复合型悬臂梁压电振子振动模型及发电试验研究

单悬臂梁压电振子俘获环境中振动能时,对环境振动频率敏感且频带有限,在谐振频率与环境振动频率不匹配的情况下,会导致压电振子俘能效率低下。基于此,设计复合型悬臂梁压电振子并建立其振动模型,采用激光测振仪对复合型悬臂梁压电振子进行扫频测试。研究结果表明,复合型悬臂梁压电振子谐振频率范围为56～72Hz,与理论分析结果基本吻合,试验验证了理论模型的正确性。相比于单悬臂梁压电振子,复合型悬臂梁压电振子有效地拓宽了其谐振频带,易于实现与环境振动源振动频率匹配以提高压电发电效率。在此基础上,进行复合型悬臂梁压电发电装置的发电能力测试,在负载为820?,工作频率为60Hz时最大输出功率达到4.9mW,产生的能量能够满足网络传感器等低耗能微电子产品的供能需求。     

圆弧螺旋型压电振动能量收集系统的设计

为了实现低频、多方向能量收集和高输出性能,提出了一种圆弧螺旋结构的压电能量收集系统。该圆弧螺旋压电能量收集系统不仅可以降低谐振频率,减少系统体积,而且圆弧型悬臂梁具有不对称性,因此可以进行多方向收集。理论分析不同弧度下能量收集系统的应力分布、谐振频率以及输出性能。加工制备了2π、3π和4π圆弧螺旋压电振动能量收集系统并进行了性能测试对比。研究结果表明,4π圆弧螺旋压电能量收集系统具有更好的输出性能,谐振频率为47 Hz,输出电压达到23 V,输出功率达到353μW。该圆弧螺旋压电振动能量收集系统可应用于人体健康检测、环境控制系统、嵌入式系统、军事安全等应用领域。     

磁力调频压电电磁复合发电设计与实验

开展了基于环境振动发电作为微电源弥补传统化学电池供能缺陷的研究。基于非线性磁力调频开发了低宽频振动能采集压电电磁复合发电系统。介绍了发电装置工作原理;利用ANSYS和Ansoft Maxwell有限元分析软件仿真分析了压电和电磁发电的输出特性;最后,搭建了压电电磁复合宽频发电装置实验测试系统,测试了发电系统在磁力自调过程中的输出特性。实验结果显示:复合发电系统在谐振频率60Hz时输出开路电压峰值为5.8V,高于压电系统(5.5V)和电磁系统(410mV)独立发电的开路电压峰值。施加磁力拓宽装置后,当压电悬臂梁沿竖直方向上下移动0~15mm时,系统适应谐振频带拓宽为45~76Hz;悬臂梁沿水平方向平移0~30mm时,谐振频带拓宽为51~70 Hz。结果表明仿真分析与实验测试结果吻合很好。该宽频带能量采集技术可用于低频振动环境的能量采集,可在频变环境中为微型低功耗系统提供低电能。     

圆弧螺旋型压电能量收集器的有限元模型研究

为了分析圆弧螺旋型压电能量收集器的振动特性和输出特性,本文提出了一种有限元模型,可以在简化模型的同时改善结果的精度。对近似前后的圆弧型压电能量收集器进行了建模、仿真和测试,得到了圆弧螺旋型能量收集器的谐振频率、输出电压与输出功率。将圆弧型悬臂梁进行有限元分割成6～16个矩形结构悬臂梁,并对不同程度的有限元近似下圆弧螺旋能量收集器的谐振频率与输出性能进行分析,结果表明在有限元个数大于等于10时,谐振频率与输出性能相对误差较小。加工制备了2π圆弧螺旋型压电振动能量收集并进行了性能测试。测试结果表明螺旋能量收集器谐振频率为158 Hz,采取10边型有限元模型的理论谐振频率为153 Hz,相对误差为3.5%;最大输出功率的测试结果为53.5μW,最大输出功率的理论结果为55.2μW,相对误差为3.18%,理论结果与测试结果较为符合。     

压电振动电阻尼与能量转换特性研究

根据压电构造方程和振动原理,建立压电振动能量收集的耦合场动力学模型。详细推导电阻尼与外接电阻和机电耦合系数之间的数学关系,并揭示外接电阻对系统固有弹性的作用效果。通过数值模拟研究电阻尼特性对谐振频率、振动幅值和功率的影响关系,并从能量转换效率的角度分析优化电阻与最大输出功率的关系。分别对多种外接电阻条件下压电梁的输出电压及功率进行实验测试,实验结果表明,电阻尼导致压电梁的谐振频率发生偏移,其大小与外接电阻值成正比,而且在外接优化电阻时输出功率最大。     

多频响应的压电振动能量采集器的性能分析与测试

为了提升压电悬臂梁采集振动能量的能力,研究了一种具有多频振动响应的振动能量采集器。在压电悬臂梁与振动激励源之间增加一个附加梁,压电悬臂梁和附加梁的末端分别安装一个质量块,压电悬臂梁和附加梁垂直连接。附加梁的末端质量被设计为远大于压电梁的末端质量,而压电梁的一阶谐振频率在附加梁的前两阶谐振频率之间。采用该设计,压电悬臂梁的振动响应是多个谐振频带的叠加。通过建立机电解析模型,描述了所提出的振动能量采集器的振动响应和发电特性,同时制作了一个振动能量采集器样机进行试验,结果表明,与传统的悬臂梁振动能量采集器相比,所提出的振动能量采集器可以在更宽的频带范围内采集更多的振动能量。     

基于压电的车载传感器自供电技术研究

由于电动汽车的广泛推广及其智能化发展的需求,车载传感器数量激增,传统供能方式诸如污染、维护困难等缺陷日渐凸显。考虑到车载环境中振动无处不在,利用压电技术对振动能量进行收集,设计压电式振动能量收集系统以用来解决微功耗传感器供能问题。文中对系统的结构以及数学模型进行了理论分析,给出了系统振动频率的数学模型以及压电输出的数学模型,在仿真分析的基础之上设计了一套压电能量收集装置,并对其共振情况下的发电性能进行了实验测试。实验结果表明提出的理论模型可以很好的预测系统的输出特性,在共振频率为11.6 Hz,加速度为0.5 g时,系统获得的最大开路电压是4.45 V,在最优负载电阻为400 kΩ时,振动能量收集装置的最大的负载功率为15.02μW。结合超级电容的储能功能,可以满足功率更大间歇式工作方式的车载传感器的能量供给。     

高性能多方向双圆弧形压电能量收集系统

为了解决传统压电能量收集系统通频带窄、功率密度低的问题,本文采用线性多模态共振法,提出一种双圆弧悬臂梁内 外反向拼接的压电能量收集系统。 两根梁上各覆盖一个压电层,压电层之间串联连接。 建立二自由度系统集总参数模型和机 电耦合模型来分析频率响应和输出性能。 对比压电层弧度不同的压电能量收集系统的输出性能,根据测试结果,当弧度为 0. 5π 时输出性能最佳。 设置激励加速度为 0. 1 g,一阶模态下,谐振频率为 82. 19 Hz,开路电压为 49. 65 V,最大输出功率为 3. 74 mW;二阶模态下,谐振频率为 119. 14 Hz,开路电压为 44. 74 V,最大输出功率为 3. 54 mW。 测试结果表明,该结构可有效 拓宽通频带宽度至 52 Hz,且功率密度高。 该压电能量收集系统结构简单易于制备,工作频带宽,可在频率波动大的环境下供 电,同时体积小、功率密度大,能在多方向激励下高效率收集能量,可应用于可穿戴设备、低功率设备等多个领域。     

宽频压电振动能量采集器的实验研究

为改善线性单频谐振式压电振动能量采集器的输出性能,研制了双自由度宽频压电振动能量采集器样机模型,搭建了样机实验测试平台,研究了系统刚度比和负载电阻等参数对能量采集器输出性能的影响。通过调节系统刚度比,不仅可以拓宽压电振动能量采集器的工作率带,还提高了压电振动能量采集器的输出电压和输出功率。结果表明:在基础振动加速度为40m/s~2和负载电阻为471kΩ条件下,双自由度宽频压电能量采集器的工作频带是单频系统的7倍,最大输出功率是单频系统的4.5倍。     

多向振动压电发电关键技术的研究

环境中振动能量收集效率低的问题是当前压电发电技术研究的焦点。为了提高环境中振动能量的收集效率,研究了一种可以收集环境中多个方向振动能量的压电发电关键技术。首先,利用压电发电技术的基础理论建立压电悬臂梁的数学模型,并对其进行振动力学分析;然后利用ANSYS对压电悬臂梁进行有限元仿真分析,优化结构使其固有频率与环境振动频率相符;最后制作多向压电发电装置,对其进行理论分析和实验测试。实验结果证明,多向振动压电发电关键技术可以有效地提高环境中振动能量的收集效率。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.