共查询到19条相似文献，搜索用时 140 毫秒
1.
模态试验中传感器优化配置的逐步削减法 总被引：8，自引：0，他引：8
讨论了模态实验中传感器的配置问题。以模态置信度MAC矩阵的最大非对角元为目标函数,利用逐步削减法得到传感器的配置,并保留结构振型矩阵的QR分解得到的自由度,提出了传感器配置必须结合优化效果和经济性两方面综合考虑。以一座具有74个可测自由度的海洋平台为算例,采用逐步削减法得到了12个最优传感器位置,并与逐步累积法进行了比较。 相似文献
2.
提出1种适用于海上风力发电支撑结构的模态振型扩阶方法。该方法无需借助转换矩阵实现振型扩阶,而是依靠实测模态并通过修正有限元模型对应振型在未测试自由度的振型值而获得空间完备的模态振型,并且所发展的方法在一定程度上可以忽略有限元模型存在的建模误差,是1种直接的估算方法,计算效率相对较高。文中采用三桩导管架式海上风力发电支撑结构验证提出方法的正确性以及在低阶模态振型扩阶上的优越性。数值结果表明,该方法对传感器位置、数量依赖程度低,尤其对于海上风电结构,仅在结构的水深较浅部位布置少数传感器即可比较精确的实现低阶模态振型扩阶,具有良好的工程应用前景。 相似文献
3.
研究线性系统在正弦扰动下的扰动抑制问题。对于一类受正弦扰动的n阶线性系统,提出了一种具有二阶动态特性的状态反馈控制算法。设计的动态反馈控制律结构由两部分构成。首先利用内模原理,在控制器中嵌入了正弦扰动的模态矩阵,实现了闭环系统的无静差扰动抑制。然后通过设计控制器中的n+2个参数,使闭环系统的极点实现任意配置,从而保证了闭环系统的指数渐近稳定性。数值仿真算例说明了控制策略的有效性。 相似文献
4.
提出了 1种能够比较准确地识别剪切型体系的结构参数 (各层质量和层间刚度 )的方法———消去刚度法。该方法从剪切型结构体系的特征值问题出发 ,利用剪切型结构系统质量矩阵和刚度矩阵的特殊形式 ,通过消去各层的刚度系数 ,得到了结构系统的各层质量比表达式。在结构总质量已知的情况下 ,仅利用系统的任意两阶模态信息就可以确定出各层质量 ,并进而计算出层间刚度 ,实现了结构物理参数的递推识别。数值模拟结果表明 ,该方法识别精度较高 ,便于工程应用 ,可以用于类似结构体系的物理参数的初步估计。 相似文献
5.
研究特征系统实现算法在模态识别过程中的噪声处理问题。特征系统实现算法为目前土木工程领域应用较为广泛的一种模态识别法。在处理实测数据时,特征系统实现算法将实测数据分解为结构真实信号和噪声信号,从而将噪声消除。分块Hankel矩阵的维数对信噪分离过程影响很大。提出当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号可以最好的分离。通过在实测信号里添加噪声(产生噪声-噪声信号),将实测信号和噪声-噪声信号识别的结果进行比较,提出了1种验证识别模态参数是否为结构真实模态的检验方法。本文应用导管架平台实例来验证提出方法的适用性。结果表明,当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号能够有效地分离,此时添加的噪声主要影响噪声信号部分。由实测信号和噪声-噪声信号识别的模态参数非常吻合。 相似文献
6.
研究特征系统实现算法在模态识别过程中的噪声处理问题.特征系统实现算法为目前土木工程领域应用较为广泛的一种模态识别法.在处理实测数据时,特征系统实现算法将实测数据分解为结构真实信号和噪声信号,从而将噪声消除.分块Hankel矩阵的维数对信噪分离过程影响很大.提出当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号可以最好的分离.通过在实测信号里添加噪声(产生噪声-噪声信号),将实测信号和噪声—噪声信号识别的结果进行比较,提出了1种验证识别模态参数是否为结构真实模态的检验方法.本文应用导管架平台实例来验证提出方法的适用性.结果表明,当分块Hankel矩阵的分块行与分块列数接近时,真实和噪声信号能够有效地分离,此时添加的噪声主要影响噪声信号部分.由实测信号和噪声噪声信号识别的模态参数非常吻合. 相似文献
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经验模态分解是目前分解非线性非平稳信号的有效方法,但其在应用时存在容易导致信号分解失真的端点效应问题。通过对现有的压制方法所存在的不足进行改进,提出了基于灰度预测的变长度经验模态分解方法,在端点处向外对称延拓一部分原始信号使其变成新的信号,进而利用基于灰度预测的经验模态分解方法计算固有模态函数。每得到一个固有模态函数之后,在两端切掉一定长度的序列,即预测不准确序列,从而避免因该序列被代入下一个固有模态函数的求解而导致中间信号被污染;随后利用正弦叠加信号和非线性非平稳信号等仿真数据进行分解实验。实验结果表明:无论是正弦叠加信号还是非线性非平稳信号,基于灰度预测的变长度经验模态分解方法的计算结果误差均小于常规经验模态分解和基于灰度预测的经验模态分解方法,同时对端点处相位信息的处理也更准确。 相似文献
9.
为实现对大跨度斜拉桥拉索损伤识别以及实际测试时结构高阶模态难以准确获取特点,提出了基于柔度差矩阵斜拉桥拉索损伤识别方法。本文首先给出柔度矩阵定义,然后阐述了基于柔度差矩阵的损伤识别机理,并以润扬大桥为试验对象模拟4种不同的损伤工况研究该方法的适用性。试验研究结果表明,该法能有效的识别出斜拉桥拉索损伤位置。 相似文献
10.
地震拖缆系统的振动是影响海上油气勘探数据采集效率的主要因素,为提高勘探作业效率,研究了地震拖缆系统的主动振动控制问题。地震拖缆系统的重阻尼特性使得实模态控制技术难以实施。在地震拖缆系统有限元模型的基础上,基于模态观测器,在独立复模态空间,通过选择合适的权重矩阵,对地震拖缆的低阶模态设计了稳定的最优控制规律。通过对带有四个水鸟的拖缆系统的主动控制仿真,证明基于复模态的地震拖缆最优控制策略,在最大程度上利用水鸟自带电池能量的基础上,有效地抑制拖缆系统的振动,既能减少悬挂式水鸟更换频率,又能提高数据采集的质量,进而提高勘探作业效率。 相似文献
11.
为平衡能量损耗并用网络生存期最大化,提出1种无线传感器网络(WSNs)中基于能量平衡的节点部署算法.此算法基于距离调整网络部署,也就是根据不同位置的节点能耗调整节点的间距.文中提出能耗最低点并不等于生存期最优.仿真证明基于这种部署策略网络的能耗大大降低,网络生存期比均匀部署策略高160%,同时给出调整距离、网络半径、节点传递范围和节点数量之间的参考关系. 相似文献
12.
The formation of acoustic images in real-time requires an enormous computational burden. To reduce this demand the use of sparse arrays for beamforming is mandated. The design of these arrays for adequate mainlobe width and low sidelobe level is a difficult nonlinear optimization problem. A new approach to the joint optimization of sensor placement and shading weights is discussed. Based on the concept of importance sampling an optimization method is presented and some examples given to illustrate its effectiveness. 相似文献
13.
A navigational primitive: biorobotic implementation of cycloptic helical klinotaxis in planar motion
Long J.H. Jr. Lammert A.C. Pell C.A. Kemp M. Strother J.A. Crenshaw H.C. McHenry M.J. 《Oceanic Engineering, IEEE Journal of》2004,29(3):795-806
A broad diversity of microorganisms and larval aquatic animals swim along a helical trajectory. Helical movement toward or away from stimuli involves the detection of gradients, alteration of the helical trajectory, and gradient tracking. Using sensory and neural circuitry models from swimming simulations of tadpole-like ascidian larvae (Phylum Chordata, Subphylum Urochordata), we built and tested a single-sensor, surface-swimming, tail-flapping robot that swims up a light gradient and holds station at an orbital around an area of high intensity. We implemented the same neural circuitry in a terrestrial, wheeled robot with a single photoresistor; it exhibited similar navigational behavior. We also mathematically modeled single-sensor robots navigating in plane. The simulated robots showed the importance of sensor placement and excitation field on navigational behavior. When the sensor placement and excitation field of the simulated robot matched that of the embodied robots, navigational behavior was similar. These results 1) tested and supported a proposed neural circuitry model, 2) showed the simplicity and effectiveness of using a single light sensor for navigation, and 3) demonstrated the use of helical motion in two dimensions. 相似文献
14.
Using simulation results from three different regional ocean models (HOPS, ROMS and FVCOM) we show that only a few spatio-temporal POD (proper orthogonal decomposition) modes are sufficient to describe the most energetic ocean dynamics. In particular, we demonstrate that the simulated ocean dynamics in New Jersey coast, Massachusetts Bay and Gulf of Maine is energetically equivalent to the wake dynamics behind a cylinder at low Reynolds number. Moreover, the extrema of the POD spatial modes are very good locations for sensor placement and accurate field reconstruction. We employ a modified POD theory to incorporate a limited number of measurements in reconstructing the velocity and temperature fields, and we study systematically the corresponding reconstruction errors as a function of the sensor location, number of sensors, and number of POD modes. This new approach is quite accurate in short-term simulation, and hence it has the potential of accelerating the use of real-time adaptive sampling in data assimilation for ocean forecasting. 相似文献
15.
Bettina Knig Oliver Kohls Gerhard Holst Ronnie N. Glud Michael Kühl 《Marine Chemistry》2005,97(3-4):262-276
We describe the fabrication of organically modified sol–gel (ORMOSIL) planar optodes for mapping the two-dimensional oxygen distribution in sediments. All sensor foils were based on the use of ruthenium(II)-tris-(4,7-diphenyl-1,10-phenantrolin)-perchlorate, which is a fluorescent dye quenched dynamically by oxygen. Sensors made with different sol–gel immobilisation matrices, different concentrations of precursors and indicator dye, as well as different types of scattering particles co-immobilised in the sensor foil were investigated systematically. Optimal sensor performance was obtained with dye concentrations of 2–10 mmol/kg in an immobilisation matrix made of diphenyldiethoxy-silan and phenyltriethoxy-silan precursors with addition of organically coated TiO2 particles. The sensors exhibited a good mechanical stability and a high sensitivity from 0% to 100% oxygen, which remained constant over at least 36 days. The planar optodes were used with a fluorescent lifetime imaging system for direct mapping of the spatio-temporal variation in oxygen distribution within marine sediment inhabited by the polychaete Hediste diversicolor. The measurements demonstrated the spatio-temporal heterogeneity of the oxygen distribution in bioturbated sediments due to burrow structures and non-constant irrigation activity of the polychaete, which is difficult to resolve with microsensors or with traditional biogeochemical techniques. 相似文献
16.
《Oceanic Engineering, IEEE Journal of》2006,31(2):504-510
A new method for estimating directions-of-arrival (DOA) of multiple spatial narrowband signals in the presence of spatially nonuniform independent sensor noise with unknown covariance is presented. An estimate of the colored noise-covariance matrix is given first. The received data for parameter estimation is then prewhitened using the estimated noise covariance, hence, overcoming the highly biased estimates. Furthermore, the performance improvement of standard MUSIC method is confirmed by computer simulations. 相似文献
17.
This paper reports the development and experimental evaluation of two in situ least squares techniques for estimating the alignment matrix of Doppler sonars commonly used for precision navigation of oceanographic submersibles. Most previously reported methods addressed the problem of single degree-of-freedom heading alignment using bottom-lock Doppler sonar data and global positioning system (GPS) navigation data. This paper reports and evaluates two techniques for three degree-of-freedom calibration of attitude and Doppler sonar sensors using sensor data available to vehicles at full ocean depth. The first technique provides a general linear least squares estimate of the alignment matrix. The second technique results in a least squares alignment matrix estimate constrained to the group of rotation matrices. The performance of these estimates is evaluated with a laboratory remotely operated vehicle (ROV) and a field-deployed autonomous underwater vehicle (AUV). Experimental results are reported which demonstrate that Doppler navigation employing the reported alignment calibration techniques significantly improves navigation precision. The experiments show that the latter technique provides calibration estimates that improve Doppler navigation precision not only on the calibration data set itself, but also provide improved precision over a wide variety of vehicle trajectories other than the calibration data set. 相似文献
18.
Many high-resolution bearing estimators require the explicit calculation of the eigenvectors and eigenvalues of the cross-spectral matrix of the sensor outputs. Once the eigenvectors have been calculated, various estimators can be derived by altering the eigenvalues to give a reweighting of the eigenvectors. These weighting functions are reminiscent of ideal filter responses in analog filter theory, where practical filters are designed by using polynomial approximations to the ideal desired response. The approximation theory developed for filter design is used to derive high-resolution bearing estimators that do not require explicit calculation of the eigenvectors 相似文献
19.
Victor S. Kuwahara Grace Chang Xiaobing Zheng Tommy D. Dickey Songnian Jiang 《Journal of Oceanography》2008,64(5):691-703
Buoy-mooring platforms are advantageous for time-series validation and vicarious calibration of ocean color satellites because
of their high temporal resolution and ability to perform under adverse weather conditions. Bio-optical data collected on the
Bermuda Testbed Mooring (BTM) were used for comparison with satellite ocean color data in an effort to further standardize
sampling and data processing methods for high quality satellite-mooring comparisons. Average percentage differences between
satellite-measured and mooring-derived water leaving radiances were about 20% at the blue wavelengths, decreasing to as low
as 11% in the blue-green to green wavebands. Based on a series of data processing methods and analyses, recommendations concerning
rigor of quality control for collected data, optimal averaging of high-frequency data, sensor self-shading wind corrections,
and instrumentation placement requirements are given for the design and application of optical moorings for ocean color satellite
validation. Although buoy-mooring platforms are considered to be among the very best methods to validate ocean color satellite
measurements, match-up discrepancies due to water column variability and atmospheric corrections remain important issues. 相似文献