新型电液激振试验台的高频特性研究

电液激振试验台是在振动机架上安装电液激振器,由激振器产生激振力,作用在实验对象的某一局部区域,使其产生强迫振动。该文根据液压马达的大功率、大扭矩的特点,提出了一种由马达驱动高频激振阀的新型电液激振试验台研究方法。该方法主要是通过液压马达对2D激振阀阀芯的旋转进行驱动,采用流量阀控制进入马达的流量达到控制阀芯转速的目的。应用流体动力学和系统动力学理论建立电液激振试验台数学模型,对建立的试验台进行实验研究,同时测得液压缸活塞输出的激振力波形。实验表明:该试验台可以大幅度地提高激振频率,达到1200Hz以上的激振频率,激振输出波形近似为一正弦波。马达驱动2D阀的新型电液激振试验台是提高液压振动的激振频率的有效途径。     

2D阀控高频电液振动台的设计及其特性分析

该文在分析目前电液振动技术的基础上,采用2D伺服阀控制激振缸,用2D阀的转速和直线位移来控制振动频率和振幅。文章介绍了2D阀控电液振动台的工作原理,以及振动台控制系统的硬件组成。最后在各种频率下进行激振实验,分析了激振波形,总结了实验结果。结果表明2D阀控电液振动台能实现高频振动。     

高频电液振动台振动特性实验研究

传统电液振动台由于受伺服阀频响特性的限制,其工作频率难以提高到较高的水平。为此提出一种基于2D激振阀的高频电液振动台,由于2D激振阀是一种特殊结构的转阀,通过提高2D激振阀阀芯的转速可以使电液振动台的工作频率实现大幅提高。分析了高频电液振动台的工作原理,并建立了其数学模型,为了验证理论分析以及高频电液振动台工作时的实际输出振动波形,设计了高频电液振动台并进行了实验研究。实验结果表明：基于2D激振阀的电液振动台能大幅提高振动频率,振动台输出的振动频率达到800Hz,远远高于现有传统电液振动台的振动频率。     

高频电液颤振器振动特性仿真与实验

一种由两位三通激振阀和单作用缸组成高频电液颤振器,高频激振阀采用转阀结构,控制油液交替进出液压缸,从而使弹性端盖产生受迫振动。采用AMEsim分析了液压颤振器的低频振动特性。实验中测量了不同压力与不同弹性端盖质量时电液颤振器在1 Hz~4 000 Hz的振动频率下的压力、加速度、位移以及流量特性。分析表明,高频激振阀的工作频率可以达到4 000 Hz,激振器的谐振频率为320 Hz时,谐振时弹性端盖振动振幅明显增加,此时颤振器所需输入功率很小,最理想的工作频率为320 Hz。     

振动拉削用双阀激振系统耦合增益特性分析与实验研究

电液伺服激振系统(Electro-Hydraulic Excitation system,EHES)其振幅增益特性往往难以描述和预测。针对上述问题,以双伺服阀并联EHES为研究对象,综合考虑伯努利流体汇流耦合和阀控非对称缸特性,建立了系统数学模型;分别通过Matlab/Simulink仿真计算和实验系统测试,研究汇流耦合影响下双阀并联有效振幅增益的规律特性。实验结果表明:所建立的数学模型能有效描述实际系统的增益特性;而汇流耦合主要影响了激振缸的负载流量饱和特性,使得双阀并联激振所输出的振幅增益随激振频率和控制信号幅值的变化,其有效增益在50%~70%间浮动。     

高频电液振动台谐振特性研究

传统电液振动台的工作频率受伺服阀频宽的制约难以提高到较高的水平,为了解决这一难题,提出一种由2D激振阀和数字伺服阀联合控制差动式液压缸所构成的新型高频电液振动台,旨在大幅提高电液振动台的振动频率。阐述了高频电液振动台的工作原理并建立其数学模型,利用Simulink构建了系统仿真模型,对高频电液振动台在谐振点工作时的振动波形进行了仿真研究。为了验证理论分析以及高频电液振动台在谐振点时实际输出的振动波形,设计了高频电液振动台并进行了实验研究。实验结果表明:高频电液振动台的振动频率由2D激振阀阀芯的转速决定,当2D激振阀的激振频率与电液振动台的固有频率相等时,振动台输出的幅值会被突然放大(即产生谐振现象),过了谐振点后振动台输出的幅值则会快速下降。     

电液激振器的谐振特性研究

电液激振器作为疲劳试验机的关键部件,其发展趋势是向着高频率发展的同时,能保证其较大的激振力输出,以满足工程试验对激振器的高频率大激振力的需求,为此电液激振器的谐振特性研究显得尤为重要。电液激振器系统是由2D阀驱动单出杆液压缸活塞以某一振动中心位置作周期性往复运动。根据流体力学和系统动力学的理论对该系统进行数学建模。通过实验研究与分析发现,随着电液激振器的激振频率的上升,激振力的输出会逐渐减小,但在中间的某个频率段激振力会突然增大,且输出波形更趋近于正弦波,因此可以确定在这一频率段激振器发生了谐振。     

振动钻削过程中液压颤振器的振动特性分析

提出一种液压颤振器,该颤振器可用于振动切削的激振装置,它主要有高频激振阀和单作用颤振缸组成,该颤振器可输出500 Hz的受控振动。采用ANSYS Workbench对颤振器的关键部件弹性端盖进行静态和模态仿真。实验测量了钻孔和不钻孔情况下该颤振器的压力特性、加速度特性和位移特性,并对数据对比分析,结果表明,工件的振动频率能跟随激振阀的激振频率,能量集中在激振频率;该液压颤振器与不钻孔时的振动特性均未发生太大变化,说明该液压颤振器的稳定性是极好的;谐振频率300 Hz,谐振时振幅明显增加。     

2D阀控电液激振器的优化设计和实验研究

为了进一步提高电液激振器的激振频率和控制精度,并降低其加工和安装难度,提出了2D高频激振阀的新结构和控制方法。通过增加2D阀阀芯沟槽与阀套窗口的沟通次数,改进与无刷直流伺服电机连接的高速齿轮箱传动机构,设计混合式直线步进电机与堵头连接以控制阀芯轴向位移,实现了对2D高频激振阀的结构优化。经理论以及实验研究表明：新型2D高频激振阀的结构简单,控制精度高,激振频率最高可达3000Hz。     

激振频率对裂纹梁系统振动特性的影响

用ZK-4VIC型振动与控制实验台和ZK-1型电动式激振器分别对相同的Q235裂纹梁系统加载大小相同频率不同的简谐激振力(F=1.12N,w=17Hz、19Hz、21Hz、23Hz),对裂纹梁的振动疲劳过程进行模拟。记录实验过程中裂纹梁的振动幅值随时间变化的趋势,分析在不同激振频率的激振力作用下,疲劳裂纹对裂纹梁振动特性的影响。结果表明:加载简谐激振力的激振频率与固有频率的关系对裂纹梁系统的振幅变化影响显著;裂纹产生后,刚性系统受裂纹的影响大于柔性系统受裂纹的影响,寿命较短;刚性系统比柔性系统更容易从振动变化上发现裂纹故障的存在。     

On the rational dynamic modes of vibrating machines with an unbalanced vibration exciter of limited power

The aspects of choosing the design parameters of a vibrating machine made according to the scheme of a series two-mass vibrating system, as well as of the modes of its oscillations excited by two synchronously rotating unbalanced vibration exciters with a drive of limited power, are considered. The limitations on possible modes of oscillation excitation caused by taking the designed features of the vibration exciter into account are determined. At the specified masses and stiffnesses of a vibrating system, as well as for the specified parameters of oscillations of the actuating element, the rational values of the parameters of vibration exciter and the damping in the components of the vibrating system and dynamic modes, which are characterized by low expenditures of energy and a small dynamic effort transmitted to the foundation of the machine, are determined. The oscillation modes in which changing the mass of the actuating element leads to the smallest changes of the amplitudes of its oscillations are determined.     

低预紧扭矩螺栓连接悬臂梁的2倍谐振响应

为准确获得光电设备中螺栓连接对系统结构动态响应特性的影响,研究了装配连接环节导致的非线性振动特性。采用单螺对栓连接悬臂梁模型,对螺栓连接引起的结构振动特性的改变进行了研究和实验。利用接触有限元方法对低预紧扭矩下结构非线性振动特性进行了时域数值积分仿真分析,给出了不同激励量级周期受迫激励下的相轨迹曲线;结合快速傅里叶分析方法,指出此模型在低预紧扭矩下存在1/2频率激励下的谐振现象。基于激振器实验,给出了实验自由振动响应幅值和受迫振动响应幅值的变化,证实了仿真结果的准确性。数值仿真和激振器实验均表明:激励量级越大,螺栓连接引起的非线性振动中自由振动分量对结构动态响应的影响越大。该方法对开展后续连接结构的非线性振动特性的研究有指导意义。     

齿轮联轴器不对中转子系统的稳态振动特征分析

对不对中齿轮联轴器连接的轴承－转子系统进行了动力学分析，讨论了齿轮联轴器不对中力的组成。理论分析表明，齿轮联轴器的不对中而产生的作用力是联轴器内齿套的惯性力和联轴器内阻尼共同作用的结果，转子系统的稳态响应振幅与齿轮联轴器的不对中量、内阻尼、转子的转速和齿轮联轴器的结构参数有关。数值模拟结果显示在弯曲振动中转子系统会产生工频的2，4，6，8，…等偶数倍频分量，而在扭转振动中会产生工频的1，3，5，7，…等奇数倍频分量，并且这些倍频分量在齿轮联轴器附近处表现得非常明显。     

液压缸非线性弹簧力下的轧机特性及控制

建立了非线性弹簧力约束作用下的轧机辊系振动模型,采用平均法求得轧机辊系的幅频响应方程。仿真分析了不同非线性弹簧力和活塞杆初始位移的幅频特性曲线,以及系统分岔响应随外激励幅值的变化规律。引入吸振器控制装置,比较了吸振器加入前后的时域曲线和幅频曲线,仿真分析了吸振器质量、弹簧力和摩擦力对幅频曲线的影响。研究结果表明：非线性弹簧力和外激励都会改变轧机辊系振动特性的规律,吸振器的控制效果与吸振器质量、弹簧力和摩擦力有关。     

Experimental investigation into the effects of exciter motions on the primary calibration of single-ended accelerometer

It is widely known that in the primary calibration of accelerometers by using a laser interferometer, a device under test (DUT) and the laser interferometer should measure vibration at the same reference position. However, this is not applicable to single-ended accelerometers because of the limitation of their design. One way of overcoming this limitation is to measure the vibration at several positions on the exciter table surface which connects DUT to a vibration exciter. However this can present the effects of rocking motions of the exciter. Although the motions of vibration exciters are presented in several studied, the different model of exciters might have different characteristics. This paper aims to study the motions of an air-bearing exciter (model 2911) used at National Institute of Metrology (Thailand) in order to expose their characteristics, their effects on the calibration results and the measurement errors due to these effects. The motions of the exciter are shown in terms of magnitude and phase shift distributions of sensitivities. These can be obtained by measuring the magnitudes and phase shifts at several positions on the exciter surface. The effects of exciter motions are measured in terms of how much the magnitudes and phase shifts at each measured positions deviate from the average values. To illustrate these effects, parametric studies were conducted. The influences of four parameters, i.e. the angular positions of the laser points, the distance of the laser positions from the centre of the exciter surface, the number of measured positions to be averaged and the mass loading effect, were examined experimentally. The frequency of interest is between 10 Hz and 15 kHz.     

Effect of a vibration drive on vibrotransportation

A dynamic analysis of a machine for vibrotransportation whose drive (a dynamic vibration exciter and a vibration system (a pan)) transfers motion to a concentrated mass by means of Coulomb friction is performed. In the first approximation of the averaging method, the dynamic characteristics and the stability of the stationary regimes of vibrotransportation under forced vibrations are studied. A method for analyzing the transient regimes of the machine represented as a system with an instantaneous change in mass is presented. The proposed method is compared to the classical theory of motion without loss of contact, and the area of applicability of the classical theory is determined. The regions of the parameters of the “hard” transportation regime that are not possible in the classical theory for the considered system are found. Recommendations on the practical use of the identified regimes are made.     

应用于振动平台的智能激振器的设计与建模

在分析研究超磁致伸缩材料(GMM)伸缩现象及产生机理的基础之上,对应用于振动平台的智能激振器进行了整体的结构设计,同时根据振动台性能要求所提供的参数,完成了GMM棒几何参数、线圈参数、预压力装置等部件的设计.最后采用集总参建模方法对智能激振器建立了动态模型,推导出了智能激振器输出位移和输入电流的传递函数,为进一步研究智...     

电动机--复合材料连杆机构系统的动态响应

以三相交流电机——含三维编织纤维复合材料构件的连杆机构系统为研究对象,根据电机轴存在横振和扭振这种普遍情形以及三维编织复合材料的细观结构及特点,应用有限单元法建立了包含复合材料参数、电磁参数和机构的结构参数的系统动态方程,推导出了系统的自激惯性力,得出了自激惯性力及系统的非线性特性,通过研究发现了该系统的动态响应不仅与复合材料的细观结构参数与组分材料参数、连杆机构的结构参数和电机的电磁参数有关,而且还与电机轴的横振有关。最后通过实例仿真进行了验证。     

Non-contact electromagnetic exciter design with linear control method

A non-contact type force actuator is necessary for studying the dynamic performance of a high-speed spindle system owing to its high-speed operating conditions. A non-contact electromagnetic exciter is designed for identifying the dynamic coefficients of journal bearings in high-speed grinding spindles. A linear force control method is developed based on PID controller. The influence of amplitude and frequency of current, misalignment and rotational speed on magnetic field and excitation force is investigated based on two-dimensional finite element analysis. The electromagnetic excitation force is measured with the auxiliary coils and calibrated by load cells. The design is validated by the experimental results. Theoretical and experimental investigations show that the proposed design can accurately generate linear excitation force with sufficiently large amplitude and higher signal to noise ratio. Moreover, the fluctuations in force amplitude are reduced to a greater extent with the designed linear control method even when the air gap changes due to the rotor vibration at high-speed conditions. Besides, it is possible to apply various types of excitations: constant, synchronous, and non-synchronous excitation forces based on the proposed linear control method. This exciter can be used as linear-force exciting and controlling system for dynamic performance study of different high-speed rotor-bearing systems.     

A novel torsional exciter for modal vibration testing of large rotating machinery

A novel exciter for applying a dynamic torsional force to a rotating structure is presented in this paper. It has been developed at IPP in order to perform vibration tests with shaft assemblies of large flywheel generators (synchronous machines). The electromagnetic exciter (shaker) needs no fixture to the rotating shaft because the torque is applied by means of the stator winding of an electrical machine. Therefore, the exciter can most easily be applied in cases where a three-phase electrical machine (a motor or generator) is part of the shaft assembly. The oscillating power for the shaker is generated in a separate current-controlled DC circuit with an inductor acting as a buffer storage of magnetic energy. An AC component with adjustable frequency is superimposed on the inductor current in order to generate pulsating torques acting on the rotating shaft with the desired waveform and frequency. Since this torsional exciter does not require an external power source, can easily be installed (without contact to the rotating structure) and provides dynamic torsional forces which are sufficient for multi-megawatt applications, it is best suited for on-site tests of large rotating machinery.