激励脉冲宽度对加速度计冲击校准误差的影响

加速度计准静态校准要求激励信号的频率与加速度计谐振频率相比足够低,以减小校准误差.通过加速度计数学模型建立了激励加速度脉冲宽度、加速度计谐振频率和校准误差之间的关系式;针对Hopkinson杆冲击校准装置,理论计算和实验结果表明,激励加速度脉冲宽度决定于应力脉冲前沿宽度,受应力波弥散影响,而与加速度计安装座长度无关.为选用和产生满足要求的激励脉冲信号提供了依据.     

压电加速度计能力验证结果分析与经验总结

根据参加的三次全国压电加速度计校准能力验证结果,分析了实验室比较法振动标准装置各频率点的测量能力,针对参考值偏差较大频率点,阐述了可能的影响因素。总结了参加压电加速度计能力验证的一些经验,对提高压电加速度计校准能力有一定的帮助。     

加速度计的静态校准

本文介绍了几种校准加速度计的静态方法。说明了用离心机校准加速度计的基本原理、误差分析、注意事项及可达到的精度     

动态补偿法在压电传感器静态校准中的应用

提出了采用动态补偿法解决小放电时间常数压电传感器静态校准问题的新方法,并将其用于某压力传感器的静态校准.理论分析和试验结果表明采用该方法可以很好解决压电传感器的低频响应问题.该方法对压电传感器的现场静态校准具有普遍意义.     

基于S/PDIF信号解码的数字加速度计校准方法

Polytec公司的外差激光干涉仪可输出24位精度、固定输出延时与量化采样率的索尼/飞利浦数字接口格式（sony/philips digital interface format, 简称S/PDIF）数字信号。常规外差激光干涉法的数字加速度计动态校准存在处理数据量较大、导致时间开销或系统成本增加的问题。利用现场可编辑逻辑门阵列（field programmable gate array,简称FPGA）对Polytec外差激光干涉仪输出S/PDIF数字信号的实时解码,实现了以S/PDIF数字信号对其他传输协议的微机电系统（micro electromechanical systems, 简称MEMS）数字加速度计的振动台动态校准。通过与常规外差激光干涉法校准结果对比,证实了该方法具有较高的校准精度。本方法有效减少了校准系统的数据处理量,使其适用于低频振动校准,且具有较强的抗干扰能力。     

压电加速度计谐振频率的校准

[本文首先给出了压电加速度计的电导纳方程,由电导纳方程的讨论提出了压电加速度计谐振频率的电测校准法。将压力加速度计安装在不同的质量块上,得到了在不同的附加质量条件下的压电加速度安装谐振频率。特别地,在附加质量等于零时,得到表征传惑器,固有特性的自由谐振频率。这样,就将压电加速度计自由谐振频率与安装谐振频率统一起来,也说明了不同方法有不同校准结果的原因。最后,将电测法与ISO组织推荐的方法作了比较,结果证明:电测法是一种测量精度高,容易推广,不需专门仪器简便可行的方法。]     

压电加速度计高频校准中的问题

本文着重讨论由于高频时相对运动带来的问题,肯定了高频校准时存在的负载修正问题。并认为在高频校准压电加速度计时,应采用绝对法或不同负载与频响修正后的比较法给出加速度计的固有响应;同时也必须给出加速度计的安装响应,两者不可缺一。     

超低频振动校准自动控制系统的研究

针对超低频振动校准过程中测试时间长且效率较低的问题,设计了一种基于个人计算机及虚拟仪器技术开发的超低频振动校准自动控制系统.该系统由超低频标准振动台、功率放大器、激光测振仪、位移传感器、信号发生器、频比计数器、数据采集卡、计算机与测控软件等组成.通过线性逼近与逐步移频相结合的算法,精确控制振动台在超低频时迅速到达设定振...     

高量程加速度计动态线性校准系统

设计了双弹头霍普金森杆用于精确标定高g值加速度计的动态线性参数。基于一维应力波传播理论和弹性波叠加原理,分析了双弹头霍普金森杆为不同尺寸时对获取所需激励加速度信号的影响。利用ANSYS/LS-DYNA有限元仿真软件对不同设计条件下双弹头霍普金森杆的冲击效果进行了仿真分析。通过对不同影响因素的对比,确定了结构参数,设计了直径为30mm,长度为1 200mm的双弹头霍普金森杆,即高量程加速度计动态线性校准系统。利用设计的双弹头霍普金森杆对高量程加速度计进行了动态线性校准和试验验证,结果显示加速度计动态线性误差在5%以内,证明了设计的装置可对高量程加速度计进行动态线性校准,校准结果基本满足冲击校准的要求。     

用离心法校准加速度计

所谓静态校准加速度计,就是用模拟的惯性力作用在仪表敏感元件的惯性质量上,或者将已知量值的恒值加速度作用到仪表上的方法。对某些有惯性质量敏感元件的加速度计,常用两种方法校准。 地球重力校准：将仪表敏感轴方向与地球重力场方向重合,即再分别反转 90°、 180°角,便可得到－ 9.8～ 0～＋ 9.8m/s2的加速度输出信号。 负载法校准：即将重量为敏感元件的等效重量整数倍 n的负荷按敏感轴方向加到敏感元件惯性中心上,可得到 (n－ 1)倍的加速度信号输出。 第一种方法较精确,但使用范围很小,仅适合于少数加速度计;另外,不同区…     

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...     

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.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.