A new approach to detect broken rotor bars in induction machines by current spectrum analysis

This paper deals with a new technique to detect broken rotor bars in polyphase induction machines. Like most techniques, we employ the Fourier Transform of the stator current to make detection. But where the other methods use the Fourier Transform modulus, this alternative approach proposes to analyse its phase. As shown by results, the Fourier Transform phase allows to detect one broken rotor bar when the motor operates under a low load but the method robustness decreases for a half-broken rotor bar. So, in order to improve the diagnosis and to permit the detection of incipient broken rotor bar, the analysis is completed with the Hilbert Transform. This transform provides good results and a partially broken rotor bar can be detected when the load torque is equal or greater than 25%. The main advantage of these methods is that the final decision on the rotor cage state is took without the healthy motor reference.     

相位式激光测距谱分析鉴相的无偏改进

针对相位式激光测距中的鉴相误差,建立了谱分析鉴相的误差模型,提出了在数据预处理中引入希尔伯特变换来消除相位差估计偏差的测量方法.分析了传统谱分析鉴相的偏差和方差,指出这些测量偏差受初相位的影响,在高速测距中不容忽略.提出了一种无偏改进方法,通过窗函数法设计正弦信号的简易希尔伯特变换器,将离散傅里叶变换的对象转换为解析信号,在仅增加4次加减法运算和2次移位操作的情况下,实现了近似无偏谱分析鉴相.仿真分析和实验验证结果表明,鉴相均值与真实相位差相同;当信噪比为40 dB时,每秒百万次高速鉴相的误差为0.1°;当调制频率为100 MHz时,测距精度达到0.4 mm.实验表明,将希尔伯特变换应用于谱分析鉴相,可实现高准确度相位差测量,并可应用于高速相位式激光测距.     

钻削监控传感及诊断

对有关钻削加工中的刀具磨损和失效的监控试验和报告作了综述.对监控中用到的间接测量方法有所涉及,如轴向切削力和扭矩、刀具振动、电机电流和功率以及加工中的声发射等.对所用的传感器和信号分析技术,包括统计方法和参数、快速傅里叶和小波变换以及倒谱技术均有所提及.对结果的诊断多数采用人工神经网络技术.     

Experimental study of through-wall human detection using ultra wideband radar sensors

Measurement of weak signals is very challenging since the signals may be buried by noise. In this paper, we study measurement of sense-through-wall signals using UWB radar sensors, and measurements show that the collected signals due to respiratory movement of human target are very weak. Based on the measurements, we perform through-wall human detection. The detection of human targets hidden by walls, or trapped in buildings is of interest for rescue, surveillance and security operations. In this paper, experiments on through-wall human detection using the ultra wideband (UWB) radar PulsOn 220 in monostatic mode are carried out in two scenarios: through gypsum wall, and through wooden door. And three analytic methods are employed for the detection: normalized difference square matrix method, reference moving average method with Discrete Fourier Transform (DFT), and Empirical Mode Decomposition (EMD) from Hilbert Huang Transform, of which the breathing information of the human target is contained in the third intrinsic mode function (IMF3). The experimental results for the human target detection behind the wall are demonstrated and thus compared using these three methods. It shows that the distance of the human target to the UWB radar could be approximately estimated by the normalized difference square matrix method and the reference moving average method. As to Hilbert Huang Transform, even though the existence of the through-wall human target can be clearly detected, the range information is ambiguous.     

面向等离子熔射快速制模可视化系统的三维形状检测技术

提高金属原型等离子熔积成形的精度是使该技术走向实用化的关键之一。本文将傅立叶变换轮廓法用于等离子熔积成形过程中零件的三维形状检测，来对模型的尺寸和成形过程工艺参数进行修正和补偿，提高成形精度。文章详细论述了该方法的测量原理、零件形状与所求得的相位之间的关系，建立了三雏形状测量的系统构架，最后给出了测量结果并提出了误差来源和改进措施。     

Detection of broken rotor bar faults in induction motor at low load using neural network

The knowledge of the broken rotor bars characteristic frequencies and amplitudes has a great importance for all related diagnostic methods. The monitoring of motor faults requires a high resolution spectrum to separate different frequency components. The Discrete Fourier Transform (DFT) has been widely used to achieve these requirements. However, at low slip this technique cannot give good results. As a solution for these problems, this paper proposes an efficient technique based on a neural network approach and Hilbert transform (HT) for broken rotor bar diagnosis in induction machines at low load. The Hilbert transform is used to extract the stator current envelope (SCE). Two features are selected from the (SCE) spectrum (the amplitude and frequency of the harmonic). These features will be used as input for neural network. The results obtained are astonishing and it is capable to detect the correct number of broken rotor bars under different load conditions.     

改进的视角鲁棒KAZE特征匹配算法

针对KAZE特征匹配算法对视角变化敏感,在大视角场景下不能实现正确匹配的问题,提出了一种视角鲁棒的PKAZE(Perspective-KAZE)算法。该算法在原KAZE描述符的基础上,计算特征点邻域内的二阶梯度均值,形成新的扩展的80维描述符;然后利用透视变换模型对待匹配影像进行多视角模拟,在模拟影像上提取改进的KAZE描述符,再进行特征匹配。最后,选取5对含有最多正确匹配数量的影像上的匹配对作为初始结果,利用随机抽样一致算法对初始结果提纯。对多组图像进行了匹配实验,结果表明:与KAZE、尺度不变特征变换(SIFT)和加速鲁棒特征(SURF)算法相比,所提算法对视角变化具有更强的鲁棒性;与透视尺度不变特征(PSIFT)和仿射尺度不变特征(ASIFT)算法相比,本算法匹配正确率更高,分别为PSIFT的2~10倍,ASIFT的2~7倍。提出的算法对视角变化具有很好的鲁棒性,不仅对模拟影像的视角变化很稳健,而且适用于真实三维复杂场景拍摄的大视角影像,具有一定的实用价值。     

基于DTCW-ERE的小电流接地系统故障选线

小电流接地系统发生单相接地故障时,各馈线的小波能量分布各不相同。本文提出了一种基于故障线路小波综合能量相对熵的选线新方法。双树复小波变换(DTCWT)具有很好的近似平移不变性和抗混叠性;能量相对熵(ERE)具有对信号间细微差别进行识别的超强能力。结合双树复小波变换与能量相对熵的优点,根据故障线路综合小波能量相对熵最大的原则进行选线,能够使故障选线更直观、快速有效。仿真结果表明,该方法可以准确有效的进行配电网故障选线。     

多点闭环成形中基本体群曲面描述方法的研究

探讨了在多点闭环成形中，基本体群曲面的数值矩阵描述和离散傅里叶变换描述方法；通过实例验证了离散傅里叶变换描述方法的有效性和对随机测量误差的鲁棒性；从闭环成形的实验结果可以看出，应用离散傅里叶变换描述能够体现板材多点成形时各基本体之间的相互耦合关系，提高了多点成形工件的精度。     

A palmprint based biometric authentication system using dual tree complex wavelet transform

Palmprint identification has emerged as one of the most popular and promising biometric modalities for personal identity verification due to its ease of acquisition, non-invasive procedure, high user acceptance and reliability. This paper proposes the development of a new method for palmprint based biometric authentication which utilizes the textural information available on the palmprint by employing the Dual Tree Complex Wavelet Transform (DTCWT). The method proposes to construct a region of interest (ROI) for the scanned color images of the palm, and then determine a histogram of the two dimensional image. This enables to utilize a feature extraction module, implemented using the one-dimensional (1D) Dual Tree Complex Wavelet Transform (DTCWT) on the histogram signal. The DTCWT is an improvement over the discrete wavelet transform (DWT) as it provides nearly shift invariant performance, reduced aliasing and directional wavelets in higher dimensions. Backpropagation neural-network (BPNN) based binary classifiers are developed for authentication utilizing the features extracted. The system is developed on the basis of several scanned color images of palms of individuals in real-life, in our laboratory. The experimental results obtained from the data have demonstrated the utility of the proposed system, by exhibiting an overall mean accuracy as high as 98.35%.     

实物测量造型技术中的数据分块方法

对测量造型技术中的数据分块问题进行了深入细致的讨论，提出了几个实用的测量数据分块方法。这些方法已在实际工程中得到了应用     

Diagnosis of subharmonic faults of large rotating machinery based on EMD

The vibration signals always carry the abundant dynamic information of a machine and are very useful for the feature extraction and fault diagnosis. In practice, most subharmonic signals have a close relationship to time variables and can manifest large amplitude fluctuation, transient vibration, or modulation signals in time domain. In view of this, this paper describes an effective method to search the features of subharmonic faults of large rotating machinery based on empirical mode decomposition (EMD). Case study on some actual vibration signals of machine parts shows that EMD is an adaptive and unsupervised method in feature extraction and it provides an attractive alternative to the traditional diagnostic methods.     

数控机床几何误差非接触圆轨迹检测方法研究

几何误差是评定数控机床精度的主要指标之一。本文提出一种基于圆测法,利用两台激光干涉仪及可控移动平台实现数控机床几何误差检测的新方法。介绍了该方法的基本原理,完成了测量系统的设计,并推导出单项误差分离的模型。使用该方法与球杆仪法分别在MCV-510数控加工中心上进行模拟测量。试验表明:两种方法测得数据的最大绝对误差是0.8μm,从而证明该方法的可行性和正确性。     

Fourier transform profilometry employing novel orthogonal elliptic band-pass filtering for accurate 3-D surface reconstruction

The article proposes a novel orthogonal elliptic band-pass filtering methodology in Fourier Transform Profilometry (FTP) for significant improvement of accurate 3-D measurement surface reconstruction with arbitrary object colors. Compared with phase shifting profilometry (PSP), FTP using fringe projection can achieve a general 3-D surface profilometry more efficiently by employing one-shot imaging. However, a challenging problem commonly encountered by FTP using fringe projection is its unreliable extraction of precise spectral information from the spectral domain especially when the spectral domain is complicated to process. Various filtering methods previously proposed in FTP have been proved unsuccessful or nonrobust. Thus, a new band-pass filter is developed from an adaptive orthogonal elliptic region to achieve higher accuracy of 3-D surface reconstruction. A comprehensive theoretical analysis is performed to investigate the physical measurement limits of the proposed method. The experimental results obtained confirm that the measurement accuracy of dimension and sphericity can be greatly enhanced when compared with that achieved by the traditional circular band-pass filter. The proposed method is proved to outperform all the other existing FTP band-pass filtering approaches. The maximum dimensional error measured can be controlled within 1.25% of the overall measuring height with various surface colors. However, it is also verified that the traditional three-step PSP can achieve slightly better measuring repeatability than the proposed method.     

Quality assessment of electrical drives with strongly deformed supply waveform

In the characterization of electrical drives it is necessary to carry out power measurement on highly distorted signals with low uncertainty and in some cases on-line; this involves the adoption of suitable test station and adequate measurement techniques. In addition, EMI sources not only produce electrical network pollution but also involve a reduction of motor performance and require special instrumentation and appropriate investigation methods. This paper reports three different approaches to variable speed drive characterization: performance testing in static and dynamic working conditions and EMI analysis. It then proposes a measurement station which is VXI-based both for VSD static performance testing and EMI analysis and uses a real-time special purpose instrument for dynamic testing.     

Detection of tubule boundaries based on circular shortest path and polar‐transformation of arbitrary shapes

In studies of germ cell transplantation, counting cells and measuring tubule diameters from different populations using labelled antibodies are important measurement processes. However, it is slow and sanity grinding to do these tasks manually. This paper proposes a way to accelerate these processes using a new image analysis framework based on several novel algorithms: centre points detection of tubules, tubule shape classification, skeleton‐based polar‐transformation, boundary weighting of polar‐transformed image, and circular shortest path smoothing. The framework has been tested on a dataset consisting of 27 images which contain a total of 989 tubules. Experiments show that the detection results of our algorithm are very close to the results obtained manually and the novel approach can achieve a better performance than two existing methods.     

TENSON 27型傅立叶变换红外光谱仪及应用

介绍TENSON 27型傅立叶变换红外光谱仪的特点,根据不同类型样品选择红外测量附件和样品制备方法以及仪器的日常维护。     

基于激光诱导荧光成像技术的截面含气率检测研究

截面含气率作为气液两相流动过程中的基本参数之一,对石油管道的开采、输运,核反应堆冷却塔的设计等过程具有重要意义。本文提出了基于激光诱导成像技术和高速摄录系统的截面含气率直接检测方法,有效的避免管道曲率和介质折射率导致的光学畸变。在河北大学多相流循环装置进行实验,测量了18个流量点,液相流量测量范围10～35 L/min,气相流量测量范围2.0～3.0 L/min。运用计量比对的思想,对两种检测技术获得的截面含气率值求取偏差并进行修正,最大偏差仅为0.014 59。结果表明两种方法得到的截面含气率值具有较好的一致性,证明本文提出的荧光成像技术对气液两相分层流截面含气率的检测是有效的。     

采用非采样Contourlet变换与区域分类的红外和可见光图像融合

提出基于多尺度变换和区域相结合的红外与可见光图像融合方法,用于有效保留红外图像与可见光图像中的空间信息及热目标信息,提升融合图像的可观测性和可理解性。首先,基于非采样Contourlet变换(NSCT)方法对红外和可见光图像进行初步融合,采用基于局部能量的规则融合低通子带系数,根据尺度内各方向子带的相关性原则融合带通方向子带系数。然后,计算初次融合后所得的融合图像与源图像的结构相似性(SSIM),根据源图像与初次融合图像的结构相似程度对图像进行区域分类,得到相似区域分类标识图。最后,依据区域内各自的相似度特性,分别采用不同的融合策略进行二次融合,从而得到最终的融合结果。实验结果表明:该方法能够充分提取源图像的区域特征和纹理特征,融合结果在主观和客观评价上均优于目前流行的融合方法。与仅使用NSCT法进行融合相比,实验所采用的两组图像的质量评价指标分别提高了16%、85%、54%、36%和18%、102%、84%、41%。表明该方法在主客观评价上均优于双树复杂小波变换(DTCWT)、NSCT、冗余离散小波变换(RDWT)等方法。     

傅里叶变换在莫尔测偏法中的应用

本文针对非球面莫尔测偏法提出了采用相移技术结合傅里叶变换进行数据处理的新方法,在对莫尔条纹图作二维傅里叶变换后可获取相应于被测表面高度的相位信息,然后用相移来确定该位信息的正负号,以最终正确重构测表面的三维形貌,对有限宽莫尔条纹图因栅线夹角引起的倾斜项误差要用最小二乘法加以剔除,用该法进行了非球面测量。