Modeling And Simulation Of Automotive Steering System Based On Modelica

Vehicle handling and stability is the important evaluation standard of the driving safety. Among the vehicle subsystems, the steering system has the great influence on the vehicle handling stability. Therefore, establishing an accurate and reasonable steering system dynamics model is the key point to accurately predict the vehicle handling and stability performance.First of all, to investigate the steering characteristics of the hydraulic power steering system in the low-speed truck, a Modelica-Based modeling approach is proposed. On the basis of dynamics analysis, steering system module, torque calculation module, non-linear tire module and vehicle module are modeled in multi-domain unified modeling language--Modelica. In the simulation platform of Dymola, the vehicle dynamics model is constructed by connecting those modules according to their interactional relations. The evaluation results of vehicle handling and stability performance can be generated by the model simulation.In addition, since the built model contains a number of undetermined parameter, an automobile steering system test bench is set up for parameters identification. Characteristic features such as transmission ratio, stiffness and dry friction are estimated by bench test. At the same time, by actual measurement calculation and inspection manuals to determine the rest of the pending parameters.Furthermore, in order to validating the proposed model, the vehicle steering performances are measured in the bench test and in the field experiments which test maneuvers include the parking-lot steering and the lemniscate-shape path following. By driving the model with steering wheel angle signals measured in tests, the simulation results provide estimated performance of the hydraulic power steering system. The comparison between experiment data and simulation results validate the correctness of the model, and demonstrate the feasibility of proposed approach.At last, in order to investigate and improve the on-center handling performance of low-speed truck, the parameter sensitivity analysis approach is proposed. According to the on-center handling performances evaluation, steering ratio, stiffness, dry friction and kingpin caster of the steering system model were adjusted to investigate their influences on the on-center handling performance. The results demonstrate the effectiveness of the parameter sensitivity analysis method. Finally, the reasonable advice and solution is proposed to solve the practical issue of the manufacturers.