基于遗传算法的信号识别技术

将遗传算法应用于识别气浮式动平衡测量装置准静态信号的参数 ,提出了二次磨光法的数据预处理方法。首先采用二次磨光法消除坏点并进行快速傅利叶变换以确定信号的频率成分 ,并设定各频率成分信号的幅值和初相位的取值范围 ,然后以实测信号与识别结果的差值定义适应度 ,最后经过基本遗传操作和迭代得出最优解。仿真结果和试验实例表明 ,该方法精度很高 ,幅值识别误差不超过 1 %,初相位误差小于 2°,满足了实际工程需求。     

基于AD9833的多通道信号发生器设计

系统以高速微控制器为核心，利用直接数字频率合成（DDS）技术，产生多通道、多类型的单一输出信号（正弦、方波、三角信号及直流），同时可将这些单一信号作为傅立叶级数的各项分量，合成一路任意周期的输出信号。各单一信号频率、幅值、初相位可通过小键盘及LCD设定，DDS芯片产生设定频率和初相位、但幅值固定的输出信号，数字电位器、微控制器片内A／D则实现了信号幅值的闭环调节，极大地降低了幅值误差，实测结果表明该系统输出信号具有较高的精度。     

振频法索力监测中自振频率的频谱倍增方法

利用振频法对索力进行长期在线监测时,为高效准确地自动识别拉索的自振频率,就必须避免拉索随机振动信号的非平稳性和频谱微弱等不利条件,减小随机噪声及干扰.根据斜拉索振型的特征,提出频谱倍增法:对单组振动信号频谱幅值进行m次数组乘积,或者对m组相邻频谱幅值进行一次数组乘积;并通过理论分析证明了该方法能够将信噪比至少提高m倍,是常规累加平均法的(√ˉm)倍.以重庆马桑溪长江大桥斜拉索为研究对象进行现场对比试验,分别采用频谱倍增法和累加平均法进行自振频率的自动识别,倍增法基频识别结果误差减少至4％以内,且识别效率提高了5～10倍.试验结果表明:倍增法不仅提高了识别结果的精度,还缩短了识别所需的时间,提高了识别效率.     

交流电压智能传感器中信号处理的相关性分析

针对交流电压智能传感器中重要却难测的电力参数电压有效值U、初相位θ,提出了相关性分析方法和利用误差最小均方法对第一个采样点(0)的估计及其对测试精度的影响,并将它们与传统的定义法进行了分析、比较,指出相关性分析法能有效降低采集信号中干扰的影响,基于误差最小均方法的(0) 估计能显著提高θ的测试精度,从而降低对电路性能的要求,简化系统,降低成本,提高测试性能.实验表明:相对于定义法,相关性分析法并结合基于误差最小均方的(0)估计可降低采样频率近3倍,信号中干扰幅值的要求从远小于信号幅值的3%可放宽到信号幅值的12%.     

旋转机械状态监测中提高FFT线性谱精度的一种方法

针对旋转机械状态监测中振动信号一般以离散频率成分为其主要频率构成的特点，讨论一种改善ＦＦＴ线性谱精度的方法。应用该方法对代表某谐和分量的谱峰参数进行适当修正，能获得该分量较精确的频率、幅值和相位。其中相位分析误差小于５°     

旋变二次谐波测角误差自校正

旋变幅值误差和正交误差在角速度频谱上表现为旋变转频的二次谐波,是旋变测角误差的主要来源,影响伺服系统角速度控制精度和稳定度。本文提出了一种基于特征频率参考的二次谐波误差自校正方法。首先,分析旋变测角误差产生的机理,获知其幅值误差和正交误差的互不相关性,并证明对旋变输出信号进行幅值调整和相位差调整可实现二次谐波误差校正。然后,在旋变和旋变数字信号转换器（Resolver-to-Digital Converter,RDC）之间设计基于比例放大的幅值校正器和基于交叉调节的相角校正器。最后,根据误差信号在线性控制系统中特征频率不变的特性,对伺服系统进行匀速控制,以角速度频谱中二次谐波频率的幅值为参考基准,分别调整幅值校正器和相角校正器,校正二次谐波误差。实验结果表明：本方法可将旋变二次谐波测角误差幅值降低78.5%,伺服系统速率波动量降低40.5%。本方法实现了旋变二次谐波测角误差的自校正,大幅提升了旋变的测角精度和伺服系统的转速控制稳定度。     

计及负频率的极高频信号离散频谱校正新方法

对于机械振动与故障诊断等领域中常见的极高频(接近奈奎斯特频率)信号,传统的离散频谱校正方法存在着较大误差,负频率成分干涉严重是影响其频谱分析精度的重要因素。为提高极高频信号的频谱分析与校正精度,给出了一种计及负频率影响的离散频谱校正新方法。该方法基于Blackman窗,依据离散频谱的周期性并利用局部谱峰附近的3条谱线,建立包含正负频率贡献的离散频谱校正模型,通过对模型的求解获得频率、幅值和相位校正公式。采用频段内扫描的方式对频谱校正公式进行了仿真验证,结果表明所提方法可有效降低负频率成分对极高频信号频谱的干涉影响,提高其频率、幅值和相位校正精度。     

针对 3×3 耦合器幅相非对称的光纤水听器解调方法

基于3×3耦合器法的光纤水听器解调容易受耦合器分光比非理想对称特性影响,导致水听器解调结果及测量信号不准确。为解决实际中3×3耦合器普遍存在的幅度、相位非对称引入的解调偏差问题,提出基于微分交叉相乘的干涉信号幅度和相位修正解调方法。通过对三路非对称干涉信号进行两两最小二乘椭圆拟合,得到干涉信号的实际幅度和相位参数,经去直流、归一化消除幅度不对称,并将所得包含非对称相位信息的信号两两微分交叉相乘,经三角函数变换解算信号相位及其修正系数,从而实现对光纤水听器输出信号的准确解调。仿真对比了本文方法和仅考虑幅度非对称情况的解调结果,并分析比较了两种处理方法随声信号频率、幅值变化的解调误差,前者得到接近理想信号波形的解调结果和更小的解调误差。依托消声水池开展了光纤水听器解调实验,在5～30 kHz频率范围对解调方法进行了对比验证,证明了本文解调方法的有效性和稳定性。     

基于零相位数字带通滤波的旋转机械不平衡量提取方法

针对动平衡测试中FFT频谱法难以从非整周期采样信号中提取不平衡相位的问题,提出一种基于零相位数字带通滤波提取旋转机械不平衡量的方法。首先将采集的振动信号通过中心频率为转速频率的零相位带通滤波器,得到无相位差的转速同频信号,然后计算信号峰值点幅值和相位的算数平均值,得到不平衡量。实现了非整周期采样下不平衡幅值和相位的精确提取。仿真和实测验证了方法的有效性,相位提取误差小于2°,动平衡效率大于80%。该方法无需专门的硬件跟踪滤波电路,具有较高的工程实用价值。     

轮毂电机行星传动系统传递误差研究

以轮毂电机中行星传动系统为研究对象,考虑时变啮合刚度、啮合相位和当量啮合误差等影响因素,建立了系统的运动微分方程,并运用Runge-Kutta法求解得到系统传递误差。基于传递误差曲线,分析了各类误差和支撑刚度变化对系统传递误差幅值的影响,并对误差初相位进行优化。结果表明,误差值的大小与系统传递误差幅值呈正比,误差初相位的变化可以在不改变构件精度的条件下减小系统传递误差幅值,支撑刚度的大小与系统传递误差幅值成反比。研究工作为行星传动系统的设计提供指导作用,降低了制造难度和安装成本。     

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...     

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...     

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。     

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。     

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.     

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.     

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。     

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....     

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.