单质体非线性系统谐波锐共振的谐振同步分析

基于单质体非线性系统的动力学模型,推导出系统在谐波锐共振(主共振频率比z=0.95～1.05)情况下,反向回转的双激振电动机在平衡奇点处的谐振同步条件。并通过数值仿真,研究在不同初始条件下,推导的谐振同步条件的正确性。理论推导过程和仿真试验结果及实际试验数据表明:在系统特性参数保持一定的情况下,单质体非线性系统谐波锐共振的谐振同步现象与系统的谐波锐共振阶次p/q、谐振同步阶次n/m有直接关系,且只有当参与激振的两电动机在符合一定的系统特性条件下的某p/q及n/m比值处,方可出现谐振同步现象,并且主振同步远比谐振同步容易实现。为进一步开发高效的非线性锐共振振动机,提供理论支持和试验依据。     

层合板复合材料连杆机构非线性动态分析模型

以层合板复合材料连杆机构为研究实例,考虑层合板构件大变形导致的非线性因素影响,用拉格朗日方法建立此类机构的弹性动力学模型,得到机构的非线性有限元动态方程。所建模型体现了非线性因素对机构动态性能的影响,为提高层合板复合材料机构动力学模型的精度,以改善机构的设计和动态性能,提供了一定理论依据;并为进一步研究该类机构的内共振、主共振,以及各种组合共振、多重共振等非线性振动特性打下了基础。     

摆动式柔性递纸机构的动力学分析及研究

分析了定心上摆式递纸机构的运动过程,建立了机构的动力学模型.该模型为一存在弹性变形的四杆机构,运用Lagrange方程建立了该模型的动力学运动方程,通过摄动分析对模型进行了求解,得到了与实际运行相一致的结论.分析表明,弹性连杆机构动力学系统中存在内共振和组合共振,运动副间隙、机构边界条件、阻尼和机构尺度均可能引起机构产生非线性振动,而机构弹性构件的变形是导致机构产生非线性振动的关键因素.     

控制器参数对电磁轴承系统非线性特性的影响

研究了PID控制的单自由度电磁轴承-转子系统由于力-电流/位移的非线性特性所引起的非线性振动.讨论了当控制器参数改变时,系统表现出软/硬弹簧特性;分析了主共振区的跳跃谐振现象和对控制器参数改变时系统在主共振区的特性.     

控制器参数对电磁轴承系统非线性特性的影响

研究了PID控制的单自由度电磁轴承-转子系统由于力-电流/位移的非线性特性所引起的非线性振动.讨论了当控制器参数改变时,系统表现出软/硬弹簧特性;分析了主共振区的跳跃谐振现象和对控制器参数改变时系统在主共振区的特性.     

转子弯扭耦合振动非线性动力学特性研究

对Jeffcott转子的非线性弯扭耦合振动微分方程进行了理论分析，得出了在弯扭组合共振区内弯曲振动和扭转振动的频率特征，利用数值方法对转子系统在较宽的参数域内进行分岔研究，得出了弯扭组合共振为概周期运动的结论，求出了弯扭组合共振区与不平衡量之间的关系，分析结果为转子的安全运行和弯扭组合共振故障的判别提供了理论依据。     

非线性振动系统基于频率俘获现象的谐振同步分析

基于单质体非线性振动系统的机电耦合动力学模型,在对非线性振动系统起动过程中出现的频率俘获现象定量描述的基础上,考虑非理想振动系统的激振源与系统非线性振动运动的相互影响,研究了双激振源非线性振动系统基于频率俘获作用,实现谐振同步的理论条件。并依据激振电动机驱动系统与振动机械系统之间的耦合动力学模型及试验测定的试验台机械特性参数,通过数值仿真及试验,验证和解释了非线性振动系统频率俘获现象下,系统双激振源的谐振同步问题,指出非理想非线性振动系统的频率俘获现象,以及该现象下的多激振源谐振同步运动与振动系统的非线性强度、刚度、阻尼等参数之间的关系。研究结果对多激振源激励非线性振动系统的谐振同步运动现象分析,提供一定的理论支持和试验依据。     

高速弹性连杆机构振动的鲁棒H∞控制

在含有压电元件的弹性机构振动主动控制有限元模型的基础上，基于复模态理论，研究了高速机构的鲁棒H∞振动主动控制问题，给出了时变系统在模态截断下的输出反馈控制器设计方法。该方法可有效抑制系统的持续干扰，并可以解决由于模态截断引起的控制溢出问题。针对一曲柄摇杆机构的仿真计算表明，本方法可以有效地控制系统的在线弹性振动，同时系统原低阶谐振现象也得到了较好的控制。     

基于虚拟样机技术的混合驱动机构动态响应分析

混合驱动机构采用双电机驱动,为避免共振确定机构的固有频率是必须的.应用MSC.ADAMS软件,通过一个实例,针对弹性五杆机构建立机构多体系统模型,进行了动力学分析,并在所建模型基础上提出了一种系统固有频率的计算方法,能够快速求解出柔性体模型振动的固有频率及相应振型,通过利用MSC.ADAMS/Vibration模块频域分析工具分析其动态响应特性,仿真结论证实在远低于系统固有频率的转速下机构也可能发生低阶谐振现象,两个电机转速及转向的选择对系统响应是重要的,因此在机构设计中要对系统进行动态响应分析以避免此现象发生.     

一种新型可控机构式机器人机构振动特性

可控机构式机器人将驱动电机和减速器安装在机架或机架附近,使机构运动惯量显著减小,改善了机器人机构的动态性能.为了研究这种新型的机器人机构的动态性能,避免其发生异常振动,本文以一种所研制的机器人机构为研究对象,对其弹性动力学进行了建模,并对其振动特性进行了研究.首先对该机器人机构进行运动学分析,然后基于有限单元法建立其弹性动力学模型,在此基础上运用多尺度法求解系统动力学响应,并对机构在自激惯性力作用下的振动机理进行分析,研究其非线性振动特性及主共振、组合共振的条件.结果 表明,在自激惯性力作用下,机器人机构的驱动电机角速度近似于系统的某阶固有圆频率时,系统将发生主共振现象;而当多个驱动电机的角速度与系统的固有圆频率达到特定条件时,可能发生组合共振现象.发生共振时系统动态响应的幅值增大,为了避免可控机构式机器人在运行过程中发生共振,应注意使驱动电机的角速度远离机器人机构的共振条件.     

Effectiveness of a passive-active vibration isolation system with actuator constraints

In the prediction of active vibration isolation performance, control force requirements were ignored in previous work. This may limit the realization of theoretically predicted isolation performance if control force of large magnitude cannot be supplied by actuators.The behavior of a feed-forward active isolation system subjected to actuator output constraints is investigated. Distributed parameter models are developed to analyze the system response, and to produce a transfer matrix for the design of an integrated passive-active isolation system. Cost functions comprising a combination of the vibration transmission energy and the sum of the squared control forces are proposed. The example system considered is a rigid body connected to a simply supported plate via two passive-active isolation mounts. Vertical and transverse forces as well as a rotational moment are applied at the rigid body, and resonances excited in elastic mounts and the supporting plate are analyzed. The overall isolation performance is evaluated by numerical simulation. The simulation results are then compared with those obtained using unconstrained control strategies. In addition, the effects of waves in elastic mounts are analyzed. It is shown that the control strategies which rely on tmconstrained actuator outputs may give substantial power transmission reductions over a wide frequency range, but also require large control force amplitudes to control excited vibration modes of the system. Expected power transmission reductions for modified control strategies that incorporate constrained actuator outputs are considerably less than typical reductions with unconstrained actuator outputs. In the frequency range in which rigid body modes are present, the control strategies can only achieve 5-10 dB power transmission reduction, when control forces are constrained to be the same order of the magnitude as the primary vertical force. The resonances of the elastic mounts result in a notable increase of power transmission in high frequency range and cannot be attenuated by active control. The investigation provides a guideline for design and evaluation of active vibration isolation systems.     

四列氮氢气往复压缩机外力及其平衡的分析与计算

以4M50-27.3/18.5-260型氮氢气往复压缩机为研究对象,分析了作用在其曲柄连杆机构上的各作用力,从振动的角度对其受力进行分析与分类,可知往复惯性力、旋转惯性力及倾覆力矩能传到机器外部而引起压缩机的振动,属于“外力（或外力矩）”,并用Matlab软件,计算分析且绘制了压缩机列的气体力、往复惯性力、往复摩擦力和活塞力图.利用添加基础或弹性支承或者通过各列曲拐错角的合理配置的方法,对引起振动的外力进行平衡,有效减小机器的振动与噪声.     

TRANSDUCER INERTIA AND STINGER STIFFNESS EFFECTS ON FRF MEASUREMENTS

In order to study methods for measuring complete driving point frequency response function (FRF) characteristics for forces and moments, it was necessary to evaluate which test technique had the best chances of success. Impulse testing has consistency problems with input magnitudes and direction as well as mixing windows for signal processing. The chirp has excellent signal-to-noise ratios and generally superior coherence when compared to both random and impulse testing. It was found that stinger resonances within the test frequency range and later outside the test frequency range caused measurement complications for certain test structure natural frequencies. These complications were effectively predicted using the transducer's inertial properties, the stinger's stiffness properties, and the structure's linear and angular driving point FRF characteristics (as determined from impulse tests) when stinger resonance effects were removed from the chirp data.     

三环减速器环板惯性力平衡和实验研究

分析了三环减速器环板惯性力对动力性能的影响，提出了平衡惯性力的方法，通过实验证明了惯性和不平衡是引起振动的主要原因，并可以通过配重平衡来改善运动平稳性。     

Inertial parameter estimation for the dynamic simulation of a hydraulic excavator

This paper presents a systematic method for estimating the inertial parameters of an excavator. The method utilizes dynamic excavator models with the pressure and displacement measurements of the hydraulic actuators. Provided that the geometrical parameters of the mechanical linkages are obtained with relatively high accuracy, the dynamic model is factored into the unknown inertial parameter vector and the known kinematic matrix. The contribution of each inertial parameter on the actuator force under the specific motion is explored through a dynamic sensitivity analysis. The results are then used to investigate various properties of the inertial parameters and categorize them into identifiable, unrelated to dynamics, and known parameter groups, according to numerical properties of the kinematic matrix. Then the identifiable inertial parameters are estimated sequentially, and the guideline for the optimal excavator position at each estimation step is suggested in order to minimize estimation error. The practicality of this method is demonstrated via data acquired using an actual hydraulic excavator.     

Mapping of valence energy losses via energy-filtered annular dark-field scanning transmission electron microscopy

The advent of electron monochromators has opened new perspectives on electron energy-loss spectroscopy at low energy losses, including phenomena such as surface plasmon resonances or electron transitions from the valence to the conduction band. In this paper, we report first results making use of the combination of an energy filter and a post-filter annular dark-field detector. This instrumental design allows us to obtain energy-filtered (i.e. inelastic) annular dark-field images in scanning transmission electron microscopy of the 2-dimensional semiconductor band-gap distribution of a GaN/Al₄₅Ga₅₅N structure and of surface plasmon resonances of silver nanoprisms. In comparison to other approaches, the technique is less prone to inelastic delocalization and relativistic artefacts. The mixed contribution of elastic and inelastic contrast is discussed.     

A study of the horizontal inertial forces acting on the suspended load of slewing cranes

When designing a crane's load-carrying structures, a static analysis is still central to a preliminary determination of the dimensions required. However, to bring the results of these calculations closer to reality, different quasi-static procedures are introduced. These procedures take account of various dynamic effects by means of appropriate coefficients. In this paper, a new procedure is proposed for determining the maximum horizontal inertial forces in a radial direction that are acting on a load suspended from the jib during a crane's slewing motion. Based on a previously developed and verified mathematical model of a general-type slewing crane, we undertook the following. Firstly, we verified that the horizontal inertial forces in the radial direction are of no less importance (no smaller in terms of their magnitude) than the forces in the tangential direction, and that their maximum values can easily be a few times greater than the nominal centrifugal force. Based on this we introduced a new coefficient of radial horizontal inertial force, and we calculated a diagram for the rapid determination of this coefficient. We also present a brief report of the horizontal inertial forces in the tangential direction.     

考虑基本变量模糊随机性的弹性连杆机构广义可靠性分析

对弹性连杆机构的基本变量既具有随机性又具有模糊性的情况下，提出模糊随机可靠性分析的广义响应面法，在弹性动力学（Kineto—elastodynamic，KED）分析的基础上，编制计算弹性连杆机构随时间变化的模糊随机广义失效概率的响应面法分析程序，并对弹性连杆机构的广义可靠性进行具体计算，得到连杆机构的强度、刚度及混合广义失效概率随时问的变化曲线。结果表明，广义响应面法与直接Monte Carlo法计算结果一致，从而为连杆机构的广义可靠性设计及分析提供依据。     

后缘小翼智能旋翼有限偏角减振效果分析

建立了适合带后缘小翼的缩比模型智能旋翼减振优化分析方法。考虑小翼运动引起的气动力和惯性力对旋翼系统的影响,建立带后缘小翼的旋翼气动弹性分析模型,使用一种高效的代理模型方法计算带后缘小翼的翼型气动力。使用隐式梯形公式求解气弹耦合动力学方程得到桨叶的弹性响应,采用力积分法计算桨叶剖面振动载荷与桨毂载荷。以小翼操纵输入为设计变量,以桨毂载荷幅值为目标函数建立优化问题,使用最速下降法求解最佳减振效果对应的小翼偏转规律。结果表明本模型计算的结构与气动载荷可靠,对不同前进比状态,后缘小翼都能有效降低桨毂垂向振动载荷。使用直接约束法和目标权重法都能模拟小翼偏转能力不足的情况,小翼偏转能力对减振效果有明显影响,偏转能力不足时后缘小翼仍具有一定的减振效果。     

Active low-frequency vibrational-isolation system with compensation of dynamic forces

The feasibility of an active low-frequency vibrational-isolation system with compensation of the dynamic forces on the housing by means of antiphase inertial forces is considered. This system effectively reduces the forces transmitted to the housing from vibrations of an elastically suspended mass in the low-frequency subresonance range.