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Regression Models to Predict Coastdown Road Load for Various Vehicle Types

Singh, Yuvraj
http://rave.ohiolink.edu/etdc/view?acc_num=osu1595265184541326

Abstract Details

2020, Master of Science, Ohio State University, Mechanical Engineering.
The fuel economy label (window sticker) is used by every vehicle manufacturer in the United States to report fuel economy for two purposes. First, the values reported on the sticker are certified by the United States Environmental Protection Agency (EPA) and are used for certifying emissions regulations like the Corporate Average Fuel Economy (CAFE). Second, the fuel economy numbers are used by consumers to compare competing vehicles in the marketplace. These fuel economy numbers are generated through a process that involves standardized testing on a chassis dynamometer using standard drive cycles. As a result, the test requires an accurate replication of the resistive forces that a vehicle experiences in the real-world, which requires an accurate estimation of road load applied by the road and the surroundings opposing the vehicle motion. The estimation also depends on the type (aerodynamic shape, drivetrain configuration, etc.) of vehicle being tested. To get a description of road load that is as close as possible to reality, several noise factors and residuals need to be estimated as well, which forms the bulk of this thesis. Vehicle coastdown method is widely used to determine road load coefficients for testing vehicles on a chassis dynamometer for fuel economy certification. However, apart from being a time-consuming procedure for each variant in a mass production vehicle lineup, the repeatability of track coastdown testing procedure is sensitive to environmental conditions, the track surface condition as well as on the type of vehicle being tested (for example, SUVs, sedans, hybrid vehicles, manual transmissions, etc.). As a result, several attempts have been made to accurately model the coastdown road load parametrically. This thesis explores various ways in which such parametric models can be obtained and methods to minimize risks related to overfitting and collinearity of variables. Since, the vehicle’s road load is dependent on several physical phenomena, various lab testing methods are employed to determine the road load components (rolling resistance, aerodynamic drag and driveline parasitic loss) individually to come up with a model for road load force that can be applied on the chassis dynamometer. The model obtained from lab tests is defined as a second order polynomial in vehicle speed using the linear least squares curve fit procedure specified by SAE standards J1263, J2263 and J2264. Lab testing is carried out using various equipment under a well-defined testing procedure. Wind tunnels are used for aerodynamic drag testing, parasitic measurements are performed by disconnecting various powertrain components iteratively and rolling resistance measurement is performed for the tires using appropriate tire drum apparatus. However, this model developed solely through lab tests ignores certain noise factors that cause a significant deviation (residual) between the track coastdown force and the model developed in the lab by adding all road load components. This thesis explores the various regression modeling techniques and recommended practices for estimating residual force and the associated residual horsepower. Additionally, different models for various clusters of vehicles based on certain characteristics have been explored.
Giorgio Rizzoni (Advisor)
Yann Guezennec (Committee Member)
Adithya Jayakumar (Committee Member)
206 p.
Automotive Engineering; Mechanical Engineering; Statistics
coastdown testing; fuel economy certification; chassis dynamometer testing; road load; statistical modeling; regression; exploratory data analysis; kernel density estimation; wind tunnel testing; aerodynamic drag;

Recommended Citations

Citations

  • Singh, Y. (2020). Regression Models to Predict Coastdown Road Load for Various Vehicle Types [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595265184541326

    APA Style (7th edition)

  • Singh, Yuvraj. Regression Models to Predict Coastdown Road Load for Various Vehicle Types. 2020. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1595265184541326.

    MLA Style (8th edition)

  • Singh, Yuvraj. "Regression Models to Predict Coastdown Road Load for Various Vehicle Types." Master's thesis, Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595265184541326

    Chicago Manual of Style (17th edition)

osu1595265184541326
924
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