剪切型阻尼U型柔性铰链设计与实验分析

根据柔性铰链的无阻尼结构特点,并利用黏弹性阻尼材料的剪切损耗特性,提出一种剪切型阻尼U型柔性铰链的结构模型,并结合GHM(Goulla-Hughes-MacTavish,简称GHM)黏弹性理论模型建立带阻尼铰链动力学方程。该铰链通过提高外加黏弹性阻尼层材料的剪切效应,达到增强结构阻尼目的。为了测试剪切型阻尼结构对该U型铰链的振动抑制效果,对其进行自由振动信号测试和动态力学分析(dynamic mechanical analysis,简称DMA)实验。结果显示,该阻尼结构能使铰链结构在120~150Hz的共振频段内因振幅增大,阻尼层剪切效应加剧,出现明显的阻尼损耗峰值,有效增强了铰链的结构阻尼。     

平台振动控制中粘弹性阻尼器及其位置优化

针对结构复杂的多自由度海洋平台模型，设计了粘弹性阻尼器，研究了基于粘弹性阻尼器的海洋平台振动控制及阻尼器的位置优化，考虑到粘弹性阻尼器的减振原理，采用层间相对位移的均方差作为阻尼器的定位准则，使海洋平台受控点的位移响应降低到允许的范围内。针对一个实际的7自由度的海洋平台计算模型，在随机波浪载荷作用下进行了平台振动响应分析及阻尼器的位置优化设计。结果表明，大跨安装阻尼器后平台位移响应谱幅度大大地降低。     

含弹性约束复合阻尼板的振动机理与特性

为了实现对磁致伸缩和压电材料迟滞特性的描述,建立高精度前馈补偿系统,对Preisach模型一阶回转曲线的预测方法进行了研究。首先,介绍了一阶回转曲线及经典插法预测一阶回转曲线的基本原理,着重指出线性经典插值法对Preisach模型一阶回转曲线的预测存在不足;其次,在此基础上,利用非线性变换的思想,提出了辅助线法预测一阶回转曲线;最后,实验比较了超磁致伸缩材料（giant magnetostrictive material,简称GMM）与压电陶瓷（piezoelectric ceramic transducer,简称PZT）两种迟滞情况下,辅助线法和经典插值法对迟滞一阶回转曲线的预测结果。实验结果表明：在GMM迟滞下,对任意一阶回转曲线的预测数据,辅助线法的均方根误差（root mean square error,简称RMSE）最大减少为经典插值法的14.22％;对所有预测数据,辅助线法的RMSE减少为经典插值法的29.42％;在PZT迟滞下,对任意一阶回转曲线的预测数据,辅助线法的RMSE最大减少为经典插值法的18.18％;对所有预测数据,辅助线法的RMSE减少为经典插值法的41.07％。辅助线法对一阶回转曲线的预测精度整体高于经典插值法,且迟滞效应的非线性误差越高,预测精度较经典插值法越优异。     

含弹性约束复合阻尼板的振动机理与特性

针对汽车车身减振降噪需求,开发新型复合黏弹性阻尼材料。基于经典的自由阻尼和约束阻尼耗能原理,提出了一种含弹性约束的具有剪切和弯曲复合耗能机制的复合阻尼层结构。基于层间位移连续关系和薄板理论建立了阻尼复合板的位移方程和应变能能量方程,针对局部阻尼敷设及四边简支边界条件,结合假设模态法,推导出了复合阻尼板的运动微分方程、振动频率特征值方程等,求解得到了复合阻尼板的固有频率及损耗因子。复合阻尼层可用于研究单相材料不同参数特性及多相材料性能对比,且随着弹性层的上移,减振性能越好。复合耗能机理公式的推导,也为其在汽车上应用提供理论依据。     

阻尼对高速凸轮机构动力学的影响分析

建立了考虑阻尼因素的等效单自由度高速凸轮机构的动力学模型,以正弦加速度运动规律方程为激振函数,推导出了从动件系统主振段和余振段的位移和加速度动态响应方程并绘制出了动态响应变化曲线,得出了不同阻尼比和周期比对主振段和余振段的动态响应,从而为高速凸轮机构的合理设计提供了一定的理论依据。     

带颗粒减振剂碰撞阻尼的减振特性

传统碰撞阻尼的工作原理大都建立在动量交换、摩擦耗能的范围内,动量交换并没有将振动能量永久地消耗掉,摩擦对于高频振动具有较好的减振效果,而对于低频振动效果较差。为此提出一种以微细颗粒塑性变形将振动能量永久消耗掉的新型的碰撞阻尼,称为带颗粒减振剂碰撞阻尼。分别对在传统单体碰撞阻尼和带颗粒减振剂碰撞阻尼作用下悬臂梁减振效果进行试验研究。试验结果表明：以微细颗粒塑性变形消耗振动能量的带颗粒减振剂碰撞阻尼具有优秀的减振效果,远远超过传统单体碰撞阻尼器。带颗粒减振剂碰撞阻尼在低频振动(低于50 Hz)中仍然具有良好减振性能,这是其他碰撞阻尼所缺乏的特性。机械振动多为低频振动,带颗粒减振剂碰撞阻尼具有广阔的应用前景。     

凸轮机构残余振动的分析

本文将凸轮从动件系统转化为单自由度动力学模型,并建立运动方程进行推导,得出不同阻尼比对应的残余震动位移响应、加速度响应,从而得出周期比、阻尼比对残余震动的影响。     

Robust control of XYZ flexure-based micromanipulator with large motion

This article describes the development of an XYZ flexure-based micromanipulator, with the features of decoupled kinematic structure, large motion range, high positioning precision, and fast response. The large motion range of flexure mechanisms is quantified by a given definition. Based on the given definition, large motion is achieved in the mechanical design of the XYZ-flexure parallel mechanism (FPM). To ensure high positioning precision and fast dynamic response, a hybrid control algorithm with both position control and vibration control are designed, using the H_∞-theory. The controller strongly solves the three common problems of flexure mechanisms simultaneously, including unmodeled uncertainties, the external disturbances and vibration caused by inherent low damping.     

Robust control of XYZ flexure-based micromanipulator with large motion

This article describes the development of an XYZ flexure-based micromanipulator, with the features of decoupled kinematic structure, large motion range, high positioning precision, and fast response. The large motion range of flexure mechanisms is quantified by a given definition. Based on the given definition, large motion is achieved in the mechanical design of the XYZ-flexure parallel mechanism (FPM). To ensure high positioning precision and fast dynamic response, a hybrid control algorithm with both position control and vibration control are designed, using the H_∞-theory. The controller strongly solves the three common problems of flexure mechanisms simultaneously, including unmodeled uncertainties, the external disturbances and vibration caused by inherent low damping.     

Modelling of viscoelastic damper support for reduction in low frequency residual vibration in machine tools

Residual vibrations deteriorate the accuracy and productivity of precision machine tools. Rocking vibration is excited by feed motion. Rocking vibration is the mode in which the entire machine vibrates and is the main source of residual vibrations at low frequencies. The characteristics of rocking vibration are influenced by the characteristics of the machine support structure. Thus, it is necessary to increase the damping of the machine support structure to reduce the residual vibrations caused by rocking vibration. In addition, it is important for machine tools to be stiff to reduce vibrations caused by the acceleration of feed drives. Conventional passive damper supports decrease the stiffness of a machine support structure while increasing the damping. Consequently, a passive viscoelastic damper system is developed to increase support damping without decreasing stiffness by focusing on the horizontal component of rocking vibration. However, the proposed damper damping capacity has a magnitude dependency. This makes it difficult to quantitatively determine the damper area in machine tools to reduce rocking vibrations to the required level. In this study, the developed damper is modeled using a viscoelastic four element model. Because of the nonlinearity of the model, an iterative time domain calculation method is introduced for the simulation. This method enables us to quantitatively estimate the effect of the damper on the machine tool. Based on the model proposed in this study, the proposed damper system can be applied to various machine tools to reduce the residual vibration without adjusting the damper area on the machine tool by a trial and error method.     

Free vibration analysis of a resilient impact damper

The free vibration of a vibratory system equipped with a resilient impact damper is studied. A simple model of impact damper is constructed using spring, mass and viscous damper. The important feature to be carried out in the analysis of this model is that the deformation of an impact damper during the collision with and the main mass can be formulated; therefore, the contact time is taken into consideration. This feature is important for a resilient rather than a rigid impact damper when the noise issue is concerned. The investigation showed that the effective reduction of the vibration response depends not on the number of impacts but primarily on the type of collision that the impact mass collides with the main mass face-to-face. Results also show that the clearance of an effective impact damper should be smaller than twice of the initial displacement of the main mass of the vibration system if the system is stimulated by an initial displacement only. Finally, an example of application of an impact damper on a cantilever beam is demonstrated.     

NANO-BEARING： THE DESIGN OF A NEW TYPE OF AIR BEARING WITH FLEXURE STRUCTURE

A new type of air bearing with flexure structure is introduced. The new bearing is designed for precision mechanical engineering devices such as mechanical watch movement. The new design uses the flexure structure to provide 3D damping to absorb shocks from all directions. Two designs are presented: one has 12 T-shape slots in the radian direction while the other has 8 spiral slots in the radian direction. Both designs have flexure mountings on the axial directions. Based on the finite element analysis (FEA), the new bearing can reduce the vibration (displacement) by as much as 8.37% and hence, can better protect the shafts.     

半主动直接输出反馈变结构控制电流变阻尼器减振研究

针对多层结构电流变阻尼器减振系统运动状态难以完全实时测量、扰动存在不确定性、系统参数容易出现摄动以及阻尼器连续可调的特点,提出了半主动直接输出反馈变结构控制策略,根据滑模运动方程稳定的Hurwitz判据选择滑模梯度参数,实现控制与扰动完全解耦;饱和非线性环节使阻尼器阻尼力不超调;阻尼力对主结构做负功控制规则保证主结构最佳减振。仿真分析表明,电流变阻尼器减振控制系统效果明显,不仅对扰动具有自适应性,而且对系统参数摄动也具有很强的鲁棒性。     

干摩擦阻尼叶片周期振动响应的解析计算

研究一个描述干摩擦阻尼器叶片振动的质量-弹簧-阻尼器振动系统。阻尼器摩擦力由黏滞模型描述,由接触面滑动或黏滞状态决定。将滞后摩擦力分为四个阶段,从而得到各个阶段上的线性振动系统,给出求干摩擦阻尼叶片周期响应的解析公式。计算表明,阻尼端压力取适当值时,阻尼器会处于最优的摩擦接触状态,获得较好减振效果。同时引入阻尼器处对叶片还起到调频作用,也可以起到使激振频率避开共振频率的作用,减小振动幅值。     

工业磁轴承电涡流阻尼伴随特性研究

针对工业磁轴承中电涡流阻尼效应暂态认知难的问题,通过分析电涡流阻尼的伴随特性定量评价了其在磁轴承控制过程中的作用。首先引入磁矢位对电磁感应定律中的线积分和面积分不同表述形式的电涡流进行了统一,进而推导了工业磁轴承在PWM控制下的工作由电流的交变特性引起电生阻尼和机械振动引起的动生阻尼简化数学模型;然后通过Matlab-Simulink对单自由度磁轴承仿真分析,并且与同控制条件下未考虑涡流效应的模型进行了对比;最后通过冲击响应仿真实验验证了伴随效应,定量评价抑制振动和工作电流特性。研究结果表明,暂态过程中动生阻尼和电生阻尼对工业磁轴承存在着自稳效应,加快了控制电流稳态响应;另外计入电涡流阻尼效应的转子振动位移峰值相对未计入的降低了10.23%。     

自耦合电流变阻尼器及其性能

电流变液与压电陶瓷组合的阻尼器是一种自耦合阻尼器。对直压式自耦合电流变阻尼器的性能进行了理论计算,并制作了直压式自耦合电流变液阻尼器。性能测试表明:压电陶瓷激励了电流变液;电流变液阻尼的变化改变了阻尼器的共振频率,并使振动幅度降低最高达30％。     

Modeling the fine particle impact damper

The fine particle impact dampers (FPIDs) using plastic deformation of fine particles as irreversible energy sink can exhaust much more vibration energy than single mass impact dampers (SMIDs) and thus can work well in low frequency domain. A numerical model is set up in this paper to capture the complex physics involved in the FPID. Experimental results on a cantilever beam with FPID showed good agreement with the model predictions. We show that in all cases the damping performances of the FPID are much better than that of the SMID, and fine particles enrolled in the FPID play a key role in vibration energy dissipation. The damper clearance and the mass ratio are two important parameters for the damping ability of the FPID, for which an optimal combination of them exists targeting the largest damping ability.     

变质量对碰撞阻尼器减振性能影响的试验研究

通过试验法,采用模拟试验装置研究碰撞体形态对阻尼器减振性能的影响。在碰撞阻尼器中加入总质量相等但大小不等的介质(即自由质量),分别测试它们在相同外力条件下的减振效果。分别对试验结果进行了振动衰减率、阻尼机理以及共振特性的分析。试验分析结果说明:在一定范围的共振区域内,具有相同质量的介质个数越多,对系统的阻尼越大,减振效果就越好。随着自由质量的数量不同,碰撞阻尼器将被考虑为变质量振动系统。     

馈能式磁流变半主动悬架协调控制研究

为了优化车辆悬架的减振控制及振动能量回收,提出了一种基于协调控制的馈能式磁流变半主动悬架。建立了1/4车二自由度悬架力学模型、磁流变减振器数学模型和馈能模型,利用MATLAB/Simulink软件对馈能特性进行了仿真分析,并进行了参数敏感性分析。分析了减振器实现自供能的条件及结构参数的影响,设计并分析了多模式协调控制下的悬架动力学特性和馈能特性。结果表明,该减振器馈能结构参数对自供能影响较大;协调控制器能够有效协调悬架系统减振与馈能关系,降低能耗,阻尼力可控性好,能够衰减车辆振动,馈能特性效果良好,验证了该结构的可行性。