Design Of Fault Tolerant Vehicle Steer By Wire System And Research Of Testbench And Development

Steering-By-Wire System has revolutionized the concept of the traditional steering system.The electronic control system is used to replace the mechanical connections between steering wheel and wheels,which makes the steering of steering system and the design of road feeling more flexible.This not only improves the driving safety,control stability and comfort,but also paves the way for the future intelligent and automation of automobiles.Therefore,Steering-By-Wire System has become a research hotspot at home and abroad.However,due to the high requirements for the working environment and the complexity,Steering-By-Wire System used in real cars is not seamless and without glitch,such as the inconsistency between the steering wheel and the driving state of the vehicle,which is a big potential safety hazard.To solve this problem,a fault-tolerant Steering-By-Wire System is proposed.The research on its control method and the construction of test bench are carried out.The main contents are as follows:(1)The steering system model is established and verified by simulation.According to the working principle of the design,the whole system is analyzed in modularization.The steering system module is built by MATLAB/simulink.The parameters of vehicle are modified by Carsim,which matches the input and output in MATLAB/simulink.Finally,the validity of the model is verified by joint simulation.(2)According to control strategy,the control system is divided into upper and lower control,which adopt different algorithms respectively.Upper control is an active fault-tolerant control based on the data fusion method of DS evidence theory,whose validity is verified by continuous sinusoidal test.The steering control in lower control is a variable transmission ratio control based on fuzzy sliding mode variable structure control,of which the stability and variable transmission ratio characteristics are verified by continuous sinusoidal tests with different vehicle speeds.The simulation control of the road feeling in lower control is a comfort control of road feeling based on fuzzy control,of which the stability and the convergence of the return time are verified by high-speed return performance test.(3)The structure design of test bench is improved,and each hardware is selected according to its required performance.The sub-components of hardware system are designed and assembled into the overall assembly diagram by UG/NX8.5.Based on that,each hardware of the steering wheel assembly and the steering actuator assembly is selected.Using xPC-target hardware in the loop platform,the type of acquisition card is determined through analyzing required analog and digital I/O channel signal in test.(4)The operational performance of test bench is verified by the simulation test of the hardware in the loop.According to the principle of test-bench construction,the processing and assembly of test-bench are completed.Different test conditions were selected to verify the active fault-tolerant control,steering execution module and road feeling feedback module designed in this paper.And the feasibility test,variable transmission ratio characteristic test,control stability and return-forward performance test are respectively carried out.