Modeling And Simulation Of Hydraulic Power Steering System With Modelica

The automotive steering system is a specialized mechanism used to maintain or change the driving direction. When driving, it guarantees coordinative steering angle relation for each steering wheel. Moreover, when vehicles are subject to occasional impacts from the road or depart accidently from the original direction, it keeps the vehicles still driving steadily with the cooperation of driving system. As a result, the performance of the steering system directly affects the handling stability, the comfort and the safty of automobiles.It was rare in the past that building structured based models for both the mechanical system and the hydraulic power system in Hydraulic Power Steering system(HPS),which just described the impact from hydraulic system with assist characteristic curves. On the other hand, currently the main method for modeling of HPS or other multi-domain systems is that building models firstly in respective domains using relevant modeling and simulation softwares, then carry out data exchange among models using the linkages of the interfaces in the softwares. However, the application of this kind of modeling method is greatly limited to the interfaces provided by the software companies. As a result, the models have neither openness nor extendsion.Considering the disadvantages of the modeling method stated above, this dissertation adopts a new modeling method, which is modeling and simulation for HPS with Modelica. Based on the consistency of mathematical expressions in physical systems, Modelica supports a model with multi-discipline models by defining the connectors among models. This method achieves the seamless integration and the data communication among models from different disciplines. Therefore, those models have high quality of reusability and extendsion.Based on the current model in our laboratory, State Key Laboratory of Automobile Dynamic Simulation at Jilin University, carry out kinematic and dynamical analysis for components in the steering system. Then build structured-based mathematical models of steering system for both mechanical system and hydraulic system.The main research works carried out in this dissertation are listed as follows: 1,Research on current modeling methods of HPS system.Analyze the modeling methods and the characteristics of representative steering system models, including the SCF steering system model, the NADS steering system model, the steering system model in ADAMS and Carsim, and the steering system model in ASCL2007. Discuss disadvantages of current modeling methods in the steering system, and then propose a new modeling mothed which is modeling and simulation for HPS system with Modelica.2,Study of Modelica modeling language.Study the syntax structure, modeling characteristics and simulation mechanism of Modelica modeling language, understand and master its application of modeling and simulation in multi-domain physical systems.3,Structure based mathematical modeling of Hydraulic Power Steering system.Based on the current ASCL2007 steering system model, abstract the physical model for mechanical system in HPS and build up mathematical models for each component; take dynamic analysis on hydraulic power system in HPS and build structure-based mathematical models for each component.4,Modeling and simulation of Hydraulic Power Steering System with Modelica.Under the modeling environment of Dymola, build up the component models and the connectors in HPS system with Modelica programming. Connect modules with connectors in order to make up a whole model for HPS system and then carry out simulation for model verification and analysis.