Research On Path Tracking Of Intelligent Vehicle Based On Coordinated Lateral And Longitudinal Control

As one of the important parts of intelligent transportation system,intelligent vehicle is a new intelligent agent which integrates many high and new technologies.And the path tracking control of intelligent vehicle is the basic problem to study self-driving.Because the vehicle’s longitudinal and lateral systems are highly nonlinear and have complex coupling relationships with each other during motion,it is difficult to design a stable and effective path tracking control system.Aiming at this problem,this paper designs a smart vehicle path tracking system based on hierarchical control theory.This study mainly includes:Firstly,based on the analysis of the force and motion state in the process of vehicle path tracking,a 7-DOF dynamic model and a non-linear tire model of the vehicle are established.Considering the influence of the non-linear characteristics of the vehicle power transmission system on the longitudinal motion control of the vehicle in the course of driving,a longitudinal powertrain model including engine,torque converter,automatic transmission,and longitudinal powertrain model including main reducer is established based on the idea of block modeling.And the longitudinal power transmission characteristics and steady-state steering characteristics of the vehicle dynamics model are analyzed by the vehicle module in Carsim,which provides a model basis for the design of the following optimal controller and speed tracking controller.Secondly,considering that the highly non-linear and complex coupling between vehicle longitudinal and lateral dynamic systems,the upper layer optimal controller of the hierarchical control system is designed.And the objective function is established by tracking performance and driving performance in the tracking process.By adaptively adjusting the relationship between the weighting matrix and the longitudinal vehicle speed,the optimal vehicle speed and the optimal front wheel angle are calculated in real time.Under the assumption that the vehicle actuator can track the output of the optimal controller stably,the simulation results are compared with the traditional constant speed tracking in different simulation conditions,verify the superiority of the variable speed tracking over the constant speed tracking.Further,based on thetheory of fuzzy PD control,the lower,speed tracking controller is designed.The control parameters of the PD controller can be adaptively adjusted by using the fuzzy rules to meet the speed tracking at different initial speeds.In addition,aiming at the influence of the non-linear part of the model on the control accuracy,a transverse compensation controller is designed to compensate the front wheel rotation angle in real time.The longitudinal and lateral coordinated control strategy is desig ned with the longitudinal speed as the coupling point.The stability and effectiveness of the control algorithm are verified in the Carsim/Simulink joint simulation environment.Finally,in order to further verify the effectiveness and real-time performance of the longitudinal and lateral coordinated control algorithm,the simulation platform NI is redeveloped.The vehicle simulation model is downloaded to the HCU real-time simulator by compiling and the designed path tracking control algorithm is downloaded to the controller based on the principle o.f D2P.Then,the simulation experiment is carried out under the conditi.on with virtual smooth path.The results show that the longitudinal and lateral coordinated control algorithm designed in this paper can run in real electronic components and its real-time performance and effectiveness meet the requirements.