压电悬臂梁发电机能量转换效率研究

为提高车轮轮毂振动下的压电悬臂梁发电机能量转换效率,根据哈密顿原理建立了发电机能量转换效率模型,利用数值模拟和试验分析的方法研究了发电机结构尺寸和材料特性对其能量转换效率的影响规律。研究表明,金属基板过厚或太薄、杨氏模量太小都不利于提高发电机的能量转换效率。在金属基板材料不同时,存在一个最佳厚度比(金属基板与总厚度之比)使发电机能量转换效率最高,铜、铝、钼3种金属基板材料的发电机最佳厚度比分别为0.67、0.72、0.45;在相同厚度比(0.5)条件下,钼基板的发电机能量转换效率较高,随着杨氏模量比(金属基板的杨氏模量与陶瓷的杨氏模量之比)的增大,发电机能量转换效率增高,但当杨氏模量比大于4时,发电机的能量转换效率变化不明显。     

基于压电陶瓷的人体能量收集系统的研制

为利用压电材料收集人体能量,设计了一种人体能量收集系统,它可在人行走过程中产生电能,该机构被安装在人腿的膝盖部位,选择性地在腿部摆动结束阶段连续地按压电陶瓷片参与发电,另外还设计了压电发电装置的能量存储与控制电路,并实验了其发电特性,该装置适合给假肢或其他便携式医学设备充电。     

低频压电陶瓷驱动器驱动电源研制

针对压电扫描驱动器的工作特点研制了一种压电陶瓷驱动器专用功率放大器 ,它可给驱动器提供很高的电压输出 (± 2 0 0 V(峰 -峰值 ) ) ,并且使驱动器在 5 0～ 2 0 0 Hz的工作频率进行扫描 ,也可适用于以逆压电效应为基本原理的压电器件在以动态输出为主要目的情况下应用。在同时考虑压电陶瓷驱动器的电子和机械两种性质的情况下 ,提出了一种新的功率放大器的设计方案 ,利用添加补偿电容和补偿电阻的方法来补偿自激的反馈极点     

一种基于压电片的能量转换装置及其优化设计

为完成环境能量向电能的转化,设计了一种利用压电元件转化环境能量的能量转换装置。该装置利用风力驱动悬梁臂式压力发电组件旋转,同时使压电片振动而产生电能。依据压电材料的基本理论建立了装置的输出模型,并采用基于状态空间模型的进化算法对装置进行优化设计。开展了能量转换装置的实验测试,实验结果表明,该装置可高效地完成环境能量向电能的转化。本装置的设计为清洁环境能源的收集提供了新方法,也指出了振动能量采集装置的研究前景。     

A Pneumatic Pressure Cycling System for an Artificial Heart

Included in this paper is a discussion of the operating principle, design, construction and testing of a stroke-limited, transistorized, pneumatic pressure cycling system for a single-chambered artificial heart. The system is free of valve-stiction catastrophes, and reveals that conventional calculations of heart power based on mean blood pressure, cardiac output and kinetic energy of the aortic blood should be augmented substantially to account for turbulence, valve resistance and pneumatic feedline distensibility. Graphs are presented to illustrate the over-all performance data.     

Three-Phase Low-Frequency Commutation Inverter for Renewable Energy Systems

The connection of distributed power sources with the utility grid generally needs an electronic power converter for processing the locally generated power and injecting current into the system. If the source provides a dc voltage, the converter must be able to produce a low-distortion high-power-factor ac current. The same aspects related with the voltage and current distortion produced by nonlinear loads can be considered for the injection of power into the grid. In the absence of a specific standard, this paper takes as a reference the limits for current harmonics given by international standards. The justification for this approach is that, from the resulting line voltage degradation, there is no difference between injected and absorbed currents. This paper presents a three-phase inverter using low-frequency commutation. An auxiliary circuit is added to the inverter topology to reduce the output voltage distortion, thus improving the current waveform. The main advantages of this approach are the minimization of the switching losses and the elimination of the electromagnetic interference, which avoids high-frequency filters necessary in high-frequency commutation inverters     

Toward Artificial Cells: Novel Advances in Energy Conversion and Cellular Motility

The demand to discover every single cellular component has been continuously increasing along with the development of biological techniques. The bottom‐up approach to construct a cell‐mimicking system from well‐defined and tunable compositions is accelerating, with the ultimate goal of comprehending a biological cell. From among the available techniques, the artificial cell has been increasingly recognized as one of the most powerful tools for building a cell‐like system from scratch. This review summarizes the development of artificial cells, from a pure giant unilamellar vesicle (GUV) to a controllable, self‐fueled proteoliposome, both of which are highly compartmentalized. The basic components of an artificial cell, as well as the optimal conditions required for successful, reproducible GUV formation and protein reconstitution, are discussed. Most importantly, progress in studying the metabolic reactions in and the motility of a reconstituted artificial cell are the main focus of the review. The ability to perform a complicated reaction cascade in a controllable manner is highlighted as a promising perspective to obtaining an autonomous and movable GUV.     

Energy Conversion Efficiency in an Ultrawideband Pulse Emitter

Journal of Communications Technology and Electronics - A calculation model of a plane aperture with nonuniform asynchronous excitation is constructed. The calculated results are in good agreement...     

悬臂式压电能量采集器模型修正

该文以悬臂式压电能量采集器为研究对象,针对Erturk推导的分布参数模型速度频率响应函数（VFF）仿真时发现在0~20 Hz时存在偏差问题,提出了VFF修正方法。首先介绍了含集中质量块的分布参数模型的VFF推导过程;然后通过0~20 Hz内的仿真分析,发现出现较大误差的原因是VFF表达式的第一项,因此,引入含参数α的正弦函数来减小误差。考虑到正弦函数的引入又将导致第二项产生误差,在第二项中引入含参数β的正切函数来减小误差;最后通过误差分析确定参数α、β的最优取值范围,并进行实例分析。结果表明,修正后分布参数模型下的速度频率响应与实验结果吻合。     

基于压电效应的能量收集

介绍了利用压电陶瓷元素进行能量收集,并对其进行了理论分析.为能对负载进行供电,使用DC-DC变换器对电压进行变换,同时增加了输出功率.最后实验结果对前面的模型理论分析进行了验证.     

Energy Conversion Efficiency of an Exponentially Graded Thermoelectric Material

This work describes an analytical model that predicts the effects of property gradients on the energy conversion efficiency of a functionally graded thermoelectric material (FGTEM) with an exponentially varying Seebeck coefficient S, electrical resistivity ρ, and thermal conductivity k. The figure-of-merit parameter, Z = S ²/(ρk), thus also varies exponentially. A closed-form solution for the temperature distribution in the FGTEM and the efficiency as a function of current density are obtained. The peak efficiency and the optimal current density are determined from the efficiency solution. It is found that the efficiency may be increased by about 30% using appropriate property gradients.     

应用于压电能量收集器的PZT PZN系陶瓷材料

压电材料作为环境振动能量收集器的核心功能材料,是制备高性能能量收集器的关键。该文从提高能量收集效率入手,研究适合于能量转换的高性能压电陶瓷材料。采用两步合成工艺制备出了0.7Pb(Zr0.51Ti0.49)0.99O3-0.3Pb(Zn1/3Nb2/3)O3(PZT-PZN)压电陶瓷,研究了La2O3掺杂对其微观结构和机电性能的影响。实验结果表明,掺杂少量的La2O3能显著提高PZT-PZN陶瓷的压电系数(d33)、机电耦合系数(k31、kp)、介电常数(εr)等。当掺杂量为4%(摩尔分数)时,在1 200℃烧结PZT-PZN,显示出良好的压电和介电性能:d33=560pC/N,k31=0.376,kp=0.642,s1E1=16.5×10-12 m2/N,εr=3 125。     

悬臂梁式压电振动能量收集器的疲劳分析

建立了悬臂梁式压电振动能量收集器的有限元模型,通过模态分析求解了其一阶固有频率,并通过实验验证了求解结果的准确性。对所建立的有限元模型进行静态分析后将静态分析的结果导入ANSYS nCode DesignLife中进行疲劳分析,结果表明,随着激励位移幅值的增大,压电层的应变与其成线性关系增大,而疲劳寿命迅速缩短,当激励位移增大1倍时,疲劳寿命缩短了284倍。因此在实际应用中,要综合考虑压电悬臂梁的输出电压及压电陶瓷层的疲劳寿命,才能实现最大的电能输出。     

压电能量回收的自适应机械开关电路

压电能量回收装置离不开能量提取电路,传统标准电路的能量提取效率不高,而采用同步切换开关的能量提取电路能有效提高了能量提取效率。该文提出采用粘性材料作为自适应机械开关结构的移动电极,它不需额外的电子器件,且可自适应悬臂梁的位移幅值,获得更高功率。分别采用正弦激励和噪声激励对粘性材料的参数进行了分析。结果表明,激励不同时,粘性材料的参数选择也不同,同时还证明了自适应机械开关的性能。     

Flexible Inorganic Piezoelectric Acoustic Nanosensors for Biomimetic Artificial Hair Cells

For patients who suffer from sensorineural hearing loss by damaged or loss of hair cells in the cochlea, biomimetic artificial cochleas to remedy the dis­advantages of existing implant systems have been intensively studied. Here, a new concept of an inorganic‐based piezoelectric acoustic nanosensor (iPANS) for the purpose of a biomimetic artificial hair cell to mimic the functions of the original human hair cells is introduced. A trapezoidal silicone‐based membrane (SM) mimics the function of the natural basilar membrane for frequency selectivity, and a flexible iPANS is fabricated on the SM utilizing a laser lift‐off technology to overcome the brittle characteristics of inorganic piezoelectric materials. The vibration amplitude vs piezoelectric sensing signals are theoretically examined based on the experimental conditions by finite element analysis. The SM is successful at separating the audible frequency range of incoming sound, vibrating distinctively according to varying locations of different sound frequencies, thus allowing iPANS to convert tiny vibration displacement of ≈15 nm into an electrical sensing output of ≈55 μV, which is close to the simulation results presented. This conceptual iPANS of flexible inorganic piezoelectric materials sheds light on the new fields of nature‐inspired biomimetic systems using inherently high piezoelectric charge constants.     

Piezoelectric Water Drop Energy Harvesting

Piezoelectric materials convert mechanical deformation directly into electrical charges, which can be harvested and used to drive micropower electronic devices. The low power consumption of such systems on the scale of microwatts leads to the possibility of using harvested vibrational energy due to its almost universal nature. Vibrational energy harvested using piezoelectric cantilevers provides sufficient output for small-scale power applications. This work reports on vibrational energy harvesting from free-falling droplets at the tip of lead zirconate titanate piezoelectric-based cantilevers. The harvester incorporates a multimorph clamped–free cantilever made of lead zirconate titanate piezoelectric thick films. During the impact, the droplet’s kinetic energy is transferred to the form of mechanical stress, forcing the piezoelectric structure to vibrate and thereby producing charges. Experimental results show an instantaneous drop-power of 2.15 mW cm^?3 g^?1. The scenario of a medium intensity of falling water drops, i.e., 200 drops per second, yielded a power of 0.48 W cm^?3 g^?1 per second.     

基于压电晶体的声波激励小型化低频天线技术研究

水下信息实时传输的需求与日俱增,水声通信和光通信等传统通信手段在传输安全性与稳定性方面具有先天难以弥补的劣势,且在传输速率方面难以形成突破,因此亟待对新技术进行研究。为解决此问题,近年一些学者提出一种新机理、新材料和新工艺的小型化天线,有望实现低频天线在尺寸和性能上的跨越,实现水下通信技术的变革。该文对此类声波激励小型化天线进行研究。首先阐述并建立了天线辐射机理及理论模型,分析了不同材料参数对天线性能的影响;然后根据模型参数设计加工了基于铌酸锂(LiNbO₃)晶体的压电型声波激励天线样机,实验结果表明在40.83 kHz谐振频率处,与同尺寸单极子天线相比,其接收电压峰值为后者的22倍,辐射效率为400多倍;最后对天线进行了方位测试和辐射效率计算。上述结果表明：基于压电晶体的声波激励天线技术在低频段小型化、机动化水下无线通信设备的应用中具有巨大潜力。     

Giant Piezoelectric Coefficients in Relaxor Piezoelectric Ceramic PNN‐PZT for Vibration Energy Harvesting

It is well known that the piezoelectric performance of ferroelectric Pb(Zr,Ti)O₃ (PZT) based ceramics is far inferior to that of ferroelectric single crystals due to ceramics' polycrystalline nature. Herein, it is reported that piezoelectric stress coefficient e₃₃ = 39.24 C m^?2 (induced electric displacement under applied strain) in the relaxor piezoelectric ceramic 0.55Pb(Ni_1/3Nb_2/3)O₃–0.135PbZrO₃–0.315PbTiO₃ (PNN‐PZT) prepared by the solid state reaction method exhibits the highest value among various reported ferroelectric ceramic and single crystal materials. In addition, its piezoelectric coefficient d₃₃* = 1753 pm V^?1 is also comparable with that of the commercial Pb(Mg_1/3Nb_2/3)O₃‐PbTiO₃ (PMN‐PT) piezoelectric single crystal. The PNN‐PZT ceramic is then assembled into a cymbal energy harvester. Notably, its maximum output current at the acceleration of 3.5 g is 2.5 mA_pp, which is four times of the PMN‐PT single crystal due to the large piezoelectric e₃₃ constants; while the maximum output power is 14.0 mW, which is almost the same as the PMN‐PT single crystal harvester. The theoretical analysis on force‐induced power output is also presented, which indicates PNN‐PZT ceramic has great potential for energy device application.     

Piezoelectric Nanogenerators Derived Self-Powered Sensors for Multifunctional Applications and Artificial Intelligence

With the arrival of the Internet of Things (IoTs) era, there is a growing requirement for systems with many sensor nodes in a variety of fields of applications. The demands for wireless, sustainable and independent operation are becoming more and more important for large-scale sensor networks and systems. For these purposes, a self-powered sensory system that can utilize the self-harvested energy from its surroundings to drive the sensors and directly sense external stimuli has attracted great attention. The invention and rapid development of piezoelectric generators (PENGs), which take Maxwell's displacement current as the driving force, has been pushing forward research on self-powered active mechanical sensors, electronic skins, and human-robotic interaction. Here, this review starts with a brief introduction of piezoelectric materials, fabrication, and performance improvement. Then, the energy harvesters used for self-power systems based on recent progress are reviewed. After that, PENGs applications toward recent self-powered active sensors are divided into four aspects and highlighted, respectively. Moreover, some challenges and future directions for the self-powered multifunctional sensors are put forward. It is believed that through the continuous investigations into PENG-based self-powered active sensors, they will soon be used in touch screens, electronic skins, health care, environmental monitoring, and intelligence systems.     

压电能量收集中储能器件的研究

目前压电振动能量收集成为微能量领域的研究热点.由于收集的能量较小,因此需要储能器件把收集的能量存储起来以便为电子元件供电.比较了常用的储能器件,包括电阻、电解电容器、超级电容器和可充电电池.研究了这些器件的充放电特性和应用状况,比较了这些器件的优缺点,结果发现,超级电容器可在低压状态下为电子元件有效供电,适合在压电能量收集中推广应用.