Estimation of structural parameters in time domain: A substructure approach

1991 ◽  
Vol 20 (8) ◽  
pp. 787-801 ◽  
Author(s):  
Chan Ghee Koh ◽  
Lin Ming See ◽  
Thambirajah Balendra
Keyword(s):  
Time Domain ◽  
Structural Parameters ◽  
Substructure Approach

Application of the EKE and LSE-UI Based Substructure Approach for Damage Detection with Limited Output Measurements

2011 ◽  
Vol 255-260 ◽  
pp. 4171-4175
Author(s):  
Ying Lei ◽  
Chao Liu
Keyword(s):  
Damage Detection ◽  
Least Squares ◽  
Structural Damage ◽  
Structural Parameters ◽  
Least Squares Estimation ◽  
Complex Case ◽  
Benchmark Problem ◽  
Unknown Inputs ◽  
Limited Output ◽  
Substructure Approach

This paper presents an effort to apply the EKE (extended Kalman estimator) and LSE-UI (least squares estimation for unknown input) technique to detect structures damage with limited output measurements. This technique can be extended to detect structural local damage in complex structures based on substructure approach. Structural parameters and the unknown inputs are identified by a recursive algorithm based on sequential application of the extended Kalman estimator for the extended state vector and the least squares estimation for the unknown inputs. Only a limited number of measured acceleration responses of the benchmark structure subject to unmeasured excitation inputs are utilized. This structural damage detection method is applied to the ASCE SHM benchmark building to test its efficacy and provide a solution to the complex case of the Phase I benchmark problem. Damage detection results indicate that the proposed technique can detect and localize structural damage of the complex benchmark problem with good accuracy.

Optimal Accelerometer Locations for Structural Health Monitoring Using Time-Domain System Identification

2006 ◽  
Vol 321-323 ◽  
pp. 273-277 ◽  
Author(s):  
Soon Jung Kwon ◽  
Hae Sung Lee ◽  
Soo Bong Shin
Keyword(s):  
System Identification ◽  
Structural Health Monitoring ◽  
Fisher Information ◽  
Health Monitoring ◽  
Time Domain ◽  
Fisher Information Matrix ◽  
Structural Parameters ◽  
Hessian Matrix ◽  
Information Matrix ◽  
Structural Health

The paper presents two algorithms for determining optimal accelerometer locations for structural health monitoring when structural condition is assessed by a system identification scheme in time-domain. The accelerometer locations are determined by ranking the components of an effective independent distribution vector computed from a Fisher information matrix. One of the proposed algorithms formulates a Fisher information matrix by multiplying acceleration matrix with its transpose and the other as a Gauss-Newton Hessian matrix composed of acceleration sensitivities with respect to structural parameters. Since the structural parameters cannot be known exactly in an actual application, a statistical approach is proposed by setting an error bound between the actual and the baseline values. To examine the algorithm, simulation studies have been carried out on a two-span planar truss. The results using locations selected by the two algorithms were compared.

scholarly journals Time Domain NMR in Polymer Science: From the Laboratory to the Industry

2019 ◽  
Vol 9 (9) ◽  
pp. 1801 ◽  
Author(s):  
Denise Besghini ◽  
Michele Mauri ◽  
Roberto Simonutti
Keyword(s):  
Time Domain ◽  
Process Development ◽  
Structural Parameters ◽  
Polymer Science ◽  
Vulcanized Rubber ◽  
Recent Developments ◽  
Product And Process ◽  
Space Requirements ◽  
New Generation ◽  
Analytical Tools

Highly controlled polymers and nanostructures are increasingly translated from the lab to the industry. Together with the industrialization of complex systems from renewable sources, a paradigm change in the processing of plastics and rubbers is underway, requiring a new generation of analytical tools. Here, we present the recent developments in time domain NMR (TD-NMR), starting with an introduction of the methods. Several examples illustrate the new take on traditional issues like the measurement of crosslink density in vulcanized rubber or the monitoring of crystallization kinetics, as well as the unique information that can be extracted from multiphase, nanophase and composite materials. Generally, TD-NMR is capable of determining structural parameters that are in agreement with other techniques and with the final macroscopic properties of industrial interest, as well as reveal details on the local homogeneity that are difficult to obtain otherwise. Considering its moderate technical and space requirements of performing, TD-NMR is a good candidate for assisting product and process development in several applications throughout the rubber, plastics, composites and adhesives industry.

Research on the 1.06 μm Reflectivity of Subwavelength Surface-Relief Structure via Finite Different Time Domain Method

2009 ◽  
Vol 79-82 ◽  
pp. 1679-1682
Author(s):  
Wen Juan Huang ◽  
Chun Hua Lu ◽  
Wei Min Tan ◽  
Yan Zhang ◽  
Zhong Zi Xu
Keyword(s):  
Electromagnetic Wave ◽  
Time Domain ◽  
Circular Tube ◽  
Structural Parameters ◽  
Fdtd Method ◽  
Hollow Structure ◽  
Outer Diameter ◽  
Incident Wavelength ◽  
Relief Structure ◽  
Finite Different Time Domain

In this paper, setting 1.06 μm Gaussian modulated pulse electromagnetic wave as irradiation sources, the influences of structural parameters on reflectivity are analyzed by finite different time domain (FDTD) method. The results show that the filled factor and height are key factors for circular tube relief structure with non absorption. The optimal height could be set to 0.2 μm, which is one odd time of the ratio of incident wavelength λ and four equivalent refractive index 4N, then the best filled factor is between 0.7 and 0.9, the ratio of inner and outer diameter could be set between 0.4 and 0.6, and the structure period has little significant influence. Compared with cylinder solid structure, it has been discovered that circular tube hollow structure could weaken the backward energy of electromagnetic wave, and it would be more suitable for antireflection structure than solid cylinder structure. Moreover, we design two another circular tube relief structures simulations with different extinction coefficients, it is found that the reflectivities are lower up to 0.00016% than the non absorption one.

Chatter stability of the constrained layer damping composite boring bar in cutting process

2019 ◽  
Vol 25 (16) ◽  
pp. 2204-2214 ◽  
Author(s):  
Zhang Yuhuan ◽  
Ren Yongsheng ◽  
Tian jishuang ◽  
Ma jingmin
Keyword(s):  
Dynamic Model ◽  
Time Domain ◽  
Structural Parameters ◽  
Frequency Domain Method ◽  
Constrained Layer Damping ◽  
Chatter Stability ◽  
Analysis Model ◽  
Structural Dynamic ◽  
Boring Bar ◽  
Cutting System

Traditional boring bars are generally made up of isotropic metallic materials and exhibit extremely poor chatter suppression ability. For enhancing the chatter stability, using anisotropic composite materials in the preparation of boring bars proves to be an effective method so as to enhance the boring bar’s natural frequency and damping. Additionally, the addition of constrained layer damping (CLD) technology on the composite boring bar can further improve the damping performance. This study aims to develop a theoretical analysis model for the prediction of the chatter stability of the CLD composite boring bar and explore the effectiveness and practicability of the CLD technology in suppressing the chatter of composite boring bar. Based on Euler–Bernoulli beam theory and the complex stiffness method of CLD, the structural dynamic model of the CLD composite boring bar was derived, and some structural parameters of the bar mainly including the ply angle of the composite material, the thicknesses of both damping layer, and constrained layer were also optimized. By combining the linear model of cutting force with a regenerative delay effect and the established dynamic model, the chatter analysis model of the CLD composite boring bar was constructed and the lobe diagram of the chatter stability of the cutting system was plotted by means of frequency domain method. The effects of the ply angle of the composite boring bar, the thicknesses of damping layer, and constrained layer on the chatter stability were examined. By performing time integral of the delay equation of motion, the time-domain response curves of the cutting system are obtained. The chatter stability prediction results based on the lobe diagram fit well with the prediction results on the basis of dynamic stiffness calculation and time-domain numerical integral results.

Innovative substructure approach to estimating structural parameters of shear structures

2018 ◽  
Vol 25 (4) ◽  
pp. e2139 ◽  
Author(s):  
Lijun Xie ◽  
Akira Mita ◽  
Longxi Luo ◽  
Maria Q. Feng
Keyword(s):  
Structural Parameters ◽  
Shear Structures ◽  
Substructure Approach

Time domain estimation of structural parameters

1988 ◽  
Vol 10 (2) ◽  
pp. 95-105 ◽  
Author(s):  
Chin-Hsiung Loh ◽  
Yuan-Huei Tsaur
Keyword(s):  
Time Domain ◽  
Structural Parameters

Structural Modal Parameter Identification Based on Natural Excitation Technique

2013 ◽  
Vol 859 ◽  
pp. 167-170
Author(s):  
Qiang Pei ◽  
Long Li
Keyword(s):  
Parameter Identification ◽  
Time Domain ◽  
Structural Parameters ◽  
Engineering Practice ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Response Data ◽  
Exponential Method ◽  
Time Series Method ◽  
Natural Excitation Technique

Natural excitation technique has found an increasingly wide utilization in civil engineering field. Modal parameter identification in time domain method can identify the structural parameters in the use of impulse response data as input data. The theory of NExT method is presented. By constructing a numerical simulation example under white-noise excitation, and calculating the data by NExT method, the modal parameters can be identified according to complex exponential method and time series-method in time domain. The results and analysis indicate the validity of the method and provide a reference for engineering practice.

scholarly journals Applications of Thermo-TDR Sensors for Soil Physical Measurements

2021 ◽  
Author(s):  
Yili Lu ◽  
Wei Peng ◽  
Tusheng Ren ◽  
Robert Horton
Keyword(s):  
Electrical Properties ◽  
Time Domain ◽  
Structural Parameters ◽  
Time Domain Reflectometry ◽  
State Variables ◽  
Physical Measurements ◽  
Bulk Electrical Conductivity ◽  
Potential Applications ◽  
Thermal And Electrical Properties ◽  
Ice Content

Advanced sensors provide new opportunities to improve the understanding of soil properties and processes. One such sensor is the thermo-TDR sensor, which combines the functions of heat pulse probes and time domain reflectometry probes. Recent advancements in fine-scale measurements of soil thermal, hydraulic, and electrical properties with the thermo-TDR sensor enable measuring soil state variables (temperature, water content, and ice content), thermal and electrical properties (thermal diffusivity, heat capacity, thermal conductivity, and bulk electrical conductivity), structural parameters (bulk density and air-filled porosity) and fluxes (heat, water, and vapor) simultaneously. This chapter describes the theory, methodology, and potential applications of the thermo-TDR technique.

III-Posedness and Regularization Method for Nonlinear Identification Equations in Time Domain

2012 ◽  
Vol 166-169 ◽  
pp. 3282-3289
Author(s):  
Xian Zhong Xie ◽  
Feng Zhang ◽  
Yang Li ◽  
Yong Tan
Keyword(s):  
Least Squares ◽  
Tikhonov Regularization ◽  
Time Domain ◽  
Regularization Method ◽  
Least Squares Method ◽  
Structural Parameters ◽  
Nonlinear Identification ◽  
Calculating Method ◽  
Ill Posed ◽  
Damped Least Squares

The ill-posedness of nonlinear identification equation in time domain of structural dynamics system is studied and a new calculating method to weaken the influence of ill-posedness is proposed. Damped least squares method is an algorithm of Jacobian matrix positive-definable, which can obtain the solution of ill-posed nonlinear identification equation. But the solution is sensitive to the test noise of response in time domain of the structure. To solve the problem of instability of the solution, a new calculating method is proposed which combines damped least squares method with Tikhonov regularization method. First, the estimate of structural parameters is introduced to Tikhonov regularization function, and a more stable identification equation in time domain can be obtained. Second, the identification equation is solved with damped least squares method, and the iterative result is an approximate solution of the former ill-posed problem. The numerical example shows that the new method in this paper is efficient to solve the ill-posed nonlinear identification equation in time domain.

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