Optimal design of an ultrasonic transducer

An ultrasonic transducer, consisting of two piezoelectric ceramic disks and two resonance rods, is optimized with respect to the shape of the two resonance rods in order to maximize the amplitude of the vibrating tip. The mathematical model is presented and a finite element model of the transducer is set up. Harmonic analysis (forced vibration) is used for calculation of resonance frequency, vibration mode, amplitude and phase. The resulting optimal shape is presented. The numerical analysis shows that the new design improves the amplitude 4.0 times. The improved transducer has been tested against the standard transducer and experiments show good agreement with theoretical results. A special design of the ultrasonic transducer for sonar applications has also been investigated. Applications of the improved ultrasonic transducer are more efficient transducers in high energy applications such as ultrasonic welding, drilling, disruption, cleaning, and sonar and underwater communication.     

Forced vibration analysis of piezoelectric quartz plates in resonance

Quartz is a widely used piezoelectric material and quartz resonators are the primary components in many industrial applications due to the piezoelectric effect. To have a thorough understanding on the vibration characteristics of quartz plates, the experimental measurement of resonant frequencies and mode shapes is indispensable. In this paper, two experimental techniques, amplitude-fluctuation electronic speckle pattern interferometry (AF-ESPI) and laser Doppler vibrometer (LDV), which are, respectively, full-field and point-wise displacement measurement methods, are used to obtain the out-of-plane vibration characteristics of AT-Cut quartz in real time. The resonant frequencies and the corresponding vibration mode shapes are successfully obtained at the same time from AF-ESPI method. However, only the resonant frequencies of the out-of-plane vibration modes are determined by the LDV. The cantilever and completely free quartz plates are used in this study and the experimental results are verified by the finite element method (FEM) analysis. The cantilever quartz plates are excited from applying voltage and acoustic waves. Furthermore, three designs of electrode for a quartz plate with free-boundary condition are studied. Excellent agreement between the measured data from the optical method and the numerical results predicted by FEM are found for both resonant frequencies and mode shapes.     

基于压电的大尺寸原理样机模型和实验

为了实现环境振动能量的低频收集,分析了压电式振动能量收集技术的特点,并建立了其数学模型。利用数值分析软件对能量收集器的性能进行了仿真模拟,压电式能量收集器更适用于低频环境下的能量收集。成功制造了具有四根环形悬臂梁结构的大尺寸原理样机,实验得到了在外界0～500 Hz低频扫频下,不同加速度激励下的开路电压、负载电阻的电压输出,并与理论分析结果对比。     

Resonant-Type Smooth Impact Drive Mechanism Actuator with Two Langevin Transducers

A smooth impact drive mechanism (SIDM) is a unique piezoelectric actuator that is widely used as a camera focusing mechanism, cell phone lens movement mechanism, etc. This principle enables a compact driving mechanism; however, it cannot generate high-speed movement because a soft-type multilayered piezoelectric transducer (PZT) is utilized at off-resonant movement. This paper proposes a resonant-type SIDM actuator driven with hard-type PZTs to realize high-speed and powerful operation. The fundamental principle is also based on the conventional SIDM; therefore, a saw-shaped movement is required. To generate a high-power ultrasonic output, two Langevin transducers are adopted instead of a soft-type multilayered PZT. One Langevin transducer was a stator and the other was slider whose tip was adhered to a carbon fiber reinforced plastic (CFRP) rod. The CFRP rod was connected to the stator transducer with the frictional force. To obtain quasi-saw-shaped vibration, the longitudinal vibration for each Langevin transducer was excited and these movements were added at the connection point at the CFRP rod. In order to combine these vibration modes, the lengths of the stator and slider Langevin transducers were designed to make the resonant frequencies ratio to be 1:2. By using the proposed principle, the slider Langevin transducer was successfully driven with the speed of 0.11 m/s and the output force was 1.8 N with no load.     

基于ANSYS的压电圆片振子径向振动模式分析

压电陶瓷问世不过几十年,然而发展非常迅速,压电陶瓷振子的应用日趋广泛.为了更深入研究压电振子的特性,在ANSYS的软件平台上,对压电圆陶瓷片振子进行建模仿真;利用有限元分析方法,得到压电圆陶瓷片的多阶振动模式.再根据谐振理论,对其输入导纳-频率关系进行分析.结合模态分析结果文件进行筛选,得到了压电陶瓷圆片径向振动频率,最后通过理论分析和实验测试,验证了仿真值比理论值更接近测试值.相对传统的振动模式分析方法,此方法更为简单、准确、直观.     

Comparative study of conventional and magnetically coupled piezoelectric energy harvester to optimize output voltage and bandwidth

Energy harvesting has experienced significant attention from researchers globally. This is due to the quest to power remote sensors and portable devices with power requirements of tens to hundreds of μW. Hence, ambient vibration energy has the potential to provide such power demands. Thus, cantilever beams with piezoelectric materials have been utilized to transduce mechanical energy in vibrating bodies to electrical energy. However, the challenge is to develop energy harvesters that can harvest sufficient amount of energy needed to power wireless sensor nodes at wide frequency bandwidth. In this article, piezoelectric energy harvester (PEH) beams with coupled magnets are proposed to address this issue. With macro fiber composite as the piezoelectric transducer, mathematical models of different system configurations having magnetic couplings are derived based on the continuum based model. Simulations of the system dynamics are done using numerical integration technique in MATLAB software to study the influence of magnetic interactions in generating power and frequency bandwidth due to base excitations at low frequency range. Experimental results comparing conventional system and the proposed piezoelectric beam configurations with coupled magnets are also presented. Finally, the optimal beam separation distance between the magnetic oscillator and PEH is presented in this work.

     

压电传感器在动平衡测量系统中的设计与应用

传感器是动平衡测量系统中的重要元件之一,是一种将不平衡量产生的振动信号不失真地转变成电信号的装置.利用压电式力传感器作为动平衡测量系统中的敏感元件来测量不平衡质量引起的振动.重点阐述了该压电式力传感器的结构设计、安装位置设计及振动信号检测中的关键问题.同时,详细分析了该传感器的信号调理电路特点.现场实验结果表明,设计的压电式力传感器在动平衡测量中的性能良好.     

基于BP神经网络的矩形压电振子振动模态区分*

采用BP神经网络,把矩形压电振子的各阶振型位移输入到神经网络中进行训练,提取各阶模态的振型特征,可实现矩形压电振子的共振振幅分布和振动模态阶次的非线性映射,以此区分各个模态。仿真实验结果显示,建立的神经网络模型可以从ANSYS输出的各模态中准确识别出矩形压电振子的B(3,1)模态,对训练样本外的尺寸也有一定的识别效果,表明所建立的BP神经网络可以有效地用于该矩形压电振子的振动模态区分。     

基于STM32的燃气轮机振动监测系统的设计

为了能够准确、实时的提取燃气轮机关键部位在关注频段内的振动数据,设计了一种燃气轮机振动监测系统.该系统以STM32为核心处理器,通过加速度传感器对振动信号进行采集,利用积分放大电路、外置高精度模数转换电路和数模转换电路等进行信号调理,辅助FIR的数字滤波窗函数进行频段内振动数据的提取,并用仿真分析验证其滤波算法的准确性.经实际试验结果验证,该振动监测系统具有工作稳定、精度高、频段提取准确的优点,能够满足实际工程要求.     

一种高频宽带水声换能器的研制

研制了一种宽带、高频压电复合材料圆环阵水声换能器.该换能器的宽带结果是通过采用降低压电材料机械品质因数Qm值和多模耦合振动两种方法实现的.通过径向切割压电陶瓷圆环、灌注环氧树脂得到压电复合材料圆环,再将不同壁厚的压电复合材料圆环轴向叠堆而成敏感元件,对敏感元件进行模具封装,引出电极引线,得到换能器.利用ANSYS软件对结构进行仿真,得到敏感元件谐振频率和带宽随压电陶瓷圆环厚度、高度和平均半径的变化规律,并根据仿真结果确定了换能器敏感元件的最优设计方案.将由最优参数得到的两个压电复合材料圆环轴向叠堆,制作了双圆环叠堆复合材料换能器.经测试,该换能器形成了明显的双模耦合振动,该换能器谐振频率为375 kHz,其-3 dBd工作带宽为90 kHz,最大发送电压响应达148 dB.实现了换能器的高频、宽带、水平全向发射声波的设计目标.     

水平剪切声板波的激发机理及其特性研究

水平剪切声板波(SH-APM)是在板状固体结构中传播的一种声波,其质点振动垂直于传播方向和界面法线。针对SH-APM的激发机理和激发特性两个方面展开研究。首先通过分析压电介质的Christoffel方程组解耦情况来研究SH-APM的激发机理,推导出为了在压电板上激发出SH-APM,压电基片的材料常数所必须满足的条件;然后在此基础上,建立了SH-APM器件的理论分析模型,并以PZT-5H压电陶瓷为例,研究了SH-APM的激发特性,包括激发模态、传播速度、激发效率、振动位移等;最后,通过实验以及理论计算与相关文献对比,证明了理论模型的正确性及研究结果的有效性。     

Structural response of composite plates equipped with piezoelectric actuators

We propose the modelling of piezoelectric elements perfectly bonded on an elastic structure. The study aims at predicting the static and dynamic (vibration) electromechanical responses of the structure. The model is mostly based on the kinematic assumption of the Love–Kirchhoff thin plate theory including shear function with a quadratic variation of the electric potential along the thickness direction of the piezoelectric parts. A variational formulation of piezoelectricity leads to the equations of motion for an elastic plate equipped with piezoelectric elements. An important feature of the present investigation is that the stiffness and inertial contributions of the piezoelectric patch is not neglected. Moreover, the numerical simulations demonstrate the influence of the actuator position on the global and local responses of the elastic plate for two situations (i) bilayer and (ii) sandwich configurations. A number of benchmark tests are considered in order to characterize the plate deformation when applying an electric potential to the piezoelectric patch faces. Plate vibration problem is also presented and the frequencies for the axial and flexural modes are obtained. The spectra of vibration for the plate with a time-dependent electric potential are computed.     

Tonpilz型压电陶瓷超声传感器的设计

超声传感器是一种电声转换器件,其敏感元件压电陶瓷控制传感器的主要性能。设计了一种谐振频率为140 kHz的Tonpilz型压电陶瓷超声传感器,从压电方程入手,建立了不同的理论模型,对等效网络法和有限元法2种不同的设计方法进行了比较。相应的试验表明:有限元法的分析结果直观明了、建模快捷、分析准确,其误差可控制在5%以内。设计研制的Tonpilz型传感器工艺简单、造价低廉、性能稳定。     

压电纤维复合材料层合壳的非线性动力学研究

本文对横向激励作用下的1-3型压电纤维复合材料层合壳进行了非线性动力学分析,并研究了压电特性对结构振动响应的影响.首先建立了压电纤维复合材料层合壳的非线性动力学方程,并且在已知的几何结构和材料特性基础上考虑了电场属性.然后根据位移边界条件,选择合适的振型函数,通过Galerkin方法将运动控制方程转化成两自由度的非线性常微分方程.通过数值模拟方法分析了横向激励和压电系数对压电纤维复合材料层合壳非线性振动特性的影响.通过波形图、三维相图、庞加莱图和分叉图等来研究壳体不同类型的周期和混沌运动.结果表明,外激励作用下结构存在复杂的非线性振动响应,同时压电参数对层合壳结构振动响应具有很强的调节作用.     

Structural damage identification for thin plates using smart piezoelectric transducers

An impedance-based structural damage identification method for thin plates is presented in this paper using piezoelectric ceramic (PZT) transducers. The local damages are characterized by introducing a damage parameter in each finite element. A two-dimensional electromechanical impedance model is proposed to predict the electric admittance of the PZT transducer bonded to the plates. The general equations for generating structural dynamic stiffness from normal modes are formulated based on finite element analysis. The first-order perturbation method is introduced to obtain the electric admittance change on PZT transducers due to damage. A damage identification scheme for solving nonlinear optimization problem is proposed to locate and quantify the damage by matching the numerical and experimental electric admittance change on PZT transducers. The proposed technique is verified through numerically simulated damage identification tests.     

Design of piezocomposite materials and piezoelectric transducers using topology optimization— Part III

Summary Following the topic introduced in [1, 2] this paper discusses the design of piezoelectric transducers used in applications such as acoustic wave generation and resonators. These applications require goals in the transducer design such as high electromechanical energy conversion for a certain transducer vibration mode and narrowband or broadband response. The development of these devices has been based on the use of simple analytical models, test of prototypes, and analysis by the finite element method. However, in all cases the design is limited to a parametric optimization where only some dimensions of a chosen transducer configuration are optimized. By changing the topology of these devices or their components, we may obtain devices with better performance since the design space of solutions is enlarged. Based on this idea, we have proposed the use of topology optimization for designing these devices. This method consists of finding the distribution of the material and void phases in the design domain that optimizes a defined objective function. The optimized solution is obtained using Sequential Linear Programming (SLP). Considering acoustic wave generation and resonator applications, three kinds of objective functions were defined: maximize the energy conversion for a specific mode or a set of modes; design a transducer with specified frequencies; and design a transducer with narrowband or broadband response. Although only two-dimensional plane strain transducer topologies have been considered in order to illustrate the implementation of the method, it can be extended to three-dimensional topologies. Transducer designs were obtained that conform to the desired design requirements and have better performance characteristics than other common designs.     

基于Patran和MSC Nastran的压电智能桁架结构振动模态分析

用Patran和MSC Nastran分析压电智能桁架结构振动模态,验证基于有限元法建立的智能桁架结构机电耦合动力学模型的正确性和有效性.结果表明：采用Patran和MSC Nastran针对2种典型压电智能桁架结构开展振动模态分析的结果,与采用基于有限元法建立的数学模型计算得到的模态频率及实验测试模态频率近似相等,验证基于有限元法模型的正确性和有效性,为开展主动振动控制器的设计提供模型和技术支持.     

柔性智能结构的振动主动控制仿真和实验研究

基于模态坐标表示的含压电片结构横向振动系统方程,采用独立模态法直接针对系统的高阶模型设计控制律,利用劳斯判据证明由所设计的控制器引起的控制溢出可被有效抑制,极大地降低了由于模型降阶引起的误差。同时,对压电柔性悬臂梁的高阶振动模态进行主动控制仿真模拟和实验研究,结果表明施加主动控制后柔性悬臂梁的模态阻尼显著提高,受控悬臂梁的振动得到了快速抑制。仿真计算和实验结果取得了良好的一致性。研究结果表明,利用压电陶瓷作为驱动元件,采用独立模态控制法实现柔性结构的振动抑制是一种高效的振动主动控制方法,在航天航空等领域中     

基于滚压的压电叠堆压电转换特性仿真分析

本文提出一种基于滚压的压电俘能器结构,结合Cymbal压电换能器和压电振子叠堆,利用滚珠作为激励源,可以把机构的往复振动转换为对压电振子的单向压迫.使用仿真软件对俘能器结构中滚珠压迫压电单元的力,以及该俘能器结构在并联和串联模式下输出的电压和俘获的电能进行仿真分析,得到该结构的压电转换特性.仿真结果表明,滚珠对压电叠堆的压迫力与压电陶瓷层数并不是单向递减,1-5层时递增,5层以后压迫力逐渐减小.在压电陶瓷的总层数不变的情况下,并联和串联时压电叠堆所俘获的总电能是不变的.两种联接模式下总电能随层数的变化关系为5层以内时随层数的增加而减小,超过5层后逐渐增加.     

提高振动发电机充电效率实验研究

为提高压电单晶悬臂梁振动发电机充电效率,建立集能量捕获存储于一体的振动发电储能系统,测试了同一规格陶瓷片贴于梁不同位置发电机的发电与充电性能,试验发现:在一阶与二阶振动模态下,各存在一个最佳粘贴位置可使发电机充电效率得到显著提高.在一阶模态下,陶瓷片贴于悬臂梁根部时,发电机充电时间最短;对于二阶模态,陶瓷片贴于梁中间位...