Research On Control Strategy And Simulation Of EPS Base On The Artificial Immune Algorithm

Electric Power Steering system (abbr. EPS) is a new kind of mechatronics and intelligence power steering system. It meets the requirements of vehicle low-move steering portability and high-move road feeling, and improves the system handling performance. Compare with the traditional steering systems, EPS has some advantages in engine efficiency, environmental protection, safety, flexibility, simple structure, and easy installation.As a result, EPS is becoming the development and the research hot pot of modern vehicle's steering system.This paper first introduced the working principle, structure of EPS, as well as the general methods of building steering system model. Then according to the relevance literatures, the simplified model of EPS established by the order reduction method, combining with a vehicle model of two degrees of freedom constitutes the full vehicle system equipped with EPS. According to Lyapunov stability theory, the stability of EPS mentioned above was analyzed by constructing the Lyapunov function.Secondly, the control algorithm and strategy of EPS were addressed. The assistant characteristics and curves were emphatically analyzed. Immune-feedback-PID control strategy was put forward and designed to control EPS, based on intelligence-PID of assistance control for EPS. The test results showed that immune-feedback-PID control strategy, compared with genetic algorithm, is more efficiency on account of optimization for control parameters.Thirdly, in order to verify the algorithm mentioned above, whose correctness of EPS model and validity of EPS optimization the control parameters equipped with immune algorithm were further validated, the commercial software-CARSIM closing to the actual vehicle was employed. The Co-simulation technology was used through CARSIM and MATLAB/Simulink, in CARSIM, vehicle parameters and simulation condition were set, and in MATLAB/Simulink, EPS simulation model was established. Under the same conditions, the results of simulation and test prove that the vehicle model equipped with the EPS has good reliability and assistant characteristics, compared with the vehicle model with the hydraulic power steering system.Two methods were brought forward during simulation and test in controlling current assist motor. One is immune-feedback-PID control; the other is PID algorithm control. The simulation results show that EPS using immune-feedback-PID control strategy is more lightweight, stable, which is effective to control EPS.Finally, the main work of this thesis was summed up,and the shortcomings of thesis and the prospects of the future work was introduced, which determine the future working direction.