径向弹簧型双质量飞轮扭转减振器扭振固有特性研究

在分析径向弹簧型双质量飞轮扭转减振器工作原理的基础上,提出了汽车动力传动系径向弹簧型双质量飞轮扭转减振器扭振固有特性的减振设计方法。基于所建立的动力传动系多自由度集总质量一弹簧扭振分析模型,对比分析了采用径向弹簧型双质量飞轮扭转减振器和离合器从动盘式扭转减振器的动力传动系扭振固有特性,结果证实了该方法设计的扭转减振器具有很好的减振效果。     

振动压路机振动轮减振系统的减振效果

振动压路机振动轮减振系统主要由橡胶减振块组成,该系统一方面要利用振动轮中偏心装置旋转产生的周期性振动,对路面进行压实,另一方面要减少振动轮向机架以及其他系统传递的振动,从而提高机器的可靠性和舒适性能。本文通过试验,验证振动轮减振效果。1.橡胶减振器的受力特点橡胶减振器制作简单,减振刚度理论计算方法也比较成熟。振动压路机橡     

基于有限元的液压双腔减振刚度性能优化研究

液压减振器在高铁、重型机械和汽车中广泛应用。针对液压减振系统刚度易受不同液压油压缩性、粘压性和抗剪性等特性影响的问题,分析对比不同液压油阻尼特性,获得具有最佳阻尼特性的油液介质。为了优化液压减振刚度,分析计算具有浮动活塞隔离的减振系统的理论刚度。基于流固耦合原理,采用ADINA有限元分析软件,建立了两种硅油减振介质的流固耦合模型,获得了弹性模量和粘度等对刚度的影响程度。仿真结果表明,它与理论计算刚度相差1%,获得了较好的契合度,也验证了采用浮动密封块结构形成上下两级弹簧腔的液压减振器可变刚度的方案的可行性,为减振器的优化设计提供了很好的参考。     

钢丝网型减振器的设计研究

对橡胶材料和钢丝网进行对比分析,发现钢丝网的性能优于橡胶材料,因此选用钢丝网作为减振材料.将由钢丝网制成的钢丝网型减振器应用到冰箱压缩机上,对冰箱压缩机的工作原理及减振系统进行分析,计算减振器的刚度、固有频率及系统的实际减振效率,最后对钢丝网型减振器的结构尺寸进行设计改进,为进一步探索和研究钢丝网型减振器的设计改进及制作奠定基础.     

两种扭振减振器减振性能的对比仿真和试验

以国产某中型柴油车为研究对象,应用ADAMS软件建立了汽车传动系统虚拟样机,对于目前两种典型汽车摩擦离合器扭振减振器即:从动盘式扭振减振器(CTD)和双质量飞轮式扭振减振器(DMF)在传动系中的减振作用进行了对比仿真分析,并结合物理仿真试验,充分说明了双质量飞轮式扭振减振器的减振优势和采用ADAMS软件模拟分析汽车传动系统性能的可行性。     

山地车车架动态试验与仿真

采用试验和动态仿真手段,并借鉴国标ISO2631-1中人体对振动反应的评价标准,研究了某全减振山地车车架在简谐激励条件下对不同类型后悬架减振器的动态响应特性,并对试验和仿真结果进行了对比分析.试验结果表明:当激振频率小于5Hz时,气压减振器减振效果优于液压和弹簧减振器;当激振频率大于5Hz时,弹簧减振器的减振效果略优于其它两种减振器,但相差不大.利用动力学仿真分析软件ADAMs对系统进行相同激励条件下的仿真试验,结果表明:对于采用弹簧减振器的车架系统,仿真与试验结果吻合较好,将该仿真模型做为山地车性能分析的依据具有一定的可靠性.     

汽车悬架磁流变减振器的优化设计及仿真

基于磁流变减振器在汽车悬架减振系统半主动控制中的广泛应用,根据磁流变液的特点和磁流变减振器阻尼力与结构参数的关系,设计了新型的磁流变减振器,并对影响磁流变减振器性能的参数进行了优化和仿真.仿真计算表明,该磁流变减振器设计是一种能优化阻尼力的有效算法.     

光刻机模拟工作台的精密隔振系统方案设计研究

提出了高精密设备光刻机模拟工作平台隔振系统的设计方法和系统结构;根据国内外现行的减振方法,建立了整个模拟工作台的结构模型;根据减振要求,选择了适当的减振器.由于光刻机所处激励环境的复杂性和系统内部存在的非线性,采用了主动控制方法BP神经网络 PID控制的主动控制方法来控制整个减振系统.     

基于多智能体的斜拉索分布式智能减振控制系统

目前磁流变减振器已越来越多地被应用于斜拉桥拉索减振,但是这种减振器装置在主、被动工作模式间还缺乏有效的自动转换机制,往往需要人工切换。为了解决该装置在灵活性、自主性和自适应性等方面的不足,本文在斜拉索减振控制系统中引入多智能体技术,提出了基于多智能体技术的斜拉索分布式智能减振控制系统的结构模型和功能,该模型将传统控制系统的功能划分入不同的智能体层,分析了系统的体系结构和工作原理,研究了其实现方式,并将系统应用于洞庭湖大桥上。应用结果表明,该系统在原有装置基础上具有了较高的智能性,表现出更快的反应性和更好的自适应性。     

机车用油压减振器常见故障分析

油压减振器是列车减振的关键部件,保障列车运行的安全性和舒适性,常用的油压减振器有单循环式和往复循环式两种,国内和谐型机车主要选用荷兰的KONI,德国的SACHS,法国阿尔斯通的DISPEN等厂家生产的油压减振器。油压减振器在使用中经常出现漏油、连接故障、阻尼力超标以及环境因素导致的各种问题,在使用中应采用合适的方法处理油压减振器故障问题,保障列车安全舒适运行。     

圆筒式磁流变液离合器设计的理论研究

理论研究了一种圆筒式磁流变液离合器的结构设计.基于Bingham模型描述了磁流变液的本构方程,分析了磁流变液离合器的工作原理;建立了圆筒式磁流变液离合器传递转矩与输出转速的计算模型,并导出了其设计计算公式;利用导出的设计计算公式,选用两种磁流变液材料,设计计算了两种圆筒式磁流变液车用风扇离合器的结构参数.理论研究表明,磁流变液离合器的传递转矩和输出转速都可通过改变磁流变液工作间隙中的磁场强度加以调控;所选择的磁流变液的性能对离合器的结构参数起决定性作用.     

Research on the design of non-traditional dynamic vibration absorber for damped structures under ground motion

An analytical approach is presented to investigate the optimal problem of non-traditional type of Dynamic vibration absorber (DVA) for damped primary structures subjected to ground motion. Different from the standard configuration, the non-traditional DVA contains a linear viscous damper connecting the absorber mass directly to the ground instead of the main mass. There have been many studies on the design of the non-traditional DVA for undamped primary structures. Those studies have shown that the non-traditional DVA produces better performance than the standard DVA does. When damping is present at the primary system, there are very few works on the non-traditional dynamic vibration absorber. To the best of our knowledge, there is no study on the design of non-traditional DVA for damped structures under ground motion. We propose a simple method to determine the approximate analytical solutions of the nontraditional DVA when the damped primary structure is subjected to ground motion. The main idea of the study is based on the criterion of the equivalent linearization method to replace approximately the original damped structure by an equivalent undamped one. Then the approximate analytical solution of the DVA’s parameters is given by using known results for the undamped structure obtained. Comparisons have been done to validate the effectiveness of the obtained results.     

Fast, high bit number pattern generator for electron and ion beam lithographies

High resolution electron and ion beam lithographies, fundamental tools for nanofabrication and nanotechnologies, require fast and high precision (high bit number) pattern generators. In the present work a solution for increasing the bit number, and preserving the speed of the system, is presented. A prototype with effective 18 bit resolution and with a write speed as fast as 10 MHz has been successfully tested: details of the adopted hardware solution are presented and described. This solution is very general and can be used in all those applications that require the generation of control voltages with an high bit number (high precision) at high speed, such as, for example, the scanning probe microscopy and nanomanipulation. Software solutions for increasing the data transfer efficiency are also presented; the aim of the adopted solutions is to preserve the flexibility and adaptability of the pattern generator to different writing strategies.     

Dynamic analysis of rotating damped beams with an elastically restrained root

The vibration of a rotating damped blade with an elastically restrained root is investigated. The effects of viscous damping and the translational and rotational damping at the root of blade are considered. The flow-indued force and moment between the tip of a blade and the casing are simulated by using the time-dependent boundary conditions. A simple and efficient algorithm for deriving the semi-analytical steady state solution of the general system is proposed. The governing equation is divided into two coupled real differential equations. The two coupled equations are uncoupled into an eighth-order characteristic differential equation. The eight corresponding boundary conditions are obtained. The eight linearly independent homogenous semi-analytical solutions of the eighth-order characteristic differential equation are derived. If the coefficients of the uncoupled governing differential equation are constant, the exact fundamental solutions are obtained. The exact steady state solution is obtained by using Green's function in terms of the eight homogenous solutions. Moreover, the influence of the translational, rotational and viscous damping constants on the frequency response curves of a rotating beam are investigated. The opposite influence of the transverse viscous damping constant and the root damping constants on the frequency of resonance is revealed.     

多目标混合流水车间作业调度的演化算法

针对多目标条件下混合流水车间作业调度的优化问题,提出了一种在优化进程中能够动态调整适应度分配的演化算法。该算法采用矩阵编码描述多阶段并行机调度方案,结合问题的优化模型,对每一代Pareto解在各目标方向上的改善程度进行度量,进而通过多目标的选择性权重系数计算种群个体的适应度,以获得在改善指示方向上的选择压力。通过BENCHMARK问题测试和实际算例分析,表明新算法的性能优于现有的求解算法,特别是对于高维多目标优化问题,能够获得较高的演化收敛速度。     

多楔带传动系统的频率灵敏度分析

为了对实际多楔带传动系统进行振动分析与设计优化,系统地研究多楔带传动系统的固有频率对关键设计参数的灵敏度。给出反映带轮、张紧臂等离散部件转动振动与各段皮带这类移动弹性体横向振动之间彼此耦合的运动方程。根据方程耦合与否以及求解的需要将该系统一分为二。对于具有运动耦合的子系统,建立矩阵形式的自由振动方程,推导出固有频率对设计参数的灵敏度表达式,由此导出固有频率对自动张紧机构设计参数和皮带传动速度的灵敏度的显式计算式。针对一多楔带传动系统,计算固有频率对张紧臂长度、扭转弹簧刚度、安装角以及带速的灵敏度,并运用有限差分法结果予以验证。     

基于挤压-剪切模式的高转矩磁流变离合器设计与实验

本文设计了一种基于挤压-剪切混合模式磁流变离合器,建立了用于测试其传动性能的实验装置。首先,介绍了磁流变离合器的工作原理;接着,利用ANSYS有限元仿真分析软件分析了磁路的磁感应强度分布特性;最后,搭建了磁流变离合器的传动性能实验测试装置,测试了磁流变离合器的静态传动性能和动态响应特性。实验结果表明:转速对磁流变离合器的转矩影响不明显,而电流和挤压应力对磁流变离合器转矩的影响比较大,转矩随电流及挤压应力的增加而增加;在1.0A的电流和40r/min的转速下,挤压应力为150kPa时,挤剪式磁流变离合器的转矩可达到146Nm,比剪切模式下的磁流变离合器转矩提高了约6.6倍;响应时间常数先随电流(电流小于0.6A)的增加而减小,而后受电流影响不明显;响应时间随挤压应力和转速的增加而下降;总体接合响应时间在77ms以内。所研制的基于挤压-剪切混合模式的磁流变离合器传动性能良好,控制灵敏。     

Nonlinear Dynamic Analysis of a Rigid Rotor Supported By a Spiral-Grooved Opposed-Hemisphere Gas Bearing

The nonlinear dynamic behavior of a rigid rotor supported by a spiral-grooved opposed-hemisphere gas bearing is investigated in this article, focusing particular attention on its whirl motion. The finite element method combined with the finite difference method is employed to solve the time-dependent Reynolds equation that is coupled with the rotor motion considering five degrees of freedom. The rotor responses to the initial disturbance and synchronous and nonsynchronous excitations are investigated. To analyze the complicated dynamic behavior of the rotor–bearing system, the trajectories of the rotor centerline, time responses, phase portraits, power spectra, Poincare maps, and bifurcation diagrams are obtained from the numerical procedure. The results show that the conical whirl instability appears earlier than the cylindrical whirl instability with increasing rotational speed for the rotor–bearing system with no unbalance mass. Moreover, it reveals that the complex dynamic behavior of the system excited by unbalance mass varies with rotational speed and rotor mass. In addition, bifurcation diagrams employing the rotating speed and rotor mass as bifurcation parameters are obtained. Finally, the nonsynchronous excitation responses are presented, which behave in a different way than the synchronous excitation responses. The results of this study offer a further understanding of the nonlinear characteristics of spiral-grooved opposed-hemisphere gas bearings.     

Free vibration of SDOF systems with arbitrary time-varying coefficients

A new analytical approach for determining the exact solutions for free vibration of single-degree-of-freedom (SDOF) systems with non-periodically time-varying coefficients (mass and stiffness) is presented herein. In this paper, the function for describing the variation of mass of a SDOF system with time is an arbitrary one, and the variation of the stiffness is expressed as a functional relation with the mass function and vice versa. Using appropriate functional transform, the governing differential equation for the title problem is reduced to a Bessel’s equation or other analytically solvable equations. Exact solutions for free vibration of SDOF systems with non-periodically varying coefficients are obtained for six important cases. In order to simplify the free vibration analysis of a SDOF system with multi-step time-varying coefficients, the fundamental solutions that satisfy the normalization conditions are constructed based on the exact solutions derived. It is more convenient to determine the displacement response of the SDOF system by using the fundamental solutions and a recurrence formula developed in this paper. Numerical example shows that the proposed procedure is a simple, efficient and exact method.     

Saturation-based active absorber for a non-linear plant to a principal external excitation

The use of active non-linear absorber to control the high-amplitude vibration of the non-linear plant subjected to primary external excitation is investigated. The absorber exploits the saturation phenomenon that is known to occur in dynamical systems with quadratic non-linearities and a two-to-one internal resonance. The dynamic behaviour of the plant is described by an oscillator, which includes velocity-dependent damping forces, polynomial and differential-polynomial non-linearities. First, the approximate solutions to the governing equations are obtained by using the method of multiple scales. Then a bifurcation analysis is conducted to examine the stability of the system and the performance of the control strategy is studied. A parametric investigation is carried out to see the effects of changing the damping ratio of the absorber, the value of the feedback gain and the detuning frequency of the absorber on the responses of the plant and absorber. The instantaneous power of the control law is also calculated. Finally, the numerical simulations are performed to demonstrate and validate the saturation control method.