Modeling And Controlling Of EPS Based On The Whole Vehicle Dynamics Analysis

Electric power steering system is the inevitable developing direction for automobile power steering, which is much superior to hydraulic power steering system. The thesis, on the base of using advanced theories in the field, the system modeling and control theory are particularly studied in this paper.The force analysis of electric power steering system is developed, and the mathematical model and the state space model is established. The control strategy and algorithm of electric power steering system is analyzed, bringing neural network control strategy, combined with 11 freedom full vehicle model and tire vertical sliding and sideslip joint working conditions semi-empirical E index tire model, and the whole vehicle EPS simulation model is finally established.In this paper, EPS system' key-the assist characteristic is analyzed and studied. Based on the mathematics model and the assist characteristic, the arithmetic of calculating the nonlinear relationship between steering wheel torque and motor torque at any vehicle speed is worked out. Considering the nonlinear assist characteristic in electric power steering system, such as steering dead zone, steering assist zone, steering saturation zone, and the blind zone caused by discrete vehicle speed, a new method to describe assist characteristic which utilizes neural network is presented. The simulation is carried out. The original data coincide with target output results quite well. The nonlinear steering assist in full speed range is realized and the blind zone is eliminated.Steering wheel track characteristics when different input,the impact of system parameters,response curves at different control method,response curves at different vehicle speed,response curves at different front angle,variety curve at different braking deceleration were analyzed by simulating. The results show that system equipped with the controller in this paper has better dynamic performance such as faster response, less over-altitude, better stabilization and so on.