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Investigation of the Effect of Tire Deformation on Open-Wheel Aerodynamics

Graz University of Technology-Philipp Eder, Cornelia Lex
U.A.S. Graz-Thomas Gerstorfer, Thomas Amhofer
  • Technical Paper
  • 2020-01-0546
To be published on 2020-04-14 by SAE International in United States
This paper introduces a finite element (FE) approach to determine tire deformation and its effect on open-wheeled racecar aerodynamics. In recent literature the tire deformation was measured optically using cameras during wind tunnel testing. Combined loads like accelerat-ing at corner exit are difficult to reproduce in wind tunnels and would require several camer-as to measure the tire deformation. In contrast, an FE approach is capable of determining the tire deformation in combined load states accurately and additionally provides the possibility to vary further parameters, for example, the coefficient of friction. The FE tire model was validated using stiffness measurements, contact patch measurements and steady-state cornering measurements on a flat belt tire test rig. The deformed shape of the FE model was used in a computational fluid dynamics (CFD) simulation. A sensitivity study was created to determine the effect of the tire deformation on aerodynamics for un-loaded, purely vertically loaded and combined vertical, lateral and longitudinal forces. In addition, the influence of these three tire deformations was investigated in a CFD study using a full vehicle…
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Heavy Vehicles Kinematics of Automatic Emergency Braking Test Track Scenarios

NHTSA-Devin Elsasser
Transportation Research Center Inc-M. Kamel Salaani, Christopher Boday
  • Technical Paper
  • 2020-01-0995
To be published on 2020-04-14 by SAE International in United States
This paper presents the test track scenario design and analysis used to estimate the performances of heavy vehicles equipped with forward collision warning and automatic emergency braking systems in rear-end crash scenarios. The first part of this design and analysis study was to develop parameters for brake inputs in test track scenarios simulating a driver that has insufficiently applied the brakes to avoid a rear-end collision. In the second part of this study, the deceleration limits imposed by heavy vehicles mechanics and brake systems are used to estimate automatic emergency braking performance benefits with respect to minimum stopping distance requirements set by Federal Motor Vehicle Safety Standards. The results of this study were used to complete the test track procedures and show that all heavy vehicles meeting regulatory stopping distance requirements have the braking capacity to demonstrate rear-end crash avoidance improvements in the developed tests.
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A Smart Measuring System for Vehicle Dynamics Testing

Politecnico di Torino-Enrico Galvagno, Stefano Mauro, Stefano Pastorelli, Antonio Tota
  • Technical Paper
  • 2020-01-1066
To be published on 2020-04-14 by SAE International in United States
A fast measurement of the car handling performance is highly desirable to easily compare and assess different car setup, e.g. tires size and supplier, suspension settings, etc. Instead of the expensive professional equipment normally used by car manufacturers for vehicle testing, the authors propose a low cost solution that is nevertheless accurate enough for comparative evaluations. The paper presents a novel measuring system for vehicle dynamics analysis, which is based uniquely on the sensors embedded in a smartphone and completely independent on the signals available through vehicle CAN bus. Data from tri-axial accelerometer, gyroscope, GPS and camera are jointly used to compute the typical quantities analyzed in vehicle dynamics applications. In addition to signals like yaw rate, lateral and longitudinal acceleration, vehicle speed and trajectory, normally available when working with Inertial Measurement Units (IMU) equipped with GPS, in the present application also the steering wheel angle is measured by artificial vision algorithms that use the phone camera.. The latter signal, besides being important for identifying the maneuver imposed by the driver, it enables the usage…
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Effects of training on learning and use of an adaptive cruise control system

Exponent Failure Analysis-Audra Krake, Rachel Jonas, Christian Hoyos, Caroline Crump, Benjamin Lester, David Cades, Ryan Harrington
  • Technical Paper
  • 2020-01-1033
To be published on 2020-04-14 by SAE International in United States
This study examined the effects of formalized training on driver behavior and understanding of an adaptive cruise control (ACC) system with drivers experienced with ACC. Sixteen participants drove an ACC-equipped vehicle while following a lead vehicle around a test track. Participants completed three laps, each featuring different lead vehicle behaviors, such as making a lane change or stopping at a red light, that test the limitations and capabilities of ACC. Immediately before driving, half of the participants watched a training video describing how the ACC system would respond to these lead vehicle behaviors. Braking behavior and use of ACC was recorded by cameras, and participants’ knowledge of the ACC system limitations was assessed by a pre- and post-test questionnaire. Surprisingly, compared to the participants who did not receive training, those who did receive training showed significantly more use of the brake versus allowing the ACC to slow or stop the vehicle for them during certain conditions. We did not observe significant differences between the two groups in time spent using ACC, though participants who did…
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NHTSA's 2018 Heavy Vehicle Automatic Emergency Braking Test Track Research Results

NHTSA-Devin Elsasser
Transportation Research Center Inc-M. Kamel Salaani, Christopher Boday
  • Technical Paper
  • 2020-01-1001
To be published on 2020-04-14 by SAE International in United States
This paper presents National Highway Traffic Safety Administration’s 2017 and 2018 test track research results with heavy vehicles equipped with forward collision warning and automatic emergency braking systems. Newly developed objective test procedures were used to perform and collect performance data with three single-unit trucks equipped with the crash avoidance systems. The results of this research show that the test procedures are applicable to many heavy vehicles and indicate that performance improvements in heavy vehicles equipped with these safety systems can be objectively measured.
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Nonlinear Model Predictive Control of Autonomous Vehicles Considering Dynamic Stability Constraints

Tongji University-Xunjie Chen, Guangqiang Wu, Meng Ren
  • Technical Paper
  • 2020-01-1400
To be published on 2020-04-14 by SAE International in United States
The autonomous vehicle performance is increasingly highlighted in many highway driving scenarios, which leads to more priorities to vehicle stability as well as tracking accuracy. In this paper, a nonlinear model predictive controller for autonomous vehicle trajectory tracking is designed and verified through a real-time driving simulator of a virtual test track. The dynamic stability constraints of nonlinear model predictive control (NLMPC) are obtained by a novel quadrilateral stability region criterion instead of the conventional phase plane method using the double-line region. First, a typical lane change scene of overtaking is selected and a new composited trajectory model is proposed as a reference path that combines smoothness of sine wave and comfort of linear functional path. Reference lateral velocity, azimuth angle, yaw rate, and front wheel steering angle are subsequently taken into account. Then, by establishing a nonlinear vehicle dynamics model where Magic Formula of nonlinear tire model is adapted, the quadrilateral vehicle stability region is defined in consideration of designed velocity, road adhesion coefficient, and front wheel steering angle. Working condition-variant constraints determined by…
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Validation of a Theoretical Model for the Correction of Heat Transfer Effects in Turbocharger Testing through a Quasi-3D Model

Politecnico di Milano-Gianluca Montenegro, Matteo Tamborski, Augusto Della Torre
Universita Degli Studi di Genova-Silvia Marelli
  • Technical Paper
  • 2020-01-1010
To be published on 2020-04-14 by SAE International in United States
In the last few years, the effect of diabatic test conditions on compressor performance maps has been widely investigated leading some Authors to propose different correction models. The accuracy of turbocharger performance map constitute the basis for the tuning and validation of a numerical 1D procedure, usually adopted for the engine-turbocharger matching. Actually, it is common practice in automotive applications to use simulation codes, which require as an input the value of efficiency. Therefore, the ability to correct the measured performance maps taking into account internal heat transfer would allow the implementation of commercial simulation codes used for engine-turbocharger matching calculations. The practical purpose of an adiabatic test program is to obtain an accurate measurement of the work transfer, and of the real efficiency of compressor and turbine (unaffected by internal and external heat transfer rates). In fact, the heat flow leads to an apparent increase of the power absorption and an apparent drop in efficiency of the compressor. However, lack of understanding of the heat transfer effects as well as the high costs associated…
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Chassis Lightweighting Hole Placement with Weldline Evaluation

Ford Motor Company-Gavin Song
  • Technical Paper
  • 2020-01-0493
To be published on 2020-04-14 by SAE International in United States
Vehicle weight driven design comes amid rising higher fuel efficiency standard, and must meet the criteria - pass Proving ground test events that is equivalent customer usage. CAE Fatigue analysis for proving ground (CFP) is behind a success push to digitally simulate vehicle durability performance in high fidelity. The need for vehicle weight reduction often arises late in vehicle development phases when CAE Methods, time, and tangible cost effective opportunities are limited or non-existent. It is necessary to deploy a new CAE Method to identify opportunities for light-weighting hole placement in Chassis structures to deliver a cost effective light-weighting opportunity with no impact on fatigue life. The successful application of this methodology is on truck frame, which is key structural parts for vehicle chassis to support body and suspension and powertrain. By means of artificially adjusting the magnitude of load time history and material fatigue properties S-N curve, fatigue life calculation can highlight potential areas for lightweighting holes. Weldline fatigue is further carried on to verify the impact from those lighting holes.
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Volume of Fluid vs. Cavitation CFD-Models to Calculate Drag Torque in Multi-Plate Clutches

SIMERICS GmbH-Rudi Niedenthal
Technical University of Munich-Daniel Groetsch, Katharina Voelkel, Hermann Pflaum, Karsten Stahl
  • Technical Paper
  • 2020-01-0495
To be published on 2020-04-14 by SAE International in United States
Wet running multi-plate clutches and brakes are important components of modern powershift gearboxes and industrial powertrains. In the open stage, drag losses occur due to fluid shear. Identification of drag losses is possible by experiment or CFD-simulation. For calculation of the complex fluid flow of an open clutch CFD-approaches such as the Volume of Fluid (VoF) method or the Singhal cavitation model are applicable. Every method has its own specific characteristics. This contribution sets up CFD-calculation models for different clutches with diverse groove designs. We present results of calculations in various operating conditions obtained from the Singhal cavitation model and the VoF-method. Despite the high spatial resolution of the calculation models the usage of a modern commercial CFD-solver and mesher (Simerics MP+) results in very short calculation times. The developed CFD-models consider the geometry of a complete clearance consisting of the friction plate, the gap between the plates, the steel plate and the flow conditions arising from the design of the inner and outer plate carrier. The full 360-degree modeling makes it possible to take…
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Improved PSD Fatigue Approach for large FE models with wide frequency range

Faurecia-Huai-Ren Shih
  • Technical Paper
  • 2020-01-0499
To be published on 2020-04-14 by SAE International in United States
Fatigue damage calculation are traditionally based on the time domain approach. Acceleration time history inputs are used to excite the system and the outputs are in a form of stress time history. This transient dynamic approach, as time history is intuitive to understand, provides straightforward and reasonable result. Nevertheless, a typical automotive proving ground test consists of 20 to 30 road events, it is not only computationally intensive but could be also a grueling process for engineer to carry out as it requires iteration for each event in the schedule before fatigue calculation. Alternatively, a frequency domain fatigue calculation is widely used. In this approach, both the dynamic loading and response are expressed in terms of Power Spectral Density (PSD) functions and the dynamic structure is treated as a linear transfer function. The transfer function is then multiplied with event PSD to get the PSD of the stress. This PSD approach can simplify the problem considerably as it requires simulation to be run only once. However, the approach itself still has some issues when it…