基于单个压电振子的湍流边界层主动控制

利用安装在壁面上的单个压电振子周期振荡,采用开环主动控制方案,实现了对平板湍流边界层相干结构猝发的主动控制和壁湍流减阻.根据不同的输入电压幅值和频率,完成了10种工况的实验.在压电振子下游2mm处,用热线风速仪和迷你热线单丝探针,精细测量湍流边界层不同法向位置瞬时流向速度信号的时间序列,分析了在Re_?=2183压电振子振动对湍流边界层平均速度剖面、减阻率和相干结构猝发过程的影响.实验结果表明,施加控制的工况使平均速度剖面对数律层上移,产生减阻效果;压电振子振幅越大,减阻率越高,减阻效果越明显;通过对施加控制前后流向瞬时速度的多尺度湍涡结构脉动动能的尺度分析,当压电振子振动频率与壁湍流能量最大尺度的猝发频率相近时,减阻率达到最大,为25%,说明控制壁湍流能量最大尺度相干结构的猝发是实现壁湍流减阻的关键;通过对比相干结构猝发的流向速度分量条件相位平均波形,发现施加控制的工况中相干结构猝发流向速度分量的波形幅值明显降低,且流向速度在扫掠后期高速阶段迅速衰减,缩短了高速流体的下扫过程,说明压电振子的振动能抑制相干结构的高速流体下扫过程,减弱高速流体与壁面的强烈剪切过程,并使近壁区域相干结构的振幅显著减弱,迁移速度加快,从而减小壁面摩擦阻力.      

有机铵十聚钨酸盐在溶液中的光致变色性质研究

有机铵十聚钨酸盐具有显著的光致变色性质,电子自旋共振研究表明光致变色是由于光照过程中有五价钨生成,发生了光还原反应。本文研究了二异丙胺和六氢吡啶十钨酸盐(分别简写为DIAW_(10)和PIPDW_(10)在溶液中的光致变色性质,考察了水、乙腈、二甲基甲酰胺(DMF)、二甲基亚砜(DMSO)对光致变色性质的影响,对比研究了四丁基铵盐(NBuW_(10))的情况,还测定了不同光照时间下W(V)浓度,可见吸收光谱和循环伏安,提出了光致变色性质与体系中所含活泼氢的定量关系,初步揭示有机铵十聚钨酸盐光致变色的本质。     

滑动摩擦主动控制的试验研究

以一种铁磁流体和添加剂为润滑介质,研究了ＧＣｒ１５钢销－盘摩擦副在边界润滑状态下受外加电场作用后磨擦系数的变化情况,并对试验结果和电场作用机理进行分析,结果表明,不同方向的直流电场导致摩擦系数的不同变化趋势,其最大变化率达３５％,且试验数据稳定,变化过程可逆,说明此铁磁流体具有独特的可通过外加电场对滑动磨擦系数进行主动控制功能。     

基于LQG最优控制法的压电智能结构独立模态空间控制

采用压电材料作为传感器和驱动器对智能结构振动主动控制进行研究,基于机电耦合的压电智能结构传感和驱动方程,将振动控制动力学方程变换到模态空间对方程进行解耦。通过计算结构最大应变,确定压电元件的最佳粘贴位置。考虑到系统过程噪声和量测噪声的影响,设计Kalman滤波器,采用基于线性二次型高斯(LQG)最优控制的独立模态空间控制方法对压电智能结构的振动进行控制。最后以压电智能悬臂梁为例进行控制仿真,验证了此方法的有效性。     

Mechanics of soft active materials with phase evolution

This paper studies the mechanics of soft active materials where the actuation is generated due to the formation of phases that are stress-free at the moment of their creation and therefore experience no deformation in the associated configuration. Phase formation is a continuous time-dependent process, which results in individual phases forming at different times and in different configurations of the material body, and thus it is coupled with mechanical deformation. Subsequent deformation of the material body results in individual phases experiencing different states of deformation and the overall material response results from the combined responses of the individual phases weighted by their respective volume fractions. Therefore, a great challenge in modeling the mechanics of soft active materials with evolving phases is to track the deformation and evolution of individual phases formed at different times and in different configurations. In this paper, a generalized one-dimensional model framework is presented to address this challenge. However, this model proves to be computationally inefficient. In response, an effective phase model is developed that tracks the combined deformation histories of new phases through a single, effective deformation. Both the general and effective phase models are evaluated with two fundamentally distinct phase evolution rules for three common mechanical problems: extension, stress relaxation, and creep. The first evolution rule represents a discrete transition from one phase to another while the second rule corresponds to a general transition from several phases into one phase. The effective phase model demonstrates excellent agreement with the generalized theory for all three mechanical problems considered under both types of evolution rules.     

大挠性航天桁架结构动力学及其主动控制研究进展

针对大挠性桁架结构在航天领域的工程应用背景, 对大挠性航天桁架结构进 行系统分类, 综述了几种常见的大挠性桁架结构(桁架式空间站/空间承载结构、网状反射天 线的支撑结构、环形张紧桁架可展开天线、变几何桁架结构)的研究进展、结构动力学建模 进展、主动杆建模进展以及主动控制理论和实验研究进展, 并结合大挠性航天桁架动力学和 主动控制的现状, 对这一领域的研究进行展望.     

地表潜在断错位移的概率评价方法

目前跨活动断层的线状工程的抗断设防一般是以断层位错确定性评价为基础 ,考虑的是最大位错量 ,与抗御灾害的风险设计的实际要求不相符。本文将走滑断层上最大位错点的位置分布及最大位错点两侧的位错展布 ,与可产生地表断错位移的强震复发模型联合 ,构造出评估走滑活动断层各部位地表潜在断错位移的概率性评价方法。最后 ,以鲜水河走滑断裂中带西北部的松林口 -乾宁段为例 ,对其未来 10 0年潜在断错位移的危险性做出定量评估 ,可给出断层段上各点不同超越概率水平下的潜在位移。这一研究结果 ,可为跨断裂的线形工程进行抗御地表潜在断错位移的风险设计提供科学依据.     

LINEAR ACTIVE STRUCTURES AND MODES （ Ⅰ ） — BASIC CONCEPTS AND PROPERTIES

Some basic concepts about the active structures were firstly explained, and the main subjects to study in the field of active structure dynamics were synthesized. For the linear active structures, the annotations on the modes were done in detail. The physical meanings of the right and left eigenvectors were explained. The right eigenvectors are the modal shapes and the modal responses of an active structure depend on the left ones. The adjoint structure of an active structure was defined and the reciprocity theorem was interpreted. For two active structures, which are adjoint to each other and with the reciprocal gain-matrices, the right and left eigenvector are reciprocal The relationship between an active structure and the corresponding passive structure is expressed with the transfer functions, which is employed to resolve the estimation problems.     

控制力矩陀螺用主动电磁轴承数字控制系统设计与实现

讨论了以TMS320VC33为核心的数字控制系统硬件结构。针对磁悬浮控制力矩陀螺转子的大惯量、小跨距、扁平转子和高速旋转时的陀螺效应，采用积分分离和不完全微分PID加交叉反馈控制策略。实验证明，该系统能够有效地抑制高速转子的陀螺效应，达到控制力矩陀螺电磁轴承高速稳定运行的要求。     

噪声有源控制系统的性能预测

研究有源噪声控制中系统性能的实验预测方法,通过原理分析表明利用原始声场和次级声通道传递函数测试数据,能够预测有源噪声控制系统的性能并优化设计系统;结合飞机舱内的应用实际,给出了有源噪声控制系统性能预测和优化设计的基本方法和过程。该方法已被应用于国产运七飞机舱内噪声有源控制实验,取得了满意的结果。