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SAE International Journal of Aerospace

  • Journal
  • V128-1EJ
To be published on 2019-06-28 by SAE International in United States
This is the electronic format of the journal

Heavy-duty aerodynamic testing for CO2 certification: A methodology comparison

Intl. Council on Clean Transportation-J. Felipe Rodriguez, Oscar Delgado
University of Technology Graz-Martin Rexeis, Martin Röck
  • Technical Paper
  • 2019-01-0649
To be published on 2019-04-02 by SAE International in United States
Air drag testing is a key component of the CO2 certification schemes for heavy-duty vehicles around the world. This paper presents and compares the regulatory approaches for measuring the air drag coefficient of heavy-duty vehicles in Europe, which uses a constant-speed test, and in the United States and Canada, which use a coastdown test. Two European trucks and one North American truck were tested using the constant-speed and coastdown methods. When corrected to zero yaw angle, a difference of over 10% was observed in the measured drag coefficients from the US coastdown procedure and the EU constant-speed test. The differences in the measured air drag coefficient can be attributed to the data post-processing required by each methodology, the assumptions in the speed-dependence of the tire rolling resistance, unaccounted frictional losses in the differential axle and transmission, as well as the behavior of the automated manual transmission during the coastdown run.

How to model real-world driving behavior? Probability-based driver model for energy analyses

Daimler AG-Tobias Schuermann, Tobias Goedecke, Stefan Schmiedler, Daniel Goerke
University of Applied Sciences Esslingen-Kai André Boehm
  • Technical Paper
  • 2019-01-0511
To be published on 2019-04-02 by SAE International in United States
A wide variety of applications such as driver assistant and energy management systems are researched and developed in virtual test environments. The safe testing of the applications in early stages is based on parameterizable and reproducible simulations of different driving scenarios. One possibility is modelling the microscopic driving behavior to simulate the longitudinal vehicle dynamics of individual vehicles. The currently used driver models are characterized by a conflict regarding comprehensibility, accuracy and calibration effort. Due to the importance for further analyses this conflict of interests is addressed by the presentation of a new microscopic driver model in this paper. The proposed driver model stores measured driving behaviors with its statistical distributions in maps. Thereby the driving task is divided into free flow, braking in front of stops and following leading vehicles. This makes it possible to display the driving behavior in its entirety. The comprehensibility of this driver model is given by its simplicity and the calibration effort is low with existing measurement data. These data are recorded with a testing vehicle by a map-…

Development of a standalone application in MATLAB to generate brake performance data

Indian Institute of Technology, Madras-Harsh Kumar Singh
  • Technical Paper
  • 2019-01-0513
To be published on 2019-04-02 by SAE International in United States
Predicting the brake performance and characteristics is a crucial task in the vehicle development activity. Performance prediction is a challenge because of the involvement of various parts in the brake assembly like booster, master cylinder, calipers, disc and drum brakes. Determination of these characteristics through vehicle level tests requires a lot of time and money. This performance prediction is achieved by theoretical calculations involving vehicle dynamics. The final output must satisfy the regulations. This project involves the creation of a standalone application using MATLAB to predict the various brake performances such as: booster characteristics, adhesion curves, deceleration and pedal effort curves, behavior of brakes during brake and booster failed conditions and braking force diagrams based on the given user inputs. Previously, MS Excel and an application developed in the TK Solver environment was used to predict the brake performance curves. Debugging and inclusion of new modules was a major issue in old applications. Also, the previous applications lacked ABS module, which after the new government norms will be implemented in every vehicle. Thus, there was…

Sensitivity Analysis of Tire-Soil Interaction using Finite Element Analysis and Smoothed Particle Hydrodynamics Techniques

UOIT-Mirwais Sharifi, Moustafa El-Gindy
Univ of Ontario Institute of Technology-Zeinab El-Sayegh
  • Technical Paper
  • 2019-01-0174
To be published on 2019-04-02 by SAE International in United States
This paper presents the modelling, calibration and sensitivity analysis of LETE Sand using Visual Environment’s Pam Crash. LETE sand is modelled and converted from Finite Element Analysis mesh (FEA) to Smooth-particle hydrodynamics (SPH). The sand is then calibrated using terramechanics published data by simulating a pressure sinkage test and shear box test using the SPH LETE sand particles. The material properties such as tangent modulus, yield strength and bulk modulus are configured so the simulation’s results match those of theoretical values. Sensitivity analysis of the calibrated LETE sand material is then investigated. The sensitivity analysis includes mesh size, plate geometry, smoothing length, max smoothing length, artificial viscosity and contact thickness. The effect of these parameters on the sand behaviour is analyzed. Finally, SPH LETE Sand is used to determine the rolling resistance coefficient of RHD truck tire size 315/80R22.5 for different mesh size sand particles. The results found within this paper will be continued in regard to achieving better understanding of vehicle dynamics for tire-terrain interaction.

An Investigation of Aerodynamic Characteristics of Three Bluff Bodies in Close Longitudinal Proximity

Coventry University-Geoffrey Le Good, Peter Boardman, Max Resnick, Brian Clough
  • Technical Paper
  • 2019-01-0659
To be published on 2019-04-02 by SAE International in United States
The benefit in fuel-saving for road vehicles travelling in close longitudinal proximity stems from the potential reduction in total aerodynamic drag compared to the sum of that for the same number of vehicles when travelling alone. Research in the 1980s considered travelling in close proximity, termed “platooning”, as a means for reducing congestion, but the aerodynamic drag reduction and fuel-savings found in wind tunnel tests and road-trials became the primary focus of further investigations. Practical application was limited by the lack of systems to control vehicle spacing which was critical to the aerodynamic efficiency of the platoon and for safety. However, vehicle communication and control systems associated with the recent development of connected and autonomous vehicles has provided greater opportunity for platooning to be considered again within future traffic management systems. Early research involving passenger cars, and also more recent studies using heavy goods vehicles, has been based on ‘vehicle spacing’ as the test variable. Platoons were of homogeneous constituents and the aerodynamic characteristics of most vehicles in these studies comprised large separated wakes –…

Effect of Space Weather on Autonomous Vehicle Navigation

University Of Detroit Mercy-Alan S. Hoback
  • Technical Paper
  • 2019-01-0694
To be published on 2019-04-02 by SAE International in United States
Autonomous vehicle systems integrate multiple information systems. Navigation is reliant on global positioning systems (GPS) which are supported by a satellite network. However, satellites and radio signals are subject to interference from sunspots. Sunspots happen on regular cycles at varying strengths but their occurrence can’t be exactly predicted. The likelihood of a severe solar event is roughly twelve percent per decade. Moderate solar events could impair navigation. Results will show the likelihood of each event and its consequence on autonomous vehicle navigation. In the worst case scenario, satellites could even be permanently damaged by severe sunspots. As autonomous vehicles become a more significant portion of the economy, it is necessary that they have resilience operate in extreme conditions. Alternative navigation procedures are proposed to enhance the resiliency of autonomous vehicles. Artificial intelligence related to place identification, inertial position tracking, relative geographic navigation, and storage of most common routes are some of the options.

Hierarchical vehicle active collision avoidance based on potential field method

Changan intelligent vehicle R&D center-Gang Yi
Chongqing University-Ling Zheng, Yinong Li, Wei Yang
  • Technical Paper
  • 2019-01-1016
To be published on 2019-04-02 by SAE International in United States
In this paper, a closed loop path planning and tracking control approach of collision avoidance for autonomous vehicle is proposed. The two-level model predictive control(MPC) is proposed for the path planning and tracking. The upper-level MPC is designed based on the simple vehicle kinematic model to calculate the collision-free trajectory and the potential field method is adopted to evaluate the collision risk and generate the cost function of the optimization problem. The lower-level MPC is the trajectory-tracking controller based on the vehicle dynamics model that calculates the desired control inputs. Finally the control inputs are distributed to steering wheel angle and motor torque via optimal control vectoring algorithm. Test cases are established on the Simulink/Carsim platform to evaluate the performance of the controller. The simulation results demonstrate that the proposed control has satisfactory path tracking performance and could avoid the potential collisions effectively during the high way driving.

Customer Oriented Vehicle Dynamics Assessment for Autonomous Driving in Highway

Centro Ricerche Fiat-Giovanni Gabiati
Fiat Chrysler Automobiles-Silvio Data
  • Technical Paper
  • 2019-01-1020
To be published on 2019-04-02 by SAE International in United States
Nowadays, thanks to continuous improvement in IT, carmakers spend great efforts on studies regarding Autonomous driving. Autonomous driving is the most advanced and focused research area for what concerns the automotive field and Carmakers are mainly investing money in this field but in most cases the analysis is centered towards the efforts on control logic, legal issues or possible benefits of autonomous driving. This paper’s objective is to evaluate the vehicle dynamic response of an autonomous driven vehicle, in particular, evaluation of vehicle/driver performance for a highway overtake maneuver. Obviously in this new scenario the vehicle will be driven autonomously, so performance evaluation means comfort evaluation. For this reason, the acceleration magnitude of peaks must be observed in a complete different logic eventually with new thresholds, as well as new magnitudes. Lateral acceleration variation (jerk) for example is going to be a key parameter for this evaluation. RMSs remain interesting indicators for comfort like the best practice for NVH evaluations, but in this kind of maneuvers horizontal accelerations should also be considered. In this very…

An Optimization of Small Unmanned Aerial System (sUAS) Image Based Scanning Techniques for Mapping Accident Sites

Kineticorp LLC-Neal Carter, Alireza Hashemian, Nathan Mckelvey
  • Technical Paper
  • 2019-01-0427
To be published on 2019-04-02 by SAE International in United States
Small unmanned aerial systems have gained prominence in their use as tools for mapping the 3-dimensional characteristics of accident sites. Typically, the process of mapping an accident site involves taking a series of overlapping, high resolution photographs of the site, and using photogrammetric software to create a point cloud or mesh of the site. This process, known as image-based scanning, is explored and analyzed in this paper. A mock accident site was created that included a stopped vehicle, a bicycle, and a ladder. These objects represent items commonly found at accident sites. The accident site was then documented with several different unmanned aerial vehicles at differing altitudes, with differing flight patterns, and with different flight control software. The photographs taken with the unmanned aerial vehicles were then processed with photogrammetry software using different methods to scale and align the point clouds. The point cloud data produced with different vehicle / flight pattern / altitude combinations was then quantitatively compared to terrestrial LiDAR scan data. The results are presented here, as well as recommendations based on…