Dynamic Characteristic And Hardware-in-loop Simulation Research For Automobile Electric Power Steering System

As a pivotal part which has big influence on vehicle's control stability, drive safety and comfort, Vehicle steering system has being an important project in the vehicle lateral dynamics research. Electric Power steering has become the research focus of the power steering technology due to the advantages of energy saving, environmental protecting, drive safety, higher steering performance and better road feeling. At present, the technology of EPS in external countries has been matured, and it is still in primary period in our country. It is necessary for our automobile industry to master this high-tech as soon as possible. Therefore, it is of great importance to study and develop this kind of steering system.The dynamic characteristic of EPS was investigated. And the Hardware-in-loop technology of EPS was researched aim to design and explore the EPS product. This dissertation finished main research contents on these following aspects:Nonlinear dynamic model of EPS was built and the formation principal and characteristic of steering torque was analyzed. Combining with a nonlinear Magic Formula half-experiential tire model and 3 freedom whole vehicle models, a relative perfect dynamic whole system model was built.Steering portability, steering return-ability, steering sensibility, road feeling and maneuverability are adopted to be evaluation indexes of EPS performance. According to the response in frequency domain of EPS, steering sensitivity and steering road feeling are researched. The transfer functions of these two evaluation indexes are induced. Based on the functions, the effects of EPS on these two evaluation indexes are analyzed. The influence of several main parameters of EPS such on steering sensitivity and steering road feeling are investigated.Based on three normal assist characteristic curves, linear type assist characteristic curve was designed. The assist current of the motor was decided through assist control model and return control model, the switch of which are judged through steering angle signal. The object current is followed through PID control algorithm and the simulation result showed that the following characteristics can meet the requirement of EPS.Based on MATLAB/Simulink platform, the simulation models of EPS and whole vehicle steering system and adopted control strategy are established. According to the response in time domain of EPS, dynamics characteristics of EPS were analyzed through the adopted five evaluation indexes of EPS performance. The simulation results showed that the vehicle with EPS had better steering portability and road feeling, enhanced return-ability and maneuverability.At last, based on the analysis of existing EPS test-bed, Hardware-in-loop simulation of EPS was investigated. The software and hardware platform of hardware-in-loop was established, through which the foundation of EPS performance explore, researching control strategy and product development was built.