Passive piezoelectric DC sensor applicable to one-wire or two-wire DC electric appliances for end-use monitoring of DC power supply

A passive, non-contact piezoelectric DC electric current sensor to satisfy the increasing needs of DC power supply for monitoring the electricity consumption by either one-wire or two-wire appliance cord was proposed, and the sensing principle was schematically described and experimentally verified. A micro magnet was integrated into the proposed DC sensor and the appropriate position for locating the micro magnet was theoretically pinpointed. A prototype DC sensor was fabricated, and an impulse piezoelectric voltage output was detected when a DC electric current was applied to a two-wire electrical appliance cord, by using the constructed measurement setup for demonstration. A linear relationship between the detected peak value of the impulse output voltage and the applied DC electric current was further obtained based on the empirical measurements. In light of the above preliminary results, the proposed piezoelectric DC sensor is thus believed to be useful to various kinds of DC electricity end-use monitoring systems without consuming power electricity and using cord separators even in the case of the two-wire appliances.     

一种采用压电复合音叉的电流传感器研究

针对当前非接触电流测量方式存在的灵敏度低、结构复杂等问题,本文提出了一种采用压电复合音叉的电流传感器用于非接触低频微弱电流测量,其结构由永磁体、弹性音叉、压电片及底座组成.当该传感器处于电线周围交变磁场中时,永磁体在磁场作用下产生扭矩并驱动弹性音叉臂及压电片产生形变;因压电效应,形变的压电片两端电极之间输出交变电压信号,从而实现电流的测量.由于磁扭矩效应,这种传感器具有较高的谐振灵敏度,大约是压电悬臂梁式电流传感器的4.0倍;在负载电阻为10 MΩ、频率为41.7 Hz时,灵敏度可达1.393 V/A,线性度约为0.57%.这种压电复合音叉式电流传感器模型还可以应用于微弱振动、磁场信号探测等.     

A single-magnet nonlinear piezoelectric converter for enhanced energy harvesting from random vibrations

Power harvesters from mechanical vibrations are commonly linear mechanical resonators that are most effective when excited at resonance. Differently, under wideband vibrations, linear converters are suboptimal. A nonlinear converter is here proposed that implements nonlinearity and bistability by employing a single external magnet, in order to improve conversion effectiveness while simplifying device fabrication. The converter is composed of a piezoelectric bimorph on a ferromagnetic cantilever. The fabrication technology is based on the screen printing of a PZT low-curing-temperature paste on harmonic steel substrate. The ferromagnetic cantilever converter, under proper coupling with the external magnet, bounces between two stable states when excited by random vibrations and generates an electric output via the piezoelectric effect. According to theoretical predictions, when bistable behaviour is present, experimental results demonstrate an improvement of about 400% of the rms voltage generated by the converter with respect to the linear case.     

Integration of displacement sensor into bulk PZT thick film actuator for MEMS deformable mirror

Bulk PZT thick film actuator integrated with displacement sensor, the so-called self-sensing actuator, is presented in this paper. The PZT film is used as not only an actuating layer but also a displacement sensor, which is achieved by dividing the electrode on the top surface of the PZT film into two parts: central top electrode for actuating and outer annular sensor electrode for piezoelectric displacement detection. When the actuator moves, the piezoelectric charge is induced in the outer annular PZT due to the piezoelectric effect. The total amount of accumulated charge is proportional to the stress acting on the PZT, which is in turn proportional to the actuator displacement. By collecting the piezoelectric charge, the actuator displacement can be detected. A theoretical model is proposed to determine the structure parameters of the sensor and predict the sensor sensitivity. Experiments were performed on the micro-fabricated sensor integrated PZT thick film actuator, and the measured piezoelectric charge is close to the theoretical predictions. The integrated piezoelectric sensor has a displacement sensitivity of approximately 4 pC/nm. In addition, the integration of displacement sensor into the actuator needs no additional fabrication process and has no influence on the actuator performances.     

供能于无线传感器网络的微型振动发电机结构性能研究

应用微机电加工技术制造的振动发电机可以无限、持续地为无线传感器网络提供能源。为了提高发电能力,通过有限元仿真与实验分析了单压电片型式、双压电片并联型式和双压电片串联型式振动发电机的结构参数对发电能力的影响规律。结果表明,厚度比小的双压电片串联型式发电机输出开路电压较高;存在某一最优负载,在给定的激励频率下,使得输出功率最大;相同材料、结构参数下,双压电片串联和双压电片并联型式发电机的输出功率基本相同且高于单压电片型式发电机。     

基于压电双晶片的微型无人机增稳驱动系统研究

研究了一种,基于压电双晶片的微型无人机增稳驱动系统,并设计了一种基于升压电路原理的压电驱动电源,该驱动电源采用机载电池供电,通过 0～5V 控制信号控制其运动,对驱动电源的动态特性进行了测试.同时为实现对整个驱动系统的自适应控制,采用光纤 Bragg 光栅(FBG)传感器对压电双晶片的位移变化特性进行了测量.研究结果表...     

一种非电耦合直流传感器的研制及应用

研制了一种非电耦合直流传感器———磁耦合传感器。该传感器主要应用磁耦合原理,当直流系统发生接地故障时,该传感器可以准确地将故障信号检测出来,故障电流的检测范围为±5mA。该传感器具有体积小、测量准确、灵敏度高、抗干扰能力强、对直流操作回路无任何影响的特点,已成功地在线运行到发电厂、变电站的直流系统接地选线之中。     

MEMS压电-磁电复合式振动驱动微能源的设计

在单一效应的MEMS振动驱动微能源的基础上,提出了一种MEMS压电-磁电复合振动驱动微能源器件。该微能源由八悬臂梁-中心质量块结构和永磁铁两部分组成,环境振动使中心质量块振动,PZT压电敏感单元由于压电效应产生电势差;同时中心质量块上集成的高密度线圈切割磁感线产生感应电动势,将压电转换与磁电转换相结合把振动能转换为电能。建立了该结构的数学模型并用有限分析软件Ansys12.0对该器件进行力学特性分析,最后对加工出的微能源进行性能测试。测试结果表明,该微能源谐振频率为8 Hz,易与环境发生共振;在共振条件下,施加1 gn 的加速度,器件压电发电开路输出电压峰峰值达154 mV,磁电发电开路输出电压峰-峰值达8 mV,有望为无线传感网络节点提供稳定的能源。     

直流偏置对PZT微传感器的谐振频率的影响

在直流偏置电压对PZT压电微悬臂梁谐振频率的影响研究中,建立了理论方程,并通过激光干涉测试实验对所建方程进行了验证。理论方程和实验均表明:直流偏置电压对PZT微悬臂梁的谐振基频的影响是二阶函数。在直流偏置电场小于1×107 V/m时,直流偏置电压和谐振基频存在线性变化区。此结论可以用于改善谐振式PZT微悬臂梁传感器的信号检测系统,即利用扫描直流偏置电压取代频谱分析。     

Deflection of coupled elasticity–electrostatic bimorph PVDF material: theoretical,FEM and experimental verification

Piezoelectric materials have wide applications in the field of mechanical, aerospace and civil engineering because of its voltage dependent actuation. Piezoelectric material goes through voltage generation whenever deflection is induced in it and vice versa. Piezoelectric bimorph beam has been widely used for sensing and actuating. In the actuation mode, an electric field is applied across the beam thickness, one layer contracts while the other expands. This results in the bending of the entire structure and tip deflection. In the sensing mode, the bimorph is used to measure an external load by monitoring the piezoelectric induced electrode voltages. In this research work, a 2D bimorph piezoelectric actuator model having two layers made of polyvinylidene fluoride (PVDF) material was developed to examine the inverse piezoelectric effect. Finite element analysis (FEA) was carried out on specially designed actuator model by using MATLAB Partial Differential Equation (PDE) Toolbox™. Theoretical analysis has been carried out to measure the tip deflection under applied electric field. The laboratory test was performed to investigate the deformation behavior of piezoelectric actuator. It is observed that, more the electric field applied, more the material would be deformed in a particular direction. The experimental results are in good agreement with numerical results.

     

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.     

基于偏磁薄膜矫正的直流光学电流传感器设计

针对高压输电中直流的检测,提出一种基于偏磁薄膜矫正的直流光学电流传感器.偏磁薄膜固定磁场在石榴石材料中的方向提高了传感器测量精度,采用偏振计直接检测偏振角的方法消除了偏振面预偏角度误差对测量系统的影响.对传感器实现直流检测进行理论分析,设计了传感器的光路结构,并使用传感器进行直流检测实验.结果表明：该传感器能兼顾灵敏度和测量范围的需要且测量输出线性度高,线性拟合度为0.999 53,多次测量重复性好,误差小于0.4％.     

升压型DC/DC MAX756应用研究

针对无线传感器网络节点的供电问题,应用升压型DC/DC MAX756设计了具有输出电压选择与电池监视功能的无线传感网络节点供电单元。给出了供电单元的原理图设计与印制电路板的设计要点;得到了供电单元的转换效率与输入电压的关系,转换效率随输入电压升高而升高,随输出电流的增大而增大;测试了供电单元的负载瞬态响应能力。结果显示,负载发生突变时输出电压有较大噪声,说明电源的滤波设计需要改进。     

Development of a sensor system for collecting tactile information

This paper presents the development of a sensor system for collecting tactile information. An active sensing system using the piezoelectric effect and the pyroelectric effect of a PVDF (Polyvinylidene fluoride) film is proposed. The active sensing is designed with human motions for tactile perception in mind. First, as the pretest, the distinction examination of six fabrics with different textures is carried out through human tactile perception. Next, the proposed sensor system is assembled. The sensor is composed of a PVDF film and a soft rubber. The surface of the sensor can be heated through temperature control. The sensor is attached on the tip of a robot finger driven by a piezoelectric bimorph strip and the root of the finger is mounted on a linear slider. Two kinds of active sensing are introduced. First, the heated sensor is contacted with an object and pyroelectric output signals are collected in order to obtain the information on tactile warmth. Next, the heated sensor is slid over the object and piezoelectric output signals are collected in order to obtain the information on feelings of vibration. Through the discussion about each sensing, three indexes representing features of the collected data are extracted and proposed as the sensor outputs for the evaluation of tactile sensation. The measurement using the sensor system is done on the samples used in the distinction examination. Comparison with the results shows that the sensor system extracts features on feelings of vibration and warmth.     

一种基于MEMS技术的压电微泵的研究

介绍了一种基于MEMS技术的压电微泵。该微泵利用聚二甲基硅氧烷(PDMS)作为泵膜,使用了一个主动阀和一个被动阀,并利用压电双晶片作为驱动部件。压电双晶片和PDMS泵膜的组合可以产生较大的泵腔体积改变和压缩比,显著降低了加工成本,并提高了成品率。对压电微泵的输出流量进行了测试,结果显示:电压、频率以及背压对流量均有显著影响。在100 V,25Hz的方波驱动下,该压电微泵的最大输出流量为458μL/m in,最大输出压力为6 kPa。     

基于PVDF的三维机器人触觉传感器有限元分析

为了解决压电层合板层间应力连续性问题,从而更为准确地预测传感器的实际输出,利用COMSOL Multiphysics对基于PVDF压电薄膜的三维机器人触觉传感器进行有限元建模。利用三维线性理论建立了压电层半解析轴对称有限元模型,得出分别沿三个方向施加单向力时触觉传感器各压电薄膜的电压响应。仿真结果与标定值之间的误差小于6%,验证了设计的合理性和可行性。     

双晶片悬臂梁式压电传感器的有限元仿真研究

压电传感器作为一种便捷、高效的传感器类型,越来越受到人们的青睐.为研究压电传感器机电耦合能力,将压电高聚物聚偏氟乙烯(PVDF)黏结而成的压电双晶片悬臂梁作为研究对象,利用有限元分析软件ANSYS Workbench,首先完成对模型的构建和模态分析,得出模型的固有频率和固有振型,再建立压电材料的压电本构方程,对压电双晶片悬臂梁模型发电量进行模拟仿真,最后将仿真结果与前人研究结果相对比.分析得出:在10 mm的形变量下,能够产生最大320 V左右的瞬时电压,这与前人的研究结果相近,验证了仿真结果的准确性,同时也证实了压电双晶片悬臂梁作为压电传感器的可行性.     

一种新型传感结构的光纤直流电流传感器

提出了一种用于高压直流电流测量的光纤传感器的新结构,采用这种光学结构的传感器能够克服原有传感器光路在光输出不对称时,测量误差较大,无法实现对被测量高准确度解调的缺点。实验结果表明:即使双光路间的衰减系数差异5倍时,被测直流电流的相对误差小于0.2%。     

基于模糊PID控制的双向DC/DC变换器研究

双向DC/DC变换器是指在保持变换器两端的直流电压极性不变的情况下,根据实际需要完成能量双向传输的直流变换器。它在直流不间断电源系统、分布式电站、电动汽车以及太阳能电池阵中有广泛的应用。通过对双向半桥变换器的分析,并将其与蓄电池相结合使用,完成能量的双向传输和电池能量对电网的回馈。由于DC/DC变换器在升降压的过程中产生的严重的非线性问题,在控制方案上,采用模糊PID控制的电压、电流双闭环控制。仿真表明,与传统的PID控制相比,该控制方案有效提高了变换器的鲁棒性,减小输出电压波动,能够实现能量的双向流动。     

Two-Axial Piezoelectric Actuator Controller Using a Multi-Layer Artificial Neural Network Featuring Feedback Connection for Tactile Displays

Although some compensation method is required when using a piezoelectric actuator because of hysteresis, a sensor feedback method is not suitable for an actuator array. In this study, we design a controller using a neural network to apply it to a tactile display composed of two-axial miniature actuators. This paper describes the two-axial miniature actuator, which is composed of two bimorph piezoelectric elements and two small links connected by three joints. A control system for the two-axial miniature actuator is designed based on a multi-layered artificial neural network to compensate for the hysteresis of piezoelectric elements. The output neuron emits the time derivative of voltage, a two-bit signal expressing increment or decrement condition is generated by two input neurons, and two input neurons calculate current values of voltage and displacement, respectively. The neural network is outfitted with a feedback loop including an integral element to reduce the number of neurons. In the experiment, if the result of the left piezoelectric element is compared to that of the right element, the displacement amplitudes and the inclinations coincide on the right and left piezoelectric elements. Although precise hysteresis characteristics such as loop width are considerably different, the present neural system can follow the difference.