Mass-weighting methods for sensor placement using sensor set expansion techniques

Placement of sensors is one of the most important tasks performed during pretest planning. The purpose of this work was to develop and investigate the use of an iterative Guyan expansion for mass weighting of target modes for sensor placement analogous to the common iterative Guyan reduction technique. The goal was to determine the appropriate mass-weighting approach to use in conjunction with effective independence sensor set expansion. In either sensor set expansion, or reduction, mass weighting requires a reduction of the FEM mass matrix to the current sensor set size Test-Analysis-Model (TAM). A general theory is presented for target mode mass weighting that can accommodate any type of reduction technique. The theory predicts that sensor set expansion using static mass weighting will result in sensor configurations that produce poor static TAMs. In contrast, sensor set expansion using modal mass weighting exactly reproduces the correct mass distribution during the expansion process. The results of a numerical example corroborate the theory. The modal mass sensor set expansion process produced significantly more accurate static TAMs than the static mass expansion. The modal expansion process was not quite as accurate as the iterative static reduction approach, but modal expansion was over 1600 times faster.     

智能移动机器人超声波测距定位系统的研究

移动机器人技术是机器人研究领域的一个重要分支。为了赋予机器人智能控制和自主导航的能力,解决机器人开发过程存在着成本高、功耗大等问题,研究设计了一套基于超声波传感器的智能移动机器人测距定位系统,同时使机器人具有报警、避障及定位等功能。     

Analysis of the sensor placement for optimal temperature distribution reconstruction

The temperature distribution as a function of time and space is reconstructed over a non-homogeneous media having an arbitrary three-dimensional geometry. This is done by applying an inverse problem to the collected data from optimally placed sensors on the boundary surface of the object under study. Sensor positioning and the choice of the number of sensors are optimized in terms of the resolution of the reconstructed temperature field and the error propagation of the method in case of uncertain measurements. The method can be performed in real time since the major computation burden is performed off-line.     

输电铁塔双轴加速度传感器优化布置

研究输电铁塔结构振动测量用双轴加速度传感器的优化布置问题。以三维模态置信准则(TMAC)为基础,提出一种新的考虑减小冗余度的二维模态置信准则法(RRBMAC法),以实现双轴加速度传感器优化布置,该方法基于改进的二维列主元QR分解获得传感器初始布点,再结合BMAC矩阵非对角元最大值和测点冗余度建立目标函数进行寻优。采用EFI2法和RRBMAC法对钢管塔进行传感器优化布置,采用两个水平方向的模态置信准则和最大奇异值比值对布点方案进行评价,结果显示两种方法的优化效果均首先随传感器数量增加而增强,而后趋于平稳,RRBMAC法较EFI2法能够获得更好的布置效果,且在传感器数目较少的情况下,RRBMAC法即表现出较好的优化能力。另外,采用EFI2法和RRBMAC法对一基格构式输电铁塔进行传感器优化布置,对比分析结果显示RRBMAC法能够获得较好的布置方案。采用优化的传感器布置方式对铁塔进行风振响应实测,并采用NEx T-ERA方法识别铁塔固有频率和阻尼系数,与模态分析结果对比显示NEx T-ERA方法能够提取得到较精确的频率结果。     

面向家庭健康监护的传感网中继节点部署方法

针对面向家庭健康监护的传感网对数据收集和人员定位的特殊需求,研究了在这类传感网中如何部署中继节点的问题。将该问题归纳为构建最小连通k-支配集(k≥3)问题。由于系统部署在室内环境,明确考虑到了室内障碍物对无线传播的影响,提出了计算中继节点最优部署位置的高效算法ORPA。仿真实验表明,相比于随机部署和两阶段部署法,提出的ORPA只需要较少的中继节点就能满足监护系统的需求,并可通过相应的参数设置在节点代价、定位精度和系统能耗之间权衡。所提方法对于在室内环境中部署传感网系统具有有益的参考价值。     

基于LS-SVM与遗传算法的数控机床热误差辨识温度传感器优化策略

提出一种在数控机床热误差辨识建模过程中,利用最小二乘支持向量机结合遗传算法对温度传感器进行筛选与优化的新方法。对布置在一台数控车床上的温度传感器进行了优化,首先根据热模态理论,对传感器进行分组,利用最小二乘支持向量机方法构建数控机床热误差辨识模型,再根据遗传算法对其进行传感器优化布置。结果表明,遗传算法与最小二乘支持向量机方法的结合,不但很好地避免温度测点的相互影响,保证模型精度,而且节约了硬件成本,提高了辨识建模速度。     

应变传感器优化配置研究

传统传感器优化配置准则是以位移模态为目标对传感器的位置进行优化配置，不适用于应变传感器位置的优化。为此，本文针对应变传感器优化配置问题，理论推导出应变模态具有正交性，并以此为基础提出基于应变模态保证准则的虚变传感器优化配置准则，对利用应变模态矩阵信息阵初步拟定出的一小组传感器位置进行了研究。最后以一个复合材料四端简支板为例，对本文方法的可行性进行分析研究，结果表明，本文所建议的方法能更加有效地配置虚变传感器。     

基于IGBT中频感应加热电源的研究

中频电源已广泛应用于工业加热领域。结合实际讨论了一种新型晶闸管感应加热电源主电路结构及工作原理,该电源采用成熟的变频技术,由全控型器件构成串联谐振式逆变电路,解决了工频加热效果差和浪费电能等问题,具有功率调节范围宽,频率变化小的优点,适用于中小功率系统。     

Weld deviation detection based on wide dynamic range vision sensor in MAG welding process

Weld deviation detection is a precondition for welding automation. Capturing high-quality welding images and extracting deviation information using image processing methods are two steps for weld deviation detection. In this paper, based on the analysis of the imaging characteristics during metal active gas (MAG) welding process, real-time welding images are acquired clearly and steadily using a wide dynamic range vision sensor. According to the connection relationship between the top of the arc and the end of the wire during MAG welding process, a method for determining the wire centreline is proposed. After extracting the precise arc region, the region of interest (ROI) is segmented along the welding direction. To detect the two edges of the V-groove, an improved Canny algorithm is developed. Furthermore, both the Hough Transform and a screening method based on prior knowledge are used to connect V-groove edges. The V-groove centreline is then determined. As a result, the weld deviation between the wire centreline and the V-groove centreline is calculated. Further experiments showed that the precision range of deviation detection can be controlled within ±0.25 mm, which can meet the requirement of real-time welding. This deviation can be used as the input variable for a welding robot, thus laying the foundation for MAG welding automation.     

Data correlation analysis for optimal sensor placement using a bond energy algorithm

Optimal sensor placement is one of the crucial and fundamental factors for constructing a cost-effective structural health monitoring system and is related to the effective evaluation of the state of the structure. Structural responses are correlated to some extent, as the structural behavior is continuous. Based on the above two considerations, the question arises of how to obtain the maximum amount of information for understanding the structure using measurements from limited sensors and not be limited to direct monitoring at the placements where the limited sensors are located. Data correlation analysis for optimal sensor placement is proposed using a bond energy algorithm, in which the objectives, such as structural response evaluation covering the maximum structural responses using measurements from sensors located at the optimal placements, are taken into account. The data correlation analysis is conducted for the structural responses, and the correlation matrix is established. Furthermore, the optimal sensor placements and the correlation of the responses at element locations can be determined using the bond energy algorithm. A Schwedler single-layer spherical lattice dome-like structure, which is a common large space steel structure, is used to simulate the structural responses and verify the effectiveness of the proposed method by discussion of different scenarios of parameter selection.     

无线传感器网络簇头半径自适应调节路由算法

针对LEACH(low energy adaptive clustering hierarchy)算法以随机概率轮选簇头,存在簇头分布不均匀、簇头数量波动大以及簇头选取时未考虑节点剩余能量等问题,提出簇头半径自适应层次型路由算法(cluster-head range adaptive adjustment clus-tering routing,CRACR),引入节点剩余能量作为权重因子选取簇头,采用自适应调节机制控制簇头广播消息的广播半径大小,根据节点的位置和剩余能量分配时隙。通过仿真实验,结果表明CRACR算法的第1个节点死亡"回合"数比LEACH提高了55%以上,节能性能得到了明显的提高。     

Design and analysis of an infrared range sensor system for floor-state estimation

Most blind and vision-impaired people use a white cane or a guide dog to aid their walking. The conventional white cane helps the user to perceive the environment simply by identifying the presence of nearby obstacles. In the present study, three infrared range sensors were used to identify the floor state. The sensor system, affixed to the user’s belt, does not require swinging motion or any other movement by the user. The three sensors are configured radially, and the design parameters are selected based on the sensor characteristics. The main difference from the conventional range sensor system for the blind is that the infrared range sensor system identifies three discrete states (even surface, ascending stair, descending stair). The condition for the state transition was derived from a sensor system model. Additionally, the effects of sensor system movement were verified by covariance analysis.     

A note on fast computation of effective independence through QR downdating for sensor placement

A simple and fast computational algorithm of the Effective Independence for sensor placement is presented in the paper. It is based on the relationship between the Effective Independence and Modal Kinetic Energy method, and on a downdating algorithm of the QR decomposition for a reduced modal matrix. Traditional computations of the Effective Independence, which tries to render the target modes as linearly independent at possible and is significant and influential in the field of sensor placement, require the eigenvalue decomposition or inversion of the Fisher Information matrix, and both are costly. By virtue of the connection between the Modal Kinetic Energy and Effective Independence derived by the authors, the norms of the orthonormal rows after the QR decomposition of the modal matrix can be employed to compute the Effective Independence. Moreover, new downdating steps of the QR decomposition based on the combination of the modified Gram–Schmidt and Householder transformations are implemented, which further improved its efficiency by eliminating unnecessary expensive QR decompositions in the iterations. The computational burden for traditional methods and the proposed ones are investigated in terms of the floating point operations required. Finally, a numerical example shows that the new algorithms run much more quickly with fewer computation steps, has the advantages of simplicity and clarity in physical significance, and is stable.     

Frequency response adaptation of PI controllers based on recursive least-squares process identification

The frequency domain approach to adaptive control or autotuning of proportional plus integral (PI) controllers is considered in this paper. The frequency response of the process is computed from an overparametrized recursive least-squares (RLS) model and used at sample intervals to tune the PI. By simulations it is shown that the frequency response estimates converge more quickly and are more constant in the presence of disturbances than the RLS coefficients from which they are calculated. The frequency response estimates are therefore more reliable for controller tuning. The method can handle concurrent gain variation of 50% and time constant or delay variations of 100%. The method is implemented and experimentally verified on a pilot distillation column.     

Optimal robot placement using response surface method

This paper is concerned with a new approach for optimal placement of a prescribed task in the workspace of a robotic manipulator. The approach is resulted by applying response surface method on concept of path translation and path rotation. A robotic optimization tool based on this approach is developed as an add-in to RobotStudio. The methodology has been carefully verified by optimizing the position of several kinds of industrial robots and paths in four showcases to attain minimum cycle time. The results indicate that an increase in productivity up to 37%, compared to the admissible location with the highest cycle time, is achieved by optimally positioning the task in the robot workspace.     

基于RCSA与GA的铣刀刀尖点频响函数预测

基于响应耦合子结构分析法建立了铣刀刀尖点的频响函数预测模型,针对其中主轴—刀柄基座系统频响函数矩阵难以理论计算和实验测试的问题,提出了基于实验模态测试与遗传算法寻优相结合的主轴—刀柄基座系统频响函数矩阵的优化拟合方法。以VMC850E型立式加工中心主轴系统为研究对象,基于上述方法对铣刀刀尖点频响函数进行了预测,并与其实测频响函数进行对比。结果表明:刀尖点的预测频响函数曲线与实测频响函数曲线符合较好,预测频响函数的固有频率与实测固有频率在0~4 000Hz范围内的相对误差小于4.37%。     

Frequency slice wavelet transform for transient vibration response analysis

This paper introduces a new kind of time–frequency signal analysis method, called frequency slice wavelet transform (FSWT), by means of extension of short-time Fourier transform (STFT) defined directly in frequency domain. The original signal can be decomposed by frequency slice function (FSF), which is similar with the wavelet base but can be designed very freely. At the same time, the original signal can be reconstructed by a FSWT representation in an easy way without the strict limitation of wavelet theory. Some new characteristics of its time–frequency window will be shown. Due to these features, FSWT is more flexible to fit ever-changing signals, and convenient to analyze and control in application. Next, the frequency resolution ratio of signal and Dirac function, etc., are employed to study FSWT, and to select a new scale parameter. The new scale is a good balance factor between time and frequency resolution. Moreover a fast discrete algorithm of FSWT is completed. Its application is focused on transient vibration signal analysis in this paper. FSWT can not only individually represent each modal signal in frequency domain, but also correctly show its details in time domain. FSWT helps to discover some new features of the experimental signal obtained from a small laboratory bridge monitoring system. By using FSWT, the filtering under high noise, and the segmenting of signal with high damping and close modes of frequency, will be discussed. Finally, the summary shows that this paper will be able to provide a more available tool for signal analyzing simultaneously in time–frequency domain, and further to refine the wavelet theory.     

Frequency response function shape-based methods for structural damage localisation

The ultilisation of structural shape signals for damage localisation has shown some promise, especially in the applications where an accurate finite element model of the structure is not available. For this purpose, traditional shape signals, like mode shapes, flexibility matrices, uniform load surface (ULS) and operational deflection shapes (ODS) have been widely used. Using frequency response function (FRF) shapes for structural damage localisation is however, a relatively new but promising technique. Unlike mode shapes, ULS and ODS, FRF shapes are defined on broadband data and so have potential to reveal damage location more clearly. Another advantage of using FRF shapes is that the test data can be directly used without the necessity of conducting modal identification. Nevertheless, some problems associated with this approach still remain to be solved. No solid foundation or deduction about the use of FRF shapes for damage localisation has been given in any literature so far. In addition, it has been observed that this method only works for a low-frequency range. This limitation of FRF shapes has not been explained or well treated so far. In this study, a scheme of using FRF shapes for structural damage localisation is proposed. Methods within this scheme include some important modifications like using the imaginary parts of FRF shapes and normalising FRF shapes before comparison. The theoretical explanation of using FRF shapes for damage localisation is presented and the limitations of the previous FRF shape methods have been overcome. The proposed methods have shown great potential in structural damage localisation.