Research On Path Planning And Path Tracking For Automobile In Two Steering Conditions

With the rapid development of world automobile industry, vehicle bring convenience to people’s daily life, at the same time, it has brought the increasing road traffic accidents. Advanced driver assistance systems can reduce the driver’s fatigue, and which can reduce road traffic accidents. Many automobile manufactures and scholars at home and abroad have paid their attention to develop advanced driver assistance systems from the earliest anti-lock braking system and electronic stability program to the latest automatic parking system and emergency collision avoidance system in past 30 years. The key research issues in this paper are path planning and path tracking for parallel parking and emergency collision avoidance. Our group have developed the parallel parking system indendently by adopting the method of combining theoretical analysis and engineering practice. The main research results are as follows:(1) One backward motion and repeated forward/backward motion are put forward for parallel parking steering situation. Using reverse way of thinking, the fuzzy control method is used to choose the suitable parking starting position considering the possible collision with the surrounding obstacles in parallel parking process. ? spline theory is used for curve fitting, which can reduce the path adjustment time. Using ? spline theory and Sigmoid function to design the emergency collision avoidance path, which can solve high lateral acceleration and discontinuous curvature problems.(2) Active disturbance rejection control(ADRC) method is applied in path tracking for the first time, which can solve the high-precision lateral control problem when the vehicle is parking in a low speed. During parallel parking, the parking speed is affected by the external disturbance owing to the roughness of road surface and road bumps, the model uncertainty is existed in steering kinematics for the complex steering mechanism, and there is a delay time in the steering system. In order to diminish the impacts of external disturbance, model uncertainty and steering system delay on path tracking, the path tracking controller based on ADRC method is built. Using preview follower theory, a linear extended state observer based on lateral displacement is designed. Consider vehicle yaw angle, a non-linear combination combined lateral displacement error with yaw angle error is designed, which uses monotone bounded hyperbolic tangent function. Using the experimental vehicle for real vehicle tests, the test results verify the effectiveness of the path tracking controller. Sliding mode iteration approach is used to design error feedback loop, which improve the ADRC control structure. The sliding mode ADRC approach solve the path tracking robustness problem for different wheelbasevehicles.(3) Propose linear extended state observer LESO to estimate longitudinal road friction coefficient between the tyre and road. Tire-road friction coefficient can provide the theoretical basis for emergency avoidance control systems. The vehicle wheel slip controller is established using sliding mode variable structure control at the basis of half vehicle braking dynamics model. Integral switch surface is used to eliminate the chattering problem of sliding mode controller. The tire-road friction coefficient of braking system can be observed by linear extended state observer, which can estimate the coefficient in real time.(4) Propose two path tracking methods for emergency collision avoidance based on vehicle yawing angular velocity and path curvature. Using two degrees of freedom vehicle dynamic model,two ADRC path tracking controllers for emergency collision avoidance based on vehicle yawing angular velocity and path curvature are established, respectively, and the control effect is compared with the path tracking controller based on LQR method. To simulate the driver emergency collision avoidance procedures, the optimal preview time is determined by simulating the driver emergency collision avoidance procedure. In order to verify the proposed path tracking strategy, this paper adopts co-simulation method using Carsim and Simulink. The simulation results coincide with the real vehicle experiment results with experienced driver very well. Different simulation conditions are used to verify the robustness of the path tracking controller, such as different vehicle mass, different tire cornering stiffness, lateral wind interference and μ-split roads.