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Alleviating the Magnetic Effects on Magnetometers using Vehicle Kinematics for Yaw Estimation for Autonomous Ground Vehicles

Michigan Technological University-Ahammad Basha Dudekula, Jeffrey D. Naber
  • Technical Paper
  • 2020-01-1025
To be published on 2020-04-14 by SAE International in United States
Autonomous vehicle operation is dependent upon accurate position estimation and thus a major concern of implementing the autonomous navigation is obtaining robust and accurate data from sensors. This is especially true, in case of Inertial Measurement Unit (IMU) sensor data. The IMU consists of a 3-axis gyro, 3-axis accelerometer, and 3-axis magnetometer. The IMU provides vehicle orientation in 3D space in terms of yaw, roll and pitch. Out of which, yaw is a major parameter to control the ground vehicle’s lateral position during navigation. The accelerometer is responsible for attitude (roll-pitch) estimates and magnetometer is responsible for yaw estimates. However, the magnetometer is prone to environmental magnetic disturbances which induce errors in the measurement. The present work focuses on alleviating magnetic disturbances for ground vehicles by fusing the vehicle kinematics information with IMU senor in an Extended Kalman filter (EKF) with the vehicle orientation represented using Quaternions. In addition, the error in rate measurements from gyro sensor gets accumulated as the time progress which results in drift in rate measurements and thus affecting the vehicle…
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Direct Yaw Moment Control of Electric Vehicle with 4 In-Wheel Motors to Improve Handling and Stability

China FAW Group Corporation-Jinlong Cui, Zehui Zhou, Yang Fang, Deping Wang, Tianqiang Zhang, Aibin Wu, Qichun Sun, Yang Zhao
College of Automotive Engineering Jilin University-Yongqiang Zhao
  • Technical Paper
  • 2020-01-0993
To be published on 2020-04-14 by SAE International in United States
More and more OEMs are interested in in-wheel-motor drive vehicles. One of the in-wheel-motor drive vehicle key technologies is multi-motor torque distribution. A direct yaw moment control strategy for torque distribution was introduced in this paper to improve 4 in-wheel-motor electric vehicle’s handling and stability. The control method consists of three components: feedback control based on target yaw rate, feedforward control based on current lateral acceleration and deceleration control based on under/oversteer situation. Feedback control is used to make vehicle’s real yaw rate following the driver’s target yaw rate and improve vehicle yaw rate response and stability. The target yaw rate is calculated by 2DOF vehicle model and limited by lateral acceleration and vehicle current steering condition. The feedforward control is used to increase the vehicle yaw rate gain and reduce the vehicle understeer characteristic when accelerating in a curve. The deceleration control can reduce the driving torque of each motor to slow down the vehicle when in critical steering condition. The proposed control strategy was verified by an in-wheel-motor drive electric vehicle test and…
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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 therefore 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 such as yaw rate, lateral and longitudinal acceleration, vehicle speed and trajectory, normally available when working with Inertial Measurement Units (IMU) equipped with GPS, in the presented application the steering wheel angle is also measured, without additional sensors. The latter signal, besides being important for identifying the maneuver imposed by the driver, enables the usage of Kalman filters based on dynamic…
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On Road Fuel Economy Impact by the Aerodynamic Specifications under the Natural Wind

Honda R&D Co., Ltd.-Yasuyuki Onishi, Kenta Ogawa, Jun Sawada, Youji Suwa, Fortunato Nucera
  • Technical Paper
  • 2020-01-0678
To be published on 2020-04-14 by SAE International in United States
According to some papers, the label fuel economy and the actual fuel economy experienced by the customers may exhibit a gap. One of the reasons may stem from the aerodynamic drag variations due to the natural wind. The fuel consumptions are measured on the bench test under the several driving modes by using the road load as input conditions. The road load is measured through the coast down test under less wind ambient conditions as determined by each regulation. The present paper aims to analyze the natural wind specifications encountered by the vehicle on the public road and to operate a comparison between the fuel consumptions and the driving energy. In this paper, the driving energy is calculated by the aerodynamic drag from the natural wind specifications and driving conditions. This driving energy and the fuel consumptions show good correlation. The fuel consumption is obtained from the vehicle ECU data. The driving energy is calculated by the aerodynamic drag and the vehicle driving conditions through the time history data on the road. Aerodynamic drag is…
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Development of a Passenger Vehicle Seat Center-of-Gravity Measuring Device

SEA, Ltd.-Scott Zagorski, Dale Andreatta, Gary Heydinger
  • Technical Paper
  • 2020-01-1061
To be published on 2020-04-14 by SAE International in United States
A machine has been developed to measure the center-of-gravity (CG) location of a seat. This machine uses a system of pivots, a yaw bearing and two sensors to get the X, Y and Z CG of the seat. Test object mass is measured separately on a scale. A stable pendulum arrangement is used to get the CG location. Governing equations for the machine are shown in the paper and a typical test procedure is discussed. An error analysis is discussed and shows the requisite accuracy of platform angle, geometric dimensions, seat weight and applied weight in order to achieve the desired 3 mm accuracy target. A full system statistical analysis demonstrates that all X and Y CG locations, when compared with theoretical values, are off by less than 1 mm and well within the 3 mm accuracy target. For Z CG, the errors were shown to be 3.3 mm or lower with 95 percent confidence.
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SUV Kinematics during a Steer-Induced Rollover Resolved Using Consumer-Grade Video, Laser Scans and Match-Moving Techniques

MEA Forensic Engineers & Scientists-Cole R. Young, David J. King, Gunter P. Siegmund
  • Technical Paper
  • 2020-01-0642
To be published on 2020-04-14 by SAE International in United States
Rollover crashes are complex events that generate motions in all six degrees of freedom (6DOF). Directly quantifying the angular rotations from video can be difficult and vehicle orientation as a function of time is often not reported for staged rollover crashes. Our goal was to evaluate the ability of using a match-moving technique and consumer-grade video cameras to quantify the roll, pitch and yaw angles and angular velocities of a rollover crash. We staged a steer-induced rollover of an SUV at 106 km/h. The vehicle was fitted with tri-axial accelerometers and angular rate sensors, and five consumer-grade video cameras (2 on tripods, 2 on drones, 1 handheld, ~30 fps) captured the event. Roll, pitch and yaw angles were determined from the video using specialized software. We then compared the vehicle orientation angles from the video data to the integrated angular rate data measured by onboard sensors, and also compared the angular rates from the differentiated video data to the angular rates measured directly by the sensors. We found that both methods of measuring the 3D…
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Research on Yaw Stability Control of Unmanned Vehicle Based on Integrated Electromechanical Brake Booster

Jilin University-Dexing Lao, Jian Wu, Rui He, Bing Zhu, Jian Zhao, Zhicheng Chen
  • Technical Paper
  • 2020-01-0212
To be published on 2020-04-14 by SAE International in United States
The Electromechanical Brake Booster system (EMBB) integrates active braking and energy recovery and becomes a novel brake-by-wire solution that substitutes the vacuum booster. While the intelligent unmanned vehicle is in unstable state, the EMBB can improve the vehicle yaw stability more quickly and safely. In this paper, a new type of integrated EMBB has been designed, which mainly includes two parts: servo motor unit and hydraulic control unit. Aiming at the dynamic instability problem of intelligent unmanned vehicle, a three-layer vehicle yaw stability control structure including decision layer, distribution layer and execution layer is proposed based on integrated EMBB. Firstly, the decision layer calculates the ideal yaw rate and the side slip angle of the vehicle with the classic 2DOF vehicle dynamics model. The boundary of the stable region is determined by the phase plane method and the additional yaw moment is determined by the feedback PI control algorithm. Secondly, the distribution layer optimally selects the wheel with the highest differential braking efficiency and assigns the brake pressure to the corresponding wheel based on the…
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Quantitative High Speed Stability Assessment of a Sports Utility Vehicle and Classification of Wind Gust Profiles

CEVT (China Euro Vehicle Technology)-Erik Preihs, Ingemar Johansson
Chalmers University of Technology-Simone Sebben, Bengt Jacobson
  • Technical Paper
  • 2020-01-0677
To be published on 2020-04-14 by SAE International in United States
The automotive trends of vehicles with lower aerodynamic drag and more powerful drivetrains have increased the concern of stability issues at high speeds, since more streamlined bodies show greater sensitivity to crosswinds. This is especially important for high vehicles, such as sports utility vehicles. In addition, the competitiveness in the automotive industry requires faster development times and, thus, a need to evaluate the high speed stability performance in an early design phase, preferable using simulation tools. The accuracy of these simulation tools partly relies on realistic boundary conditions for the wind and quantitative measures for assessing stability without the subjective evaluation of experienced drivers. Hence, this study employed an on-road experimental measurements setup to define relevant wind conditions and to find an objective methodology to evaluate high speed stability. The paper is focusing in detail on the events in proximity to the drivers' subjective triggers of instability. Wind direction and magnitude, vehicle motion response, driver steering input along with the subjective event triggering were measured for several aerodynamic configurations during different conditions of the natural…
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A Study on the Effect of Tire Temperature and Rolling Speed on the Vehicle Handling Response

Eindhoven University of Technology-Abhijeet Behera
Siemens Digital Industries Software-Carlo Lugaro, Mohsen Alirezaei, Ioannis Konstantinou
  • Technical Paper
  • 2020-01-1235
To be published on 2020-04-14 by SAE International in United States
Rubber is a non-linear viscoelastic material which properties depend upon several factors. In a tire two of these factors, namely the temperature and excitation frequency, are significantly influenced by the vehicle operating conditions. In the past years, applied research studied how rubber viscoelastic characteristics affect structural and frictional tire properties. The present study focuses on how these effects interact with the vehicle handling response. Based on state of the art theory of friction, structural properties of rubber and on experimental evidence, the dependency of key tire parameters on temperature and rolling speed is established. These results are then used in combination with a single-track vehicle model to assess their impact on key vehicle parameters; as an example, the understeer coefficient, yaw resonance peak / damping and maximum acceleration are studied. Furthermore, to ensure accurate results in realistic situations, a novel tire thermodynamic model is used in combination with a detailed 14 degrees of freedom vehicle model in a numerical simulation environment. The simulations permit to study the mutual effects between tire temperature, rolling speed and…
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A Tire Work Load (TWL) Based Controller for Active Independent Front Steering System (AIFS)

Helwan University-Mohab Bahnasy, Mahmoud Atef Aly, Walid Oraby
  • Technical Paper
  • 2020-01-0648
To be published on 2020-04-14 by SAE International in United States
Vehicle Handling performance depends on many parameters. One of the most important parameters is the dynamic behavior of the steering system. However, steering system had been enhanced thoroughly over the past decade where Active Front Steering (AFS) is now present and other system as Active Independent Front Steering (AIFS) is currently in the research phase. Actually, AFS system adopt the front wheels’ angles base on the actual input steering angle from the driver according to vehicle handling dynamics performance. While, the AIFS controls the angle of each front wheel individually to avoid reaching the saturation limits of any of the front wheels’ adhesion. In this paper modeling and analysis of an AIFS is presented with Tire Work Load (TWL) based controller. Magic Formula tire model is implemented to represent the tire in lateral slip condition. A specially derived 3-DOF vehicle handling model longitudinal, lateral and yaw motion with four wheels is capable for studying AIFS implementing proposed control strategy. AIFS system is proposed to implement two main control strategies, which are PI controller only for…