浮筏隔振系统功率流特性分析

针对工程实际中浮筏隔振装置，建立了柔性基础上机组多支承弹性浮筏耦合隔振系统动力学普遍模型，提出了子系统动态特性综合分析法，给出了耦合系统动态传递方程及功率流表达式。根据工程中两机组浮筏隔振系统功率流理论计算结果，着重探讨安装频率与支承结构柔性耦合作用及其对隔振效果影响。研究结果表明：合理设计安装频率，可有效控制振动能量传输。     

复杂激励下平置板式浮筏功率流传递特性研究

针对隔振理论研究领域中舰船的振动和噪声控制问题，建立六维^[1、2]平置板式弹性浮筏的多机组隔振理论分析计算模型，导出了弹性浮筏传递功率流的表达式，从振动能量传输的角度来评价浮筏系统隔振效果，绘制了功率谱曲线，揭示机组的布置，筏架刚度等结构参数对功率流传递的影响，给出了浮筏设计中结构参数选择的一般准则。     

偏心激励作用柔性主被动隔振系统功率流特性

针对柔性基础上偏心激励作用复杂机械系统，建立了机器-柔性板基础主被动隔振系统数学模型，推导了系统动态特性传递方程。以传递到基础的功率流为评价指标，探讨不同激励及主动控制策略对主被动混合隔振效果的影响。     

机器—基础柔性隔振系统的功率流试验研究

在对楼层安装机器柔性耦合动力系统功率流理论研究的基础上，本文进一步从实验观点研究了机器—基础柔性隔振系统的功率流传递谱。建立了柔性隔振系统实验模型和功率流测试分析系统，从能量观点对机器—隔振器—弹性基础耦合系统的振动传递机理进行了实验研究。通过对称和非对称系统的功率流对比实验，揭示了功率流传递谱的非对称效应，验证了理论分析的正确性。     

FBRE系统偏心力下的功率流特性及主动控制

利用机械阻抗方法推导了偏心力作用下，机器－隔振器－柔性板基础所组成的FBRE隔振系统的动态传递方程。以传递到柔性板基础的功率流为目标函数，通过计算机仿真计算，研究了在对称系统中偏心力作用下的功率流特性，分析了和对称力、力矩作用效果的不同和联系，并探讨了主动控制策略的效果。     

基于菱形压电作动器和内模控制策略的微振动隔振研究

提出了一种以菱形压电作动器为隔振元件,并结合内模控制策略的微振动主动隔振方法。首先设计并分析了菱形压电作动器,分析其力电耦合特性;以单自由度主动隔振系统为例,建立了隔振系统的动力学模型。在此基础上,设计了基于内模控制的主动隔振策略,进行了含有模型误差、迟滞等多工况的数值仿真分析。仿真结果表明,隔振位移传递率最大可达94%。菱形压电作动器结合内模控制策略的振动主动控制技术具有较好的隔振能力,为进一步微振动平台的主动隔振设计与实验研究奠定了基础。     

齿轮传递系统振动功率流特性研究

从振动噪声传递的经典模型(即振源-路径-接受体)出发，分别对轴、轴承、箱体建立模型，进行动力学分析，其中把轴看作受到广义力作用下的空间梁，应用传递矩阵法推导其导纳矩阵；轴承采用Lim模型，箱体看作一个刚体模型。采用子结构导纳方法，推导了传递到子系统的功率流表达式，研究不同阻尼比对传递到箱体和系统的功率流的影响，为进一步研究齿轮箱类结构振动特性奠定分析基础。     

气动八作动器隔振平台的主动隔振研究

多自由度隔振平台可以有效地隔离运载器传递到卫星的振动载荷。本文采用气动八作动器隔振平台实现卫星的六自由度隔振。首先应用牛顿欧拉法建立了气动八作动器隔振平台的动力学模型,设计了平台的主动控制律,然后对平台的主、被动隔振特性进行了仿真分析。仿真分析和实验结果显示主动隔振使平台各方向的低频隔振性能均得到改善。     

惯容器对隔振系统动态性能影响研究

本文设计了一种滚珠丝杠惯容器及ISD隔振系统,通过实验研究了惯性轮的转动惯量对惯容值的影响;同时,分析了滚珠丝杠惯容器的机械动力学特性,推导了ISD隔振系统的振动传递率计算公式,探讨了惯容器对ISD隔振系统动态特性的影响。在电机被动、主动和混合隔振工况下,开展了弹簧阻尼系统和ISD隔振系统的振动性能对比实验,验证了惯容器对振动系统固有频率和减振效果的影响规律。研究结果表明,惯容器可降低振动系统的固有频率,使共振频率向低频移动,共振振幅降低;在共振频率附近,惯容器可抑制共振振幅,惯容值越高,抑制效果越明显;ISD隔振系统在低频的减振效果优于传统的弹簧阻尼系统;随着频率比的增加,ISD隔振系统的传递率趋于稳定值,惯容器会引起高频隔振性能降低。     

一种双转子罗茨鼓风机动力学传递模型

针对罗茨鼓风机振动噪声问题,将风机结构简化为转子、轴承、箱体、隔振器支撑、弹性基础等五个子结构,建立一种简化的空间柔性耦合动力学方程。采用子结构传递矩阵法推导各子系统动态传递矩阵及功率流的表达式;从结构噪声能量传输角度出发,分析了轴承刚度、箱体质量等结构参数变化对风机功率流传递性能的影响。结果表明:减小轴承的刚度,会降低输入到箱体的功率流;通过增加箱体质量,可以降低振动。此结果为具有双转子壳类机器的结构优化与动态设计提供理论基础。     

Problem of Optimal Control of the Turbulent Boundary Layer on a Permeable Surface in Supersonic Gas Flow

The problem of constructing the law of distribution of the normal component of the velocity of blowing to the turbulent boundary layer at supersonic flow velocities which ensure the minimum convective heat flow transmitted from the boundary layer to the surface is considered. The power of the control system calculated with regard to Darcy’s law of flow through a porous medium acts as the isoperimetric condition. The problemis solved using the Dorodnitsyn generalized integral relations. The numerical experiments carried out in the case of flow past a sphere showed the effectiveness of the optimal blowing laws as compared with the uniform law, namely, the gain in the minimized functional reaches 31.82%.     

主动隔振下固支薄板基础振动抑制的参数多目标优化

考虑动力设备-隔振器-薄板基础为复合主动隔振体系,并将薄板视为固支形式;以传递力作用在薄板基础上某点导纳为中间变量,在传递力、导纳、薄板振动峰值位移及峰值点距离影响因素分析的基础上,进行了系统耦联参数的多目标优化研究。优化算法采用较新的强度Pareto进化算法(SPEA2),该算法具有参数设置少、收敛速度快、寻优能力强及Pareto最优解分布均匀等优点。目标函数考虑为薄板振动的位移峰值及峰值点间的距离,目的是在有效控制薄板振动的同时,尽可能地使薄板趋于单峰值点振动,这对于板上附属操作设备及工作人员是有利的;最后,在最优参数的基础上对隔振器的安装位置进行讨论研究。数值计算结果表明,本文方法可有效地计算出隔振系统的最优参数,并为工业建筑及其他工程振动的最优隔振设计提供新思路。     

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.     

Active vibration isolation of machinery and sensitive equipment using H ∞ control criterion and particle swarm optimization method

Isolating the sensitive equipment from vibrating base or the foundation from machinery vibration is of practical importance in a number of engineering fields. With the development of the vibration control techniques and increasing requirements for the higher-performance vibration isolation in industry and everyday life, active vibration isolation exhibits the best performances. In this paper, active vibration isolation reducing vibration transmitted from vibrating base to sensitive equipment and from machinery to foundation was investigated. Controller as static output feedback was considered to design components of active isolation system. An active control is provided by using H _∞ control criteria to design this controller. This criterion is presented as a cost function and then optimized by Particle Swarm Optimization (PSO) algorithm. The approach is validated using numerical simulation. Results show that this static output feedback H _∞ controller using PSO algorithm can get good performance to reduce the effect of unwanted vibration and disturbances.     

Study on the force transmissibility of vibration isolators with geometric nonlinear damping

By a special layout of the damper in a vibration isolation system, the velocity-nth power damping of the damper can be transformed into the velocity-displacement dependent damping in the moving direction due to geometric nonlinearity. This study is mainly concerned with the mechanism of this geometric nonlinear damping and tries to find some guidelines for designing isolators with high performance, regardless of the isolator is passive or active. The model used in this study is an unconstrained two-degree-of-freedom isolation system, which is suitable for investigating vibration isolation in space vehicles. The motion equation is solved by the averaging method to obtain the amplitude–frequency equation. The influence of damping coefficients on the force transmissibility is analyzed. Results show that this kind of damping has some advantages in improving isolation performance at both the resonance and higher frequencies. Meanwhile, it can also degrade the isolation performance if unreasonable parameters are chosen.     

Optimal driver seat suspension for a hybrid model of sitting human body

In the paper a general procedure is presented for the analytical synthesis of an optimal vibration isolation system of a human body including its sensitivity to vibration. The optimal active suspension of a seat has been obtained analytically for a human body represented alternatively by apparent mass weighted by standard frequency domain curves W(s) depicting discomfort levels. The analytical functions describing the optimal vibration isolation systems (OVISs) have been obtained in the general form for random stationary acceleration excitations, general forms of apparent mass M(s) of the sitting human body and a selected criterion of isolation. Analytical forms of complex functions depicting OVIS are presented for two cases of acceleration excitation: white noise (WN) and narrow band noise (NBN). The influence of particular forms of excitation and weighting function W(s) on the resultant vibration isolation is discussed. The analytical results, illustrated by a numerical example presented in the graphical form have been included.     

Improving power-extraction efficiency of a flapping plate: From passive deformation to active control

A flapping plate flow energy harvester in a viscous uniform flow is simulated using a two-dimensional numerical approach. Our focus is to study the effects of flexibility and active control on the power-extraction capability of the flapping plate, and consequently to find a strategy to increase its power-extraction efficiency. Four typical cases with optimal kinematics predicted by previous studies are presented and discussed: a rigid plate, a flexible plate, a plate with a flexible leading segment and a rigid trailing segment, and a rigid plate with a simple active control on the leading segment. Our simulations show that with the kinematic parameters considered, the plate flexibility cannot significantly improve the power-extraction capability of the plate while the active control on the leading segment of the rigid plate increases the power coefficient by 11.3%. The analysis of flow fields shows that the changes in the power coefficient and drag force are related to the vortex structures and pressure distributions near the plate, as well as the projection area of the plate in the direction of the translational movement.