Multi-objective Optimization Design And Perormance Evaluation Of Electric Power Steering System

The electric power steering(EPS)system has become the standard configuration of the modern passenger car steering system,its performance directly determines the vehicle handling stability and driving experience is good or bad.However,the parameters optimization,vehicle matching and the design of electric power steering system are influenced and restricted by many mechanical and control parameters.Multi objective optimization method has been successfully applied in many hardware designs.Mechatronics system has greatly improved the development of automobile industry in recent years.However,control software and hardware design methods are still solved by decoupling.Due to the complex coupling relationship,when the different mechanical and electrical integration structure is optimized,the global optimization of the whole system is usually not ideal and the optimization results are far away from the Pareto frontier.It means there is still a potential for space optimization to be explored.In this paper,we put forward the combination of hardware and control software,and regard the steering sensitivity and steering sense as objective functions.On this basis,the system is optimized by genetic algorithm and particle swarm optimization algorithm.This method can promote the overall system optimization results closer to the Pareto frontier,so as to achieve the global optimal.The main research contents are as follows:First of all,the development process of the steering system is expounded,and the future development trend is analyzed.Based on the analysis of the function of EPS system,the research and analysis of the steering column booster EPS system is carried out.According to the need,the two degree of freedom vehicle model and the EP S system model are established,and the basic structure of EPS is analyzed.Based on the three typical assist curves,select the line type power characteristic curve which is more moderate.Secondly,based on the functional requirements of EPS system,the PID control strategy is designed.Moreover,the basic control mode of EPS system is introduced.To be convenient stability analysis in the next chapter,select steering sensitivity and steering sense as the objective function.And these two kinds of objective functions formula are derived.O n the basis of this,some parameters which influence the stability of the EPS system are selected,and the influence of the stability of the steering system is analyzed.Finally,combined with the characteristics of multi-objective optimization,the integrated optimization of designing mechanical parameters and control parameters is designed.The objective function and constraint conditions are obtained for the mechanical parameters optimization,the control parameters optimization and the integrated optimization.Then through the optimization of GA and PSO to obtain the Pareto optimal solution sets.And put the several obtained results into Matlab / simulink model verify the vehicle handling and stability.Finally,evaluate the results before and after the integration optimization by the four parameter method.The results show that the integrated optimization can be used to find the optimal parameters of EPS system.The maximum extent reduces the interaction and restriction of the two party,so that the EPS system can achieve the global optimal performance.