Research On Control Strategy For Steer-by-wire System Of Vehicle

Recently, automobile electronic technology is becoming more and more popular. Insome luxury automobiles, the cost of electronic products took up50%among the totalcost, it can be saying that the application of the electronic technology has alreadydeepened into all systems of the automobile. Steer-by-wire (SBW) is the most advancedstage in the development process of automobile electronic technology, and it is also arevolution in this process.SBW will further improve the automobile performanceincluding safety, comfort, economy and entertainment. SBW belongs to the category ofautomobile electronic steering, the mechanical connection between the steering wheeland the front wheel is removed, the steering task is completed by electronic control unit.The signal of steering wheel angle is transmitted to controller by electronic signal, thecontroller collects the signal and calculates the corresponding front wheel angle throughthe control algorithm, then the controller send commands to the steering motor andmakes the motor running.The development of SBW technology depends on its key technology, in order topromote the further development of SBW technology, the three key techniques includingthe advanced vehicle network, variable steering ratio and front wheel angle control whichare proposed in this article.Based on the summary of the development in domestic and abroad of SBW, theadvanced vehicle network, a key technique of SBW, is proposed in this article. Therunning mechanism of FlexRay and its application in the automobile are introduced, anew scheduling strategy of FlexRay vehicle network management data is designed, to acertain extent, it laid the foundation for the realization of the control strategy designed inthe article later.The affecting factors of the steering performance and steering stability are analyzed,the technology of variable steering ratio is studied. Firstly, the controller to controlsteering performance was designed by using fuzzy control technology and fuzzy neuralnetwork. Then, the controller which controls the steering stability is designed by usingthe linearization method of nonlinear function, it is line fitting method. Finally, based onthe vehicle running parameters, the putout weight values are dynamic adjustment byusing fuzzy soft switch technology, the putouts of two steering ratio controller aremerged to switch reasonably and gain the final steering ratio of the system.The control system for front wheel angle of SBW automobile is designed by usingthe final variable steering ratio. To verify the effectiveness of the control system, build a virtual prototype for simulation by MATLAB software and ADAMS software. Thecontrol system was build in MATLAB and the vehicle model was build in ADAMS, thenthe software interface of MATLAB and ADAMS are set to form a virtual prototype. Thesimulation tests for various vehicle states of virtual prototype were done based on thevehicle performance indicators, the effectiveness of the steering ratio control strategy andthe front wheel angle control system which are designed in this article were verified.In order to meet the requirement for tracking target path fast and stably, that is alsothe problem in this design, analyzed the problem and improvement measures of thealgorithm, and made appropriate recommendation to prepare for following studies.