Study On Hybrid Control Based Steering System For Intelligent Vehicle In High-speed Condition

With the rapid development of intelligent vehicle technology,driverless vehicle is getting closer and closer.Advanced Driver Assistant System and Multi-system Integrated control are important stage in the development of intelligent vehicles,which makes it become a research hotspot.The highway traffic accidents are characterized by more vehicles involved,serious casualties and great loss of property.And the accidents caused by lane deviation and improper operation in lane changing process occupy a large proportion,statistically.In order to reduce highway traffic accidents and improve the stability of vehicles,damping,Lane-keeping and Lane-changing controllers of steering system are designed respectively in this paper,and the research on the stability of switching process are also carried out.The content of this paper and the research status of the lane keeping system and the lane changing assistance system at home and abroad is introduced.Aims to lay a foundation for further research,active steering system model,vehicle-road reference model,and the driver model combining trajectory prediction with neuromuscular are built.Through the analysis of the working characteristics of the steering system in high speed condition,a Multi-Mode-Switching control strategy based on hybrid system theory is proposed,which uses Time to Line Crossing(TLC)and Safe Distance as switching rules.According to the steering system's performance requirements of each mode,the Damping,Lane-keeping and Lane-changing controller are designed.The damping torque is designed based on vehicle speed and steering wheel angle rate,which improves the road sense of the vehicle in high speed condition.Considering the overshoot when using optimal preview driver model,an improved linear two-degree-of-freedom vehicle model based on exponential decay lateral deviation is built,which can not only effectively prevents the overshoot,but also reduces the time for vehicles to go back to the central line of the lane.The Lane-changing model uses the Model Predictive Control(MPC)with multiple constraints to improve the stability of vehicle in lane changing process.From the angle of the tire and the hybrid system,a simple but effective stability supervisor with hierarchical structure is designed to prevent vehicle from the loss of control.Finally,the lateral driving assistance system hardware-in-loop test platform based on CarSim/LabVIEW is set up.The proposed control method is implemented on CarSim/Simulink and hardware-in-loop test platform,and the results proved the effectiveness of this strategy,and the stability of the switching process.