Research On Fault Tolerant Control Of EPS System For Intelligent Vehicle Based On Functional Safety

With the continuous development of intelligent technology,the integration and complexity of the electronic and electrical systems of the vehicle continue to increase,increasing the possibility of various failures of vehicles.Electric power steering system(EPS)is an integral part of the electrical and electronic system.It is often used as an executive system for active steering control of intelligent vehicles and its functional integrity is the key to the safe driving of the intelligent vehicle.The failure of the EPS system may cause the loss of the lateral control capability of the intelligent vehicle,which will seriously endanger the safety of the lives and property of the traffic participant.Based on the functional safety of EPS system in intelligent vehicle,this paper studies the faulttolerant control under sensor failure.Firstly,according to the design process of concept phase in ISO 26262,the system definition,hazard analysis and risk assessment of the EPS system of the intelligent vehicle are carried out in sequence.The ASIL(Automotive Safety Integrity Level)and safety goals of the system are determined,and the system functional safety requirements and corresponding safety measures are derived from the safety goals.Therefore,the main research content of this article is clarified,that is,the fault-tolerant control of the steering wheel angle sensor of the EPS system of the intelligent vehicle.Secondly,the vehicle two-degree-of-freedom dynamic model and the EPS system model are analyzed and established,and the automobile parameter mapping relationship between the steering wheel angle and the yaw rate,lateral acceleration,longitudinal vehicle speed is clarified.In order to ensure the stability and reliability of the main steering control process,by studying the tire model,the relationship between the tire lateral force and the slip angle is analyzed.The principle of the optimal preview algorithm for smart cars is expounded,and several derivations were made to establish a trajectory prediction model.Thirdly,based on the research and analysis of vehicle dynamic model and the EPS model,a steering wheel angle estimator is designed based on the Adaptive NetworkBased Fuzzy Inference System(ANFIS).In order to ensure the effectiveness of the estimator,considering the advantages of artificial neural network,a self-diagnostic method of steering wheel angle estimator based on BP(Back Propagation)neural network is designed.On this basis,the fault diagnosis strategy is studied,and a fault-tolerant compensation strategy based on smooth transition function is designed.By carrying out joint simulation in the environment of Car Sim and MATLAB / Simulink,different working conditions are set,and the reliability and adaptability of the designed steering wheel angle estimator,estimator self-diagnosis method,and fault diagnosis and fault tolerance compensation strategy are analyzed and verified.Finally,the intelligent vehicle lateral control algorithm is studied,and the trajectory tracking controller based on the approach law synovium and the active steering executive controller based on PID are designed respectively.Under the environment of Car Sim and MATLAB / Simulink,a lateral control system combined with the fault-tolerant control algorithm of the intelligent vehicle EPS system is built to simulate and verify the effectiveness of the fault-tolerant control algorithm under the trajectory tracking conditions of the intelligent vehicle.Relying on the unmanned formula racing platform,the racing platform is designed and modified.Through debugging and experimental analysis,the feasibility of the fault-tolerant control algorithm is further verified.