高冲击力减振系统的试验研究

本文采用了新型的鼓形钢丝绳减振器，对其力学特性进行了研究，在此基础上，对大型系统在高强环境冲击载荷作用下的减振问题进行了试验研究。试验结果表明本文所研究的冲击减振系统在垂向20－30g、或侧向10－15g的加速度过载的环境激励作用下，能有效的将结构响应的过载衰减到1g以下，并且该减振系统结构简单，具有多向减振性能。     

附加约束阻尼层对星箭系统动特性的影响分析

在星箭连接支架外表面附加约束阻尼层可抑制星箭对接界面的振动,从而降低卫星在发射过程中所承受的振动和噪声载荷.本文将有限元技术与矩阵特征值摄动分析方法相结合,就卫星支架局部修改(附加约束阻尼层)对星箭系统动态特性的影响进行了分析.以已有星箭系统结构的模态信息为基础,给出了支架部位附加约束阻尼层后星箭系统动态特性变化的定量计算方法,并证明了该减振技术能够不明显的改变原星箭系统的固有特性.     

并联式承载减振一体的整星隔振研究

整星隔振是一种改善卫星振动环境的有效措施,传统整星隔振方案主要通过在卫星与火箭之间插入柔性、高阻尼结构.该方案因串联柔性元件,在实现减振的同时,也导致卫星分支(卫星、卫星支架、过渡支架)及整个运载火箭的模态频率大幅降低和卫星振动位移的显著增大.前者严重影响运载火箭飞行特别是末级飞行的稳定性;后者则会大幅减小卫星与整流罩的动态间隙,严重时可能导致卫星与整流罩碰撞.为了解决串联式整星隔振存在的问题,本文提出了一种在原主承力(过渡支架)结构中并联阻尼元件的整星隔振方案,该方案不改变卫星分支结构形式、连接关系,不影响卫星分支主承力结构的强度和刚度.根据柔性航天器的特点,建立了多自由度系统动力学模型,通过仿真分析研究了不同阻尼特性对系统共振频率附近传递特性的影响,得到了增大阻尼可有效改善系统各阶共振频率附近的振动传递特性.根据某运载火箭的外激励特点、过渡支架结构形式、卫星减振需求,设计的一种黏性阻尼器及其安装支架,通过在过渡支架均匀分布8个减振单元,构建了并联式承载减振一体的整星隔振方案,有限元分析和试验结果表明,该方案与无减振状态相比,卫星分支频率变化小于±5％,共振频率处传递特性改善30％~40％.      

潜空导弹垂直发射出筒横向载荷特性

为了研究潜空导弹垂直发射过程中危险截面的受载情况,针对用适配器方式进行弹筒匹配和导向的潜空导弹,建立了出筒横向动力学模型和出筒载荷计算方法并进行仿真分析,研究了潜艇航速、适配器刚度等发射条件对潜空导弹垂直发射出筒过程的受力与出筒姿态的影响。结果表明,出筒载荷随航速的增大而增大,随适配器刚度增大而增大,对潜空导弹及其它战术导弹水下垂直发射具有指导意义。     

并联式承载减振一体的整星隔振研究

整星隔振是一种改善卫星振动环境的有效措施,传统整星隔振方案主要通过在卫星与火箭之间插入柔性、高阻尼结构.该方案因串联柔性元件,在实现减振的同时,也导致卫星分支(卫星、卫星支架、过渡支架)及整个运载火箭的模态频率大幅降低和卫星振动位移的显著增大.前者严重影响运载火箭飞行特别是末级飞行的稳定性;后者则会大幅减小卫星与整流罩的动态间隙,严重时可能导致卫星与整流罩碰撞.为了解决串联式整星隔振存在的问题,本文提出了一种在原主承力(过渡支架)结构中并联阻尼元件的整星隔振方案,该方案不改变卫星分支结构形式、连接关系,不影响卫星分支主承力结构的强度和刚度.根据柔性航天器的特点,建立了多自由度系统动力学模型,通过仿真分析研究了不同阻尼特性对系统共振频率附近传递特性的影响,得到了增大阻尼可有效改善系统各阶共振频率附近的振动传递特性.根据某运载火箭的外激励特点、过渡支架结构形式、卫星减振需求,设计的一种黏性阻尼器及其安装支架,通过在过渡支架均匀分布8个减振单元,构建了并联式承载减振一体的整星隔振方案,有限元分析和试验结果表明,该方案与无减振状态相比,卫星分支频率变化小于±5%,共振频率处传递特性改善30%～40%.     

捷联惯导系统减振设计

机抖激光陀螺的捷联惯性导航系统结构设计的关键在于惯性测量单元（IMU）的减振设计。文章描述了一种IMU减振系统设计的方法,并在实际应用当中获得良好的效果。IMU减振系统的设计方法主要分为三大内容。首先是对减振系统中减振器的布局方案进行仿真分析,建立减振系统的六自由度振动响应模型,研究减振器布局方案的频谱特性,比较得到减振效果较优的减振器方案。然后针对获得的减振器布局方案,设计IMU结构框架和各向同性的减振器,并采用有限元的方法,对IMU的减振系统进行模态分析,获得IMU减振系统的前20阶模态频率和振型,用有限元仿真分析的方法来验证减振设计。目前这种IMU减振系统的设计方法已应用到某新型捷联惯导系统当中,减少了系统陀螺精度的降低。     

利用时滞控制非线性饱和控制减振系统减振频带漂移

本文主要研究非线性饱和控制减振系统中由于内共振频率偏差引起的减振频带的漂移问题,在该减振系统中考虑时滞对振动系统减振频带漂移以及减振频带宽度的影响,从而利用时滞来控制系统减振频带的漂移问题。采用多尺度方法得到了主共振和1：2内共振同时发生时系统运动方程的解析解。研究结果表明,对原始的无时滞减振系统,由于内共振频率偏差的存在,使得系统的减振频带向主共振点上、下两个方向漂移,并且内共振频率偏差的绝对值越大减振频带漂移的程度也越大,使得减振频带的分布不合理,造成主共振点附近减振效果明显下降。然而,根据内共振频率偏差的变化,适当调节系统中的时滞参数,可以消除减振频带的漂移,同时又能够增大减振频带的宽度。研究还表明,内共振频率偏差的绝对值越大时滞对消除减振频带漂移以及增大减振频带宽度的作用越显著。本文结论对于非线性振动系统的结构振动控制在定性和定量方面都具有参考价值。     

吸振器在浮筏上减振应用的有限元分析

浮筏隔振系统是一种广泛应用的减振降噪装置,但它在低频减振方面还存在较大不足。研究表明通过安装吸振器可以改善原系统的隔振性能。本文针对吸振器在浮筏系统中减振应用的问题,采用有限元方法,通过分析比较安装吸振器前后浮筏系统频响特性的变化情况,对吸振器在实际浮筏上的减振效果进行了模拟计算;同时采用自行研制的磁流变弹性体半主动吸振器进行了吸振器在浮筏上的减振实验。通过计算结果与实验测试值的对比,验证了用该方法对吸振器在实际浮筏上的减振效果进行预报的可行性。     

基于MEMS IMU和运动约束的共享单车定位算法

由于全球卫星导航系统在城市环境中信号遮挡严重,共享单车在这类关键区域难以实现连续可靠的定位。为解决这一问题,利用MEMSIMU和自行车运动特性,设计了一种基于惯性导航系统(INS)和非完整性约束(NHC)的融合推算定位方案(NHC/INS)。尤其是深入探讨了IMU安装角误差与NHC杆臂补偿对自行车NHC/INS定位性能的影响。实验结果表明:(1)在卫星信号中断60 s的情况下,相较于传统惯性导航方案,NHC/INS方案在北向、东向以及垂向的定位精度分别提升了91%、95%和83%;(2)即使在卫星信号中断5 min的极端苛刻条件下,NHC/INS方案的北向、东向以及垂向的位置最大误差的RMS统计值也仅为4.0 m、2.5 m和4.0 m,能够满足共享单车的日常监管需要。     

蜂窝锥壳卫星适配器约束阻尼层振动抑制分析

主要研究在蜂窝锥壳卫星适配器上附加约束阻尼来抑制锥壳传递振动。尽管约束阻尼方面的研究很多，但是大多数都是针对简单的梁或者板结构，而对复杂蜂窝锥壳结构的振动抑制问题研究还很少；为此，通过对蜂窝壳的等效化处理和约束阻尼结构的有限元建模理论分析，建立起卫星一适配器结构在有无附加约束阻尼情况下的有限元模型，进一步通过模态分析和频响分析，得到不同约束阻尼层设计参数对结构振动抑制影响规律。分析结果对于经济有效的设计约束阻尼层和结构减振减重具有较好的参考价值。     

Dynamic design of a nonlinear energy sink with NiTiNOL-steel wire ropes based on nonlinear output frequency response functions

A novel vibration isolation device called the nonlinear energy sink(NES)with Ni Ti NOL-steel wire ropes(Ni Ti-ST) is applied to a whole-spacecraft system. The Ni Ti-ST is used to describe the damping of the NES, which is coupled with the modified Bouc-Wen model of hysteresis. The NES with Ni Ti-ST vibration reduction principle uses the irreversibility of targeted energy transfer(TET) to concentrate the energy locally on the nonlinear oscillator, and then dissipates it through damping in the NES with Ni Ti-ST.The generalized vibration transmissibility, obtained by the root mean square treatment of the harmonic response of the nonlinear output frequency response functions(NOFRFs),is first used as the evaluation index to analyze the whole-spacecraft system in the future.An optimization analysis of the impact of system responses is performed using different parameters of NES with Ni Ti-ST based on the transmissibility of NOFRFs. Finally, the effects of vibration suppression by varying the parameters of Ni Ti-ST are analyzed from the perspective of energy absorption. The results indicate that NES with Ni Ti-ST can reduce excessive vibration of the whole-spacecraft system, without changing its natural frequency. Moreover, the NES with Ni Ti-ST can be directly used in practical engineering applications.     

Vibration isolation performance evaluation of the discrete whole-spacecraft vibration isolation platform for flexible spacecrafts

The method for evaluating the vibration isolation performance of discrete whole-spacecraft vibration isolation of flexible spacecrafts is studied in the paper. The dynamic model of the discrete whole-spacecraft system is built and model reduction is proposed. The analysis of vibration isolation method of vibration transmissibility from the isolator to satellite is discussed. Then, the evaluation method is studied from the perspective of simulation and experiment, and the results show the correctness of the theoretical analysis. The power flow evaluation method of discrete whole-spacecraft of the flexible spacecraft is introduced. By studying the power flow of the vibration isolation, we find that this method supplements inadequacies of the vibration transmissibility. At last, it is proposed that the vibration isolation performance should be evaluated by combining the vibration transmissibility at some key points of the satellite and the power flow of the vibration isolator.     

Study on fluid-structure interaction in liquid oxygen feeding pipe systems using finite volume method

The fluid-structure interaction may occur in space launch vehicles,which would lead to bad performance of vehicles,damage equipments on vehicles,or even affect astronauts’ health.In this paper,analysis on dynamic behavior of liquid oxygen (LOX) feeding pipe system in a large scale launch vehicle is performed,with the effect of fluid-structure interaction (FSI) taken into consideration.The pipe system is simplified as a planar FSI model with Poisson coupling and junction coupling.Numerical tests on pipes between the tank and the pump are solved by the finite volume method.Results show that restrictions weaken the interaction between axial and lateral vibrations.The reasonable results regarding frequencies and modes indicate that the FSI affects substantially the dynamic analysis,and thus highlight the usefulness of the proposed model.This study would provide a reference to the pipe test,as well as facilitate further studies on oscillation suppression.     

Investigation on two-phase flow-induced vibrations of a piping structure with an elbow

The dynamic behaviors of a horizontal piping structure with an elbow due to the two-phase flow excitation are experimentally investigated. The effects of flow patterns and superficial velocities on the pressure pulsations and vibration responses are evaluated in detail. A strong partition coupling algorithm is used to calculate the flow-induced vibration (FIV) responses of the pipe, and the theoretical values agree well with the experimental results. It is found that the lateral and axial vibration responses of the bend pipe are related to the momentum flux of the two-phase flow, and the vibration amplitudes of the pipe increase with an increase in the liquid mass flux. The vertical vibration responses are strongly affected by the flow pattern, and the maximum response occurs in the transition region from the slug flow to the bubbly flow. Moreover, the standard deviation (STD) amplitudes of the pipe vibration in three directions increase with an increase in the gas flux for both the slug and bubbly flows. The blockage of liquid slugs at the elbow section is found to strengthen the vibration amplitude of the bend pipe, and the water-blocking phenomenon disappears as the superficial gas velocity increases.     

高速喷流下的柔性旋转火箭发射系统瞬态响应

对于柔性旋转火箭发射系统，考虑高速燃气喷流作用下的系统耦合振动．建立发射系统动力学模型，数值计算发射管流场结构，确定系统瞬态响应和燃气流冲击对火箭发射姿态的影响，更加真实地模拟柔性旋转火箭的发射动力学环境．     

3D Dynamic Modelling of Spatial Geared Systems

In this paper, a nonlinearly dynamic model for a spatial geared systemwith intersecting-axes, which consists of bevel gears, bearings, andshafts, is proposed based on a specific finite element theory. A newtype of spatial gear element which is consistent with the specific finiteelement theory is developed and completely describes all thedeformations that exist for the spatial motions of a pair of bevel gears,the time-variant meshing stiffness, and various types of gear errors inmanufacturing and assembly. The 3D motions of the spatial geared systemin axial, lateral, and torsional directions are coupled in the model. Theproposed approach has been coded into a software system and a dynamicanalysis for the spatial geared system is carried out. The nonlinearinfluences of axial, lateral and torsional stiffnesses of the shaft onthe vibration of the spatial geared system are especially investigated.The lateral stiffness changes the resonance peak frequencies of thespatial geared system and the torsional stiffness greatly affects thesize of the dynamic load and vibration amplitude.     

Chaotic vibrations of a post-buckled L-shaped beam with an axial constraint

Analytical results are presented on chaotic vibrations of a post-buckled L-shaped beam with an axial constraint. The L-shaped beam is composed of two beams which are a horizontal beam and a vertical beam. The two beams are firmly connected with a right angle at each end. The beams joint with the right angle is attached to a linear spring. The other ends are firmly clamped for displacement. The L-shaped beam is compressed horizontally via the spring at the beams joint. The L-shaped beam deforms to a post-buckled configuration. Boundary conditions are required with geometrical continuity of displacements and dynamical equilibrium with axial force, bending moment, and share force, respectively. In the analysis, the mode shape function proposed by the senior author is introduced. The coefficients of the mode shape function are fixed to satisfy boundary conditions of displacements and linearized equilibrium conditions of force and moment. Assuming responses of the beam with the sum of the mode shape function, then applying the modified Galerkin procedure to the governing equations, a set of nonlinear ordinary differential equations is obtained in a multiple-degree-of-freedom system. Nonlinear responses of the beam are calculated under periodic lateral acceleration. Nonlinear frequency response curves are computed with the harmonic balance method in a wide range of excitation frequency. Chaotic vibrations are obtained with the numerical integration in a specific frequency region. The chaotic responses are investigated with the Fourier spectra, the Poincaré projections, the maximum Lyapunov exponents and the Lyapunov dimension. Applying the procedure of the proper orthogonal decomposition to the chaotic responses, contribution of vibration modes to the chaotic responses is confirmed. The following results have been found: The chaotic responses are generated with the ultra-subharmonic resonant response of the two-third order corresponding to the lowest mode of vibration. The Lyapunov dimension shows that three modes of vibration contribute to the chaotic vibrations predominantly. The results of proper orthogonal decomposition confirm that the three modes contribute to the chaos, which are the first, second, and third modes of vibration. Moreover, the results of the proper orthogonal decomposition are evaluated with velocity which is equivalent to kinetic energy. Higher modes of vibration show larger contribution to the chaotic responses, even though the first mode of vibration has the largest contribution ratio.     

NEURO FUZZY MODEL FOR PREDICTING THE DYNAMIC CHARACTERISTICS OF BEAMS

An adaptive neuro-fuzzy inference system （ANFIS） is introduced to predict the dynamic behavior of beams. The effects of axial forces and large displacements are considered in the analysis. A database of tests for the dynamic characteristics of beams is developed from the experimental tests. The responses of nonlinear vibration force for the single and multiple-stepped beams are calculated from the finite element method （FEM）, experimental tests and neuro-fuzzy model for comparison. The neuro-fuzzy model provides a general framework for the combination of neural networks and fuzzy logic. It is more flexible with more options of incorporating the fuzzy nature of the real-world system and is an useful estimation tool for the dynamic characteristics of beams. Therefore, ANFIS can be a useful tool for dynamic behaviour analysis of multiple-stepped beams subjected to axial loads and large displacement.     

人体--结构系统的水平振动实验

针对静止状态人对结构水平振动特性的影响,建立实验平台,分别测试并分析了质量块-结构系统、单人-结构系统、多人-结构系统水平自振频率与阻尼比变化规律.给出了两种人-结构系统静态水平耦合模型的比较分析以及人体的水平振动频率估计.结果表明:在分析静止状态下人对结构水平振动特性的影响时,人体不可简单作为质量块或质量-弹簧-阻尼系统,而应看作带人体刚性质量的质量-弹簧-阻尼系统.结合实验测试数据和人-结构系统水平耦合模型,得到人体水平前后向频率范围为0.236～3.748 Hz,人体水平左右向频率范围为0.194～5.32 Hz.