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

General Motors-Vijai K Gopalakrishnan
  • Technical Paper
  • 2019-28-2519
To be published on 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…

Changes in user experiences of electric vehicles

General Motors-Pandurang Baliga, Tulasi KL
General Motors Technical Center India-Rudrappa Madagunki
  • Technical Paper
  • 2019-28-2489
To be published on 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,…

Study of Friction Optimization Potential for Lubrication Circuits of Light-duty Diesel Engines

General Motors-Salvatore Mafrici, Francesco Barba, Mauro Mattis
  • Technical Paper
  • 2019-24-0056
To be published on 2019-09-09 by SAE International in United States
ABSTRACT Over the last two decades, engine research has been mainly focused on reducing fuel consumption in view of compliance with stringent homologation targets and customer expectations. As it is well known, the objective of overall engine efficiency optimization can be achieved only through the improvement of each element of the efficiency chain, of which mechanical constitutes one of the two key pillars (together with thermodynamics). In this framework, the friction reduction for each mechanical subsystems has been one of the most important topics of modern diesel engine development. In particular, the present paper analyzes the lubrication circuit potential as contributor to the mechanical efficiency improvement, by investigating the synergistic impact of oil circuit design, oil viscosity characteristics (including new ultra-low formulations) and thermal management. For this purpose, a combination of theoretical and experimental tools were used. In particular, the effects of oil pressure regulation, oil pump size and speed, oil temperature and viscosity have been thoroughly evaluated. Experiments were conducted both at component test rig for oil pump and at engine test bench on…

Balancing Hydraulic Flow and Fuel Injection Parameters for Low Emission and High-Efficiency Automotive Diesel Engines

General Motors-Francesco Concetto Pesce, Alberto Vassallo, Giacomo Belgiorno
Continental-Giovanni Avolio
  • Technical Paper
  • 2019-24-0111
To be published on 2019-09-09 by SAE International in United States
The introduction of new light-duty vehicle emission limits to comply under real driving conditions (RDE) is pushing the diesel engine manufacturers to identify and improve the technologies and strategies for further emission reduction. The latest technology advancements on the after-treatment systems have permitted to achieve very low emission conformity factors over the RDE, and therefore, the biggest challenge of the diesel engine development is maintaining its competitiveness in the trade-off “CO2-system cost” in comparison to other propulsion systems. In this regard, diesel engines can continue to play an important role, in the short-medium term, to enable cost-effective compliance of CO2-fleet emission targets, either in conventional or hybrid propulsion systems configuration. This is especially true for large-size cars, SUVs and light commercial vehicles. In this framework, a comprehensive approach covering the whole powertrain is of primary importance in order to simultaneously meet the performance, efficiency, noise and emission targets and, therefore, further development of the combustion system design and injection system represent important leverage for additional improvements. For this purpose, a dedicated 0.5 litres single-cylinder engine…

Sound Analysis Method for Warble Noise in Electric Actuators

General Motors-Nathan T. Parker
Published 2019-06-05 by SAE International in United States
Multiple automotive applications exist for small electric motors that are activated by vehicle occupants for various functions such as window lifts and seat adjusters. For such a motor to be described as high quality, not only should the sound it produces be low in amplitude, but it also needs to be free from pulsations and variations that might occur during its (otherwise) steady-state operation. If a motor’s sound contains pulsations or variations between 2 and 8 cycles per second, the variation is described as warble. To establish performance targets for warble noise at both the vehicle and component level a way to measure and quantify the warble noise must be established. Building on existing sound quality metrics such as loudness and pitch variation, a method is established by which processed sound data is put through a secondary operation of Fourier analysis. Thus warble can be reduced to a single value, and in this way, noise engineers have a basis to measure and report warble, and to facilitate product development with A/B comparisons. Depending on its…
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Vibro-Acoustic Analysis for Modeling Propeller Shaft Liner Material

General Motors-Rajith R. Jayaratne, Yu Liu, Mark Gehringer, Jeff Rayce, Wallace Hill
Published 2019-06-05 by SAE International in United States
In recent truck applications, single-piece large-diameter propshafts, in lieu of two-piece propshafts, have become more prevalent to reduce cost and mass. These large-diameter props, however, amplify driveline radiated noise. The challenge presented is to optimize prop shaft modal tuning to achieve acceptable radiated noise levels. Historically, CAE methods and capabilities have not been able to accurately predict propshaft airborne noise making it impossible to cascade subsystem noise requirements needed to achieve desired vehicle level performance. As a result, late and costly changes can be needed to make a given vehicle commercially acceptable for N&V performance prior to launch.This paper will cover the development of a two-step CAE method to predict modal characteristics and airborne noise sensitivities of large-diameter single piece aluminum propshafts fitted with different liner treatments. The first step is the use of a traditional CAE software to calculate prop surface response. The second step is a boundary element simulation to calculate prop surface radiated noise under the excitation obtained from the first step. Finally, acceleration and acoustic test data are presented to assess…
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Experimental Study of Acoustic and Thermal Performance of Sound Absorbers with Microperforated Aluminum Foil

General Motors-Gang Glenn Yin, Alan Parrett, Timothy J. Roggenkamp
General Motors De Mexico S de R L de CV-Felipe G. Salazar Prieto
Published 2019-06-05 by SAE International in United States
Aluminum foil applied to the surface of sound absorbing materials has broad application in the automotive industry. A foil layer offers thermal insulation for components close to exhaust pipes, turbo chargers, and other heat sources in the engine compartment and underbody. It can also add physical protection for acoustic parts in water-splash or stone-impingement areas of the vehicle exterior. It is known that adding impermeable plain foil will impact the sound absorption negatively, so Microperforated Aluminum Foil (MPAF) is widely used to counteract this effect. Acoustic characteristics of MPAF can be modeled analytically, but deviation of perforation size and shape, variation of hole density, material compression, and adhesive applied to the back of the foil for the molding process can impact the acoustic and thermal insulation performance. Because we cannot rely on analytical tools to generate accurate performance of these materials in a production environment, this paper will focus on the acoustic and thermal experimental characterization of these materials. Studies were conducted on flat test samples which have commonly used MPAF applied to the top…
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Effectiveness of Power-Law Profile Indentations on Structure-Borne Noise

General Motors-Jeffrey Curtis
General Motors Technical Center India-Pranoy Sureshbabu Nair, Nilankan Karmakar, Seshagiri Rao Maddipati
Published 2019-06-05 by SAE International in United States
A study on the effect of indenting power-law shaped profiles on the flexible structures for investigating the vibration damping characteristics using computational simulation method is discussed. The simulation results are checked to see the impact of such features on the damping behavior of flexible structures responsible for radiating noise when excited with fluctuating loads. Though the conventional remedies for solving Noise and vibration issues generally involves tuning of structure stiffness or damping treatment this paper gives an insight on the idea of manipulation of elastic waves within the flexible structure itself to minimize the cross-reflections of the mechanical waves. The simulation studies mentioned in this paper not only hovers over the effectiveness of such features but also will be helpful for the engineers to look through a different perspective while solving N&V issues using simulation tools. In this paper, different studies are discussed to see the impact of such features on the damping effect of the vibrating structure comparing mobility response and far-field sound pressure response as well. Propagation of waves within the structure is…
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Tonal Annoyance Metric Development for Automotive Electric Vehicles

General Motors-Glenn Pietila, William Seldon, Timothy Roggenkamp, Timothy Bohn
Published 2019-06-05 by SAE International in United States
Historical metrics intended to drive the development of vehicle powertrains have focused on sounds that are characteristic of IC engines. The interior noise contribution of the propulsion system in electric vehicles has significantly more tonal noise (and much less impulsive and broadband noise) than their IC engine counterparts. This tonal noise is not adequately represented by current propulsion systems metrics. While metrics exist today that were developed to represent the presence of tones in sounds most have focused on the level aspect of the tones relative to the surrounding noise or masking level, some examples include tonality, tone-to-noise ratio, and prominence ratio. A secondary, but also important aspect of tones is the annoyance as a function of frequency. This paper will highlight the development of a tonal annoyance weighting curve that can be used to account for the frequency aspect of tonal annoyance relative to electric vehicles. This weighting curve can then be used in conjunction with the current tonal metrics to represent perceived tonal annoyance of electric vehicles. The benefit of the tonal annoyance…
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Effectiveness of Workload-Based Drowsy Driving Countermeasures

General Motors-Freddy Rayes, Maureen Short
Virginia Polytechnic Inst. & State University-Robert Llaneras
Published 2019-04-02 by SAE International in United States
This study evaluated the effectiveness of alternative workload-based interventions intended to restore driver alertness following drowsy episodes. Unlike traditional drowsy driving studies, this experiment did not target sleep-deprived individuals, but rather studied normally rested drivers under the assumption that low-workload environments could trigger drowsy driving episodes. The study served as a proof of concept for varying the nature and onset of countermeasure interventions intended to disrupt the drowsiness cycle. Interventions to combat drowsiness attempted to target driver workload, either physical or cognitive, and included two primary treatment conditions: 1) physical workload to increase driver steering demands and 2) trivia-based interactive games to mentally challenge drivers. A benchmark comparison condition using music was also investigated to contrast the relative influence of workload-based interventions with passive listening to musical arrangements. The study also varied the onset stage of the intervention, basing either early or late onset on driver drowsiness levels indexed using a Percentage of Eyelid Closure (PERCLOS) measure. Thirty drivers, aged 21-70, completed a 3-hour trip in a driving simulator. When a drowsy driving episode was…
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