压电智能环形板的主动控制

对在不同位置粘有任意多组压电传感器和压电执行器的轴对称弹性环形薄板的振动控制进行了研究．根据压电执行元件的等效作用量得到了压电智能环板的振动控制方程和传感方程,再利用分离变量法以及由传感器测得的电量和作用在执行器上电压之间的控制模式得到振动方程的全解．实行了对整体结构的主动控制．对不同的压电片布置进行了数值计算．结果表明：当离散分布压电元件布置越密,振动衰减的效果越佳     

面向压电智能结构精确变形的协同优化设计方法

智能结构集智能材料与传统材料于一体,能够实现结构的主动控制,在航空航天等领域具有巨大的应用潜力.由于其系统复杂且具有多场耦合效应,智能结构的整体式优化设计方法成为结构控制技术研究的关键之一.为了提高压电智能结构的整体性能和变形精度,提出了同时考虑压电驱动器布局(分布位置及角度)和基体结构拓扑构型的协同优化设计新方法.采用多点约束方法 (multi-point constraints,MPC)建立压电驱动器和基体结构的连接,定义一种与测量点目标位移相关的权重函数,以实现结构的精确变形控制.通过协同优化设计,压电驱动器可以获得最优的分布位置及角度,同时基体结构获得最优的拓扑构型,从而提升了压电智能结构系统的整体驱动性能和变形精度.通过进一步分析,研究了精确变形、体分比约束与结构优化构型和整体刚度的关系,以及优化结果中可能存在的传力路径畸变现象.数值算例的设计结果表明,采用协同优化设计方法,能够扩大结构的寻优空间,有效减小变形误差,实现压电智能结构的精确变形控制.     

智能抛物面天线多目标最优控制

大型天线必须保持非常精确的形状。由于载荷变化及各种随机干扰,为了保持精确的形状,这类结构宜采用主动控制。针对智能抛物面天线结构,建立了对天线反射面的最佳吻合抛物面的RMS精度和作动器能耗为综合目标的多目标优化模型。优化模型以结构强度和作动器性能作为约束条件,模型转化为二次规划问题进行求解,实现智能抛物面天线的准静态最优控制。算例表明,可以用较少的作动器,实现大型天线结构的精密控制。     

空间薄膜结构的褶皱形变预测

空间充气结构技术是一项全新的空间结构构建技术,基于该技术的空间充气结构是未来空间任务的主要需求对象．该结构主要由薄膜构成,因此结构形面精度的保持是关键问题．褶皱是薄膜特有的现象,它的存在会严重影响结构形面精度,因此进行褶皱研究很有必要．根据屈曲理论联合薄膜褶皱的实际构型建立了薄膜结构褶皱的预测模型,分析了矩形平面薄膜受面内水平剪切情况下的褶皱,得到了褶皱幅度和褶皱波长以及薄膜结构产生褶皱时的临界压缩应力,通过与已有文献结果及本文实验结果的比较验证了该分析方法的有效性和结果的正确性．     

Electric field-induced surface transformations and experimental dynamic characteristics of dielectric elastomer membranes

Acute and tunable surface transformations of a monolithic structure by application of an electric field have immediate significance for adaptive structures, morphing concepts and optical applications. Dielectric elastomer (DE) membranes are electric field-responsive materials typically employed as large strain electrostatic actuators. In this paper, it is demonstrated that an electric field will generate several symmetric surface shapes analogous to the mode shapes in the classical drumhead or stretched membrane problem. In a previous experimental study, a single surface transformation creating ripples or waves on an initially smooth surface was observed for an electrically excited DE membrane. The unexpected result led to the development of an experimental setup that would facilitate extensive characterization of the dynamic surface transformations of dielectric elastomer membranes. The new results clearly show that the electric field can be used to tune the patterns of the DE surface. Furthermore, the membrane will go through resonance when a periodic electric field is applied if the system conditions are favorable, which has not been observed before now. This presents a unique opportunity to increase the output displacement of DE membranes without electrically overloading the membrane. The experiments show that increasing the size of the chamber onto which the membrane is clamped will increase the peak deformation as well as cause the membrane's resonance peaks to shift and change in number. For DE membranes driven at 1.5 kV, at the smallest chamber volume, the maximum actuation displacement is 81 μm; while at the largest chamber volume, the maximum actuation displacement is 1431 μm. This corresponds to a 1767% increase in maximum pole displacement. The dependence on chamber volume suggests that under dynamic conditions a systems level analysis is needed for DE actuators. The effect of voltage offset as a means of modulating the dynamic deformation response is also reported in this study.     

空间充气薄膜结构的褶皱分析

引入一个表征褶皱在纹理方向收缩特性的参数``收缩系数'来替代泊松比参与计算褶皱形变,并联合褶皱产生时的应力条件和褶皱特性,实现了对空间充气薄膜结构的褶皱分析,得到了褶皱存在时的充气薄膜结构的应力场和变形. 分析中重点讨论了``收缩系数'与泊松比的关系,并讨论了引入``收缩系数'约束变形后的变形协调条件. 将两维的褶皱分析方法拓展应用到三维充气结构的褶皱分析中,分析了充气管的弯皱变形,得到了临界皱曲和极限弯矩随结构及力学参数的变化规律. 通过简单的褶皱试验,定性地分析了褶皱的形变特性并与分析结果进行了比较验证,结果一致.      

带剪切型压电激励器的板的高阶剪切变形理论

利用压电材料固有的正，逆压电效应可以对结构变形和振动进行控制。与外加电场与极化方向平行于板厚度的压电材料的拉伸作动机制相比，外加电场与极化方向垂直的压电材料的剪切作动机制可以在作动器内产生较小的应力，从而降低作动器边界产生分层破坏的危险。本文对于压电材料的剪切作动机制进行研究，应用三阶剪切变形理论建立带剪切型压电激励器的智能层合板模型。采用哈密顿原理导出带剪切型压电激励器的层合板的控制方程。采用空间法得到了各种边界条件组合条件下板的解析解。数值算例对一三层板采用高阶和一阶剪切变形理论进行计算，结果表明两种理论所得的变形曲线很相似。但对于厚度剪切型激励器而言，由于激励器是引起板的剪切变形，而高阶剪切变形理论比一阶剪切变形理论能更好地反映结构的剪切应变能，因此高阶剪切变形理论可以提供板变形的更为精确的解。因此，对于厚度剪切型激励器，剪切变形理论的选取对于板变形结果的好坏有重要的作用。     

压电曲壳结构形状控制和优化设计

板壳结构作为航空、航天工程以及控制系统中的重要工作元件,在工作状态 中,要承受机械载荷、温度载荷、冲击载荷等各种负面影响, 而航空航天部件对结构形状变化非常敏感,如飞行器机翼、信息接收天线等结构, 微小的结构变形就会引起很大的性能改变,想要在设计初始阶段充分考虑所有不 利因素的影响显然是比较困难的. 利用压电材料控制结构变形往往是现代空间结 构开关控制中一个很好的选择. 基于一般壳体有限单元法, 推导了空间任意曲壳 压电单元, 利用约束方程连接主体壳元和压电壳元, 模型中约束方程的使用大大 减少了结构自由度, 使得计算速度有了明显的提升. 在此基础上, 重点研究了压 电曲壳结构的形状控制方法, 首先利用最小二乘法优化结构的电压分布, 控制结 构形状接近最优工作状态; 其次构建了以压电壳元厚度和电压联合作为设计变量 的优化控制模型, 采用非线性优化求解方法, 取得了更好的控制效果. 数值算例 表明了该文计算模型、 优化设计和控制方法的有效性.     

Piezoelectric Actuator Placement Optimization and Active Vibration Control of a Membrane Structure

The placement optimization of piezoelectric actuators and active vibration control of a membrane structure are studied in this paper. The classical linear quadratic regulator controllers are designed to suppress the unwanted vibration. Simulation results indicate that the optimal locations of piezoelectric actuators are affected deeply by the additional mass and stiffness of actuators, the computational efficiency of particle swarm optimizer is higher than that of genetic algorithm for this particular problem, and the control performance of optimally placed actuators is better than that of non-optimally placed actuators.     

INTERACTION MODEL OF THE ENCLOSED AIR AND THE OUTER MEMBRANE

将充气膜结构内充气体假定为势流,推导得到速度势表示的内充气体小幅波动方程,并采用Galerkin法离散得到内充气体的有限元动力学方程。引入界面协调条件,建立了内充气体结点速度势与外部膜材结点位移的关系,然后联立薄膜动力方程和气体动力学方程得到充气膜系统内充气体与外部膜材的共同作用理论模型。在该理论模型基础上,建立了两类典型充气结构的数值模型进行分析,通过将数值结果与试验结果对比,验证了共同作用理论模型的准确性和合理性。     

Exact deflection solutions of beams with shear piezoelectric actuators

Exact deflection models of beams with n actuators of shear piezoelectric are developed analytically. To formulate the models, the first-order and higher-order beam theories are used. The exact solutions are obtained with the aid of the state-space approach and Jordan canonical form. A case study is presented to evaluate the performance of the authors’ previously reported models. Through a demonstrative example, a comparative study of the first-order and higher-order beams with two shear piezoelectric actuators is attained. It is shown that the first-order beam cannot predict the beam behavior when compared with the results of the higher-order beam. Further applications of the solutions are presented by investigating the effects of actuators lengths and locations on the deflected shapes of beams with two piezoelectric actuators. Some interesting deflection curves are presented. For example, the deflection curve of a H–H beam resembles saw teeth that rotate clockwise about the central location with the increase of actuators lengths. The presented exact solutions can be used in the design process to obtain detailed deformation information of beams with various boundary conditions. Moreover, the presented analysis can be readily used to perform precise shape control of beams with n actuators of shear piezoelectric.     

基于Ω形蜂窝的夹芯式大变形柔性蒙皮结构设计与性能分析

变体飞机根据不同飞行状态改变机翼形状以获得最佳的气动效能，从而提高在多工况下执行多目标任务的能力。表面结构的柔性蒙皮设计是实现变体结构的关键，需要设计具有足够协同变形能力的同时，还能够承受表面的气动载荷、保持光滑气动外形性能的柔性蒙皮结构。针对这一需要，本文提出一种基于Ω形蜂窝的夹芯式大变形柔性蒙皮结构（Ω形柔性蒙皮）。利用参数优化技术以最小化构型变形方向的刚度为目标确定Ω构型的拓扑结构；推导出Ω形蜂窝柔性蒙皮结构的面内等效弹性性能预测公式，并通过数值仿真分析了该结构的面内变形性能和面外承载能力。通过与蛇形蜂窝和正余弦蜂窝两种夹芯式柔性蒙皮结构的面内变形能力的对比分析，验证了该柔性蒙皮的良好性能。结果表明，所提出的Ω形柔性蒙皮结构具有良好的面内可恢复的大变形能力和面外承载能力。     

具有压电材料薄板弯曲控制的有限元法

考虑一均匀各向同性薄板结构,在其上下表面离散分布状压电执行元件,在横向外载和电压共同作用下,分析板的弯曲变形,并通过变化作用于执行元件上的电压对板的变形进行控制,根据逆压电效应将电压转换成作用于板上的等效作用量,用Ｈａｍｉｌｔｏｎ原理导出压电结构板弯曲变形的有限元公式,并对环形板情况进行数值计算。     

空间充气展开结构动态分析研究进展

空间充气展开结构是一种以薄膜材料为主构建而成的新型结构, 可用于构建大型的天线、太阳能集中器、太阳帆等空间结构, 为空间结构的大型化提供了一条有效的解决途径.其动态特性是充气展开结构设计过程中必须考虑的问题, 动态分析测试技术一直是充气展开结构研究过程中的关键问题, 由于充气展开结构在材料、结构形式及工作环境等方面的特殊性, 使得其动态分析和测试技术出现了很多新的问题.目前充气展开结构动态分析的研究方法主要集中在两个方面:实验研究和数值模拟.实验研究主要是针对充气薄膜结构的特点, 由接触式的测试手段向非接触式的测试手段发展, 但实验研究在真空和微重力环境的模拟上面临着很大的问题.数值模拟研究可以有效的模拟结构在真空和微重力环境下的动态行为, 并可分析重力、空气和褶皱等因素对结构振动特性的耦合影响.本文综述了空间充气展开结构动态分析的实验研究和数值研究的发展和现状, 并讨论了其中存在的问题, 在此基础上指出了该项研究的发展趋势.      

Dynamic analysis of a rigid-flexible inflatable space structure coupled with control moment gyroscopes

The vibration generated by the inflatable structure after deployment has a great impact on the performance of the payloads. In this paper, the influence of the control moment gyroscopes (CMGs) on the dynamic responses and characteristics of an inflatable space structure is studied, based on the flexible multibody dynamics in a combination of the absolute nodal coordinate formulation (ANCF) and the natural coordinate formulation (NCF). Firstly, the ANCF and NCF are used to accurately describe the large deformations and large overall motions of flexible inflatable tubes and rigid satellites, respectively. Then, instead of modeling gyroscopic flexible bodies, this paper pioneers a rigid body dynamic model of the CMG in detail by using the NCF modeling scheme, which can be attached to and coupled with any flexible bodies without any assumptions. Then, the orbital dynamic equations of the inflatable space structure coupled with distributed CMGs are obtained by considering the effects of Coriolis force, centrifugal force, and gravity gradient through coordinate transformation. The dynamic characteristics of the inflatable space structure are also analyzed by deriving the eigenvalue problem of a flexible multibody system. Finally, the accuracy of the CMG dynamic model is verified via a classic heavy top example. Several numerical examples are presented to study the influence of the magnitudes and directions of the rotor angular momentum of the CMGs on the dynamic responses and characteristics of the inflatable space structure.

     

Shape Control by Collinear Actuators

We consider a two-dimensional elastic medium bounded by a free surface. The medium deforms under the influence of actuators, which are modelled as supplying a unidirectional stress. The goal of the control mechanism provided by the actuators is to deform the body into a given shape. In a linearized situation, this means achieving a given normal displacement on the boundary. We prove that, for generic domains with smooth boundary, every normal displacement of the boundary can be achieved. We also consider “stress-free” states, for which the sum of the elastic stresses in the medium and the stress provided by the actuators vanishes. The study of these states leads to a hyperbolic boundary value problem. Accepted July 16, 2000?Published online February 14, 2001     

Wing box transonic-flutter suppression using piezoelectric self-sensing diagonal-link actuators

The main objective of this research is to study the capability of Piezoelectric (PE) self-sensing actuators to suppress the transonic wing-box flutter, which is a flow-structure interaction phenomenon. The unsteady general frequency modified Transonic Small Disturbance (TSD) equation is used to model the transonic flow about the wing. The wing-box structure and the piezoelectric actuators are modeled using the equivalent plate method, which is based on the first-order shear deformation plate theory (FSDPT). The piezoelectric actuators are used as diagonal-links. The optimal electromechanical-coupling conditions between the piezoelectric actuators and the wing are collected from previous work. Three main different control strategies; Linear Quadratic Gaussian (LQG) which combines the Linear Quadratic Regulator (LQR) with the Kalman Filter Estimator (KFE), Optimal Static Output Feedback (SOF), and Classic Feedback Controller (CFC); are studied and compared. The optimum actuators and sensors locations are determined using the Norm of Feedback Control Gains (NFCG) and Norm of Kalman Filter Estimator Gains (NKFEG), respectively. A genetic algorithm (GA) optimization technique is used to calculate the controller and estimator parameters to achieve a target response.     

Perturbations in the wall region using flush mounted piezoceramic actuators

The use of triangular shaped piezoceramic actuators in the near-wall region of turbulent shear flows is described. These actuators are very thin so that they can be flush mounted on the wall which greatly simplifies their application. The piezoceramic material was driven by an oscillating voltage that produced a mechanical deformation of the actuator. The magnitude of the deformation, and thus the amplitude of the disturbance, depended upon the voltage and geometry of the actuator. The forcing frequency was sufficiently high that the temporal aspect of the disturbance was rapidly dissipated. Measurements of the streamwise velocity component document the spatial extent of the perturbation. Received: 27 March 1998/Accepted: 20 July 1999     

Wave based active vibration control of a membrane antenna structure

This paper studies the wave based active vibration control of a membrane antenna structure. The membrane antenna structure studied in this paper has a great prospect in aerospace engineering. First, the dynamic model of the membrane antenna structure is established based on the finite element method. Then, based on the hypothesis of modal excitation mechanism, a wave-based controller is designed using the wave attenuation method. This method does not depend on the wave transfer function of the structure, so it can be applied to structures with complex shapes and boundaries. At last, the validity of the presented controller is verified through numerical simulations. Simulation results indicate that the dynamic behavior of the membrane antenna structure shows obvious wave characteristics; the presented controller can suppress the vibration of the structure effectively through holding back the formation of standing waves, and better control effect can be obtained when the actuators are placed near to the excitation point.     

大型索网天线机电耦合动力学建模与主动变形控制

索网天线因其折叠收纳比高、质量轻以及口径大等优点,成为众多空间任务的首选天线形式,但反射面精度较低限制了大型索网天线的在轨性能指标。在索网天线竖向张力索中加入压电陶瓷堆(PZT)作动器,通过主动控制提高反射面的形面精度。首先,将张紧的索网天线分为含有作动器的主动索单元和不含作动器的被动索单元,通过压电本构方程、几何方程和哈密顿原理推导出主动索单元的动力学模型,并与被动索单元一起组装得到索网天线的机电耦合动力学模型。然后,根据天线反射面的初始形面误差和所建立的天线机电耦合动力学模型,基于模型预测控制(MPC)方法计算出各作动器的控制输入电压曲线。最后,以一个10m口径的索网天线为算例,验证本文所建立的模型和控制方法的有效性。