Study On The Control Strategy Of Ideal Transmission Ratio And Front Wheel Angle Of Steering-By-Wire System

As an important part of the car,the performance of the steering system is a key factor affecting the stability and safety of the vehicle,which has become the focus of attention and research.The steer-by-wire system is a new concept of the advanced steering system.It eliminates the mechanical part between the steering wheel assembly and steering executive assembly,breaking the mechanical design of the traditional steering system,and freely designing the transmission ratio.When the car is turning,the steer-by-wire system can actively adjust the response state of the car through the main controller of the control center according to the steering state and the vehicle state parameters fed back by the sensor,which greatly improves the steering stability of the car.In this paper,the design of ideal transmission ratio and active control strategy of front wheel rotation angle for steering-by-wire system are studied.Firstly,the significance of research on steering by wire system is analyzed,and the general situation of research at home and abroad is introduced.Then the working principle of steering by wire system is elaborated.Its key technology and performance characteristics are studied.The active steering control technology is determined as the research direction and main content of this paper.According to the structure of the steering-by-wire system,the whole vehicle model of the steering-by-wire system and the ideal two-degree-of-freedom vehicle as a control standard are established.Secondly,by analyzing the steering characteristics of traditional steering system,the requirements of ideal transmission ratio design are obtained.By comparing two common constant gain design schemes,the control strategy of transmission ratio based on steady yaw rate gain constant is selected,and the yaw rate gain is optimized by using improved adaptive genetic algorithm,and the optimal gain at different vehicle speeds is obtained.For the deficiency of ideal gear ratio based on fixed gain design,fuzzy control is used to modify the design of high speed section transmission ratio.Finally,the ideal transmission ratio is determined by combining the two control strategies.Based on the design of steady-state ideal gear ratio,the front wheel angle feedforward compensation and integrated feedback control strategy are proposed.Feedforward compensation is applied to the front wheel angleaccording to the neutral steering,and then the yaw rate and lateral acceleration are selected as the variables of feedback control.The yaw rate feedback control based on fuzzy adaptive PID and the lateral acceleration feedback control based on PID control are designed.And the two are combined by weighting to form a comprehensive feedback control strategy to improve the steering stability of the car when steering.Finally,the vehicle model of steering-by-wire system established by Carsim and Matlab/Simulink is used to simulate and verify the control strategy in typical working conditions.The simulation results show that the ideal gear ratio control strategy and integrated feedback control strategy designed in this paper have a good control effect on the motion state of the car under different driving conditions,which improve the steering stability of the car,and reduce the driver's handing burden.