The Research On Path Tracking And Fault-tolerant Control Of Intelligent Vehicles

With the development of automobile industry,people’s life gets a lot of convenience,but it also comes with huge security risks,mainly reflected in road traffic safety,traffic congestion,and environmental pollution.The emergence of intelligent vehicles has greatly alleviated various problems caused by traditional vehicles.Intelligent driving technology is designed to improve the driving safety,comfort,and economy,and reduce the incidence of traffic accidents.As a key part of intelligent driving technology,path tracking control is considered to be one of the effective methods to solve traffic safety problems,which aims to make vehicles track the reference path accurately and stably.However,intelligent vehicles are unable to avoid actuator or sensor fault.Once a fault occurs,the control efficiency of the vehicle path tracking system will be greatly reduced or completely invalid,which will easily lead to serious safety accidents.Therefore,this paper focuses on the path tracking and fault-tolerant control of intelligent vehicles,aiming to provide some technical support for the safety research of intelligent vehicles.The main contents of this paper are as follows:(1)Based on reasonable assumption and simplification of the actual vehicle,a 7-DOF vehicle dynamic model including longitudinal,lateral,yaw and wheel rotation motion is established,and the ’magic formula’ tire model is chosen as the tire model to calculate the force of the wheel.The longitudinal force and lateral force of the wheel is calculated according to the general formula.Based on MATLAB/Simulink and CarSim co-simulation platform,the accuracy of the established 7-DOF vehicle dynamic model is verified.The results show that the error between the dynamic response curve of the established model and CarSim model is less than 5%,which shows that the established model has good accuracy and provides the model foundation for the following content.(2)By further assumptions,the vehicle model is simplified to a 2-DOF vehicle dynamic model.The model predictive controller is designed based on the 2-DOF vehicle dynamic model.The classical lane change path is selected as the reference path,and the simulation analysis is carried out compared with the sliding mode control method at different speeds and different road adhesion coefficients.The results show that the model predictive control method is more robust and adaptable,and the path tracking performance is better.At the same time,the fault-tolerant performance of the model predictive control method in fault conditions is simulated,and the results show that the model predictive control can compensate the error caused by the fault in time in the case of small-angle fault,but it can not guarantee the performance of the path tracking and security when the fault is serious.(3)A fault-tolerant control strategy for vehicle path tracking based on sliding mode observer is proposed.Based on the 2-DOF vehicle dynamic model,the sliding mode observer is designed to estimate the yaw rate of the vehicle and establish the state estimation error equation.The fault reconstruction equation is obtained from the state estimation error equation,and then the fault estimation value is calculated from the equivalent injection signal.The front wheel steering angle instruction obtained by model predictive controller is modified by the fault estimation value,so that the change of front wheel steering angle caused by the fault can be offset,and the actual front wheel steering angle can meet the requirement of path tracking accuracy.(4)Aiming at the proposed fault-tolerant control strategy for vehicle path tracking,two simulation conditions is designed for the steering system under high speed,low adhesion road and lane changing path,which are bias fault condition and gain fault condition,and the fault estimation performance of the sliding mode observer and the effectiveness of the fault-tolerant control strategy are simulated and analyzed.The simulation results show that the proposed sliding mode observer can effectively estimate the steering system faults,and the fault-tolerant control strategy can eliminate the influence of faults,ensure the vehicle tracking the reference path accurately,thus ensure the driving safety of vehicle.