Research On Vehicle Stability Control Based On Active Steer-by-wire System

As new technologies such as information and communications,Internet,big data,cloud computing,and artificial intelligence are widely used in the automotive field,automobiles are being transformed from intelligently controlled mechanical products to intelligent products controlled by intelligent systems.Smart cars have become the development of the automotive industry.The strategic direction.The Steer-By-Wire(SBW)system has become a research hotspot in the field of vehicle engineering as the best solution for turning smart cars.By studying the characteristics of the ideal angle-varying transmission ratio of the steer-by-wire steering system and the active steering control strategy under extreme conditions,we can give full play to the advantages of the steer-by-wire system,improve the driving comfort and active safety of the vehicle,and make the driver safer.Conveniently steer the vehicle's steering.This paper combines the major research projects of the National Natural Science Foundation of China(51258414)and the national key R&D project “Study on Key Issues of Perception,Decision and Control of Intelligent Electric Vehicles”(2016YFB0100905)on the characteristics of variable angle gear ratio and limit conditions of the steer-by-wire steering system.Under the active steering control strategy for vehicles.The main research contents of this article include:(1)Car Sim improved vehicle model based on steer-by-wire system.According to the structure and working principle of the steer-by-wire steering system,the dynamical model of the steer-by-wire steering system is established through reasonable simplification of its mechanical connection structure.Then based on the Car Sim original vehicle model,the built-in steer-by-wire steering dynamics model was used to replace its original unpowered mechanical rack-and-pinion steering gear,the Car Sim vehicle model was improved,and a vehicle-by-wire steering system was established.The improved vehicle model lays the foundation for follow-up research.(2)Simulation analysis of variable angle gear ratio characteristics of the steer-by-wire system.Based on the advantage that the angle-to-gear ratio of the steer-by-wire steering system can be designed freely,the fuzzy control theory is introduced on the basis of the ideal lag angle speed gain and the lateral acceleration gain is not changed.The variable-angle-ratio gear ratio control scheme is controlled,and the fuzzy controller is used to dynamically adjust the weight coefficient according to the vehicle yaw rate and the vehicle speed,and to integrate the ideal transmission ratio with the yaw acceleration gain unchanged and the lateral acceleration gain unchanged.This design is more conducive to the driver to control the vehicle and improve the steering angle of the vehicle ideal steering angle ratio curve.(3)Study on active steering control strategy of vehicle based on steer-by-wire system.Aiming at the situation of vehicle instability under extreme conditions,a fuzzy active steering controller is designed to enable the vehicle to track the ideal yaw rate.The fuzzy controller is dependent on subjective expert experience to determine the shortcomings of the fuzzy rules.The goal is to design the fitness function using the vehicle's ideal yaw rate,lateral slip angle of the mass center and the actual yaw rate,and the error of the slip angle of the centroid as the minimum.The genetic optimization algorithm optimizes fuzzy rules of fuzzy controllers.