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

Michigan Technological Univ-Jeffrey D. Naber
Michigan Technological Univ.-Ahammad Basha Dudekula
  • 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
Jilin University Automotive Engrg Colleg-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 studying the in-wheel motor driven vehicle. One of the in-wheel motor driven vehicle key technologies is multi-motor torque distribution and control. This paper proposes a direct yaw moment control strategy to improve 4 in-wheel electric vehicle 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 follow the driver’s target yaw rate and improve the vehicle yaw rate response and stability. The target yaw rate is calculated by two-freedom vehicle model and limited by lateral acceleration and vehicle current steering condition. So we don’t need the vehicle side slip angle or road adhesion coefficient information to prevent excessive target yaw rate, which are very different to obtain. The feedforward control is used to reduce the vehicle understeer characteristic when accelerating in a curve and increase the vehicle yaw rate. The deceleration control can reduce the driven torque of each motor to slow down the…
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A Smart Measuring System for Vehicle Dynamics Testing

Politecnico di Torino-Enrico Galvagno, Antonio Tota, Stefano Pastorelli, Stefano Mauro
  • 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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On road Fuel Economy impact by the Aerodynamic specifications under the Natural Wind

Honda-Jun Sawada
Honda R & D-youji Suwa
  • 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-Dale Andreatta, Gary Heydinger
SEA, Ltd.-Scott Zagorski
  • 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. Among other things these quantities are useful in studying ride comfort levels of a seat as well as determining the load application location needed during an endurance or strength test. The device is a derivative of a previously developed machine (C1000) that measures the three moments and three products of inertia, plus the CG location. This machine uses a system of pivots, a yaw bearing and two sensors to get the X, Y and Z CG of the seat. Object mass is measured separately on a scale. A stable pendulum arrangement is used to get the CG location. Based on the customer’s requirements one of the unique design criteria was the need to measure a light seat attached to a heavy fixture; approximately a 1:6 ratio. This resulted in having a short pivot height (13.1 in, 332.7 mm) and the need to know seat weight to 0.05 kg (0.1 lbs) or better. Governing equations for the machine are shown in the…
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Vehicle rollover prevention by active tilt control using active suspension with MPC

Clemson Univ-Yunyi Jia, Longxiang Guo
Nanjing Forestry University; Clemson Uni-Jialing Yao
  • Technical Paper
  • 2020-01-0998
To be published on 2020-04-14 by SAE International in United States
The active suspension can be used to control the lateral load transfer directly, however, existing approaches for rollover prevention with an active suspension have some limitations in preventing rollovers because these controls mostly focus on reducing the roll angle passively or causing zero roll angle at most. This project presents a methodology for rollover prevention to control an automobile to tilt toward the turning direction by using active suspension. This reverse tilt can cause the moment generated by gravity to offset that generated by the centrifugal force, and therefore reduce the lateral load transfer rate (LTR). As a result, this tilt control can effectively improve the ability of vehicle on rollover prevention. A 3-DOF vehicle model with a 2-DOF bicycle and a 1-DOF roll model is established. The desired tilt angle is determined by dynamic analysis. Considering the constraint problems such as tilt angle, vehicle slip angle, yaw rate and suspension control moment, the model predictive control theory is used to design the active tilt controller, which causes zero steady-state tilt angle error. Two severe…
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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. 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, 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 angles and angular rates generated…
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Research on Yaw Stability Control of Unmanned Vehicle Based on Integrated Electromechanical Brake Booster

Jilin Univ-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(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 Electromechanical Brake Booster can improve the vehicle yaw stability more quickly and safely. In this paper, a new type of intgarted EMBB has been designed, which mainly includes two parts: servo motor unit and hydraulic control unit. Aiming at the dynamics 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 AB)-Adam Brandt, 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 PhD, 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. The temperature and excitation frequency are the most dominant factors in a tire which are significantly influenced by the vehicle operating conditions. In the past years, applied research has been carried out on the effect of rubber viscoelastic characteristics on structural and frictional tire properties. The present study focuses on how these effects interact with the vehicle handling performance. Based on state of the art theory of friction and structural properties of rubber along with experimental evidence, the dependency of key tire parameters on temperature and tire rolling speed is established. These results are then used in combination with a single-track vehicle model to determine their impact on key vehicle parameters; as an example, the understeer coefficient, yaw resonance peak / damping and maximum acceleration are studied. Furthermore, to produce 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 simulation environment provides possibility…