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Aerodynamic Analysis of a Passenger Car to Reduce Drag Using Active Grill Shutter and Active Air Dam

ARAI Academy-Raghav Tandon
Automotive Research Association of India-Mohammad Rafiq Agrewale, Kamalkishore Vora
  • Technical Paper
  • 2019-28-2408
To be published on 2019-11-21 by SAE International in United States
Active aerodynamics can be defined as the concept of reducing drag by making real-time changes to certain devices such that it modifies the airflow around a vehicle. Using such devices also have the added advantages of improving ergonomics and performance along with aesthetics. A significant reduction in fuel consumption can also be seen when using such devices. The objective of this work is to reduce drag acting on a passenger car using the concept of active aerodynamics with grill shutters and air dams. First, analysis has been carried out on a baseline passenger car and further simulated using active grill shutters and air dams for vehicle speed ranging from 60 kmph to 120 kmph, with each active device open from 0° to 90°. The optimized model is then validated for a scaled-down prototype in a wind tunnel at 80kmph. Vehicle has been modelled using SolidWorks and the simulation has been carried out using ANSYS Fluent. The result shows a significant drag reduction of 12.23% using active grill shutters and air dams.
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Evaluating the Effect of Light Weighting Through Roll Stiffness Change on Vehicle Maneuverability and Stability

Maruti Suzuki India, Ltd.-Eric Pranesh Reuben, Raghav Budhiraja, Sreeraj N, Rakesh K, Amardeep Singh
  • Technical Paper
  • 2019-28-2406
To be published on 2019-11-21 by SAE International in United States
Objective To achieve better fuel economy and reduced carbon footprint, OEMs are reducing the sprung and unsprung mass. This translates into a reduction in stiffness which profoundly deteriorates the handling/road holding characteristics of the vehicle. To model these changes in stiffness, modifications are made to suspension roll stiffness at the front and rear. This study compares different configurations of roll stiffness and evaluates vehicle behavior using frequency response characteristics and phase change of Yaw Gain recorded. The present work associates acquired data with subjective feedback to outline the shift in vehicle balance emerging from a variation of sprung and unsprung mass ratio. Methodology To study the frequency response characteristics of the vehicle, the pulse input is chosen for this. An ideal pulse input’s Fourier transform represents constant amplitude over all the frequency ranges. By giving a single input, the system is subjected to a range of frequencies. The changes in roll stiffness at the front and rear axles are achieved through addition of Stabilizer Bars of different diameters and stiffness. The test is conducted using…
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A Heavy Tractor Semi-Trailer Stability Control Strategy Based on Electronic Pneumatic Braking System HIL Test

SAE International Journal of Vehicle Dynamics, Stability, and NVH

State Key Laboratory of Automotive Simulation and Control, Jilin University, China-Hongyu Zheng, Yangyang Miao
United States-Bin Li
  • Journal Article
  • 10-03-03-0016
Published 2019-10-15 by SAE International in United States
Aiming to improve the handling performance of heavy tractor semi-trailer during turning or changing lanes at high speed, a hierarchical structure controller is proposed and a hardware-in-the-loop (HIL) test bench of the electronic pneumatic braking system is developed to validate the proposed controller. In the upper controller, a Kalman filter observer based on the heavy tractor semi-trailer dynamic model is used to estimate the yaw rates and sideslip angles of the tractor and trailer. Simultaneously, a sliding mode direct yaw moment controller is developed, which takes the estimated yaw rates and sideslip angles and the reference values calculated by the three-degrees-of-freedom dynamic model of the heavy tractor semi-trailer as the control inputs. In the lower controller, the additional yaw moments of tractor and trailer are transformed into corresponding wheel braking forces according to the current steering characteristics. The HIL test bench of the electronic pneumatic braking system is built to verify the effectiveness of the strategy. Double lane-change maneuver, sinusoidal maneuver, and J-turn maneuver are selected as handling and stability test conditions. The LabView real-time…
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Modelling and Validation of a Control Algorithm for Yaw Stability & Body Slip Control Using PID & Fuzzy Logic Based Controllers

SITAMS-Chellappan Kavitha
VIT University-Umashankar Lath, Sanyam Kakkar, Aman Agarwal, Bragadeshwaran Ashok, Vemuluri Ramesh Babu, Sathiaseelan Denis Ashok
Published 2019-10-11 by SAE International in United States
Advanced driver-assistance systems (ADAS) are becoming an essential part of the modern commercial automobile industry. Vehicle handling and stability are determined by the yaw rate and body slip of the vehicle. This paper is a comparative study of a nonlinear vehicle stability control algorithms for steering control based on two different controllers i.e. fuzzy logic based controller and PID controller. A full vehicle 14DOF model was made in Simulink to simulate an actual vehicle. The control algorithms are based on a two-track 7-DOF model with a non-linear tire model based on Pacejka “Magic tire formula”, which was used to establish the desired response of a full vehicle 14DOF model. It was found that the fuzzy logic-based control algorithm demonstrated an overall superior performance characteristic than a PID based control algorithm; this includes a significant decrease in time lag and overshoot. The proposed control algorithms were validated through the co-simulation of Carsim and Simulink in real time.
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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
Published 2019-04-02 by SAE International in United States
Aerodynamic 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 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 up to 12% was observed in the measured drag coefficients from the US coastdown procedure and the EU constant-speed test. The differences in the measured drag coefficient can be attributed, among others, to the assumptions in the speed-dependence of the tire rolling resistance and axle spin losses, the data post-processing required by each methodology, unaccounted frictional losses in the transmission, the behavior of the automated manual transmission during the coastdown run, and the yaw angle correction.
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Accuracy and Sensitivity of Yaw Speed Analysis to Available Data

MEA Forensic Engineers & Scientists-Bradley Heinrichs, Janice Lee, Cole Young
Published 2019-04-02 by SAE International in United States
Accident reconstructionists rarely have complete data with which to determine vehicle speed, and so the true value must be bracketed within a range. Previous work has shown the effect of friction uncertainty in determining speed from tire marks left by a vehicle in yaw. The goal of the current study was to assess improvements in the accuracy of vehicle speed estimated from yaw marks using progressively more scene and vehicle information. Data for this analysis came from staged S-turn maneuvers that in some cases led to rollover of sport utility vehicles. Initial speeds were first calculated using the critical curve speed (CCS) formula on the yaw marks from the first portion of the S-maneuver. Then computer simulations were performed with progressively more input data: i) the complete tire marks from the whole S-maneuver, ii) measured vehicle mass, iii) measured suspension stiffness and damping, and iv) measured steering history. Simulations based on the complete tire marks reduced the average error compared with the CCS equation if measured accelerations were also matched. Adding the remaining input data…
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Extended Kalman Filter Based Road Friction Coefficient Estimation and Experimental Verification

APTIV PLC-Bin Li, Guobiao Song
Ford Motor Co., Ltd.-Arlene Fang
Published 2019-04-02 by SAE International in United States
Accurate road friction coefficient is crucial for the proper functioning of active chassis control systems. However, road friction coefficient is difficult to be measured directly. Using the available onboard sensors, a model-based Extended Kalman filter (EKF) algorithm is proposed in this paper to estimate road friction coefficient. In the development of estimation algorithm, vehicle motion states such as sideslip angle, yaw rate and vehicle speed are first estimated. Then, road friction coefficient estimator is designed using nonlinear vehicle model together with the pre-estimated vehicle motion states. The proposed estimation algorithm is validated by both simulations and tests on a scaled model vehicle.
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Rear-Wheel Steering Control for Enhanced Maneuverability of Vehicles

Seoul National University-Kwanwoo Park, Eunhyek Joa, Kyongsu Yi
Published 2019-04-02 by SAE International in United States
This paper proposes a rear-wheel steering control method that can modify and improve the vehicle lateral response without tire model and parameter. The proposed control algorithm is a combination of steady-state and transient control. The steady state control input is designed to modify steady-state yaw rate response of the vehicle, i.e. understeer gradient of the vehicle. The transient control input is a feedback control to improve the transient response when the vehicle lateral behavior builds up. The control algorithm has been investigated via computer simulations. Compared to classical control methods, the proposed algorithm shows good vehicle lateral response such as small overshoot and fast response. Specifically, the proposed algorithm can alleviate stair-shaped response of the lateral acceleration. In addition, through tests with low friction road and high lateral acceleration, the proposed algorithm’s performance is verified to be robust for a variety of road friction and nonlinear tire characteristics, since tire information is excluded.
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Speed Analysis of Yawing Passenger Vehicles Following a Tire Tread Detachment

Kineticorp LLC-Gray Beauchamp, David Pentecost, Daniel Koch, William Bortles
Published 2019-04-02 by SAE International in United States
This paper presents yaw testing of vehicles with tread removed from tires at various locations. A 2004 Chevrolet Malibu and a 2003 Ford Expedition were included in the test series. The vehicles were accelerated up to speed and a large steering input was made to induce yaw. Speed at the beginning of the tire mark evidence varied between 33 mph and 73 mph. Both vehicles were instrumented to record over the ground speed, steering angle, yaw angle and in some tests, wheel speeds. The tire marks on the roadway were surveyed and photographed.The Critical Speed Formula has long been used by accident reconstructionists for estimating a vehicle’s speed at the beginning of yaw tire marks. The method has been validated by previous researchers to calculate the speed of a vehicle with four intact tires. This research extends the Critical Speed Formula to include yawing vehicles following a tread detachment event. The Critical Speed Formula was found to produce results of acceptable and known accuracy, provided the appropriate inputs are used for the given situation and…
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Inter-Vehicular Sliding Friction and Crush Energy Losses in Impulse Momentum Planar Collision

Biomechanical Research & Testing-Judson Welcher
Collision Dynamics Analysis-Nicholas Carpenter
Published 2019-04-02 by SAE International in United States
New in this study is the mathematical formula for calculating energy dissipated due to sliding under the action of Coulomb kinetic friction in the context of Impulse Momentum Planar Collision (IMPC) with isotropic restitution. The surface sliding dissipated energy theorem established here is precisely consistent with the laws of physics underlying IMPC. A principal goal of distinguishing between surface sliding energy dissipation and energy dissipation due to vehicle crush is to improve the rational basis for use of crush energy analysis with IMPC. Also new in this study is a consistent interpretation of Newton's, Poisson's and Stronge's restitution hypotheses as they apply to IMPC with Coulomb kinetic friction. While this paper adds to the understanding of energy dissipation, the IMPC method presented here is not new. The IMPC method features a yaw velocity component and two translational velocity components referenced to the dynamic center of mass of each vehicle as well as an impulse vector acting at the point of impact between the colliding vehicles, all of which are related by way of Newton's laws…
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