悬臂梁式压电双晶片振动能量采集器的模型与实验研究

针对悬臂梁式双压电晶片振动能量采集器的质量效应问题,通过幅值修正方法建立了能量采集器的集总参数修正模型,利用阻抗分析和导纳圆法对模型参数进行了识别,得到了采集器在简谐基础激励作用下的机电耦合输出传递函数表达式;建立了悬臂梁压电振动能量采集器的实验系统,实验与仿真分析了悬臂梁末端质量、负载电阻等对能量采集器输出特性的影响,结果表明理论仿真结果与实验结果具有很好的吻合度,证明本文模型有利于提高压电振动能量采集器输出性能的分析预测精度。     

压电加速度计特性的研究

本文给出了用四个传感器结构参数表征的一般化压电加速度计模型。并由定义确定了这四个传感器结构参数。在建立了传感器二端口网络模型后,对二端口网络进行参数变换,得到了表征压电加速度计特性的两类函数。这两类函数给出了有关压电加速度计特性的全部信息。最后,应用所得到的结论推导国内外有关互易法校准压电加速度计绝对灵敏度表达式,结论完全一致。     

废热式温差发电器性能仿真

研究温差发电优化控制问题,温差发电技术是用回收废热转化为电能的转换器,使得温差发电运行稳定,产生大功率效能。温差发电技术涉及三大基本效应,导致其温度分布模型不清,难以实现上述目的。为了探究温差发电器的运行规律,指导温差发电器处于较大输出功率下运行,采用温差发电原理以及传热学理论,建立了一种用以求解温差发电器内部温度分布的数学模型。并以输出功率为目标函数,通过仿真计算得到温差发电器在不同工作条件下的性能特性。仿真比较发现,增强冷端散热能力是提高温差发电器输出功率的有效途径,且水冷效果相比空冷效果优势明显。实验结果可为优化温差发电器工作条件和提高其输出功率提供有价值的理论指导。     

压电电缆应用于高速公路超速超载监测的研究

介绍了目前各种高速公路超速超载传感器和相应的检测方法。分析了压电电缆传感器的原理、特点和性能参数。给出了使用压电电缆同时检测超速和超载的方案和具体实施方法,希望对我国高速公路超速超载监测有所帮助。     

压电振动能量采集器的力电耦合模型及其功率优化*

为提高传统压电振动能量采集器集总参数模型的性能预测精度,考虑悬臂梁的振型信息与轴向应变分布情况,提出了一种改进的力电耦合模型,该模型引入无因次幅值修正因子,通过曲线拟合方法确定了修正因子与振型函数和振动幅值之间的关系表达式;利用Rayleigh-Ritz模态分析法确定了力电耦合模型中的集总等效参数(如质量、刚度等),并根据弹性动力学原理建立了能量采集器的运动控制方程,得到了稳态时能量采集器的力、电输出响应表达式;最后,利用改进的模型对能量采集器的负载电阻和输出功率进行了优化,得到了负载短路和负载开路时能量采集器的最优输出特性。仿真结果与实例对比验证了提出模型的正确性,表明改进的力电耦合模型具有较高的预测精度。     

半电极含金属芯压电纤维的动态微力传感器

半电极含金属芯压电纤维(HMPF)是一种新型压电传感器.建立了HMPF的动态微力传感理论模型.根据第一类压电方程,基于振动理论,用平均电荷方法,推导出悬臂梁结构HMPF自由端受到垂直动态微力作用后,产生电荷的解析表达式;分析了长度和半径比对产生电荷的影响.实验结果表明,HMPF可以测量动态微力的频率和幅值,具有较高的动...     

压电陶瓷驱动器非线性建模研究

压电陶瓷驱动器电压位移之间的非线性特点严重影响着它的位移控制精度,建立压电陶瓷驱动器非线性模型是纳米级微位移测控中的关键环节.采用支持向量机回归的方法,通过引入核函数和损失函数将非线性回归转化成线性问题并提高回归精度,建立了一种新的压电陶瓷驱动器外环非线性模型,并就模型的准确性与其它建模方法进行了比较.试验证明,所建的基于支持向量回归的压电陶瓷驱动器非线性模型很好的描述了压电陶瓷驱动器外环非线性特点,误差控制在2%以内,并且建模过程简单,准确性高.     

二级半导体温差发电器性能优化分析

由于受温差和发电效率等因素的制约,单级半导体温差发电器已经不可能满足各种不同的需要,故提出一种二级半导体温差发电器。基于温差电技术的基本原理,采用有限时间热力学理论,建立了内外均不可逆情况下二级半导体温差发电器的理论模型和性能分析的数学模型。并以工作效率、输出功率和火用效率为目标函数,通过仿真计算分析其性能特性,计算出不同情况下半导体温差发电器的最大效率、输出功率和火用效率,进而优化了温差发电器的内部结构,确定了工作电流的最佳范围。所得结果可为二级半导体温差发电器的优化设计和最佳运行提供有价值的理论指导。     

基于多项式拟合的压电陶瓷迟滞神经网络建模

在压电陶瓷致动器优化设计的研究中,针对压电陶瓷的迟滞非线性特性,提出了一种基于多项式拟合算法的神经网络建模方法.由于压电陶瓷驱动器的迟滞现象是一种多对多的映射关系,而传统的建模方法只能对一对一映射进行建模.为解决上述问题,在对压电陶瓷迟滞现象的形成原因和特点进行深入分析的基础上,采用多项式拟合和神经网络相结合的方法对压电陶瓷驱动器的迟滞现象进行建模.仿真结果表明,采用多项式拟合算法的神经网络建模克服了传统建模方法只能对迟滞曲线进行分段建模的局限性,且拟合精度比较高,神经网络正模型的拟合误差为1.45％,神经网络逆模型的拟合误差为1.16％.表明上述神经网络模型精确地反映了压电陶瓷的迟滞特性.     

基于Yamada 模型的压电复合材料吸声性能的研究

提出了一种运用Yamada微观模型来分析压电复合材料吸声性能的方法.首先,建立了0-3型压电陶瓷/橡胶复合材料的被动吸声模型;然后,运用Yamada微观模型获得0-3型压电陶瓷/橡胶复合材料的等效参数,并将此等效参数嵌入到吸声模型;最后,对不同参数下的压电复合材料的吸声系数进行了理论计算和对比分析.结论表明:压电复合材料被动吸声时,聚合物对声能量的衰减起主要作用。     

Architectures for vibration-driven micropower generators

Several forms of vibration-driven MEMS microgenerator are possible and are reported in the literature, with potential application areas including distributed sensing and ubiquitous computing. This paper sets out an analytical basis for their design and comparison, verified against full time-domain simulations. Most reported microgenerators are classified as either velocity-damped resonant generators (VDRGs) or Coulomb-damped resonant generators (CDRGs) and a unified analytical structure is provided for these generator types. Reported generators are shown to have operated at well below achievable power densities and design guides are given for optimising future devices. The paper also describes a new class-the Coulomb-force parametric generator (CFPG)-which does not operate in a resonant manner. For all three generators, expressions and graphs are provided showing the dependence of output power on key operating parameters. The optimization also considers physical generator constraints such as voltage limitation or maximum or minimum damping ratios. The sensitivity of each generator architecture to the source vibration frequency is analyzed and this shows that the CFPG can be better suited than the resonant generators to applications where the source frequency is likely to vary. It is demonstrated that mechanical resonance is particularly useful when the vibration source amplitude is small compared to the allowable mass-to-frame displacement. The CDRG and the VDRG generate the same power at resonance but give better performance below and above resonance respectively. Both resonant generator types are unable to operate when the allowable mass frame displacement is small compared to the vibration source amplitude, as is likely to be the case in some MEMS applications. The CFPG is, therefore, required for such applications.     

Electromagnetic vibration energy harvesting device optimization by synchronous energy extraction

This paper investigates a new application of nonlinear techniques for vibration energy harvesting. The Synchronous Electric Charge Extraction (SECE) energy harvesting technique for piezoelectric generators is extended and adapted to electromagnetic generators. This new circuit, which is the dual of the SECE circuit, is named SMFE for Synchronous Magnetic Flux Extraction. A theoretical model is developed, and the harvested power is simulated. Comparisons with a classical energy extraction approach show that between 2.5 more power and 10% less power can be harvested, depending on the generator characteristics. It also allows the maximum power to be harvested whatever the value of the load. Finally, the SMFE circuit was embedded and tested on a simple centimeter-scale electromagnetic harvester. Measurements confirm the theoretical operating principle of the circuit.     

New simulation approach for tuneable trapezoidal and rectangular piezoelectric bimorph energy harvesters

Enhancing and optimizing the power and operating frequency range of energy harvesters (EH) are important objectives in designing an energy harvester generator. The application of trapezoidal shaped piezoelectric (PZT) cantilever is one way of increasing the harvested power of energy harvesters. Finite element software was used to simulate a tuneable trapezoidal and a rectangular PZT bimorph cantilevers with similar specifications. From the new simulation approach, an open circuit voltage obtained for different resonance frequencies for both generators. The simulation results are compared with the experimental and found to be in good agreement. The results have showed an increase in power over 19 % for the trapezoidal generator over the rectangular generator for a frequency range of 38–122 Hz. The trapezoidal harvester produced maximum power of 0.272 mW at resonance frequency of 34 Hz and acceleration of 2.5 m/s².

     

An improved bacterial foraging algorithm for combined static/dynamic environmental economic dispatch

Economic dispatch is carried out at the energy control center to find out the optimal output of thermal generating units such that power balance criterion is met, unit operating limits are satisfied and the fuel cost is minimized. With growing environmental awareness and strict government regulations throughout the world, it has become essential to optimize not only the total fuel cost but also the harmful emissions, both, under static as well as dynamic conditions. The static environment economic dispatch finds the optimal output of generating units for a fixed load demand at a given time, while the dynamic environmental economic dispatch schedules the output of online generators with changing power demands over a certain time period (normally one day) so as to minimize these two conflicting objectives, simultaneously. In this paper, the price penalty factor approach is employed for simultaneous minimization of cost and emission. The generator ramp rate constraints, non-convex and discontinuous nature of cost function and the large number of generators in practical power plants, make this problem very difficult to solve. Here, a fuzzy ranking approach is employed to identify the solution which offers the best compromise between cost and emission objectives.     

Nonlinear finite element analysis of a thin piezoelectric laminate for micro power generation

In this paper, a new nonlinear finite element model is presented for the analysis of piezoelectric laminates at large deflections. The element is an eight-node element with 5 mechanical degrees of freedom at each node, and the potential difference across the piezoelectric layer is introduced as an additional electrical degree of freedom on an element level. Application of this model to a clamped square piezoelectric laminate shows the strong nonlinear relationship between the terminal voltage and deflection observed experimentally. Furthermore, the numerical results also show that the electrode size is an important design parameter in maximizing the power output when the piezoelectric laminates are used as power generators.     

悬臂梁压电式振动发电机材料性能优化研究

具有高能量密度的微型压电振动发电机可以无限、持续地为无线传感器网络提供能量。为了提高有限体积悬臂梁压电式振动发电机的发电能力,通过力学模型及有限元仿真分析了单晶片型式、双晶片并联型式和双晶片串联型式压电振动发电机的材料参数与输出电压及固有频率之间的关系。结果表明,在低频工作环境下,应优先选择PZT-4、PZT-5A、PZT-5H的压电材料和不锈钢、镍合金的基板材料。     

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。     

压电式双振子微型发电机功率调节电路设计

为克服压电式单振子微型发电机通过一般整流、滤波和储能控制电路不能连续为瞬时发射功率较大的无线传感器网络发射模块供电的问题,提出了一种双振子振动发电的结构思想,介绍了双振子振动发电原理;提出了一种双振子微型发电机输出功率调节控制电路技术方案,它由主一辅整流电路、主储能器、滤波器、辅助补充能量控制电路、稳压电路、滞回比较器、开关控制电路和电子开关等组成.经实验证明:封装了该功率调节电路的压电式双振子微型发电机平均输出功率为250～950 μw,瞬时输出功率可以达到680 mw,而自身的功耗只有40微瓦以下,能满足连续振动环境中微功耗电子器件、传感器或间歇式较大功耗遥测电路供电的要求.     

Structural optimization of the pumping kite wind generator

This paper focuses on structural optimization of the so-called pumping kite wind generator whose operating principle consists in mechanically driving a ground-based electric generator by means of tethered kites. The employed mathematical model of the kite wind generator is based on the refined crosswind motion law derived under the assumption of equilibrium motion of the kite. The resulting simple approximate analytical formula for the mean mechanical power generated by the deploying kite is used for the constrained structural optimization of the pumping kite wind generator maximizing its electrical power output by adjusting the key structural parameters of the kite wind generator.