Analysis And Multi-Objective Optimization Of Ride Comfort For Wheel-side Motor Medium Bus

In the fiercely competitive passenger transport market,medium bus has the advantages of flexible transportation,economical application and high cost performance,and its market development momentum is good.The electrification of medium bus plays an important and positive role in green travel,alleviating urban traffic congestion and promoting the healthy development of urban and rural passenger transport market.As a configuration of electric bus,wheelside-driven medium bus has the characteristics of simplified structure,high transmission efficiency and easy realization under current technical conditions.Because of its special structure and layout,it brings new problems to its ride comfort.Therefore,it is necessary to conduct in-depth study on ride comfort of wheelside-driven medium bus.In view of the lack of research on ride comfort of wheelside motor-driven medium bus,this paper takes the wheelside motor-driven medium bus prototype as the research object,and analyses the acquisition method and process of the main mechanical structure,key of the motor,battery and electronic control core components and main parameters of the prototype vehicle.Through the ride comfort test and result analysis of the sample car and the benchmark vehicle,the space for improvement and optimization of the ride comfort of the sample car is determined.In theory,the pavement characteristics and motor excitation are studied,the description suitable for both is established,and the conditions for the existence of motor excitation are analyzed.Based on the actual structure and layout of the prototype car,the planar and spatial descriptions of the wheel-road excitation and wheel-side motor-driven medium bus system are carried out in theory.Based on the multi-disciplinary design and optimization platform Isight,the method of parameter impact analysis and multi-objective optimization for wheelside motor-driven medium bus is established.The main parameters affecting the ride comfort of the sample car are determined and the multi-objective optimization design is carried out.Based on the optimized main parameters,the new sample car is trial-produced and the ride comfort test is carried out to compare the ride comfort of the old and the new sample vehicle and the benchmark vehicle.The main contents of this paper are as follows:In this paper,on the basis of the existing research,layout of the main mechanical structure and the acquisition method of the main vehicle parameters of the vehicle is analyzed base on wheel-side driven medium bus,the plane and space descriptions of vehicle system vibration are established,the influence of the road and motor excitation on the prototype vehicle is analyzed,the suspension and seat parameters of the prototype vehicle are optimized by multi-objective particle swarm optimization method,and based on the optimized parameter,designing and trial-manufacturing new vehicle and real vehicle testing,the ride comfort of the new and old prototype vehicle is compared and analyzed.The specific contents as below:(1)Sample medium bus driven by wheelside motor and its main parameters acquisition.The main mechanical structures of the prototype vehicle and its chassis structure layout,body structure layout,front suspension assembly,rear suspension assembly and wheel side drive system are described.From the aspects of driving motor,power battery pack and vehicle control system,the key of the motor,battery and electronic control core components of the prototype vehicle are expounded.This paper describes the acquisition method and process of the main parameters of the prototype car from the aspects of main appearance parameters,main inertia parameters,basic suspension characteristics and tire characteristics.(2)Ride comfort test and benchmarking analysis of sample and benchmarking vehicles.Using the method of ride comfort test,the ride comfort of sample vehicle and benchmark vehicle is tested on random road surface and impulse road surface.The ride comfort of sample vehicle and benchmark vehicle is compared and analyzed by data processing.The results show that there is a need to improve and optimize ride comfort of sample car.(3)Description and Simulation of pavement characteristics and motor excitation.This paper summarizes the stochastic mathematical basis for describing pavement characteristics,introduces the concepts of pavement roughness and pavement excitation,establishes the velocity description of their statistical characteristics and their integral Gauss white noise description and integral standard Gauss white noise description,and proposes the integral description of pavement excitation standard Gauss white noise in a finite frequency and full frequency range.For switched reluctance motors,the single-phase and multi-phase processes of single-phase rotors,the motor excitation of multi-phase processes of multi-phase rotors and the minimum air gap under the eccentricity of rotor and stator are deduced.Based on the description of road surface characteristics and motor excitation,the simulation analysis of road surface excitation,motor vertical excitation and horizontal excitation in ideal and eccentric state is carried out.The results show that the standard Gauss white noise integral description of road excitation in limited frequency range can better describe road excitation.In the case of eccentricity between rotor and stator,the motor has overall vertical and horizontal excitation.(3)A plane and spatial descriptive dynamic model reflecting the actual wheel excitation and vehicle system vibration is established,which can better overcome the practical problems that the previous vibration model of bus system is too simple or can not reflect the real seat layout.The idea of using wheel acceleration as a supplementary evaluation index of ride comfort is put forward.(4)Description of vibration of wheelside motor driven medium bus systemBased on the first-order Pade approximation,the state equations of road surface excitation for front and rear wheels and road surface excitation for four wheels are established.Based on the actual structure and layout of the prototype vehicel,the plane and spatial description of the vibration of the wheelside motor-driven medium bus system is established to overcome the practical problem that the previous vibration model of the vehicle system is too simple or can not reflect the real layout of the seats.The vertical acceleration of wheels is introduced as a supplementary evaluation index of ride comfort,so as to better analyze the impact of vehicles on motors.(5)Multi-objective optimization of ride comfort of bus driven by wheel motorAiming at the influence analysis of ride comfort parameters of wheelside motor driven bus,a scheme of parameter impact analysis is designed,and a method of parameter impact analysis based on Isight and Matlab/Simulink co-simulation is established.Aiming at the multi-objective optimization problem of ride comfort of wheelside motor-driven medium bus,a multi-objective optimization method based on Isight and Matlab/Simulink joint simulation is established.The multi-objective particle swarm optimization method is used to optimize the suspension and seat parameters of the sample bus.Based on the optimized parameters,the trial production and ride comfort test of the new prototype vehicle are carried out.The results of random and impulse road test of ride comfort of the new and old prototype vehicle,the new prototype vehicle and the target vehicle are compared.The research results show that the ride comfort of the new prototype vehicle is improved.The main innovations of this paper are as follows:(1)In view of the lack of theoretical research on integrated white noise description of pavement characteristics,two concepts of pavement roughness and pavement excitation are introduced to distinguish the natural state of pavement from the input of vehicle vibration and their statistical characteristics.Based on the national and international standards,the Gauss white noise integral description of road roughness and road excitation,the Gauss white noise integral description of standard and the application description of standard Gauss white noise integral are proposed.The simulation results of the standard Gauss white noise integral description for full-frequency and limited-frequency range road excitation show that there are errors in the previous studies when the full-frequency range road excitation white noise description is used.The standard Gauss white noise integral description for limited-frequency range road excitation can better describe road excitation.(2)The description of SRM excitation is too complex,considering only the multi-phase process of single-phase rotor,without considering the whole process of rotor and stator,it is impossible to answer the question of when to excite the motor.For four-phase 8/6-pole switched reluctance motor,the single-phase and multi-phase processes of single-phase rotor,the motor excitation of multi-phase process of multi-phase rotor and the minimum air gap of rotor and stator under eccentricity are deduced using linear assumption.The simulation results of the overall vertical and horizontal excitation of the motor in the ideal and eccentric state of the rotor and stator show that in the ideal state without eccentricity between the rotor and stator,the motor has no overall vertical and horizontal excitation,and in the eccentric state between the rotor and stator,the motor has the overall vertical and horizontal excitation.(3)In view of the actual structure layout of the wheelside motor-driven medium bus,the plane and spatial descriptions reflecting the actual wheel excitation,motor excitation and vehicle system vibration are established.Introducing wheel acceleration as a supplementary evaluation index of ride comfort can not only overcome the problem that the vibration model of vehicle system is too simple or can not reflect the real layout of seats,but also evaluate the influence of vehicle on motor performance.(4)Aiming at the problem of multi-objective optimization of ride comfort of wheelside motor-driven medium bus,the method of parameter impact analysis and multi-objective optimization based on Isight and Matlab/Simulink joint simulation is established.Based on the parameters of multi-objective optimization by particle swarm optimization,a new prototype car is redesigned and trial-produced.Random and impulse road tests of ride comfort of new and old prototype cars,new prototype cars and benchmark cars are compared.The results show that the ride comfort of the new model car is better than that of the old model car.It overcomes the problems of single objective optimization without multi-objective optimization,simulation optimization without experimental support,and achieves the organic combination of experiment,modeling,simulation and optimization.