Research On Steer-by-Wire System Control Model

The Steer-By-Wire system is an emerging automobile steering system and an integral part of the future development of unmanned vehicles.SBW system uses electronic control technology,can independently choose the transmission ratio to optimize steering performance,but its reliability has yet to be examined.Therefore,the study of the driver-vehicle-road closed-loop system is the premise to explore vehicle handling stability,and the road-sense simulation control plays a key role in the evaluation of SBW system.This paper first introduces the superiority,key technology and structural principle of SBW system.Based on this,the SBW system dynamics model is further studied by using the reduced-order method,and the simulation model is established in MATLAB/Simulink software.According the Lyapunov stability theory to analyze the influence SBW system model parameters on system stability conditions.Then,aims at the reason that transmission ratio can be changed with the vehicle steering,this paper designs the ideal transmission ratio based on the constant yaw rate gain.Combined with the influence of vehicle speed and steering wheel angle,using fuzzy control technology to optimize the total transmission ratio.A three-degree-of-freedom vehicle dynamics model is established,and the LQR optimal controller is designed with side-slip angle approaching 0.The vehicle output parameters show that the LQR control model of the vehicle SBW system based on the fuzzy transmission ratio can reach stability in a short time,and it also solves the problem of the low steering sensitivity of low speed and the tendency to oversteer at high speeds.Secondly,the optimal preview lateral acceleration driver model is established,and design a fuzzy adaptive PID algorithm to optimize.The SBW system simulation model is embedded in the Car Sim platform’s Class B Hatchback model.A driver-vehicle-road closed-loop system with SBW is built,which combines with driver status feedback information and vehicle output parameters to simulate under different operating conditions to verify the stability and effectiveness of the SBW vehicle.The results show that the driver-vehicle-road closed-loop system with SBW based on fuzzy adaptive PID algorithm achieves accurate and light steering operation with less deviation from expected trajectory,which not only effectively avoids misoperation by the driver,but also improves the vehicle’s handing Stability and reliability.Finally,the simulation control strategy of SBW system is studied.Taking the traditional mechanical steering system as a reference,the road-sensing motor model and steering wheel torque model are established,and the road-sensing target moment is calculated in combination with the fuzzy transmission ratio.According to the influence of different factors on the steering wheel torque,the ideal steering wheel torque curve is designed.In order to make the road sense analog motor output the appropriate road sense torque,the fuzzy immune PID controller is designed to optimize the effect of the road sense motor to follow the target moment and enhance its anti-interference performance.The results show that the fuzzy immune PID algorithm not only improves the comfort of SBW system road sense,but also has strong adaptability.