Analysis And Optimization Of Handling Stability Of Four-Wheel Steering Vehicle

The stability and handling of cars are becoming key considerations for consumers when purchasing a car,and this change in purchasing demand has also contributed to the development of the automotive industry.How to occupy more market share,increase the competitiveness of products and further improve the handling stability of vehicle has become the key research direction of major vehicle enterprises.Based on the research of four-wheel steering vehicle,in order to further improve the handling stability of the vehicle,this paper studies the optimization of suspension parameters and the design of four-wheel steering vehicle control strategy.The main research contents are as follows:(1)Vehicle dynamics modeling and analysis.Firstly,the linear two-degree-of-freedom model,ideal reference model,and tire model of four-wheel steering vehicle were established.Then,the steering characteristics of four-wheel steering and traditional front-wheel steering vehicles at low speed and high speed were analyzed respectively.Finally,the front-wheel steering vehicle and the four-wheel steering vehicle were compared and analyzed from the time domain,steady state,and frequency domain response respectively.(2)Multi-objective optimization of the suspension hard point coordinates.Firstly,the Mc Pherson front suspension model was created based on ADAMS/Car.Secondly,the effect of wheel alignment parameters and their influence on vehicle handling stability were analyzed,and the parallel wheel jump simulation test was carried out.Then,according to the sensitivity analysis results,all the hard point coordinates of the suspension were fine-tuned,and the above steps were repeated for secondary analysis.For the hard point coordinates with higher sensitivity,multi-objective optimization was carried out with emphasis.Finally,based on the hard point coordinates before and after optimization,the parallel wheel jump simulation test is carried out respectively.The analysis results show that the optimized suspension has the ideal range of variation of wheel positioning parameters and the amount of variation is further reduced,and the suspension performance is improved,which is conducive to improving the handling stability of the vehicle.(3)Four-wheel steering vehicle control strategy design.Firstly,three classical control strategies were analyzed and their respective control characteristics were obtained.Secondly,in order to make the four-wheel steering vehicle have better stability at low and medium speeds and be more sensitive to the driver’s steering intention,vehicle speed,and changes in vehicle status,a cooperative control strategy is designed;then,in order to improve the performance of the vehicle under small and medium steering conditions at high speeds,a self-adjusting yaw rate fuzzy control strategy is designed.Finally,in order to make the vehicle have better performance under different working conditions,a multi-mode optimal control method is proposed according to the characteristics of different control strategies.(4)Co-simulation analysis based on Car Sim and MATLAB/Simulink.Firstly,the Car Sim software was introduced and the vehicle model was created.Secondly,the simulation test of four-wheel steering vehicle was carried out under different working conditions.The final results show that the proposed multi-mode optimal control method can integrate the best control effects of various control strategies,so that the vehicle has the best performance under different working conditions,and the control method has certain robustness.