Magneto-rheological engine mount design and experimental characterization

Isolation mounts using magneto-rheological (MR) fluid have increasing potential for various applications. This paper introduces new design and manufacturing aspects of MR engine mounts. CAD software was used to design MR mounts and three different types of MR mount prototypes were considered. Later, magnetostatic analyses were performed to validate the designed configuration of the electromagnetic coil, which controlled the MR fluid flow. The MR mounts were manufactured and, then, tested statically and dynamically using a servo-hydraulic rate machine. Static tests were performed with amplitudes between 0–10 mm. Dynamic tests were performed under excitation frequencies in between 0–100 Hz with amplitudes of ±0.1 mm, ±0.5 mm, ±1.0 mm and ±2.0 mm as well as under excitation frequencies in between 0–20 Hz with amplitudes of ±3.0 mm, ±4.0 mm. Besides the MR mounts, hydro mount and elastomeric top were tested adopting the same procedure. The finding of different mount properties was explained and MR mount characteristics in frequency domain were demonstrated. In addition, the measured characteristics were compared with each other for hydraulic mount and elastomeric top.     

Identifying the frequency dependent material property of a hydraulic engine mount through an iterative procedure using 3D finite element modeling

Achieving very restricted noise, vibration and harshness targets in modern vehicles, makes using the hydraulic engine mount crucial. Hydraulic engine mounts have both solid and fluid media in their structures that make their dynamic behavior complex to figure out. We present a three-dimensional model of HEM with using finite element method that encompasses elastomeric material’s nonlinearity and fluid-structure-interaction. Dynamic equivalent modulus of elasticity for elastomeric material is identified through iterative model updating procedure. To do model updating, the results (here, namely, natural frequencies and frequency response function graphs) are compared with real hydraulic engine mount behavior that derived from modal tests. The results showed that the dynamic characteristic of elastomeric material is frequency dependent and can be divided into two distinct regions: below 30 Hz (low frequency) and above 30 Hz (high frequency) with different trends.     

The effect of gas inclusions on the parameters of hydraulic vibration mounts

Problems of improving damping characteristics of hydraulic vibration mounts are considered. It is shown that, when there are nondissolved air bubbles present in a working fluid, damping characteristics are not weakened but improved significantly in a number of cases. Testing of a hydraulic vibration mount was carried out at a vibration test stand within a frequency range from 20 to 55 Hz. The vibration frequency of the vibration test stand platform was measured discretely with a step of 5 Hz. As soon as the stand’s input vibration signal was not a purely harmonic one, harmonic components from 0.5 to 100 Hz were present in its spectrum. This frequency range was exposed to spectral and cepstral processing. It was determined that efficient vibration suppression with presence of gas cavities with a total volume of 5 mL occurs in the whole range of harmonic change.     

空气弹簧液压悬置动特性及隔振特性研究

研究了具有可变刚度阻尼的发动机空气弹簧液压悬置的动特性和隔振特性。针对影响发动机空气弹簧液压悬置动特性的关键参数上液室等效体积刚度,采用理论和试验方法研究了上液室等效体积刚度的等效值,基于该等效值建立了空气弹簧液压悬置的理论模型,对空气腔开闭两种工况进行了空气弹簧液压悬置动特性的仿真和试验研究。搭建了发动机空气弹簧液压悬置系统试验台架,研究了台架各种激励频率下的空气弹簧液压悬置的隔振特性。结果表明:本研究采用的上液室等效体积刚度进行空气弹簧进行建模是正确、可行的,提高了空气弹簧建模效率和准确性;空气弹簧液压悬置在空气腔开启和关闭两种状态下,峰值动刚度增大幅值达78.5%,峰值阻尼角增大幅值达250%。台架试验表明:当台架激励频率小于25Hz时,悬置采用大刚度大阻尼;当台架激励频率大于等于25 Hz时,悬置采用小刚度小阻尼;悬置隔振率提升明显,不同频率下提升幅值达10%～67%。     

车辆发动机悬架系统现状与进展

理想的发动机悬架系统应隔离发动机工作转速范围内由发动机干扰力所引起的发动机振动，并阻止由冲击而激起的发动机弹跳，这意味着发动机悬架的动态刚度和阻尼是与频率和振幅有关的，改善依赖于频率和振幅特性的动态刚度与阻尼是发动机悬架系统发展的关键所在。传统的弹性悬架不能满足所有的要求，它仅能在静偏转和隔振之间进行折衷，特别在低频域，被动的液压悬架能比弹性悬架提供更好的特性，通常半主动技术，由于其可调性而被用来进一步改善液压悬架的特性，为了隔振、低频时主动发动机悬架系统非常硬，而在高频域内被调整的非常软，主动的发动机悬架已被认为是发动机悬架的新一代，发动机悬架系统的优化是相当可取的，但发动机悬架的优化工作出现一些局限性，文中综述国内，外发动机悬架技术的现状与进展。     

钟板对液压悬置特性的影响

为揭示钟板数量对液压悬置特性影响,首先,根据液压悬置结构搭建解耦膜、节流盘以及新节流盘液压悬置数学模型,同时分析钟板数量对液压悬置动态特性影响;其次,在高低频状态分析钟板数量对惯性通道、解耦膜通道流量以及上腔压力响应的影响;最后,分析节流盘和新节流盘液压悬置在钟板处的流量和压力响应。计算表明:低频时3种液压悬置的动态特性几乎相同,随着钟板数量增加悬置动态刚度和滞后角略有减小;在节流盘液压悬置的基础上增加钟板不影响解耦膜通道流量和上腔压力响应,但影响悬置的刚度和滞后角。     

A negative stiffness vibration isolator using magnetic spring combined with rubber membrane

The most important characteristic of a passive vibration isolator is its natural frequency and load capacity. The vibration isolation performance of a passive vibration isolator in low input frequencies is considerably improved by reducing its natural frequency. This paper presents a negative stiffness magnetic suspension vibration isolator (NSMSVI) using a magnetic spring combined with rubber membranes to obtain lower natural frequency. To study the vibration isolation performance of the NSMSVI, the stretching force of the rubber membrane is measured through experiments. The stiffness of the rubber membrane comes from the derivative of the stretching force. A parametric study of load capacity, axial magnetic stiffness, and natural frequency of the magnetic spring is also performed. Consequently, as a case study, the size dimensions of the magnetic spring are determined. An NSMSVI table is set up for experimental validation, after which the transmissibility curves of the NSMSVI are calculated and tested. Experimental results show that the lowest natural frequency of the NSMSVI reaches 1.5 Hz with a maximum attenuation of -40 dB between 0 Hz and 100 Hz, whereas the NSMSVI has the maximum load capacity at the lowest stiffness. This paper essentially provides an efficient method to construct a negative stiffness vibration isolator for practical applications.     

Optimal design of nonlinear hydraulic engine mount

This paper shows that the performance of a nonlinear fluid engine mount can be improved by an optimal design process The property of a hydraulic mount with inertia track and decouplen differs according to the disturbance frequency range. Since the excitation amplitude is large at low excitation frequency range and is small at high excitation frequency range, mathematical model of the mount can be divided into two linear models One is a low frequency model and the other is a high frequency model The combination of the two models is very useful in the analysis of the mount and is used for the first time in the optimization of an engine mount in this paper Normally, the design of a fluid mount is based on a trial and error approach in industry because there are many design parameters In this study, a nonlinear mount was optimized to minimize the transmissibilities of the mount at the notch and the resonance frequencies for low and high-frequency models by a popular optimization technique of sequential quadratic programming (SQP) supported by MATLAB^(r) subroutine. The results show that the performance of the mount can be greatly improved for the low and high frequencies ranges by the optimization method     

A system for automatically testing properties

A test system was developed at Caterpillar to automatically measure the static stiffness as well as complex stiffness and phase angle of rubber mounts used for support, and for noise and vibration isolation in our vehicles. The system consists of a load frame with a hydraulic cylinder that applies load to the mount and an instrumentation and control system interconnected with a personal computer. The computer acquires load and displacement measurements from the mount through an analog-to-digital converter connected to computer controllable signal conditioners. The computer acts on these signals and controls a programmable function generator, which supplies a command signal to a hydraulic servo controller that controls load or displacement of the mount. The test system software allows the operator to configure the test through form fill-in menus and special function keys. Following setup, the system automatically runs the tests and prints or plots results to the CRT and optionally to the system printer. Additionally, the system allows the operator to specify characteristics of the sensors being used and guides the operator through calibration of the signal conditioners.     

Vibration control of a frame structure using electro-rheological fluid mounts

A squeeze-mode electro-rheological (ER) mount has been designed, manufactured, and applied to the vibration control of a frame structure subjected to external excitations. After verifying that the damping force of the ER mount can be controlled by controlling the applied voltage, a frame structure system supported by spring mounts and the proposed ER mounts has been assembled. The governing equation of the structural system is derived in the modal coordinate and is rewritten as a state-space control model. An optimal controller, which consists of the velocity feedback signal of the frame structure and the force feedback signal transmitted from the exciting point to the mount position, is formulated in order to attenuate the imposed excitations. The controller has been optimized experimentally and control responses such as the acceleration of the frame structure and the transmitted force at each mount position are presented in both time and frequency domains.     

Decoupling analysis for a powertrain mounting system with a combination of hydraulic mounts

The existing torque roll axis(TRA) decoupling theories for a powertrain mounting system assume that the stiffness and viscous damping properties are constant. However, real-life mounts exhibit considerable spectrally varying stiffness and damping characteristics, and the influence of the spectrally-varying properties of the hydraulic mounts on the powertrain system cannot be ignored. To overcome the deficiency, an analytical quasi-linear model of the hydraulic mount and the coupled properties of the powertrain and hydraulic mounts system are formulated. The influence of the hydraulic mounts on the TRA decoupling of a powertrain system is analytically examined in terms of eigensolutions, frequency, and impulse responses, and then a new analytical axiom is proposed based on the TRA decoupling indices. With the experimental setup of a fixed decoupler hydraulic mount in the context of non-resonant dynamic stiffness testing procedure, the quasi-linear model of the hydraulic mount is verified by comparing the predictions with the measurement. And the quasi-linear formulation of the coupled system is also verified by comparing the frequency responses with the numerical results obtained by the direct inversion method. Finally, the mounting system with a combination of hydraulic mounts is redesigned in terms of the stiffness, damping and mount locations by satisfying the new axiom. The frequency and time domain results of the redesigned system demonstrate that the torque roll axis of the redesigned powertrain mounting system is indeed decoupled in the presence of hydraulic mounts (given oscillating torque or impulsive torque excitation). The proposed research provides an important basis and method for the research on a powertrain system with spectrally-varying mount properties, especially for the TRA decoupling.     

燃料电池轿车动力总成分段线性的悬置系统非线性振动特性

针对燃料电池轿车电动动力非线性总成悬置系统及其振动特性,建立一种基于平均法的动力总成悬置系统非线性振动分析方法。建立2自由度分段非线性动力学模型,基于平均法推导得到系统的幅频特性函数,通过仿真计算讨论悬置系统共振特性的非线性特征,同时分析动力总成质量、悬置非线性弹簧刚度特性、阻尼系数以及激振幅值对幅频特性的影响。分析结果表明,平均法可以用于非线性动力总成悬置系统的振动分析,悬置系统参数与激励幅值对于系统特性的灵敏度分析结果可以应用于悬置系统的匹配设计。     

三代液阻悬置非线性动特性的试验研究及其参数识别方法

目前液阻悬置是性能最佳的被动式隔振器,它是汽车动力总成隔振悬置设计开发的首选方案。以第三代液阻悬置为基础,通过对惯性通道的改造以及不同液力机构的组合,系统地研究了惯性通道、解耦膜、节流盘等液力机构以及惯性通道长度及其入口局部损失对液阻悬置动特性的影响规律,揭示了不同液力机构的工作原理以及三代液阻悬置动特性之间的继承和发展关系,为液阻悬置的设计选型提供了直观的依据,并证明了理论分析的正确性。基于动特性试验结果与理论分析结果高度一致的事实,针对液阻悬置动特性的变化特点,提出了识别上液室体积刚度以及橡胶主簧等效泵液活塞面积的新方法,该方法可以有效克服测试误差的影响,原理简单、结果可靠;可以在常规的动特性试验机上进行试验,无需设计复杂的液压试验台。     

基于线性疲劳累计损伤橡胶悬置疲劳寿命预测研究

橡胶元件疲劳寿命的有效预测是其设计开发过程中的重要环节。引入橡胶元件线性疲劳累计损伤原理,提出张量形式橡胶疲劳寿命公式,且根据橡胶材料的实际承载工况提出其失效标准。依据橡胶材料的承载变形可简化为单轴拉伸及简单切应变,设计用于承载拉伸载荷的哑铃型橡胶试柱和承载剪切载荷的环形橡胶试柱,并实测疲劳寿命数据,以最小二乘法原理拟合拉伸与剪切的疲劳寿命函数公式。以车用变速箱悬置与发动机后悬置为疲劳寿命预测研究对象,通过分析其承载位移载荷时的应变张量,利用张量形式的疲劳寿命预测公式预测两种悬置在两种典型工况下的疲劳寿命。结果发现,橡胶材料的拉伸疲劳寿命曲线与简单剪切疲劳寿命曲线的变化趋势一致、形状类似、拟合函数幂指数十分接近;张量形式的疲劳寿命预测公式可有效地预测橡胶悬置的疲劳寿命。     

BPR6螺杆转子磨床的关键技术及机床动态特性分析

螺杆压缩机转子的精加工使用专用数控螺杆转子磨床实现,目前,该机床大多由西方发达国家提供,货期长,售价高,且有限制向我国出口的潜在隐患。笔者公司研制了BPR6螺杆转子磨床,就该机床关键技术的几个特点,针对国外技术的2点不足之处提出的解决方案进行了论述;就第三方检测结果、国内外技术指标对比及用户使用情况及评价进行了详细说明。最后对机床整体及部件进行了模态分析,获得了机床整体及部件各阶频率,其中机床整体一阶频率为70.96 Hz。     

发动机液压悬置动态特性研究分析

分析了发动机液压悬置的基本结构和特性。通过实验测试了某车动力总成液压悬置的动刚度和阻尼特性。建立了液压悬置的集总参数的力学和数学模型,并利用ADAMS软件建立了液-固耦合的分析模型。对液压悬置的动态特性进行了仿真分析,并将仿真结果与实测结果进行对比分析。对比分析结果表明,仿真结果与试验结果比较吻合,验证了模型的实用性和可信性。     

复杂机械系统多维耦合振动传递矩阵分析

以特性传递矩阵描述复杂机械系统中子结构输入、输出力与速度矢量关系,提出了复杂振源激励、多弹性支承与基础板结构三维耦合隔振系统传递矩阵力学模型。考虑隔振支承多维波动效应,推证了弹性支承耦合振动传递矩阵,为复杂系统功率流特性及隔振器多维驻波效应研究确立了有效途经。数值模拟计算表明,基础板结构的前两阶弯曲共振模态是高频域系统功率流提高的主要原因。振源力矩或垂向激振力诱发的隔振器纵向谐振使系统功率流明显提高:增大基础板厚度,驻波共振峰值提高。     

Simulation Research on Dynamic Characteristics of Hydraulic Mount

At present,research on hydraulic mounts has mainly focused on the prediction of the dynamic stiffness and loss angle.Compared to the traditional finite element analysis method,the programming method can be used to analyze hydraulic mounts for a rapid and accurate understanding of the influence of the different mounting parameters on the dynamic stiffness and loss angle.The aims of this study were to investigate the nonlinear dynamic characteristics of a hydraulic mount,and to identify the parameters that affect the dynamic stiffness and loss angle using MATLAB software programs to obtain the influence curves of the parameters,so as to use suitable parameters as the basis for vibration analysis.A nonlinear mechanical model of a hydraulic mount was established according to the basic principles of fluid dynamics.The dynamic stiffness and loss angle of the dimensionless expression were proposed.A numerical calculation method for the dynamic performance evaluation index of the hydraulic mount was derived.A one-to-one correspondence was established between the structural parameters and peak frequency of the evalua-tion index.The accuracy and applicability of the mechanical model were verified by the test results.The results dem-onstrated the accuracy of the nonlinear mechanical model of the hydraulic mount,and the vehicle driving comfort was greatly improved by the optimization of the structural parameters.     

Superconducting accelerometer using niobium-on-sapphire rf resonator

An accelerometer is described which uses a rf niobium-on-sapphire resonator as its sensor element. The accelerometer uses a magnetically levitated spool as a test mass and the spool modulates the inductance of the resonator; its position is servo controlled to maintain the resonator at the external rf excitation frequency. The accelerometer has high sensitivity over the full audio frequency range, but is optimized for frequencies between 100 Hz and 1 kHz, where the calculated displacement sensitivity approaches 10(-15) cm for a 1 Hz measurement bandwidth. The system noise sources are analyzed and possible improvements are discussed.     

基于ADAMS软件的发动机右悬置总成优化设计

运用MSC Adams/view建立汽车发动机悬置系统多体动力学模型,对发动机悬置系统进行匹配设计,以满足频率合理分布、模态振型解藕、限位等诸多设计要求.通过对发动机右悬置刚度的优化,改善了发动机悬置系统的隔振性能,降低了整车怠速振动,并进行了试验验证.