology Our methodology will look at the changes at the vehicle architecture level which are inherent to the EV design. Research how are the experiences so far due to these changes. Are these just inconveniences or safety hazards? EVs have excellent NVH characteristics. A farmer may love a silent tractor, but a racing enthusiast may not like a relatively silent sports car. A silent armored vehicle may be what the army needs, but a silent car’s approach may be a last-minute surprise to an unsuspecting pedestrian,…
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Benefits and Application Bandwidth of Phenolic Piston Material in Opposed Piston Calipers

General Motors LLC-David B. Antanaitis, Mark Riefe
SBHPP-Chris Ciechoski
Published 2019-09-15 by SAE International in United States
The use of reinforced phenolic composite material in application to hydraulic pistons for brake calipers has been well established in the industry - for sliding calipers (and certain fixed calipers with high piston length to diameter ratios). For decades, customers have enjoyed lower brake fluid temperatures, mass savings, improved corrosion resistance, and smoother brake operation (less judder). However, some persistent concerns remain about the use of phenolic materials for opposed piston calipers. The present work explores two key questions about phenolic piston application in opposed piston calipers. Firstly, do opposed piston calipers see similar benefits? Do high performance aluminum bodied calipers, where the piston may no longer be a dominant heat flow path into the fluid (due to a large amount of conduction and cooling enabled by the housing), still enjoy fluid temperature reductions? Are there still benefits for judder with the much shorter length to diameter ratio the pistons have in these applications? Secondly - it is clear that the much shorter length to diameter ratio of the piston in opposed piston calipers will…
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Braking with a Trailer and Mountain Pass Descent

General Motors LLC-David B. Antanaitis, Brent Lowe
Published 2019-09-15 by SAE International in United States
A truly strange - but very interesting - juxtaposition of thought occurs when considering customer’s deceleration needs for towing heavy trailers in mountainous regions, and the seemingly very different area of sizing brakes for Battery Electric Vehicles (BEV) and other regenerative braking-intensive vehicle applications, versus brakes for heavy-duty trucks and other vehicles rated to tow heavy trailers. The common threads between these two very different categories of vehicles include (a) heavy dependence on the powertrain and other non-brake sources of energy loss to control the speed of the vehicle on the grade and ensure adequate capacity of the brake system, (b) a need to consider descent conditions where towing a heavy trailer is feasible (in the case of heavy trailer towing) or initiating a descent with a full state of charge is realistic (in the case of BEVs), which forces consideration of different descents versus the typical (for brake engineers) mountain peak descent. In this paper, a vehicle operator-based requirement is derived that integrates engine (or motor), transmission (or gearbox), driveline, brake system, brake cooling,…
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Combustion-Timing Control of Low-Temperature Gasoline Combustion (LTGC) Engines by Using Double Direct-Injections to Control Kinetic Rates

General Motors LLC-Jeremie Dernotte
Sandia National Laboratories-Gerald Gentz, Chunsheng Ji, Dario Lopez Pintor, John Dec
Published 2019-04-02 by SAE International in United States
Low-temperature gasoline combustion (LTGC) engines can provide high efficiencies and extremely low NOx and particulate emissions, but controlling the combustion timing remains a challenge. This paper explores the potential of Partial Fuel Stratification (PFS) to provide fast control of CA50 in an LTGC engine. Two different compression ratios are used (CR=16:1 and 14:1) that provide high efficiencies and are compatible with mixed-mode SI-LTGC engines. The fuel used is a research grade E10 gasoline (RON 92, MON 85) representative of a regular-grade market gasoline found in the United States. The fuel was supplied with a gasoline-type direct injector (GDI) mounted centrally in the cylinder. To create the PFS, the GDI injector was pulsed twice each engine cycle. First, an injection early in the intake stroke delivered the majority of the fuel (70 - 80%), establishing the minimum equivalence ratio in the charge. Then, a second injection supplied the remainder of the fuel (20 - 30%) at a variable timing during the compression stroke, from 200° to 330°CA (0°CA = TDC-intake, 360°CA = TDC-compression) to provide controlled…
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An Efficient Trivial Principal Component Regression (TPCR)

General Motors LLC-Balakrishna Chinta
Published 2019-04-02 by SAE International in United States
Understanding a system behavior involves developing an accurate relationship between the explanatory (predictive) variables and the output response. When the observed data is ill-conditioned with potential collinear correlations among the measured variables, some of the statistical methods such as least squared method (LSM) fail to generate good predictive models. In those situations, other methods like Principal Component Regression (PCR) are generally applicable. Additionally, the PCR reduces the dimensionality of the system by making use of covariance relationship among the variables. In this paper, an improved regression method over PCR is proposed, which is based on the Trivial Principal Components (TPC). The TPC regression (TPCR) makes use of the covariance of the output response and predictive variables while extracting principal components. A new method of selecting potential principal components for variable reduction in TPCR is also proposed and validated. Two example problems, which are highly collinear, were considered for illustration. Results are also compared with the Partial Least Squares Regression (PLS1), which is another widely used statistical method, for ill-conditioned data analysis. From these results, it…
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Strain Rate Effect on Martensitic Transformation in a TRIP Steel Containing Carbide-Free Bainite

SAE International Journal of Advances and Current Practices in Mobility

General Motors LLC-Charles Enloe, Vesna Savic, Whitney Poling, Louis Hector
Clemson University-Rakan Alturk
  • Journal Article
  • 2019-01-0521
Published 2019-04-02 by SAE International in United States
Adiabatic heating during plastic straining can slow the diffusionless shear transformation of austenite to martensite in steels that exhibit transformation induced plasticity (TRIP). However, the extent to which the transformation is affected over a strain rate range of relevance to automotive stamping and vehicle impact events is unclear for most third-generation advanced high strength TRIP steels. In this study, an 1180MPa minimum tensile strength TRIP steel with carbide-free bainite is evaluated by measuring the variation of retained austenite volume fraction (RAVF) in fractured tensile specimens with position and strain. This requires a combination of servo-hydraulic load frame instrumented with high speed stereo digital image correlation for measurement of strains and ex-situ synchrotron x-ray diffraction for determination of RAVF in fractured tensile specimens. Specifically, the potentially competing effects of strain rate on austenite transformation to martensite were investigated to determine which predominate at nominal strain rates of 0.5 s-1, 5 s-1, 50 s-1 and 500 s-1. A corresponding decrease in austenite volume fraction at a fixed true strain with strain rate suggests that austenite transformation to…
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Determining the Greenhouse Gas Emissions Benefit of an Adaptive Cruise Control System Using Real-World Driving Data

General Motors LLC-William Dvorkin, Joshua King, Marc Gray, Shyhyeu Jao
Published 2019-04-02 by SAE International in United States
Adaptive cruise control is an advanced vehicle technology that is unique in its ability to govern vehicle behavior for extended periods of distance and time. As opposed to standard cruise control, adaptive cruise control can remain active through moderate to heavy traffic congestion, and can more effectively reduce greenhouse gas emissions. Its ability to reduce greenhouse gas emissions is derived primarily from two physical phenomena: platooning and controlled acceleration. Platooning refers to reductions in aerodynamic drag resulting from opportunistic following distances from the vehicle ahead, and controlled acceleration refers to the ability of adaptive cruise control to accelerate the vehicle in an energy efficient manner. This research calculates the measured greenhouse gas emissions benefit of adaptive cruise control on a fleet of 51 vehicles over 62 days and 199,300 miles. To our knowledge, the greenhouse gas emissions benefit of an advanced vehicle technology has never been demonstrated in this manner, and no automaker has published such extensive data pertaining to adaptive cruise control. These results highlight the opportunity to further reduce consumer fuel use and…
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Development of an Alternative Predictive Model for Gasoline Vehicle Particulate Matter and Particulate Number

General Motors LLC-Elana Chapman, Mark Winston-Galant, Pat Geng
University of Michigan-Sophia Pryor
Published 2019-04-02 by SAE International in United States
The Particulate Matter Index (PMI) is a helpful tool which provides an indication of a fuel’s sooting tendency. Currently, the index is being used by various laboratories and OEMs as a metric to understand the gasoline fuels impact on both sooting found on engine hardware and vehicle out emissions. This paper will explore a new method that could be used to give indication of the sooting tendency of the gasoline range fuels, called the Particulate Evaluation Index (PEI), and provide the detailed equation in its initial form. In addition, the PEI will be shown to have a good correlation agreement to PMI. The paper will then give a detailed explanation of the data used to develop it. Initial vehicle PM/PN data will also be presented that shows correlations of the indices to the vehicle response.
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A System Safety Perspective into Chevy Bolt’s One Pedal Driving

General Motors LLC-Richard A. Kulas
General Motors Proving Ground-Helen Rieland, Jenna Pechauer
Published 2019-04-02 by SAE International in United States
The Chevy Bolt’s One Pedal Driving feature is a new electrification propulsion enhancement that allows the driver to accelerate, decelerate and hold their vehicle stationary by just using the accelerator pedal. With this new feature, the driver is relieved of having to switch between pressing the accelerator pedal and brake pedal to slow, stop and hold the vehicle stationary. While this feature provides a convenience to the driver, it also presents a paradigm shift in driver engagement and control system responsibility for executing certain functions that the driver was traditionally responsible to perform. Various system safety techniques were involved in the development of such a feature both from a traditional functional safety perspective as well as a Safety of the Intended Functionality (SOTIF) perspective. The safety considerations for this feature included not only the traditional failure scenarios of the sensors, actuators, controllers, serial data, etc. involved with the feature and its functions, but also the anticipated driver behavior that may potentially result from using the feature. For instance, when the driver releases the accelerator pedal…
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