Characterization of FGM monomorph actuators fabricated using EPD

Piezoelectric FGM monomorph actuators fabricated using electrophoretic deposition (EPD) were investigated. Both the physical and electromechanical properties were examined. The high voltage performance of the actuator in both static and dynamic state was focused. It was found that the monomorph exhibits tetragonal phase perovskite structure and the gradient variation of microstructure was observed over the cross section. The displacement keeps a wide range of linearity in the static state. In the dynamic state, the vibration displacement is both frequency and voltage dependent. The resonant frequency shifts to lower frequency range due to the higher vibration loss at higher voltages. This results in the frequency dependence of the vibration limitations. The vibration limitation is also voltage dependent. Above a cutoff voltage, the displacement may not increase. To obtain a higher resonant displacement or velocity, the frequency and voltage should match well. Temperature rise or heat generation is caused by vibration loss. The maximum temperature happens at the clamped end of the monomorph.     

Low-frequency meandering piezoelectric vibration energy harvester

The design, fabrication, and characterization of a novel low-frequency meandering piezoelectric vibration energy harvester is presented. The energy harvester is designed for sensor node applications where the node targets a width-to-length aspect ratio close to 1:1 while simultaneously achieving a low resonant frequency. The measured power output and normalized power density are 118 μW and 5.02 μW/mm(3)/g(2), respectively, when excited by an acceleration magnitude of 0.2 g at 49.7 Hz. The energy harvester consists of a laser-machined meandering PZT bimorph. Two methods, strain-matched electrode (SME) and strain-matched polarization (SMP), are utilized to mitigate the voltage cancellation caused by having both positive and negative strains in the piezoelectric layer during operation at the meander's first resonant frequency. We have performed finite element analysis and experimentally demonstrated a prototype harvester with a footprint of 27 x 23 mm and a height of 6.5 mm including the tip mass. The device achieves a low resonant frequency while maintaining a form factor suitable for sensor node applications. The meandering design enables energy harvesters to harvest energy from vibration sources with frequencies less than 100 Hz within a compact footprint.     

Quantitative Corrosion Monitoring Using Wireless Electromechanical Impedance Measurements

This article presents an experimental study for wireless monitoring of corrosion damage that might frequently occur in metallic structures. A simple beam structure made from an aluminum alloy was selected for corrosion-monitoring testing and a small lead-zirconate-titanate (PZT) patch-type sensor was surface-mounted to the structure. To obtain an electromechanical impedance data at the PZT sensor, a wireless impedance sensor node that consists of a miniaturized impedance-measuring chip, a microprocessor, and a radio frequency (RF) telemetry was employed. Three different corrosion cases with a different corroded area were artificially inflicted on the beam structure using hydrochloric (HCI) acid, and the electromechanical impedance data were collected in sequence from the wireless impedance sensor node. To quantify the corroded area, the variations of the resonant frequency that represents structural dynamic information were continuously tracked during all the damage cases. Conclusively, it has been found that the amount of the resonant frequency shift got increased when the corroded area got increased. The above experimental results verified that the proposed approach using the amount of resonant frequency shift at the measured electromechanical impedance can be effectively utilized for quantitative analysis of the corroded area in metallic structures.     

Optimal design of cubic nonlinear energy harvester device for random vibrations

Linear energy harvesters have a narrow frequency bandwidth and hence operate efficiently only when the excitation frequency is very close to the fundamental frequency of the harvester. Consequently, small variations of the excitation frequency around the harvester’s fundamental frequency drop the energy output making the harvesting process inefficient. To extend the harvester’s bandwidth, some recent solutions call for using electromechanical devices with stiffness-type nonlinearities. This work deals with the optimisation of the performance of a single degree-of-freedom electromagnetic energy harvester whose mechanical behaviour has a Duffing-type nonlinearity, as for suspended masses, to reduce the size of energy harvesting devices without affecting their power output. The vibration input is assumed as a broadband Gaussian white noise base acceleration. It is analytically shown that the optimum load resistance of the device is different to that which is dictated by the principle of impedance matching.     

间接激励压电发电机的建模仿真与试验研究

为满足旋转机械监测系统的自供电需求、解决现有压电发电机可靠性低及有效带宽窄等问题,提出一种基于移动凸轮间接激励并限幅的旋转式压电发电机(简称间接激励压电发电机).介绍了发电机的结构原理并进行了建模仿真与试验测试,获得了激励磁铁数量比、凸轮升程及升角对激振力形式/幅值、压电振子变形量/输出电压及发电机带宽等的影响规律.结...     

悬臂梁压电振动能采集器的集总参数模型和实验验证

压电振动能采集器是无线传感节点的一种理想电源,近年来受到广泛关注．考虑质量块和逆压电效应影响,建立了在基础激励作用下的悬臂梁压电振动能采集器的集总参数运动微分方程,得到了采集器固有频率的解析表达式．引入了2个反映压电层连接方式的常数,建立了对单压电层、双压电层并联和双压电层串联的悬臂梁压电振动能采集器均适用的耦合电路方程．求解以上方程,得到了简谐基础激励下的输出电压表达式．实验结果表明,固有频率和输出电压表达式的相对误差分别小于10％和20％．     

三叠片压电复合换能器弯曲振动的比较研究

用瑞利法对三叠片弯振圆盘换能器在三种不同边界条件下的振动特性进行理论研究,推导了谐振频率及有效机电耦合系数的表达式,通过数值计算分析了复合换能器的谐振频率及有效机电耦合系数随换能器各结构参数的变化规律并进行比较研究,同时将计算结果与有限元模拟结果比较,结果表明不同边界条件下换能器的结构参数对谐振频率和有效机电耦合系数影响不同:在换能器结构参数一定时,自由边界条件下谐振频率最大,简支边界条件下最小,固定边界条件下次之;有效机电耦合系数随着金属片厚度、陶瓷片厚度和陶瓷片半径变化时,分别有一个最大值;其他参数一定时,有效机电耦合系数在简支边界条件下最大,自由边界条件下的值稍大于固定边界条件下的值。上述研究结果可为三叠片弯曲振动换能器的设计和实际应用提供一定的理论支持。     

Modeling and analysis on ring-type piezoelectric transformers

This paper presents an electromechanical model for a ring-type piezoelectric transformer (PT). To establish this model, vibration characteristics of the piezoelectric ring with free boundary conditions are analyzed in advance. Based on the vibration analysis of the piezoelectric ring, the operating frequency and vibration mode of the PT are chosen. Then, electromechanical equations of motion for the PT are derived based on Hamilton's principle, which can be used to simulate the coupled electromechanical system for the transformer. Such as voltage stepup ratio, input impedance, output impedance, input power, output power, and efficiency are calculated by the equations. The optimal load resistance and the maximum efficiency for the PT will be presented in this paper. Experiments also were conducted to verify the theoretical analysis, and a good agreement was obtained.     

Design,real-time modelling,simulation and digital implementation of phase-locked loop-based auto-synchronising current-sourced converter for an induction heating prototype

Induction heating (IH) converters operate just above resonant frequency, at near unity power factor (UPF), to supply power to the targeted work-piece. Some power electronic converter-fed IH systems use power control strategies based on dynamic tracking of the changing resonant frequency as the work-piece gets heated up (since inductance changes). Therefore, the correct in-process determination of the resonant frequency is essential. A method of dynamically detecting the resonant frequency is by calculating the phase-shift between current and voltage continuously during the process. In case of CSI- (and VSI-) fed IH, the phase-shift between voltage and current is zero at resonant frequency. Hence one way of identifying the resonant frequency is by varying the frequency until the phase-shift is zero. For controlling this phase-shift between current and voltage waveforms, most of the controllers use a phase-locked loop (PLL) IC. In this paper, a novel method for the dynamic tracking of resonant frequency is proposed and the practical implementation of the same, using a field-programmable gate array (FPGA) based digital-PLL, is presented. The scheme is first simulated with generated off-line signal samples and then implemented on a real-time model of a CSI-fed IH application. Finally, the digital-PLL logic is implemented on controller hardware and practically tested in a laboratory-made experimental set-up of 2 kW at a nominal frequency of 10 kHz. The switching frequency is auto-synchronising. This fact is practically verified both by varying (i) the geometric dimensions as also (ii) the initial temperature of the work-piece. It is practically observed in the oscillograms that the phase gets locked in few cycles (and hence ensures quick tracking of the dynamically changing resonant frequency for this set-up).     

Electrical power generation characteristics of piezoelectric generator under quasi-static and dynamic stress conditions

The electrical characteristics of a piezoelectric power generator are investigated under quasi-static (duration >100 ms) and dynamic (stress duration <10 ms) stress applications. The electromechanical model of piezoelectric generator is presented and used to explain the effects of the two stress conditions. A computer simulation of the piezoelectric generator is used to compare the theoretical and experimental results. The simulation predicts that a quasi-static stress will produce a bidirectional generator output voltage, and a dynamic stress will produce a unidirectional output voltage. The simulation also predicts that, when equal stresses are applied to the generator, the dynamic stress will generate a 10/spl times/ higher output voltage than the quasi-static stress, contradicting results reported by other investigators. The output voltage is different for the two cases because of the generator's resistive capacitive (RC) time constant. The dynamic stress is applied in a time that is less than the generator's RC time constant, and the quasi-static stress is applied in a time greater than the generator's RC time constant. The piezoelectric capacitance has enough time to charge in the quasi-static case, resulting in the lower output voltage. The simulation results are experimentally verified for leaded zirconia titanate PZT 5H and PZT 5A materials. Simulated and experimental results are shown to be in good agreement.     

A novel driver with adjustable frequency and phase for traveling‐wave type ultrasonic motor

Abstract

This paper describes the design of a traveling‐wave ultrasonic motor (TWUSM) drive circuit, intended to simultaneously employ both driving frequency and phase modulation control. The operating principles and a detailed analysis of the proposed driving circuit, consisting of voltage‐controlled oscillator (VCO), voltage‐controlled phase‐shifter circuit and non‐resonant power amplifier converter, are introduced. To drive the USM effectively, a two‐phase power amplifier converter using non‐resonant output was designed to provide a balanced two‐phase voltage source. Two‐phase output driving voltages could be maintained at the same peak voltage value as the driving frequency under varying phase‐modulation processes. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.     

Study of an infrasonic generator

Summary As the result of the tests carried out by us it was established that the electromechanical infrasonic generator provides two sinusoidal voltages, displaced in phase by 90°. The phase angle error between these voltages does not exceed ±0.2 the range of the generated frequencies is 0.01–1 cps; the frequency instability does not exceed ±0.2%; the maximum output voltage is 100 v; the amplitude instability does not exceed ±0.3%; the nonlinear distortion factor does not exceed ±0.5 %; and the maximum background noise and interference at the output does not exceed 300 mv in the dynamic operating condition.The generator completely satisfies the requirements of precision measuring generators in the range of infrasonic frequencies.G. A. Martynov and Yu. I. Yanova participated in this development work.     

一种新型软开关BUCK变换器

本文提出一种新型软开关BUCK变换器。所提出的变换器具有如下的优点,零电压、零电流导通,零电压关断;不增加开关管的电压电流应力;输出电感电流工作在连续电流模式,其纹波很小;变换器可以工作在固定的频率,采用PWM控制。由于软开关的使用,变换器可以工作在很高的频率,同时其效率也很高。Pspice软件仿真验证了该电路的理论设计和分析。     

Magnetoelectric performance of cylindrical Ni–lead zirconate titanate–Ni laminated composite synthesized by electroless deposition

The cylindrical Ni–lead zirconate titanate (PZT)–Ni laminated composites with various magnetostrictive–piezoelectric phase thickness ratios were synthesized by electroless deposition. The influences of the bias magnetic field (H _dc) and the ac magnetic field frequency (f) on magnetoelectric (ME) effect are discussed. It is seen that the ME voltage coefficient depends strongly on H _dc and f. The ME voltage coefficient and electromechanical resonance frequency increase as the magnetostrictive–piezoelectric phase thickness ratio increases. The calculated resonant frequency increases with the magnetostrictive–piezoelectric phase thickness ratio, which agrees well with the experimental results. The maximum ME voltage coefficient of the cylindrical Ni–PZT–Ni laminated composite is 3.256 V cm⁻¹ Oe⁻¹, which is much higher than that of the plate laminated composite with the same magnetostrictive–piezoelectric phase thickness ratio. Electroless deposition is an efficient method to prepare ME laminated composites with complex structures. Proper resonant frequency and stronger ME effect can be obtained by optimizing the structure.     

高频热声制冷机中的压电喇叭特性

研究建立了1台5 kHz微型热声制冷实验样机,对压电喇叭谐振系统的阻抗特性,以及频率和电压响应特性进行了实验研究.初步的实验显示,压电喇叭与驱动电源和热声谐振系统之间需要在电学和声学上进行匹配,PZT5的压电陶瓷材料发热较大,且提供的声功率较小,这些是影响微型制冷的重要因素.     

基于STM32的频率和功率可调非接触供电超声电源设计

为解决接触式供电中漏电、磨损、电能传输不良以及超声电源在加工中谐振频率漂移、跟踪速度慢、输出功率不稳定等问题,文章以STM32单片机作为主控系统,设计了一种频率和功率可调的非接触供电超声电源。根据采样反馈电路采集的电压电流相位差和有效值信号,采用锁相环和模糊比例积分(Proportional Integral, PI)控制相结合的方法对频率进行跟踪,并用传统 PI 控制法控制输出功率。在 Matlab 软件中搭建电源仿真模型,利用附加电阻、附加电感和附加电容模拟加工过程中负载参数的突变,对有频率调节和功率控制子系统以及没有子系统的电源模型分别进行仿真。仿真结果表明,电源输出功率稳定在 248 W。当负载参数发生改变时,电源的谐振频率发生漂移,经过频率自动跟踪子系统的调节后,电源在 0.01 s 后重新回到谐振状态。此控制算法实现了频率快速跟踪和功率控制。     

Effect of subgrade on piezoelectric energy harvesting under traffic loads

Piezoelectric energy harvesting in roads generated by traffic loads was theoretically and experimentally investigated, and an indoor model of a layered road for piezoelectric transformation was developed using the traffic load model groove. Elastic double-layer beams resting on the subgrade soil were used to consider piezoelectric energy harvesting under traffic loads. Based on the vibration differential equations of elastic double-layer beams, the electromechanical equation was obtained using the Fourier transform. The experimental results of the piezoelectric energy harvesting were close to the theoretical ones, which indicated that the proposed method was useful in predicting piezoelectric energy harvesting from roads under traffic loads. The results also show that the influence of the transducer position on the output voltage and power should be considered, and that the thickness of the concrete panel and the condition of the subgrade soil can affect the output voltage and output power of the piezoelectric transducer. Moreover, the electrical energy was proportional to the vibration frequency and the excitation load.     

A multisource energy harvesting utilizing highly efficient ferroelectric PMN-PT single crystal

This paper demonstrates a multi-source energy harvester that is able to utilize simultaneously both piezoelectric and pyroelectric effects in lead magnesium niobate-lead titanate (PMN-PT) single crystal. The paper presents a study of PMN-PT single crystal with a (67:33) composition grown in our laboratory via a vertical gradient freeze method without any flux. The performance of the piezoelectric and pyroelectric energy harvester using unimorph device structure was evaluated via modeling and experiment. The theoretical study was implemented based on a distributed parameter electromechanical model and the modelling procedure was approximated using finite element analysis to predict the electromechanical behavior of the harvester. The maximum power density at a resonance frequency of 50 Hz and optimum resistance of 2 MΩ was 16.7 nW/(g² cm³) under a 1 g acceleration of vibration. The measured values of electrical output parameters were in good agreement with theoretical and modelling results using MATLAB and COMSOL Multiphysics, respectively. By using the pyroelectric effect along with the piezoelectric effect, the output voltage of the energy harvester was found to be enhanced at the optimum resistance and specific frequency values. It was noticed that the output voltage was increased monotonically with temperature-difference (ΔT) and reaches up to 180 % of its original value under temperature difference of 1.7 °C at a frequency value of 49 Hz.     

新型箝位式压电电机的设计研究

针对传统箝位式压电电机在谐振态下工作时,方波振动的箝位部分结构设计复杂问题,提出一种新型箝位式压电电机。该电机箝位部分与驱动部分均由同频正弦电压驱动实现正弦振动,通过定子对动子的箝位接触,实现动子单向输出运动。相较于传统箝位式压电电机和超声电机,该电机的定子结构设计无需采用模态简并,结构设计难度降低。利用有限元仿真确定定、动子结构参数,制造样机并搭建实验平台。对箝位部分分别采用正弦波与方波做激励,再对驱动部分进行波形对比,表明正弦波亦能达到预期效果。实验结果表明:准静态时,激励电压频率为250Hz、电压峰峰值Vp-p为10V时,步进距离为0.5μm,步进速度0.13mm/s;谐振态时,激励电压频率为540Hz、电压峰峰值Vp-p为70V时,步进距离为32μm,步进速度16.9mm/s;该电机可兼顾低频高分辨率和高频高速输出以实现跨尺度工作。     

Electromechanical analytical model of shape memory alloy based tunable cantilevered piezoelectric energy harvester

International Journal of Mechanics and Materials in Design - The resonant frequency of electromechanical energy harvester should be tuned to ambient frequency so as to maximize the harvester power....