Research On The Design And Control Features Of The Automobile Active Front Steering

With the rapid development of modern automobile control theory and intelligent technology,the requirements of automobile drivers on the stability,safety,sensitivity and comfort of automobiles are getting higher and higher.The AFS-Active Front Steering achieves a steering intervention that is independent of the driver's steering wheel and improves the steering response characteristics of the vehicle in emergency situations,large lateral winds,and different separation factors;To meet the driver's the portability and flexibility in the low-speed steering,the security and stability in the high-speed steering.Therefore,the active steering system is the research hotspot and development direction of the current active safety and intelligent steering technology.This article relies on the Chongqing Municipal Science and Technology Commission Research Fund project "Vehicle horizontal driving behavior identification and vehicle interaction active safety control research"(approval number: cstc2014jcyjA6007).Based on the research status at home and abroad,the study of the active steering system of the automobile is designed,and research on the control characteristics of the active steering system based on the variable transmission ratio of the double planetary gear mechanism.Specific research includes the following aspects:(1)The structural characteristics and working principle of the steering mechanism of the active steering system of the automobile are analyzed.The design idea of the active steering system is put forward,and based on the planetary gear ratio of the active steering system is designed.(2)To design and analyze the transmission mechanism such as the worm gear reducer,the planetary gear mechanism,the rack and pinion mechanism of the active steering system of the automobile.Based on the characteristics of the transmission ratio in the active steering system,Gain and lateral acceleration gain,the characteristics of the steering gear ratio with the speed change and the relationship between the steering sensitivity of the vehicle and the speed change at different steering ratios are studied.(3)Based on the working principle of the double planetary gear variable transmission ratio mechanism of the active steering system of the automobile,the ideal linear and non-linear variable ratio characteristic curves of the active steering system are designed.The simulation results show that the variable steering ratio design is reasonable,that is,the automobile active steering system can be based on the driver's steering intent and the current vehicle traffic conditions through the auxiliary angle motor to add the front wheel angle compensation and adjustment.Thus,it can better coordinate the portability in the low-speed and steering stability in the high-speed(4)In the process of automobile steering system,the control strategy of active steering motor is put forward by establishing the equivalent circuit model of active steering motor,and the control characteristic of active steering system is studied.The cascade PID control model of the active steering motor is established by MATLAB / Simulink.The time response characteristics of the current loop and the speed loop are analyzed under the condition of unload and load.Through the correction,the current response time,overshoot and peak time of the motor are greatly improved,and the effectiveness of the control strategy is verified.