【作者】 王楷焱；

【导师】 史文库；

【作者基本信息】 吉林大学 ， 车辆工程， 2011， 博士

【摘要】 近年来,国内商用车发展迅速,产量和销量逐年增加。与此同时,市场对商用车的性能尤其是舒适性也有了更高的要求。由于商用车行驶工况复杂,长途运输中驾驶时间长,驾驶员容易疲劳,会对其健康产生不良的影响,甚至可能由疲劳引发交通事故。因此提高商用车的舒适性已成为国内外汽车行业研究的一个热点问题。国内对商用隔振性能的研究大部分集中在悬架系统和动力总成悬置系统,而对驾驶室悬置系统的研究却不多。由于驾驶室悬置系统能够同时衰减动力总成和路面产生的激励,因此对驾驶室悬置系统进行优化匹配能够有效降低驾驶室内的振动。本文围绕驾驶室悬置系统的振动模态、振动传递特性和隔振能力展开研究。通过ADAMS软件建立了驾驶室悬置系统模型和整车多体动力学模型。采用有限元和多体动力学结合的方法,分析了驾驶室悬置系统的振动模态,振动响应特性,整车环境下驾驶室的振动响应和驾驶室悬置系统的隔振特性,以及参数变化对驾驶室内振动响应的影响。以提升驾驶室悬置元件的隔振性能为目标,对驾驶室悬置系统进行了优化设计,获得了良好的效果。模态是影响驾驶室悬置系统隔振特性的关键因素。如果驾驶室悬置系统模态频率和振型分布不合理,会影响驾驶室悬置系统的隔振效果,甚至会增加驾驶室内的振动。本文通过ADAMS软件建立驾驶室悬置系统模型并对其模态进行研究。为了便于研究,在建模过程中将驾驶室简化为刚体。由于驾驶室体积较大,转动惯量参数难以获取,本文采用频响函数法对其转动惯量进行测量,并通过方箱转动惯量测量试验验证了该方法的有效性。在建模过程中考虑了橡胶衬套的影响,通过有限元方法计算了衬套的静刚度并应用于模型。为了保证驾驶室悬置系统模态分析的准确性,对驾驶室悬置系统整体刚度进行了仿真,并通过整体刚度试验进行了验证。在此基础上,对驾驶室悬置系统有阻尼模态和无阻尼模态进行了分析,并通过试验验证了分析结果的正确性。采用了复模态理论分析了驾驶室悬置系统有阻尼和模态频率与无阻尼模态频率不一致的现象。通过动态分析方法研究了驾驶室悬置系统激振力和阻尼变化对复模态频率的影响。为了研究驾驶室悬置系统在中低频激励下的响应特性,建立了驾驶室悬置系统刚弹耦合模型。采用有限元法建立了白车身模型,分析了其弹性体模态并与试验结果对比,验证了模型的准确性。将有限元模型导入ADAMS中替换原有刚体驾驶室,形成驾驶室悬置系统刚弹耦合模型。采用猝发随机方式对驾驶室悬置系统进行激励,研究驾驶室悬置系统的振动响应特性。分析了响应点加速度功率谱密度曲线峰值频率与模态频率的关系,并进行了试验验证。通过试验设计的方法,研究了驾驶室悬置系统参数对振动响应的灵敏度,研究结果表明驾驶室悬置系统的阻尼和刚度是影响驾驶室内振动响应的主要因素。驾驶室的振动与整车振动密不可分,建立整车多体动力学模型,可以分析路面和动力总成激励对驾驶室振动的影响,还可以分析整车工况下驾驶室悬置系统的隔振能力。因此在驾驶室悬置系统模型的基础上建立了整车多体动力学模型。模型主要包括驾驶室悬置系统、动力总成及其悬置系统、车架、悬架、车桥、转向系统和轮胎等。在建模过程中,分析了六缸发动机激励特点及动力总成悬置系统模态;建立了车架有限元模型,分析了车架弹性体模态;研究了钢板弹簧建模方法,采用铁木辛柯梁方法建立了悬架的多片钢板弹簧模型,并通过虚拟吊耳方法解决平衡悬架中车桥与板簧接触问题。在稳定车速工况和定置定转速工况下,通过整车模型对驾驶室悬置系统进行振动仿真分析。根据国家标准《机械振动道路路面谱测量数据报告》(GB/T 7031? 2005)建立了标准B级路面模型。采用多种车速在该路面上进行仿真,分析了不同车速下车桥、动力总成悬置、驾驶员座椅和座椅滑轨位置加速度均方根值变化规律,通过对比试验结果,验证了模型的正确性;对滑轨位置加速度振动响应进行频域分析,分析了响应峰值频率与模态频率间的关系;对驾驶室悬置系统隔振能力与车速的关系进行了分析,结果表明驾驶室悬置隔振能力随车速的增加而增强。在定置定转速工况中,分析了不同发动机转速下,动力总成悬置和座椅滑轨位置的加速度均方根值的变化规律,并与试验结果进行了对比验证;对滑轨位置加速度功率谱密度曲线进行了分析,结果表明该工况下驾驶室内激励主要由发动机3阶激励引起;对定置定转速工况下驾驶室悬置系统隔振能力分析表明,驾驶室悬置系统的隔振能力随发动机转速的增加而增强。为了研究参数变化对驾驶室内振动的影响,分别在稳定车速和定置定转速两种工况下,改变悬架刚度、前悬架阻尼、驾驶室悬置刚度及阻尼、动力总成悬置刚度,分析各参数变化对座椅滑轨位置加速度均方根值变化的影响规律。结果表明,悬架刚度、驾驶室悬置刚度及阻尼、动力总成悬置刚度的增加会增大驾驶室内振动,悬架阻尼的增加会减小驾驶室内的振动,并通过试验设计方法定量的分析了各参数变化对驾驶室内振动的影响程度。整车分析结果表明,优化驾驶室悬置系统刚度和阻尼参数是提高驾驶室舒适性的有效方法。因此在对驾驶室悬置系统优化时,以驾驶室悬置系统的刚度、阻尼和元件安装位置为优化变量,以驾驶室悬置系统各向振动传递率加权求和为优化目标,采用遗传算法进行优化。针对螺旋弹簧式悬置系统优化效果有限这一问题,提出了将螺旋弹簧替换为空气弹簧以及增加横向阻尼器的改进方案。采用了分段函数法对空气弹簧的特性曲线进行设计,这种方法能够较为直观的反映空气弹簧在各工作区间内的刚度特性,便于针对各工作段特点进行设计和优化。同时对驾驶室悬置系统阻尼特性曲线也进行了设计。通过优化分析,驾驶室悬置系统的隔振能力有了较大的提升,座椅滑轨位置垂向和横向振动有了较大幅度的下降。平顺性分析结果表明,各车速下驾驶室内加权加速度均方根值降低了29.18%～34.87%,证明了改进措施的有效性。更多还原

【Abstract】 Recently, the domestic commercial vehicle went through a very fast development accompanied by the yearly increasing production and sales record. Meanwhile, there are more requirements on the performances of the commercial vehicles especially on the comfortableness. Because of the complicated traffic environments and the long driving time, drives are more easily to have fatigue, which is very bad for their health and even worse directly cause the traffic accident. Therefore, how to enhance the comfortableness of the commercial vehicles has become a hot issue to the automotive industry. The vibration on commercial vehicles mainly comes from road and the power train, as a result of which, most of the current research lies on the improvement and design optimization of the suspension and power train, while less effort has been put on the study of cab suspension system. Cab suspension system can effectively absorb the vibration generated from the road and power train, thus it is a better way to downsize the vibration in the cab if properly improved and optimized.This paper starts with study on the vibration modal, transfer characteristics, and the vibration isolation of the cab suspension. Vibration models of cab suspension and whole vehicle were built through ADAMS. Finite element and multi-body dynamics were collaborated into the analysis of the vibration modal and transfer characteristics of the cab suspension system, the response and the isolation feature of cab suspension based on the whole vehicle, and the influence of variable parameters to the vibration response. To increase the isolation ability of the suspension, improvements and optimization design were proposed and an encouraging result was obtained.The modal of the cab suspension system is the key point in the vibration. Unsuitable distribution of the modal frequencies and modal shapes will result a bad isolation or even worse could strengthen the vibration on the cab. This paper studied the vibration modal though the ADAMS model of the suspension system. The cab was assumed to be a rigid body for simplification. Because of the bulky volume, it is hard to measure the moment of inertia of the cab using traditional method. Thus, a method of frequency recognition was used in the measurement, which was verified its validity by square box modal test afterward. During modeling, the influence of rubber bushing was taken into account through obtaining the static stiffness of the bushing by finite element method. The overall stiffness of the suspension system was also simulated and tested through the whole stiffness of cab suspension test, for the accuracy of the modal analysis of the suspension system. The undamped and damped model of the suspension were analyzed and verified by modal analyzing and bench test respectively. Using complex modal analysis, the inconsistency of frequency for damped and undamped system was studied. Dynamic analysis was implemented in the analysis of the impacts from excitation and damping to the complex vibration mode.In order to study the response under medium and low frequency excitation, the cab suspension rigid-elastic coupling model was established. Based on the finite element method, the BIW(body-in-white) model was built. The vibration modal of the flexible bodies was analyzed and the results were compared with those from the test-rig for its accuracy. The finite element model was finally introduced into ADAMS and to replace the former built rigid body model. Therefore, a rigid-elastic coupling cab suspension system model was built. Burst random method was implemented to excite the cab suspension system to study the its vibration response. The relationship between the acceleration power spectral density curve peak frequency and modal on the response points were analyzed and verified by the associated bench test. Through the design of experiments method, the sensitivity of vibration response to the parameters of the cab suspension system was analyzed. The results show that the damping and stiffness are the two main factors for the vibration response.The vibration of the cab and the whole vehicle are closely related. The cab suspension system model based on the whole vehicle will help analyzing the vibration of the cab excited from the road and power train and the isolating ability of the cab suspension system. The multi-body dynamic model of the vehicle was built based on the cab suspension system. This model includes the cab and its suspension, the power train and its mount, the frame, the suspension, the vehicle-bridge, the steering system and the tires, etc. During modeling, the excitation characteristics of the 6-cylinder engine and the vibration modal of the power train mount were analyzed. Finite element model of the frame was built to analysis its modal. The modeling method of leaf spring was studied. Timoshenko beam method was used to build up the model of a multi-leaf spring. Virtual shackle was used to solve the contact problems between the leaf spring and the vehicle-bridge of the tandem SuspensionUnder stable speed and stable engine revolution, the vibration analysis was carried out on the vehicle-based cab suspension system. According to the national standard <Mechanical vibration-Road surface profiles-Reporting of measured data> (GB/T7031-2005), standard B level road model was built. Simulations were carried out fro this road based on different vehicle speed. The changing pattern of the acceleration RMS(Root Mean Square)value for the vehicle-bridge, power train mount, the driver’s seat, and the seat slide were analyzed under different vehicle speed. The acceleration RMS values were also compared with the number from the test to verify the validity of the model. The frequency response of the acceleration on the seat slide was studied to analyze the relationship between the peak frequency and the vibration modal. The relation of the vibration isolation ability of the cab suspension and the vehicle speed was also analyzed, in which the result shows the vibration isolation ability increases as the vehicle speed. Under stable engine revolution, the changing pattern of the acceleration RMS value of the acceleration for the suspension of the power train and the seat slide were analyzed under different engine revolution. Still the acceleration RMS values were compared with the number from the test. The study of the acceleration power spectral density curve shows that the excitation of the cab comes from the third order of the engine excitations. To study the impacts of the vehicle parameter to the cab vibration, the stiffness and damping of the suspension, stiffness and damping of the cab suspension, and the stiffness of the power train mount were changed according to these two working conditions, to find the changing pattern of the acceleration RMS value of the seat slide in terms of the changing of above parameters. The result shows that, the increasing of the stiffness of suspension, the stiffness and damping of cab suspension and the stiffness of the power train will enhance the vibration of the cab, while the increasing of the damping of the suspension will reduce the vibration of the cab. Design of experiments method was taken to quantitatively analyze the impacts of changing these parameters.According to the vibration analyzing results of the vehicle, improving the stiffness and damping of cab suspension is an effective way of enhance the comfortableness. Therefore, when doing the optimization of the cab suspension system, the stiffness and damping of the cab suspension as well as the position were taken as the optimization variables, while the sum of cab suspension vibration transmissibility was the optimization target. The genetic algorithm was used as the optimization method. The optimization results show that there only limited effectiveness on coil spring. So the improvement plans were proposed to replace the coil spring with an air spring and setting transverse damper. According to the plans, the original cab suspension was modified. The piecewise function method was used in fitting the characteristic of the air spring. This method can intuitionally reflect the stiffness characteristic of the air spring within its working area, thus is good for the design and optimization toward different working stage. Meanwhile, the damping characteristic curve of the cab suspension was also designed. Based on the optimization of the modified suspension, there was a great enhancement on the vibration isolation. The lateral and vertical vibration of the seat sliding decreased a lot. Though the ride comfort analysis, the weighted acceleration RMS value inside the cab was reduced to 29.18%~34.87%. The result shows the optimization and the modification were effective and correct.更多还原