【作者】 王晟；

【导师】 华林；

【作者基本信息】 武汉理工大学 ， 车辆工程， 2019， 博士

【摘要】 近年来,限于环保压力及能源短缺等问题,电动汽车成为汽车行业发展的一个主流方向。商用电动汽车里,电驱动桥汽车因具备集成度高、适用车型广而成为了商用汽车一种发展趋势。但是,该类型汽车将动力传动总成集成至驱动桥内,这种改型设计会产生车辆质量分布变化与电机不平衡磁拉力激励两个对车辆悬架系统NVH有所影响的问题。鉴于此,本论文以某电驱动桥商用汽车悬架系统为研究对象,分析路面激励与电机激励下悬架及车身结构的振动特性,研究悬架及车辆不确定性参数下的优化。研究内容包括:建立电驱动桥商用汽车悬架系统动力学模型,并对其振动特性进行研究。悬架动力学建模中考虑悬架系统非线性元件以准确模拟真实的悬架模型。提出等效分段线性化的改进增量平衡谐波法用以求解上述非线性悬架系统振动问题。研究波形路面下电动汽车改型前后悬架及车身系统振动特性,研究表明动力传动总成置换引起电动汽车的后车轮动载荷有所提高,影响了车辆安全性能,而对车身垂向加速度影响不大。研究随机路面激励下电驱动桥商用汽车悬架系统振动特性。首先,提出改进的增量平衡谐波法结合小区间积分法的方法用以求取随机激励下悬架及车身系统振动响应量的功率谱密度,并与Runge-Kutta法进行对比验证,其误差在10%范围内,但计算效率提升了380%。其次,建立考虑座椅刚度及阻尼的五自由度悬架半车动力学模型,研究随机路面激励下电动汽车垂向振动特性。最后,对主要的车身质量参数及悬架参数进行灵敏度分析,结果表明车辆质量参数对车辆舒适性及安全性影响较大,在后续的悬架设计及优化分析中应综合考虑载重量等质量因素与悬架系统刚度阻尼匹配关系。研究电机激励下电驱动桥结构振动特性。探讨永磁同步电机电磁激励特性,针对电机在电驱动桥中的运行情况,揭示转子偏心情况对电机不平衡磁拉力特性的影响规律。其次,采用基于Ansoft+ANSYS多物理场耦合方法,研究上述电机激励作用下电机壳体及后桥结构的振动特性。最后,进行相应的电驱动桥台架试验,试验验证了电机动偏心情况的存在,在电机转速为1650rpm时观察到后桥壳体处振动频谱图中转频27.5Hz、两倍电频率220Hz等处的振动峰值。研究电机激励与路面激励作用下电驱动桥汽车振动特性。首先,研究电机激励通过悬架系统传至车身结构的振动特性。其次,探讨电机转子动偏心率的不确定性对车身振动影响规律。然后,考虑电机激励和路面激励的频率特性,分析其共同作用下的车身振动特性。结果表明,与轮毂电机电动车类似,电驱动桥减速器减速比i_g对电动汽车舒适性及安全性有一定的影响,在i_g为5.0、A级路面下电机激励对车身重心处垂向加速度均方根值恶化程度达10.7%,而较大的i_g(i_g>8)能基本消除电机激励对上述车辆性能的影响。最后,给出该电驱动桥商用汽车路试结果并与之前的分析进行对比验证。研究电动汽车悬架系统优化问题。提出基于四阶矩多项式变换结合广义多项式混沌方法的可靠度指数计算方法,相比于其他方法该方法计算精度高、应用范围广且计算效率高,并采用响应面法对目标函数进行拟合以节省计算资源,拟合精度在1%内。应用上述可靠性优化方法研究电动汽车在确定装载量和不确定装载量下的悬架参数优化情况,结果表明装载量对悬架参数优化结果影响较大,可根据装载量的统计概率密度分布特性进行悬架参数的设计及优化。开展的工作对具有电驱动桥形式的商用电动汽车NVH性能研究具有一定的理论价值和工程实践意义,并可推广至其他类型的电动汽车中,同时研究结论可作为前置条件用于车身结构NVH研究中。更多还原

【Abstract】 In recent years,limited to environmental protection pressures and energy shortages,pure electric vehicles have become a mainstream direction in the development of the automotive industry.Vehicle with electric drive axle has a development trend of high integration and wide application for commercial electric vehicles.However,this type of vehicle integrates the powertrain assembly into the drive axle.This design creates two problems: the change of vehicle mass distribution variation and the electromagnetic unbalanced magnetic pull force excitation that affects the vibration of the vehicle suspension system NVH.In view of this,this thesis takes a commercial electric vehicle suspension system with electric drive axle as the research object.The vibration characteristics of suspension and body structure under the road excitation and motor excitation are studied.The uncertainty design optimization of suspension system based on road excitation is studied,and the reliability-based optimization method on uncertain parameters of the suspension and vehicle is proposed.Research content includes:The dynamic model of the electric vehicle suspension system is established and its vibration characteristics are studied.In the suspension dynamics modeling,the nonlinear characteristics of the suspension system are considered to more accurately simulate the real suspension model,and the modelling of road excitation is given.An improved incremental balanced harmonic method with equivalent linearization is proposed to solve the vibration problem of nonlinear suspension systems.Applying the above dynamic model and the proposed method,the vibration characteristics of the suspension and the body system before and after the modification of the electric vehicle under the corrugated road are studied,the research shows that the dynamic load of the rear wheel of the electric vehicle is worsened by the replacement of the power transmission assembly,which affects the safety performance of the vehicle.It has less impact on vehicle ride comfort.The vibrational characteristics of the electric vehicle under random road excitation are studied.Firstly,the incremental balance harmonic method combined with the intercell integration method is proposed to obtain the power spectral density of the vibration response of the suspension and the body system under random excitation,and compared with the Runge-Kutta method,the error is in the range of 10%while the computation efficiency is increased by 380%.Secondly,the five-degree-of-freedom suspension half-vehicle dynamics model considering seat stiffness and damping is established to study the vertical vibration characteristics of electric vehicles under random road excitation.Finally,the parameter sensitivity analysis of the main body mass parameters and suspension parameters is carried out.The results show that the vehicle mass parameters have a great influence on the vehicle comfort and safety.In the subsequent suspension design and optimization analysis,the load weight factor should be considered in the optimization design of the stiffness and damping of the suspension system.The vibration characteristics of the motor and electric rear axle structure under electromagnetic excitation are studied.The electromagnetic excitation characteristics of permanent magnet synchronous motor are discussed.According to the operation of the motor in the electric rear axle,the influence law of the dynamic and static eccentricity of the rotor on the electromagnetic force characteristics of the motor is revealed.Secondly,based on the Ansoft+ANSYS multiphysics simulation method,the vibration characteristics of the motor and the rear axle structure under the above electromagnetic excitation are studied.Finally,the corresponding electric drive axle bench test is carried out.The test results verify the existence of the motor eccentricity.When the motor speed is 1650 rpm,the frequency spectrum of the rear axle housing is observed to be 27.5 Hz,twice the electric frequency 220 Hz,etc.The vibrational characteristics of the electric vehicles with electric rear axle under electromagnetic excitation and road excitation is studied.First,the vibration characteristics of the motor excitation transmitted to the vehicle body structure through the suspension system are analyzed.Secondly,the influence of the uncertainty of the key parameters like the rotor eccentricity of the motor on the vibration of the vehicle body is discussed.Then,considering the frequency characteristics of motor excitation and road excitation,the vibrational characteristics of the vehicle body under the joint excitations are analyzed.The research results show that the reduction ratio of the electric drive axle reducer has a certain influence on the comfort and safety of the electric vehicle.When the reduction ratio is 5.0,the motor excitation of the Class A road deteriorates the root mean square value of the vertical acceleration at the center of gravity of the vehicle body by 10.7%.The larger reduction ratio ig(ig>8)can basically eliminate the influence of the motor excitation on the performance of the above vehicle.Finally,the road test of this kind of electric vehicle is given and compared with the previous analysis.The reliability-based design and optimization of the electric vehicle suspension system is obtained.The reliability-based design and optimization method are studied.The reliability index calculation method based on the fourth-order moment polynomial transformation combined with the generalized polynomial chaos method is proposed.Compared with other methods,the method has high calculation accuracy,wide application range and high computational efficiency,and the response surface methode is used to fit the objective function to save computational resources,and the fitting accuracy is within 1%.The above design and optimization method are applied to study the optimization of the suspension uncertain parameters of the electric vehicle under the determined load and the uncertain load.It indicates that the load has a great influence on the reliability-based optimization results of the suspension parameters.The design and optimization of the suspension parameters should be based on the statistical probability density distribution characteristics of the load.The work carried out has certain theoretical value and engineering practical values for the design and optimization of NVH performance of the commercial vehicles with electric drive axle.It can be extended to other types of electric vehicle systems,and the research conclusion can be used as a front-end condition in the body structure NVH study.更多还原