Performance Simulation And Control Of EPS On The Basis Of Bond-graph Theory And Adams

The steering system is critical to the handing stability, active security and comfort of the vehicle. Electric Power Steering (EPS) will be the mainstream steering technology in the future and the standard equipment in the vehicle. It will also hold the dominant position in the area of power steering. This technology meets the demand to electronical and intelligent modern vehicles and it has become the focus of researchers in automotive industry from domestic and abroad. The usual modeling and deduction process of electromechanical hybrid EPS system is complex and error-prone. Bond-graph theory provides a visual and convenient modeling method for the multi-energy coupling system, which improves the research efficiency. This article focus on the structure design, model built, control method and test evaluation for EPS system. The major contents are as follows:Firstly, on the basis of analysis performance requirements in design of EPS system, the coloumn assisted EPS system was designed and main parts of the system were checked. The structure of EPS and the virtual assembly were made on the basis of CATIA.Secondly, according to the characteristc of electromechanical hybrid EPS system, based on the Bond-graph theory, the EPS model was built. This decreased the modeling difficulties and improved the efficiency which is different from classical mechanical modeling method. Druing the modeling process, the energy transfer relationship among each energy domain was explicit. The bond graphs of each subsystem were drawn and the simulation model was built with MATLAB accord to the dynamic principle of Bond-graph theory. The steering maneuverability simulation was conducted, which showed a good and speed following assit performance. The result of simulation also showed the modeling and simulation method was effective. Based on these, in order to study the the vehicle performance with EPS under typical work conditions, the mulity body model was built with ADAMS including suspension system, steering system, tire and body, engine and brake system. This model was optimized on the Insight platform and verified accord to the road test result.The next, the vehicle with EPS performance was co-simulated by both ADAMS and MATLAB. Fuzzy PD control method was taken as a general assist control strategy for EPS system, in order to achieve the best combination of the proportion and the differential. The double lane change and step input simulations were made. The result showed the improvement in vehicle stability and fuzzy PD control is more stable than conventional control.Finally, vehicle road tests were carried out with the designed controller. According to the national standard, the pivot steer, Lemniscate test, snake test and double lane change test were carried out and evaluated. The result showed that the designed EPS system improved the vehicle handing stability.