The Research Of Simulation For Reliability And Failure Mode Of Electric Power Steering System (EPS)

As an indispensable part of the design process of products in modern enterprises, the reliability prediction and failure analysis of products have gotten more and more attention widely. Zhejiang WanDa automotive steering system company Ltd., a large private corporation in Zhejiang province, which has cooperative relations with Zhejiang University in the Project EPS Research and Development, is always attaching great importance to the reliability of their products. As a new power-assisted steering system in autos, EPS has variety of merits. For instance, it is safe, it is good for environmental protection, and its power-aid effect is much better than the traditional power-assisted steering system, etc. The EPS research in china is just beginning and there has no proof that anyone at home has reseached the reliability of C-EPS. So it is important for the research team of EPS in Zhejiang University to do some thing to study the reliability and failure mode of the new product of EPS.We firstly summarize the process of theoretical basis and technical methods in systems analysis of devices' reliability, then In systems analysis of column-assist electrical power steering device(C-EPS), we establish a fault tree model of the entire EPS system on the basis of clear knowledge of EPS' structure. At the same time, we do a lot of calculation on the failure parameters of the bottom events according the some authoritative special manuals about reliability prediction, which has made a solid foundation for the posterior work of simulation on EPS reliability and failure mode.According to the fault tree model, we do some numerical simulation on reliability of EPS, figure out several reliability eigenvalues of EPS system, including system reliability, failure rate, density of failure probability, mean time between failure, etc. At last, we analyze the simulation results theoretically.Besides that, we have developed a computer program on the basis of Fussell algorithm to go throughout the fault tree of C-EPS and work out all the minimum cute sets of it. Via that we can find out the major failure modes, then analyze them for further failure reasons and possible suggestions for enhancing the reliability of C-EPS. All these research works may be significant for the development of new C-EPS products to some extent.There has been some phenomena appeared in the EPS tests which could proof the validity of the reliability simulation we have done.