基于特征模型的压电悬臂板振动控制

航天器上悬臂板型挠性附件在扰动作用下将引起包括弯曲和扭转模态的振动,这将影响系统的稳定性和控制精度,尤其是在平衡点附近低频模态频率上的小幅值残余振动很难快速抑制。为了快速抑制压电智能挠性悬臂板系统,包括弯曲和扭转模态的振动,提出采用基于特征模型的非线性黄金分割自适应控制,组合非线性切换逻辑积分阻尼器算法。首先,优化配置压电传感器和驱动器实现了悬臂板的弯曲和扭转模态在检测和驱动上的解耦;其次,设计并建立压电挠性悬臂板试验平台,进行试验模态辨识并获得了悬臂板系统弯曲和扭转振动的模态频率和频响特性;最后,进行压电智能悬臂板的弯曲和扭转振动模态主动振动几种方法试验的比较研究。试验结果表明,采用的控制方法能够快速地抑制压电智能挠性悬臂板的振动。     

基于Lamb波的压电陶瓷/环氧树脂复合材料传感器制备及应用

风力机叶片、飞机机翼等结构均为大面积曲面板类结构,基于Lamb波的结构健康检测技术对细微损伤比较敏感,是目前最具应用前景的技术之一。传统的Lamb波传感器大都采用PZT陶瓷制成,质地脆且硬度大,不能适应于曲面结构检测。将PZT陶瓷粉末与环氧树脂复合制备了一种新型柔性0-3型压电复合材料,研究了质量比、极化电场、极化温度和极化时间等因素对压电复合材料性能参数的影响,开展了多因素正交实验来确定材料制备的最优极化工艺参数。实验研究了该压电复合材料制成的传感器对Lamb波的传感响应特性,与现有的MFC、PVDF和传统压电片等传感元件的响应特性进行了对比分析。将制备的传感器应用于翼型曲面板,利用椭圆定位方法进行损伤检测。研究结果表明,PZT陶瓷/环氧树脂压电复合材料传感器具有良好的传感响应特性,能够很好地贴合于曲面板表面,与只能部分耦合于曲面板的传统压电片相比,采集的Lamb波信号更加准确,从而为曲面板类结构健康监测提供一种新型的柔性压电传感技术。     

Propagation behavior of SH waves in layered piezoelectric plates

In this study, the propagation of SH waves in a coupled plate consisting of a piezoelectric layer and an elastic layer is analytically investigated. The piezoelectric material is polarized in the z-axis direction and perfectly bonded to an elastic layer. The mathematical model of the SH wave propagation in this plate is based on the type of surface wave solution. Dispersion relations with respect to phase velocity are obtained for electrically open and mechanically free. Numerical examples are provided to illustrate graphically and compare the variations of the phase and group velocities versus the wave number for the different layers. The thickness ratio and the properties of the two layers have a significant effect on the propagation of SH waves. The conclusions are meaningful both theoretically and practically for the design of high-performance surface acoustic wave (SAW) devices.     

含压电谱单元及其在板结构中Lamb波传播模拟中的应用

结合压电材料本构方程及Lamb波数值模拟中的谱有限元方法,建立了含压电驱动器/传感器板的谱单元,并将其应用于Lamb波的激发、在板结构中的传播和接收的数值模拟中。将模拟结果与其他文献中的数值模拟结果及采用商用有限元软件ANSYS的数值模拟结果进行了对比,验证了所建立单元的正确性,且在计算精度相差不大的情况下,该方法较传统有限元方法更为高效。最后和以前不含压电的模拟过程进行比较,压电效应使得驱动器施加在节点上的力并不那么单一,并且传感器能够将多个自由度复杂的位移信号转换为单一的电信号,这使得考虑压电片与不考虑压电片的模拟结果之间有一定的差别。     

一种低成本测量材料杨氏模量的方法

杨氏模量是一种重要的材料参数,对结构的固有频率,刚度等有着直接的影响。材料杨氏模量测量方法一般有拉伸法、共振法等,但这些传统方法通常要用到较为昂贵的设备及传感器。为了减小测量成本,文中将压电陶瓷片作为传感元件,利用悬臂梁结构,通过测量自由振动频率,并利用力学公式反推出杨氏模量。文中分析了误差的来源,利用ANSYS软件进行结构仿真,讨论了附加的压电片对悬臂梁的影响,选取较薄的压电片以减小测量误差。实验验证了这种方法可用于杨氏模量的测量。未来可以研究使用电脑麦克风进行数据采集,代替示波器以进一步减小测量成本。     

柔性杆多次撞击过程的瞬态动力学分析

对双柔性杆多次撞击过程,采用St.VENANT杆波动理论,提出应用瞬态波函数特征值展开法,分别求解多次撞击和分离过程瞬态波响应理论解.应用该理论解,由撞击过程中两杆组合结构的撞击界面应力,计算多次撞击力响应,从而实现了对多次撞击问题的分析.数值计算表明,该方法可以合理的分析多次撞击过程,较精确的计算多次撞击力响应和结构瞬态波响应,并可进一步研究"次撞击"和瞬态波传播等物理现象,以及研究系统参数对多次撞击过程的影响.研究结果可为柔性结构多次撞击过程的瞬态响应分析和结构安全评估提供参考.     

基于惯性冲击原理的非对称夹持式压电旋转驱动器的实验研究

针对目前压电驱动器主要使用锯齿波这种非对称波电信号驱动压电晶体实现驱动的现状,设计了非对称夹持构件,提出了非对称夹持压电双晶片振子的旋转驱动器的结构设计方案,使对称波电信号作用在压电双晶片振子上,产生正反两方向大小不同的周期性惯性冲击力,驱动机构实现旋转位移。建立了压电旋转驱动器的动力学模型,并分析了非对称夹持旋转驱动器实现大小不同的惯性冲击力原理以及压电旋转驱动器的运动过程。组成了压电旋转驱动器的测试系统,在不同电压幅值、频率的方波激励下,对压电旋转驱动器的平均步长进行了测试。结果表明：非对称夹持式压电旋转驱动器能实现较稳定的单向转动,最大行程360°,最大承载能力超过300g,步长分辨率5µrad,最大转动速度4000µrad/s;驱动器样机在20V、2Hz的方波激励下,平均运动步长12µrad,转动速度24µrad/s。     

Rapid localization of damage using a circular sensor array and Lamb wave based triangulation

A damage detection and imaging methodology based on symmetry of neighborhood sensor path and similarity of signal patterns with respect to radial paths in a circular array of sensors has been developed. It uses information regarding Lamb wave propagation along with a triangulation scheme to rapidly locate and quantify the severity of damage without using all of the sensor data. In a plate like structure, such a scheme can be effectively employed besides full field imaging of wave scattering pattern from the damage, if present in the plate. This new scheme is validated experimentally. Hole and corrosion type damages have been detected and quantified using the proposed scheme successfully. A wavelet based cumulative damage index has been studied which shows monotonic sensitivity against the severity of the damage, which is most desired in a Structural Health Monitoring system.     

2A12铝合金圆波纹夹芯板抗平头弹冲击特性的试验研究

为研究铝合金圆波纹夹芯板对平头弹体的抗冲击性能,通过一级气炮系统开展弹体冲击铝合金圆波纹夹芯板以及等面密度单层均质板的试验.基于冲击试验数据,分析圆波纹夹芯板对弹体冲击的防护性能、失效模式和能量吸收情况,并与单层板进行对比,以获得两种靶板抗冲击性能的差异及原因.研究结果表明:弹体冲击圆波纹夹芯板的弹道极限速度低于单层板...     

An exact solution for functionally graded piezoelectric laminates in cylindrical bending

In the present paper, the exact solutions of a simply supported functionally graded piezoelectric plate/laminate under cylindrical bending are derived. With similar derivation procedure as that used for Stroh formalism, the eigenrelation and general solutions for the problems can be expressed in very concise forms, which are convenient for further treatments of both analytic and numerical studies. The exact solutions can be served as benchmarks to verify and improve various approximate theories and numerical methods. To show the influence of material gradients, numerical examples based on the exact solutions are given, and some properties of the mechanical and electric responses of the plates under mechanical and electrical forces are discussed.     

The deflection of a simply supported plate induced by piezoelectric actuators

The coupling effects between the mechanical and electric properties of piezoelectric materials have drawn significant attention for their potential applications as sensors and actuators. In this investigation, two piezoelectric actuators are symmetrically embedded in a simply supported plate. Electric voltages with the same amplitude and opposite sign are applied to the two symmetric piezoelectric actuators, resulting in the bending effect on the plate. The bending moment is derived by using the theories of elasticity and piezoelectricity. The analytical solution of the flexural displacement of a simply supported plate subjected to the bending moment is solved by using the plate theory. The analytical solution is compared with the finite element solution to show the validation of present approach. The effects of the size and location of the piezoelectric actuators on the response of a plate are presented through a parametric study.     

基于压电纤维传感器的Lamb波传播方向识别

利用压电纤维对Lamb波传感的良好方向性,将3根压电纤维按0°,45°和90°布置并固化在聚合物基体中,制成压电纤维传感器用于检测Lamb波传播方向。理论推导了窄带激励下压电纤维对Lamb波的方向传感响应特性,通过压电耦合仿真分析和实验测试研究了不同频率下压电纤维的方向传感特性,提出了一种基于误差函数的主应变方向估计方法,分析对比了直角三角形(0°,45°,90°)、Y形(0°,120°,240°)和等边三角形(0°,60°,120°)3种压电纤维布置方案下主应变方向识别结果。研究结果表明,压电纤维传感器具有良好的Lamb波传播方向检测性能,可为无需Lamb波波速的缺陷识别方法提供传感技术支持。     

Plate bending wave propagation behavior under metal sphere impact loading

A loose part can cause component damages and material wear on nuclear power plants; thus, a mass estimation of the loose part is crucial to safety management. A bending wave propagation of a structure under the loose part impact loading is precisely simulated to accurately estimate the mass of a loose part. Lamb’s general solution for an arbitrary impact force function and Hertz impact theory have been used to identify the characteristics of the bending wave that is impacted by a metallic loose part in reactor pressure boundary components. However, these approaches cannot provide accurate information on the acceleration response that is required to identify the impact source. In this study, the bending wave propagation behavior of plate structures under a simulated loose part (Metal sphere) impact loading was modeled using a Finite element analysis (FEA) technique. The characteristics (e.g., Maximum acceleration amplitude, primary frequency, and bending wave velocity) of the impact response signal from a metal sphere were analyzed with the FEA results and were verified with experimental results. In addition, the correlation between plate thickness and characteristic length was presented. Results from this study can be utilized to estimate the location and mass of a loose part for condition monitoring and diagnostics in nuclear power plants.     

Dynamic analysis of laminated composite plates with piezoelectric sensor/actuator patches using the FSDT mesh-free method

This paper investigates the active control of laminated composite plates with piezoelectric sensor/actuator patches using an efficient mesh-free method, i.e. the element-free Galerkin (EFG) method. The formulation of the problem is based on the first-order shear deformation plate theory (FSDT) and the principle of virtual displacements. A simple control algorithm coupling the direct and converse piezoelectric effect is used to control the dynamic response of the laminate plate with distributed sensor/actuator patches through a closed control loop. Several example problems are studied to show the influence of stacking sequence and position of sensor/actuator patches on the dynamic responses of the laminate plate. These simulations provide us with the best location of the sensor/actuator patches for active control of the laminate plate.     

带硬涂层圆盘构件的固有振动特性的精确解法

研究了在广义弹性简支边界条件下的具有硬涂层的圆盘构件的自由振动的量纲一固有频率的精确解.首先利用多铁性多层圆盘的解析分析的多层板弹性理论,导出带硬涂层的圆盘结构的状态方程,其中以位移、电势、磁势、应力、电位移和磁感应强度为状态变量.利用有限Hankel变换和传播矩阵法,得到考虑压电和压磁效应的带硬涂层的圆盘的量纲一固有频率的精确解.根据算例结果,比较了压电、压磁两类硬涂层材料在单面涂层、双面涂层和不同涂层厚度的结构配置下的固有频率变化规律.     

基于槽式悬臂梁结构的微质量传感器设计

压电式微质量传感器的测试精度直接依赖于结构频率对质量变化的灵敏程度。本文利用对称槽型梁和压电薄膜组成的对称敏感结构,提出了一种提高传感器灵敏度的结构设计方法,并设计了一种高精度谐振式微质量传感器。建立了结构频率变化对吸附质量敏感性的分析模型,并研究了槽型截面参数、自振频率及振动模态对灵敏度的影响。与矩形截面结构进行了仿真与实验对比,结果表明,相同几何尺寸参数下,槽型截面悬臂梁的一阶自振频率为1 851 Hz,矩形截面悬臂梁的一阶自振频率为1 610 Hz,相应的传感器灵敏度则分别为3.12×10⁴ Hz/g和1.5×10⁴ Hz/g,前者是后者的2倍。该项设计为提高微质量传感器灵敏度提供了一种新思路。     

一种用于鸭翼控制的摇头型双圆环压电马达研究

针对制导弹药平台对舵机的紧凑、直驱等要求,提出了一种采用夹心式换能器诱发双圆环弯曲振动的复合型压电定子结构,由此可构成结构精巧的摇头型双圆环旋转压电马达,用以驱动鸭式舵翼产生特定的偏转运动。该马达中的复合定子主体为一个具有四片压电陶瓷片的夹心式换能器,分别在换能器两输出端设计了利于放大振幅的环形圆盘;夹心式换能器的摇头运动激励出两端环形圆盘的五阶弯曲模态,通过圆环将输出振幅进一步放大;两个圆盘形转子在一定的预压力作用下与复合型压电定子两端的圆环表面保持紧密接触,通过摩擦将圆环表面的椭圆轨迹转换为转子的旋转运动。设计了可用于某制导系统鸭舵偏转操纵的直驱马达结构,建立了基于夹心式换能器的双圆环形定子结构动力学模型,通过有限元软件对定子的模态进行了仿真分析,设计并加工出了样机。搭建了测试平台对样机的输出特性进行了实验,测试结果表明：该双圆环（双）输出轴马达可实现双输出轴同时旋转,在300 V峰峰值的驱动电压下,最大转速可达190 r/min,最大输出扭矩可达0.07 N·m。     

应用惯性冲击原理的非对称夹持式压电旋转驱动器的设计

针对目前压电驱动器主要使用非对称锯齿波电信号驱动压电晶体实现驱动的现状,采用对称电压信号驱动压电振子,设计了非对称夹持式压电旋转驱动器。用对称波电信号作用在压电双晶片振子上,产生正反两个方向大小不同的周期性惯性冲击力,驱动机构实现旋转位移。建立了压电旋转驱动器的动力学模型,分析了非对称夹持旋转驱动器实现大小不同惯性冲击力的原理以及压电旋转驱动器的运动过程。组成了压电旋转驱动器的测试系统,在不同电压幅值、频率的方波激励下,对压电旋转驱动器的平均步长进行了测试。结果表明:非对称夹持式压电旋转驱动器能实现较稳定的单向转动,最大行程为360°,最大承载能力超过300g,步长分辨率为5μrad,最大转动速度为4000μrad/s;驱动器样机在20V、2Hz的方波激励下,平均运动步长为12μrad,转动速度为24μrad/s。     

基于压电悬臂梁的驱动器与传感器性能分析的精确解析模型

三层压电梁结构在电场作用下发生变形后会产生诱发电势,进而改变材料整体电势分布,本文考虑此变形和电势耦合效应,基于欧拉-伯努利梁变形理论,推导出能够准确预测压电智能悬臂梁传感器与驱动器性能的解析表达式。考虑压电梁结构弯曲变形后产生的电场影响,建立了三层压电梁结构的控制方程;建立了压电梁作为驱动器时端部输出位移、驱动力矩与输入电压之间联系的解析表达式,以及作为传感器时输出电压与端部作用力之间联系的解析表达式。通过与ANSYS有限元模拟结果以及传统的驱动器和传感器性能表达式的对比,验证了所推导的解析表达式的准确性。     

基于构型优化的高阶模态微质量传感器灵敏度提升方法

高灵敏度是微质量传感器准确探测细菌、病毒和气体等物质的关键指标。虽然借助微型化的高阶模态梁振动可以有效提升探测灵敏度,但微尺度效应也降低了传感器的抗环境干扰能力。因此,如何在特定尺度约束下提升高阶模态传感器的灵敏度已成为谐振式微传感器设计的前沿问题。本文在研究弹性梁几何构型、压电层尺寸与有效质量分布对振动模态影响关系的基础上,建立了压电驱动多阶梯梁式微质量传感器的灵敏度分析模型,以传感器灵敏度提升最大为目标,建立了高阶振动模态下悬臂梁几何构型优化设计模型,得到了在不同振动模态下具有最高灵敏度的悬臂梁构型,使同尺寸传感器的灵敏度提升了10.0~15.0倍。考虑驱动位置与制造成本约束,设计并研制了具有六阶梯梁结构的高阶模态微质量传感器。实验结果表明,总长度为17.6mm的六阶梯梁微质量传感器的灵敏度为18.8×10~4 Hz/g,考虑制造误差的影响,其二阶模态灵敏度为同尺寸等截面梁传感器的10.0倍,较一阶模态同尺寸传感器灵敏度提升了19.8倍,从而验证了所提出的高阶模态微质量传感器灵敏度提升方法的有效性和可行性。