| With the development of vehicle technology,the characteristics of high efficiency and energy saving had made electric vehicle the main products of automobile manufactures.After going through sluggish development,electric vehicle,which has driving diversity except for engine-concentrated power,came back into consumers’ life gradually.In-wheel motor electric vehicle gained much attention in the wave of electric vehicle developing process because of its good dynamics controllability,simplified structure and highly integration level.In current,the related researches on the ride comfort of the in-wheel motor electric vehicle had been carried out,while the researches to analysis the ride comfort of the in-wheel motor electric vehicle with the combination of unsprung mass increase and in-wheel motor excitation force had poorly done.Besides,the studies for multi-objective optimization of in-wheel motor vehicle had not included wheel acceleration as index to evaluate the ride comfort.In this paper,on the basis of the existing research,the influence of unsprung mass increase and in-wheel motor excitation force on the ride comfort is analyzed based on the quarter vehicle model,and then the ride comfort is discussed based on six degree of freedom half vehicle model with two different presence of eccentric forms between front wheel and rear wheel.Based on Isight,the influence of vehicle parameters on ride comfort is analyzed by means of design of experiment method,deterministic multi-objective optimization and robust multi-objective optimization are carried out.The specific contents as below:(1)Road stochastic excitation model is built by Simulink according to filtered white noise method.Based on the linear model of switched reluctance motor,in-wheelmotor excitation force model is built by Simulink,the vertical and horizontal excitation force is analyzed.The two degrees of freedom quarter vehicle vibration model of in-wheel motor electric vehicle is built based on Simulink.Wheel acceleration is added as one of the ride comfort index.The simulation of vehicle comfort is carried out on the basis of unsprung mass increased and in-wheel motor excitation force.(2)Six degrees of freedom half vehicle vibration model of in-wheel motor electric vehicle is established.Take two different cases of motor eccentric as examples,the effect of different eccentric direction of motors on the ride comfort is analyzed.By using Latin hypercube design method,taking 10km/h and 60km/h as examples,the influence of parameters on ride comfort is analyzed.The results show that the influence of vehicle parameters on ride comfort is consistent both at low vehicle speed and cruise vehicle speed,which provide the principle for choosing variable parameters for optimization based on response surface model.(3)The response of six degrees of freedom half vehicle vibration model is approximated by response surface model;the accuracy of the response surface model is evaluated by decision coefficient.Based on Isight,deterministic multi-objective optimization by using NSGA-II algorithm is used to improve the ride comfort.Optimized parameters are substituted to half vehicle model to compare optimized results with initial results.The feasibility of response surface model to optimize the ride comfort of the in-wheel motor electric vehicle is verified.Robust multi-objective optimization is carried out by considering the fluctuation of vehicle parameters.Deterministic optimization and robust optimization are compared to indicate deterministic optimization result has good robustness.Considering the two factors in the field of unsprung mass increase and motor excitation force,the ride comfort of the in-wheel motor electric vehicle is analyzed,which is more consistent with the actual situation.Response surface model is used to replace the half vehicle model to optimize vehicle parameters for improving the ride comfort,which is helpful to converge to the global optimum quickly and improvethe efficiency of optimization,robust optimization in particular.Analysis and parameters optimization of in-wheel motor electric vehicle has certain theoretical basis and guiding significance for structural design and performance optimization of in-wheel motor electric vehicle. |
