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A Maneuver-Based Threat Assessment Strategy for Collision Avoidance

SAE International Journal of Passenger Cars - Electronic and Electrical Systems

Beihang University, China-Weiwen Deng
General Motors LLC, USA-Jinsong Wang
  • Journal Article
  • 07-12-01-0003
Published 2019-08-22 by SAE International in United States
Advanced driver-assistance systems (ADAS) are being developed for more and more complicated application scenarios, which often require more predictive strategies with better understanding of the driving environment. Taking traffic vehicles’ maneuvers into account can greatly expand the beforehand time span for danger awareness. This article presents a maneuver-based strategy to vehicle collision threat assessment. First, a maneuver-based trajectory prediction model (MTPM) is built, in which near-future trajectories of ego vehicle and traffic vehicles are estimated with the combination of vehicle’s maneuvers and kinematic models that correspond to every maneuver. The most probable maneuvers of ego vehicle and each traffic vehicles are modelled and inferred via Hidden Markov Models with mixture of Gaussians outputs (GMHMM). Based on the inferred maneuvers, trajectory sets consisting of vehicles’ position and motion states are predicted by kinematic models. Subsequently, time to collision (TTC) is calculated in a strategy of employing collision detection at every predicted trajectory instance. For this purpose, safe areas via bounding boxes are applied on every vehicle, and Separating Axis Theorem (SAT) is applied for collision prediction…
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Accurate Pressure Control Strategy of Electronic Stability Program Based on the Building Characteristics of High-Speed Switching Valve

Jilin University-Zhicheng Chen, Jian Wu, Bing Zhu
Published 2019-04-02 by SAE International in United States
The Electronic Stability Program (ESP), as a key actuator of traditional automobile braking system, plays an important role in the development of intelligent vehicles by accurately controlling the pressure of wheels. However, the ESP is a highly nonlinear controlled object due to the changing of the working temperature, humidity, and hydraulic load. In this paper, an accurate pressure control strategy of single wheel during active braking of ESP is proposed, which doesn’t rely on the specific parameters of the hydraulic system and ESP. First, the structure and working principle of ESP have been introduced. Then, we discuss the possibility of Pulse Width Modulation (PWM) control based on the mathematical model of the high-speed switching valve. Subsequently, the pressure building characteristics of the inlet and outlet valves are analyzed by the hardware in the Loop (HiL) experimental platform. After that, the single closed loop pressure control strategy for the inlet valve and the cascade control strategy for the outlet valve are designed. Finally, the parameters of the control strategy are set and verified through the HiL…
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Regenerative Braking Pedal Decoupling Control for Hydraulic Brake System Equipped with an Electro-Mechanical Brake Booster

Jilin University-Jian Zhao, Zhiqiang Hu, Bing Zhu
Published 2019-04-02 by SAE International in United States
Electrification and intelligence are the important development directions of vehicle techniques. The Electro-Mechanical Brake Booster (Ebooster) as a brake booster which is powered by a motor, can be used to replace the traditional vacuum booster. Ebooster not only improves the intelligence level of vehicle braking and significantly improves the braking performance, but also adapts to the application in new energy vehicles and facilitates coordinated regenerative braking. However, Ebooster cannot complete pedal decoupling independently. It needs to cooperate with other components to realize pedal decoupling. In this paper, a pedal decoupling control algorithm for regenerative brake, which is based on the coordination control of Ebooster and ESP, is proposed. First, regenerative braking strategy is designed to distribute the hydraulic brake force and regenerative braking force. Then, the coordinated control strategy of Ebooster and ESP is proposed, and the decoupling of brake pedal and brake wheel cylinder is realized. Finally, series of simulations are carried out under regenerative braking condition. The results show that the control algorithm introduced in this paper can achieve the decoupling of brake…
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Model-Based Pneumatic Braking Force Control for the Emergency Braking System of Tractor-Semitrailer

Jilin University-Bing Zhu, Yao Feng, Jian Zhao
Published 2018-04-03 by SAE International in United States
As bottom layer actuator for the AEB system, the active brake system and the brake force control of tractor-semitrailer have been the hot topics recently. In this paper, a set of active pneumatic brake system was designed based on the traditional brake system of tractor-semitrailer, which can realize the active brake of the vehicle under necessary conditions. Then, a precise mathematical model of the active pneumatic brake system was built by referring the flow characteristics of the solenoid valve, and some tests were implemented to verify the accuracy and validity of the active brake system model. Based on the model, an active pneumatic brake pressure control strategy combining the feedforward and feedback controlling modes was designed. By generating the PWM control signal, it can precisely control the desired wheel cylinder brake pressure of the active brake system. Finally, the brake pressure control strategy was validated both by simulation tests and bench tests. The tests’ results showed that the PWM control strategy for the active pneumatic brake system was both practical and reliable, and it can…
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Studies on Drivers’ Driving Styles Based on Inverse Reinforcement Learning

General Motors LLC-Jinsong Wang
Jilin University-Yuande Jiang, Weiwen Deng, Bing Zhu
Published 2018-04-03 by SAE International in United States
Although advanced driver assistance systems (ADAS) have been widely introduced in automotive industry to enhance driving safety and comfort, and to reduce drivers’ driving burden, they do not in general reflect different drivers’ driving styles or customized with individual personalities. This can be important to comfort and enjoyable driving experience, and to improved market acceptance. However, it is challenging to understand and further identify drivers’ driving styles due to large number and great variations of driving population. Previous research has mainly adopted physical approaches in modeling drivers’ driving behavior, which however are often very much limited, if not impossible, in capturing human drivers’ driving characteristics. This paper proposes a reinforcement learning based approach, in which the driving styles are formulated through drivers’ learning processes from interaction with surrounding environment. Based on the reinforcement learning theory, driving action can be treated as maximizing a reward function. Instead of calibrating the unknown reward function to satisfy driver’s desired response, we try to recover it from the human driving data, utilizing maximum likelihood inverse reinforcement learning (MLIRL). An…
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Modelling and Validation for an Electro-Hydraulic Braking System Equipped with the Electro-Mechanical Booster

Jilin University-Jian Zhao, Jun Huang, Bing Zhu
Published 2018-04-03 by SAE International in United States
The intelligent and electric vehicles are the future of vehicle technique. The development of intelligent and electric vehicles also promotes new requirements to many traditional chassis subsystems, including traditional braking system equipped with vacuum boosters. The Electro-Mechanical Booster is an applicable substitute of traditional vacuum booster for future intelligent and electric vehicles. It is independent of engine vacuum source, and can be combined with electric regenerative braking. A complete system model is necessary for system analysis and algorithm developing. For this purpose, the modeling of electro-hydraulic braking system is necessary.In this paper, a detailed electro-hydraulic braking system model is studied. The system consists of an electro-mechanical booster and hydraulic braking system. The electro-mechanical booster which mainly contains a permanent magnet synchronous motor (PMSM) and a set of transmission mechanism is the critical component. First, the electro-mechanical booster model and hydraulic braking system model are built. Then, based on experimental data, the electro-mechanical booster model and hydraulic braking system model are validated separately. Finally, the two models are integrated and validated. The results show that the…
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A Lane-Changing Decision-Making Method for Intelligent Vehicle Based on Acceleration Field

SAE International Journal of Passenger Cars - Electronic and Electrical Systems

Jilin University-Bing Zhu, Shuai Liu, Jian Zhao
  • Journal Article
  • 2018-01-0599
Published 2018-04-03 by SAE International in United States
Taking full advantage of available traffic environment information, making control decisions, and then planning trajectory systematically under structured roads conditions is a critical part of intelligent vehicle. In this article, a lane-changing decision-making method for intelligent vehicle is proposed based on acceleration field. Firstly, an acceleration field related to relative velocity and relative distance was built based on the analysis of braking process, and acceleration was taken as an indicator of safety evaluation. Then, a lane-changing decision method was set up with acceleration field while considering driver’s habits, traffic efficiency and safety. Furthermore, velocity regulation was also introduced in the lane-changing decision method to make it more flexible. Afterwards, the polynomial trajectory planning method was matched up with this lane-changing decision-making method and simulations based on Matlab/Simulink were finally conducted to verify the method presented in this article. As the simulation results showed, adopting the lane-changing decision-making method based on acceleration field, the lane-changing measurements such as starting position, span and driving speed can be optimized with driver’s habits involved. At the same time, the…
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Pressure Control for Hydraulic Brake System Equipped with an Electro-Mechanical Brake Booster

Jilin University-Jian Zhao, Zhiqiang Hu, Bing Zhu
Published 2018-04-03 by SAE International in United States
The Electro-Mechanical Brake Booster (Ebooster) is a critical component of the novel brake system for electric intelligent vehicles. It is independent of engine vacuum source, provides powerful active brake performance and can be combined with electric regenerative braking. In this paper, a brake control algorithm for hydraulic brake system equipped with an Ebooster is proposed. First, the configuration of the Ebooster is introduced and the system model including the permanent magnet synchronous motor (PMSM) and hydraulic brake system is established by Matlab/Simulink. Second, a Four-closed-loop algorithm is introduced for accurate active brake pressure control. Finally, according to the requirement of different brake force, series of simulations are carried out under active braking condition. The results show that the control algorithm introduced in this paper can ensure the brake hydraulic pressure tracking a target value precisely and show a good control performance.
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Travelling Resistance Estimation and Sandy Road Identification for SUVs

General R&D Institute, China FAW Group-Jian Zhang
Jilin University-Weixiang Wu, Jian Zhao, Bing Zhu
Published 2018-04-03 by SAE International in United States
The mechanical properties of sandy road are quite different from those of hard surface road. For vehicle control systems such as EMS (engine management system), TCU (transmission control unit) and ABS (antilock brake system), the strategies and parameters set for solid surface road are not optimal for driving on sandy road. It is an effective way to improve the mobility of all-terrain vehicles by identifying sandy road online and shifting the control strategies and parameters of control systems to sandy sets. In this paper, a sandy road identification algorithm for SUVs is proposed. Firstly, the vehicle signals, such as engine torque and speed, gear position, wheel and vehicle speed, are acquired from EMS, TCU and ESP (electronic stability program) through CAN (controller area network) bus respectively. Based on the information and longitudinal force equilibrium equation, the travelling resistance of vehicle is estimated. The hydraulic torque converter is divided into several parts to calculate the acceleration resistance instead of using the rotational inertia coefficient. Then, the sandy road identification algorithm is proposed mainly based on the…
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Steering Control Based on the Yaw Rate and Projected Steering Wheel Angle in Evasion Maneuvers

Beihang University-Weiwen Deng
Jinlin University, ASCL-Yifan Ye, Jian Zhao, Jian Wu, Bing Zhu, Yang Zhao
Published 2018-04-03 by SAE International in United States
When automobiles are at the threat of collisions, steering usually needs shorter longitudinal distance than braking for collision avoidance, especially under the condition of high speed or low adhesion. Thus, more collision accidents can be avoided in the same situation. The steering assistance is in need since the operation is hard for drivers. And considering the dynamic characteristics of vehicles in those maneuvers, the real-time and the accuracy of the assisted algorithms is essential.In view of the above problems, this paper first takes lateral acceleration of the vehicle as the constraint, aiming at the collision avoidance situation of the straight lane and the stable driving inside the curve, and trajectory of the collision avoidance is derived by a quintic polynomial. Based on the control of the steering wheel angle by the optimal preview control algorithm, the differential braking control is carried out by using the feedbacks of yaw rate and the projected steering wheel angle information to improve the accuracy of trajectory tracking and the stability of the ego vehicle in evasion maneuver.Simulation analysis based…
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