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Technical Paper
2014-04-01
Mona Einolghozati, Mohammad Kankarani Farahani, Hamid Reza Lari, Abbas Bahri
Abstract Modern high-cycle fatigue criteria were implemented in structural wind turbine parts using finite element method. As a result of a test carried out for two fatigue criteria, it was concluded that the Dang Van hypothesis has more conservative results than S-N method. The complete algorithm of the fatigue calculation was illustrated by applying the proposed procedures to a wind turbine hub which is subjected to multi-axial, non-proportional and non-constant amplitude high-cycle loadings and then a structural optimization method is used to reduce the weight and moment of inertia of the wind turbine rotor. ANSYS Workbench and nCode design life are used in the structural and fatigue modeling of the hub.
Technical Paper
2014-04-01
Joohan Kim, Gyujin Kim, Hoon Lee, Kyoungdoug Min
Abstract Direct-injection spark-ignition (DISI) engines are regarded as a promising technology for the reduction of fuel consumption and improvement of engine thermal efficiency. However, due to direct injection, the shortened fuel-air mixing duration leads to a spatial gradient of the equivalence ratio, and these locally rich regions cause the formation of particulate matter. In the current study, numerical investigations on pollutant formation in a DISI engine were performed using combined flamelet models for premixed and diffusion flames. The G-equation model for partially premixed combustion was improved by incorporating the laminar flamelet library. Gasoline fuel was represented as a ternary mixture of gasoline surrogate and its laminar flame speeds were obtained under a wide range of engine operating conditions. For the flame propagation in a partially premixed condition, the presumed shape of the probability density function approach was adopted, whereas the burned gas compositions were determined from the steady laminar flamelet library.
Technical Paper
2014-04-01
Thomas Juergen Boehme, Markus Schori, Heiko Rabba, Matthias Schultalbers
Abstract Most energy management systems for hybrid electric vehicles still use rule-based energy management systems that rely on information stored in lookup tables, to define the current mode of operation and set-points for the low-level control laws. Because of the high number of parameters, the calibration of such energy managements can be a cumbersome task for the engineers. Mathematical tools are therefore inalienable to the calibration process. In this paper, it will be demonstrated, how the theory of hybrid optimal control can be used to calculate an initial parameter set for the energy management of charge-sustaining hybrids. The calculation procedure includes the solution of a hybrid optimal control problem to determine the controls for the optimal operation of the vehicle over a given cycle. The results can then be used to automatically calculate lookup-tables for optimal gear shifts, optimal torque-split between motor/generator and internal combustion engine and the determination of the drive mode (electric or hybrid mode).
Technical Paper
2014-04-01
Daniel Wood, Martin A. Passmore, Anna-Kristina Perry
The use of simulation tools by vehicle manufacturers to design, optimize and validate their vehicles is essential if they are to respond to the demands of their customers, to meet legislative requirements and deliver new vehicles ever more quickly. The use of such tools in the aerodynamics community is already widespread, but they remain some way from replacing physical testing completely. Further advances in simulation capabilities depend on the availability of high quality validation data so that simulation code developers can ensure that they are capturing the physics of the problems in all the important areas of the flow-field. This paper reports on an experimental program to generate such high quality validation data for a SAE 20 degree backlight angle notchback reference model. This geometry is selected as a particularly powerful test case for the development and validation of numerical tools because the flow exhibits a realistic impingement and A pillar regime, significant three dimensional structures and the backlight/boot-deck exhibits a local separation and reattachment.
Technical Paper
2013-10-15
Denis Neher, Maurice Kettner, Fino Scholl, Markus Klaissle, Danny Schwarz, Blanca Gimenez Olavarria
A large number of small size gas-fired cogeneration engines operate with homogenous lean air-fuel mixture. It allows for engine operation at high efficiency and low NOx emissions. As a result of the rising amount of installed cogeneration units, however, a tightening of the governmental emission limits regarding NOx is expected. While engine operation with further diluted mixture reduces NOx emissions, it also decreases engine efficiency. This leads to lower mean effective pressure, in particular for naturally aspirated engines. In order to improve the trade-off between engine efficiency, NOx emissions and mean effective pressure, numerical investigations of an alternative combustion process for a series small cogeneration engine were carried out. In a first step, Miller and Atkinson cycles were implemented by advanced or retarded inlet valve closing timings, respectively. By keeping the effective compression ratio constant, the expansion ratio is increased, resulting in higher engine efficiency.
Technical Paper
2013-09-17
Vincent Goudreault
The take-off of a departing aircraft is subjected to varying forces, the largest of which are function of the speed of the aircraft itself: the thrust of a jet engine, the aerodynamic drag of the airframe are essentially polynomial function of the airspeed. First principle field performance determination has relied for the last half century on stepwise integration, a brute force approach that requires properly tuned integration steps, which has the benefit of being fairly reliable but with relatively low computational efficiency. An alternate, mathematically more formal approach would be to algebraically integrate an accelerative function combining all the forces in presence. While comparatively complex, the derivation of the solution equations permits fast and accurate integration between boundary conditions, which could be orders of magnitude more efficient than stepwise integration, even with relatively high degree of polynomial force functions, while being essentially free of any round-off error which may accumulate at each step of a linearized stepwise integration as the result would instead be derived strictly from the value at the integration limits; the speed advantage remains for most practical models, up to a 6th degree acceleration to speed polynomial function.
Technical Paper
2012-10-02
M. E. Guzzo, J. E. M. Barros, R. Huebner, R. M. Valle
The focus of this study was to create a methodology to evaluate spray characteristics in a gasoline direct injection injector by means of an automatic process. Computational codes were used to get information about cone angle and breakup length based on images got from injection process. A mathematical function was created to locate the boundaries of the spray and the cone angle was studied as the angle of arcs situated within these boundaries. The centre of the arc was located on the orifice of the injector and a value of angle was associated with several distances from orifice. The breakup length was associated as a distance from the orifice of an arc formed by a group of pixels with the maximum standard deviation related to the values of these pixels. The velocity field was studied by the Particle Image Velocimetry technique. Three fluids were tested at this work: water, ethanol and gasoline.
Technical Paper
2012-10-02
Edson Luciano Duque, Rodrigo Alves Augusto
The continuous research for better performance and reduction of fuel consumption demanded the development of analytical techniques to better understand the rattle mechanism, with complex non-linear models being widely used for simulation. In regards to the fuel, the “flexible” engines, which can work with any mixture of gasoline/ethanol, are already a reality in the Brazilian market. These flex-fueled vehicles present higher values of irregularity, creating a specific scenario for this market. Several models with static approach of the clutch damper can be found in the available literature with limited measured data, which makes life difficult to validate or correlate these models. For this reason, the analytical formulation of dynamic clutch dampers developed high importance for solving and/or reducing clearance-induced vibro-impact problems which leads to rattle noise. In this study, models of the clutch damper with static and dynamic hysteresis are implemented using Matlab/Simulink® programming, and results are compared to real vehicle measurements.
Book
2012-03-01
W. Charles Paulsen
This is a book for people wanting to learn the language of Science, Technology, and Engineering, and is intended to complement traditional text books in Mathematics. It puts the fun back into mathematics by demystifying confusing symbols and terminology – Think of this book as your personal journey leading to an eventual understanding of calculus, using everyday language to introduce new concepts in small manageable steps. Extensive use of color diagrams, pictures, and graphs are used throughout the book. Microsoft Excel is introduced early to show how mathematics can be made visual. Excel’s hidden equation solving talents are revealed. What to expect from this title: • Part I – Numbers, constants, and variables, the components of equations. • Part II – Equations for the line, circle, and other geometries frequently encountered are presented. • Part III – Solving many equations simultaneously, the basic of matrix algebra. • Part IV – Equations and graphs of interest. • Part V – Slopes and areas, the basics of differential and integral calculus.
Book
2011-11-01
J. Gilbert Kaufman
Relational analysis, defined as quantitative analysis of the relationships of high- and low-temperature properties in relation to their room-temperature values, provides a useful technique for estimating the properties of similar metals and alloys for which limited or no data are available. This book demonstrates how to use relational analysis methodology to extrapolate and estimate properties of metallic alloys at high temperatures from lower temperature data, and for estimating the properties of alloys for which scant property data exists. Data tables and graphs are presented for a wide range of aluminum alloys. Also shown, is how to apply relational analysis to other alloy systems including steels, magnesium alloys, and titanium alloys.
Technical Paper
2011-10-18
Hugo Pervier, Devaiah Nalianda, Ramon Espi, Vishal Sethi, Pericles Pilidis, David Zammit-Mangion, Jean-Michel Rogero, Ricardo Entz
The aviation sector has played a significant role in shaping the world into what it is today. The rapid growth of global economies and the corresponding sharp rise in the number of people now wanting to travel on business and for pleasure, has largely been responsible for the development of this industry. With a predicted rise in Revenue Passenger Kilometers (RPK) by over 150% in the next 20 years, the industry will correspondingly be a significant contributor to environmental emissions. Under such circumstances optimizing aircraft trajectories for lowered emissions will play a critical role amongst various other measures, in mitigating the probable environmental effects of increased air traffic. Aircraft trajectory optimization using evolutionary algorithms is a novel field and preliminary studies have indicated that a reduction in emissions is possible when set as objectives. The paper describes a preliminary study undertaken for the Systems for Green Operation Integrated Technology Demonstrator for the Clean Sky Project (FP7) and uses a customized algorithm NSGAMO2 (a proposed variation of the Non-dominated Sorted Genetic Algorithm II).
Technical Paper
2011-10-18
Gabriella Caporaletti
The paper presents feasibility and effectiveness of an innovative algorithm for spacecraft attitude determination, based on the real time fusion of raw data measurements provided by APS cameras, less limited by metrological constraints than traditional cameras used for star detection, and MEMS gyros, characterized by low-mass, low-power and low recurrent costs. The basic concept and the followed S&T methodological approach is described, which includes the use of cameras and gyros, even if the above basic concept states that gyros measurement data are neither strictly necessary, nor are increasing the attitude measurement accuracy in steady state conditions. Indeed, the availability of the gyro measurement data significantly contributes to the robustness of the spacecraft attitude measurement system particularly in “lost in space” and in “occulted camera” conditions. High quality gyros are not required. Angular rate measurements are fused with camera star measurements at raw data level.
Technical Paper
2011-10-06
Park Jooil
In most popular steering angle sensor, the calculation method for steer angle is that the angular positions of two smaller sized angle measurement gear wheels, being coupled to the steering hub on the steering column, are measured. The two angle measurement gear wheels differ from each other by more one gear tooth, each gear wheel bearing magnetic pole pairs. With these two angle values, it is possible to determine the steering angle of the steering wheel as soon as the power up without non volatile memory. There are many calculation methods to solve absolute angle. This paper introduces the easy and optimal method to calculate the steer angle among the many approach.
Technical Paper
2011-08-30
Kiyoshi Kawasaki, Koji Yamane, Tatsuro Ikawa
This study derives regression equations for predicting the cetane number of biodiesel fuels based on chemical analysis data. For conducting the regression analysis, 34 fuel samples with a wide variety of ignition qualities were made by mixing five kinds of biodiesels and five kinds of fatty acid methyl ester (FAME) reagents. The relationship between the cetane number, measured in a constant-volume combustion chamber, and fuel properties such as iodine value, saponification number, and boiling point, was investigated. Based on the results, four regression equations were proposed and their accuracies were compared. The results show that the regression equation based on fuel composition gives a cetane number with high accuracy, whereas it can be only be approximately predicted from the iodine value.
Technical Paper
2011-06-13
Marco Fossati, Rooh-ul-Amin Khurram, Wagdi G. Habashi
The irregular shapes that glaze ice may grow into while accreting over the surface of an aircraft represent a major difficulty in the numerical simulation of long periods of in-flight icing. In the framework of Arbitrary Lagrangian-Eulerian (ALE) formulations, a mesh movement scheme is presented, in which frame and elasticity analogies are loosely coupled. The resulting deformed mesh preserves the quality of elements, especially in the near-wall region, where accurate prediction of heat flux and shear stresses are required. The proposed scheme handles mesh movement in a computationally efficient manner by localizing the mesh deformation. Numerical results of ice shapes and the corresponding aerodynamic coefficients are compared with the experimental results.
Technical Paper
2011-06-13
Peng Ke, Xinxin Wang
Lagrangian approach has been widely adopted in the droplet impingement analysis for aircraft icing simulation. Some improvements were proposed, including: 1) The heat and mass transfer consideration in droplet dynamics; 2) More efficient droplet localization method, which could and facilitated to find the initial cell in Eulerian grid; 3) New computation method of impingement efficiency, which uses the cover ratio to transform the impingement efficiency of arbitrary impinged region to that of the cell element of body surface and avoids the iterative computation to find the trajectories reaching the corner of the panel or cell element. A numerical solver was built and integrated with the capabilities to deal with super-cooled large droplet (SLD) conditions by considering the splashing and bouncing of SLD. The computational results were validated with the experiment data, which shown good agreements in the impingement limitations and tendency.
Technical Paper
2011-06-13
Jason Mickey, Eric Loth, Colin Bidwell
A new technique is proposed for computing particle concentrations and fluxes with Lagrangian trajectories. This method calculates particle concentrations based on the volume of a parcel element, or cloud, at the flux plane compared against the initial volume and is referred to as the Lagrangian Parcel Volume (LPV) method. This method combines the steady-state accuracy of area-based methods with the unsteady capabilities of bin-based methods. The LPV method results for one-dimensional (1D) unsteady flows and linear two-dimensional (2D) steady flows show that a quadrilateral element shape composed of a single parcel (with four edge particles) is capable of accurately predicting particle concentrations. However, nonlinear 2D flows can lead to concave or crossed quadrilaterals which produce significant numerical errors. This problem was solved by dividing the quadrilateral parcel into two triangular semi-parcels (each with three edge particles), such that triangular shapes are maintained regardless of trajectory crossing effects.
Technical Paper
2011-05-17
Thank-Son Dao, Aden Seaman, John McPhee, Koichi Shigematsu
The recent increase in oil prices and environmental concerns have attracted various research efforts on hybrid electric vehicles (HEVs) which provide promising alternatives to conventional engine-powered vehicles with better fuel economy and fewer emissions. To speed up the design and prototyping processes of new HEVs, a method that automatically generates mathematics equations governing the vehicle system response in an optimized symbolic form is desirable. To achieve this goal, we employed MapleSim T M , a new physical modeling tool developed by Maplesoft Inc., to develop the multi-domain model of a series-HEV, utilizing the symbolic computing algorithms of Maple software package to generate an optimized set of governing equations. The HEV model consists of a mean-value internal combustion engine (ICE), a chemistry-based Ni-MH battery pack, and a multibody vehicle model. Simulations are then used to demonstrate the performance of the developed HEV system. Simulation results show that the model is viable and the number of governing equations is reduced significantly, resulting in a computationally efficient system.
Technical Paper
2011-05-17
Ienkaran Arasaratnam, Saeid Habibi, Christopher Kelly, Tony J. Fountaine, Jimi Tjong
Advanced engine test methods incorporate several different sensing and signal processing techniques for identifying and locating manufacturing or assembly defects of an engine. A successful engine test method therefore, requires advanced signal processing techniques. This paper introduces a novel signal processing technique to successfully detect a faulty internal combustion engine in a quantitative manner. Accelerometers are mounted on the cylinder head and lug surfaces while vibration signals are recorded during engine operation. Using the engine's cam angular position, the vibration signals are transformed from the time domain to the crank-angle domain. At the heart of the transformation lies interpolation. In this paper, linear, cubic spline and sinc interpolation methods are demonstrated for reconstructing vibration signals in the crank-angle domain. Finally, the ensemble-averaged mean squared-error criterion is introduced as the fault-detection metric to determine whether the engine under test is faulty or not.
Technical Paper
2011-04-12
Arkadeb Ghosal, Paolo Giusto, Prakash Peranandam, Purnendu Sinha, Haibo Zeng
Recent trends in the automotive industry show growing demands for the introduction of new in-vehicle features (e.g., smart-phone integration, adaptive cruise control, etc.) at increasing rates and with reduced time-to-market. New technological developments (e.g., in-vehicle Ethernet, multi-core technologies, AUTOSAR standardized software architectures, smart video and radar sensors, etc.) provide opportunities as well as challenges to automotive designers for introducing and implementing new features at lower costs, and with increased safety and security. As a result, the design of Electrical/Electronic (E/E) architectures is becoming increasingly challenging as several hardware resources are needed. In our earlier work, we have provided top-level definitions for three relevant metrics that can be used to evaluate E/E architecture alternatives in the early stages of the design process: flexibility, scalability and expandability. These definitions provide qualitative and quantitative measurements of ability of an architecture to accommodate changes.
Technical Paper
2011-04-12
H Pandarinath, J Sureshkumar, Ramalingam Sivanantham, S Prabhakar, S R Nagendiran
Vacuum pumps are predominantly used in diesel engines of passenger cars and trucks for generating vacuum in servo brake applications. With the emission norms getting stringent, there is a need for vacuum signal for EGR actuation, turbo-charger waste gate actuation and other servo applications. These multi-functional applications of vacuum pumps and the functional criticality in application like braking system demand an effective and reliable performance. In gasoline engines, the vacuum generated in the intake manifold is tapped for braking. The recent technology of gasoline direct injection compels the use of vacuum pump in gasoline engines also due to scarce vacuum in intake manifold. The performance of the vacuum pump is highly dependent on the opening and closing of the check valve sub-system, which is positioned between the vacuum reservoir and the pump at the suction side. Hence, it becomes critical to investigate and optimize the airflow through the check valve sub-system, upfront during the concept and design verification stage.
Technical Paper
2011-04-12
Sergey Kirillov, Aleksander Kirillov Sr, Olga Kirillova
This paper introduces architecture of an integrated system of preventive diagnostics and mathematical and computational methods, based on which such a system is being developed. The present work aims to: describe the methods of preventive diagnostics based on mathematical models and computing algorithms, allowing to detect the hidden harbingers of engine dysfunctions and future failures; describe the architecture of the system of preventive diagnostics, its further evolution; describe the process of integration of preventive diagnostics system to the car engine. A necessary condition for the development system of preventive diagnosis is the condition of their economic efficiency, including the requirement of low cost sensors and computing systems of diagnostics. The paper shows: A set of telemetry data for preventive diagnostics should include data of the crankshaft rotation angle sensor and data of vibrations of the engine case, received by means of the sensor control of vibrations installed additionally on its case; The basis for the analysis of preventive signs of dysfunction and future failures of engine is the analysis of stochastic components in indications of established sensors, crankshaft rotation angle sensor and vibration sensor.
Technical Paper
2011-04-12
Hossein Javaherian, Alan W. Brown, Michael P. Nolan
A frequency-domain approach to balancing of air-fuel ratio (A/F) in a multi-cylinder engine is described. The technique utilizes information from a single Wide-Range Air-Fuel ratio (WRAF) or a single switching (production) O₂ sensor installed in the exhaust manifold of an internal combustion engine to eliminate the imbalances. At the core of the proposed approach is the development of a simple novel method for the characterization of A/F imbalances among the cylinders. The proposed approach provides a direct objective metric for the characterization of the degree of A/F imbalances for diagnostic purposes as well as a methodology for the control of A/F imbalances among various cylinders. The fundamental computational requirement is based on the calculation of a Discrete Fourier Transform (DFT) of the A/F signal as measured by a WRAF or a switching O₂ sensor. For real-time applications, the approach is iterative in nature and the intended goal of A/F balancing is achieved quite accurately and fast in around 1-2 seconds.
Technical Paper
2011-04-12
Thomas A. Timbario, Thomas J. Timbario, Melissa J. Laffen, Mark F. Ruth
Currently, several cost-per-mile calculators exist that can provide estimates of acquisition and operating costs for consumers and fleets. However, these calculators are limited in their ability to determine the difference in cost per mile for consumer versus fleet ownership, to calculate the costs beyond one ownership period, to show the sensitivity of the cost per mile to the annual vehicle miles traveled (VMT), and to estimate future increases in operating and ownership costs. Oftentimes, these tools apply a constant percentage increase over the time period of vehicle operation, or in some cases, no increase in direct costs at all over time. A more accurate cost-per-mile calculator has been developed that allows the user to analyze these costs for both consumers and fleets. Operating costs included in the calculation tool include fuel, maintenance, tires, and repairs; ownership costs include insurance, registration, taxes and fees, depreciation, financing, and tax credits. The calculator was developed to allow simultaneous comparisons of conventional light-duty internal combustion engine (ICE) vehicles, mild and full hybrid electric vehicles (HEVs), and fuel cell vehicles (FCVs).
Technical Paper
2011-04-12
Vijitashwa Pandey, Efstratios Nikolaidis, Zissimos Mourelatos
Multi-attribute decision making and multi-objective optimization complement each other. Often, while making design decisions involving multiple attributes, a Pareto front is generated using a multi-objective optimizer. The end user then chooses the optimal design from the Pareto front based on his/her preferences. This seemingly simple methodology requires sufficient modification if uncertainty is present. We explore two kinds of uncertainties in this paper: uncertainty in the decision variables which we call inherent design problem (IDP) uncertainty and that in knowledge of the preferences of the decision maker which we refer to as preference assessment (PA) uncertainty. From a purely utility theory perspective a rational decision maker maximizes his or her expected multi attribute utility. We show how this is inherently inconsistent with providing the decision maker with alternatives on the Pareto Front unless the decision maker trades off attributes or some function thereof linearly.
Technical Paper
2011-04-12
Toshiaki Kobayashi
A multi-objective optimization model using a piston behavior simulation for the prediction of NV, friction and scuffing was created. This model was used to optimize the piston skirt form, helping to enable well-balanced forms to be sought. Optimization calculations, involving extended analyses and numerous design variables, conventionally necessitate long calculation times in order to achieve adequate outcomes. Because of this, in the present project data was converted into functions in order to help enable the complex piston skirt form to be expressed using a small amount of coefficients. Using the limit values for manufacturability and the degree of contribution to the target functions, the scope of design variables was restricted, and the time necessary for the analysis was significantly reduced. This has helped to enable optimal solutions to be determined within a practical time frame. In addition, these methods were employed in expanding the functions obtained for the piston skirt form in order to search for the optimal solution in a broader sense.
Technical Paper
2011-04-12
M. Cagri Cevik, Emre Kanpolat, Martin Rebbert
Due to increasing demand for environment friendly vehicles with better fuel economy and strict legislations on greenhouse gas emissions, lightweight design has become one of the most important issues concerning the automobile industry. Within the scope of this work lightweight design potentials that a conventional single cylinder engine crankshaft offers are researched through utilization of structural optimization techniques. The objective of the study is to reduce mass and moment of inertia of the crankshaft with the least possible effect on the stiffness and strength. For precise definition of boundary conditions and loading scenarios multi body simulations are integrated into the optimization process. The loading conditions are updated at the beginning of each optimization loop, in which a multi body simulation of the output structure from the previous optimization loop is carried out. Equivalent static loads method, which is an embedded feature in OptiStruct, is applied to obtain the loading scenarios for the most critical time steps of the corresponding dynamic simulation.
Technical Paper
2011-04-12
Zhigang Wei, Fulun Yang, Henry Cheng
The equilibrium mechanism, which can be considered as the basis of least squares method for linear curve fitting, is investigated in this paper. Both conventional methods, such as vertical offsets method, and total least squares methods, such as perpendicular offsets method, are examined. It is found that both methods have the equilibrium bases. However, the conventional methods may give inaccurate prediction if using vertical offsets method to fit data with variation in horizontal direction or using horizontal offsets method to fit data with variation in vertical direction while the perpendicular method can give best fit solution to data with variation in both vertical and horizontal directions. The application of these methods is also presented in fatigue S-N curve data analysis and two-parameter Weibull distribution in exhaust component fatigue life prediction. Finally, the perpendicular offsets method is recommended in durability analysis for data with variation in both vertical and horizontal directions due to its simplicity and a sound equilibrium basis.
Technical Paper
2011-04-12
Anthony George Konstantino, Mark A. Levine
This paper summarizes the Fast Fourier Transform (FFT) methodology, special equipment, set-up and testing that is recommended to properly characterize the surface of bearing journals that will not result in objectionable noise or vibration. Traditional surface profiles and finish callouts do not capture some of the key characteristics for addressing what is often the customer's greatest complaint, noise. Noise can vary based on the sensitivity of the vehicle but understanding how to accurately describe (design, test, and measure) a surface for a given vehicle can result in an optimized design and reduce process time during manufacturing. Furthermore, this paper will recommend techniques for determining the proper limits of the FFT callouts.
Technical Paper
2011-04-12
Joseph A. Schudt, Rajanagaprasad Kodali, Manish Shah, Glenn Babiak
Measured vehicle loads have traditionally been used as the basis for development of component, subsystem and vehicle level durability tests. The use of measured loads posed challenges due to the availability of representative hardware, scheduling, and other factors. In addition, stress was placed on existing procedures and methods by aggressive product development timing, variety in tuning and equipment packages, and higher levels of design optimization. To meet these challenges, General Motors developed new processes and technical competencies which enabled the direct substitution of analytically synthesized loads for measured data. This process of Virtual Road Load Data Acquisition (vRLDA) enabled (a) conformance to shortened product development cycles, (b) greater consistency between design targets and validation requirements, and (c) more comprehensive data. Further, the vRLDA process was predicated on accurately quantified vehicle components, with the analytical model serving to aggregate the component models.
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