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Composite Steering Strategy for 4WS-4WD EV Based on Low-Speed Steering Maneuverability

Tongji University-Yang Yang Wang, Zhi Guang Liu, Yuan Xing Jiang
Published 2019-11-04 by SAE International in United States
A composite steering control strategy, which combines four-wheel steering (4WS) and differential steering, is proposed in this paper, to optimize steering maneuverability in the conditions where the vehicle speed is below 15 Km/h, mainly for U-turning and parking conditions. A dynamic model is developed for the steering system and the tire system. Taking different steering wheel inputs into consideration, a 4WS control strategy proportional to the front wheel steering angle is quoted to improve the steering maneuverability in the low speed conditions and guarantee the manipulability by controlling the side slip of the vehicle. Based on the 4WS system, this paper explores the possibility of further improving the low-speed maneuverability of the vehicle through differential steering. And the differential steering control strategy is developed, including four hub-motor output modes. A composite steering controller is designed based on the 4WS-4WD electric vehicle platform. Through the real vehicle calibration tests, the output torque distribution coefficient of the hub motor in the differential steering control strategy is obtained, and the composite steering control strategy optimal for maneuverability is…
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An Outer Loop of Trajectory and an Inner Loop of Steering Angle for Trajectory Tracking Control of Automatic Lane Change System

Tongji University-Yang Yang Wang, Yuan Xing Jiang, Zhi Guang Liu, Guang Da Chen
Published 2019-11-04 by SAE International in United States
Automatic Lane Change (ALC) function is an important step to promote the currently popular Advanced Driver Assistance Systems (ADAS) within a single lane. The key issue for ALC is accurate steering angle and trajectory tracking during the lane changing process. In this paper, an MPC controller with a receding horizon is designed to track the desired trajectory. During the tracking process, other objectives such as safety and smoothness are considered. Considering of the practical mechanism and parameter uncertainties, an SMC controller is designed to track the target steering angle. For validation, a Hardware-in-the-Loop (HIL) experiment platform is established, and experiments of different control algorithms under different conditions are carried out successively. Comparisons of the experiment results of MPC+SMC and PID+SMC schemes indicate that both the trajectory error and the steering angle error of the former combination are smaller. Specifically, the peak trajectory error in Y direction of MPC+SMC is by about 50% smaller under velocity from 60km/h to 80km/h, and lane change duration is also shorter than the PID+SMC scheme. And compared to the servo…
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Study on Lane Change Trajectory Planning Considering of Driver Characteristics

Chongqing Changan Automobile Co. Ltd-Rong Feng
Tongji Univ.-Yang Yang Wang, Ding Pan, Zhiguang Liu
Published 2018-08-07 by SAE International in United States
Automatic lane change of intelligent vehicles is a complex process. Besides of safety, feelings of the driver and passengers during the lane change are also very important. In this paper, a lane change trajectory planner is designed to generate an ideal collision-free trajectory to satisfy the driver’s preference. Various lane changing modes, gentle lane change, general lane change, radical lane change and personalized lane change, are designed to meet the needs of different passengers on vehicles simultaneously. In this paper, the condition of the two-lane change is studied. One vehicle is in front of the ego vehicle at the same lane and one is at the rear of the ego vehicle at the target lane. A trajectory planning method is then established based on constant speed offset and sine curve, vehicle distances and speed difference, etc. The key factors which can reflect drivers’ lane change characteristics are then acquired. Based on the key factors, lane change decision model and lane change state model are established, which can reflect drivers’ personalized lane change selection and habits…
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Modified Car Following and Lane Changing Simulations Model for Autonomous Vehicle on Highway

Tongji Univ.-Yang Yang Wang, Guangda Chen, Zhiguang Liu
Published 2018-08-07 by SAE International in United States
Being one of the most simple and basic driving scenarios, highway scenario can be one of the first scenarios to achieve autonomous driving. Both car following (CF) and lane changing (LC) are the most basic and frequent maneuver during highway driving tasks, and therefore become two key issues to focus on in recent researches about autonomous vehicle (AV). Different from conventional CF and LC researches that attach much importance to the character, psychology, perception ability, and driving experience of human drivers, more timely and accurate reactions based on fast perception and communication technology as well as the automatic actuator are hypotheses for this research. Moreover, based on these hypotheses, a modified intelligent driver model (MIDM) is proposed for AVs’ following behavior to alleviate the fluctuations caused by lane changing behaviors. As for lane change, decision rules based on signals from environment perception system instrumented in the subject vehicle are designed for the purpose of improving the traffic efficiency. Then, for validation, simulation environment of autonomous driving scenario on highway is established in MATLAB. In addition,…
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Precise Steering Angle Control of Lane Change Assist System

Tongji Univ.-Yang Yang Wang, Guangda Chen, Xuanjing Ao, Shuhao Fan, Han Mei, Wei Li
Published 2017-09-23 by SAE International in United States
After obtaining the optimal trajectory through the lane change decision and trajectory planning, the last key technology for the automatic lane change assist system is to carry out the precise and rapid steering actuation according to the front wheel angle demand. Therefore, an automatic lane change system model including a BLDCM (brushless DC motor) model, a steering system model and a vehicle dynamics model is first established in this paper. Electromagnetic characteristics of the motor, the moment of the inertia and viscous friction etc. are considered in these models. Then, a SMC (Sliding Mode Control) algorithm for the steering system is designed to follow the steering angle input. The control torque of the steering motor is obtained through the system model according to steering angle demand. After that, the control current is calculated considering of electromagnetic characteristics of the BLDCM. Debugging and optimization of the control algorithm are done through simulations. Also, different steering input and uncertain disturbance torque are successively loaded on the simulation model to test the tracking performance and robustness of the…
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