Ride Performance Study Of Distributed Electric Drive Vehicles

In recent years,distributed electric drive vehicles have attracted widespread attention in the automotive industry due to their simple packaging characteristics,flexible multiple driving modes,and readiness to accommodate relevant new energy technologies.However,the introduction of in-wheel motors can potentially result in the degradation of vehicle ride and handling performance.Researchers and automotive industry practitioners have been actively conducting researches to study the negative impact of in-wheel-motors on vehicle ride and handling performance and at the same time,trying to develop methods to mitigate the potential negative impact.At present,research has been conducted on the ride comfort of distributed electric drive vehicles.In order to evaluate any potential ride performance degradation,a comparative study is conducted using an electric vehicle,already in production and a prototype in-wheel-motor electric vehicle built from the same platform as the production vehicle by replacing the original electric drivetrain with 4in-wheel motors.To better correlate with user ride experience,both the vehicle body and seat dynamic response is used as the ride performance evaluation metrics.This thesis studies ride comfort of the modified prototype vehicle with both road excitation and in-wheel-motor induced excitations.This study has focused on the following aspects.(1)An eight-degree-of-freedom(8 DOF)dynamic model is established for the distributed electric drive vehicle to explore the impact of increased unsprung mass and suspension parameter variations on ride comfort in the frequency domain.To facilitate the study,both mathematical and simulation models for rough road,through white noise,and speed bumps are established with considerations of four-wheel input correlation characteristics.Finally,the influence of the increased unsprung mass on ride comfort of the distributed electric drive vehicle is analyzed in time domain.(2)In order to evaluate potential vehicle performance as a result of in-wheel-motor induced excitations,an analytical model of non-eccentric air-gap magnetic field is built.Utilizing the air-gap magnetic field model,analytical models of static eccentric excitation force and dynamic eccentric excitation force are derived using the permeability correction coefficient method.For simulation purposes,a finite element model the in-wheelmotor is constructed using ANSYS Maxwell software.The rotor excitation force caused by the air gap radial static eccentricity and the air gap radial dynamic eccentricity are simulated respectively.Finally,the combined influence of the motor induced vertical excitation force and the random road surface excitation on vehicle ride comfort is obtained through time-domain simulation analysis.(3)To improve ride comfort of distributed electric drive vehicles a response surface is established using Isight software to represent the ride responses of the vehicle.The NSGA-II algorithm was utilized to perform multi-objective optimization of distributed electric drive vehicles.A comparative study is conducted between newly designed prototype vehicle after multi-objective optimization and the original vehicle.The study results indicate that the ride comfort of distributed electric drive vehicles can be improved by optimizing the vehicle suspension parameters.