scholarly journals Multi-Input-Multi-Output Continuous Swept-Sine Vibration Test Realization by Inverse Multistep Prediction Model

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Wei Zheng ◽  
Huaihai Chen ◽  
Zhengbo Luo ◽  
Amr A. Nassr
Keyword(s):  
Prediction Model ◽  
Time Domain ◽  
Original System ◽  
Inverse System ◽  
Vibration Test ◽  
System Method ◽  
Frequency Domain Methods ◽  
Vibration Tests ◽  
The Time Domain ◽  
Drive Signals

As frequency-varying sine excitations in rotating machines are always emerging during run-ups and shutdowns, the multi-input-multi-output (MIMO) swept-sine test is of utter significance in product validation. At present, swept-sine vibration tests are mostly conducted with frequency-domain methods, where drive spectra are generated and updated by frequency response function (FRF), and drive signals are then generated with sinusoid oscillators. In this paper, a time-domain approach using an inverse system method based on a multistep prediction model is developed to realize the MIMO continuous swept-sine vibration test. First, the multistep prediction model of the original system is estimated in the time domain. Then, the inverse multistep prediction model is derived. After that, this model is truncated to guarantee the robustness of the inverse system and the smoothness of the generated drive signals. At last, the proposed method is validated by a simulation example with a cantilever beam and an actual test by using a three-axis shaker. The results show that the MIMO continuous swept-sine vibration test can be operated effectively by the proposed method.

Signal Acquisition and Analysis of Shaft Unbalance Vibration Test

2014 ◽  
Vol 945-949 ◽  
pp. 1090-1093
Author(s):  
Hai Peng Zhang ◽  
Hong Wu Chen ◽  
Bin Hu ◽  
Cheng Tian
Keyword(s):  
Fault Diagnosis ◽  
Time Domain ◽  
Time Domain Analysis ◽  
Rotating Machinery ◽  
Vibration Test ◽  
Signal Acquisition ◽  
Analysis Method ◽  
Characteristic Parameters ◽  
Test Platform ◽  
The Time Domain

This paper simulated the unbalance vibration conditions by the vibration test platform, measuring some common characteristic parameters of unbalance vibration fault diagnosis. This paper chose the time-domain analysis method, processing the characteristic parameters of the test, so as to achieve the purpose of vibration diagnosis. Through a large number of experimental data, this paper verified the feasibility and the effectiveness of the proposed approach to the unbalance fault diagnosis. The method proposed in this paper not only can be applied to unbalance fault diagnosis, but also can be promoted to apply to the fault diagnosis of other rotating machinery.

Comparing Frequency and Time Domain Simulations for Geometry Optimization of a Floating Offshore Wind Turbine Mooring System

2018 ◽  
Author(s):  
Ajit C. Pillai ◽  
Philipp R. Thies ◽  
Lars Johanning
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Pareto Front ◽  
Geometry Optimization ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Mooring System ◽  
Efficient Design ◽  
Frequency Domain Methods ◽  
The Time Domain

This paper explores geometry optimization of an offshore wind turbine’s mooring system considering the minimization of the material cost and the cumulative fatigue damage. A comparison of time domain simulations against frequency domain simulations is made to explore the suitability of these methods to the design process. The efficient design options, the Pareto front, from the frequency domain study are also re-evaluated using time domain simulations and compared against the time domain Pareto front. Both the time and frequency domain results show optimal results utilizing similar design philosophies, however, the frequency domain methods severely under predict the fatigue loads in the mooring system and incorrectly class infeasible solutions as feasible. The frequency domain is therefore not suitable for optimization use without some external means of applying engineering constraints. Furthermore, re-evaluation of the frequency domain solutions provides guidance to the uncertainty and the necessary design fatigue factors required if implementing frequency domain methods in design.

On the Extension of a Harmonic Balance Method for the Simulation of Compressor Casing Treatments

2016 ◽  
Author(s):  
Christian Voigt ◽  
Graham Ashcroft
Keyword(s):  
Time Domain ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Balance Method ◽  
Nonlinear Frequency ◽  
Transonic Compressor ◽  
Frequency Domain Methods ◽  
Blade Tip ◽  
The Time Domain ◽  
Casing Treatments

In recent years both linear and nonlinear frequency domain methods have become increasingly popular in the simulation and investigation of time-periodic flows in turbomachinery. In this work the extension of an alternating frequency/time domain Harmonic Balance method to support arbitrary inter-domain block interfaces, with possibly different frames of reference, is described in detail. The approach outlined is based on the time-domain, area-based interpolation algorithm originally developed for the investigation of casing treatments. In this paper, it is shown that by solving the domain coupling problem in the time-domain it is possible to accurately and efficiently capture the flow physics of such complex, nonlinear problems as blade tip interaction with casing treatments in transonic compressors. To demonstrate and verify the basic algorithm the advection of a simple entropy disturbance in a subsonic duct flow is first computed. Secondly, unsteady flow due to rotor-stator interaction in a transonic compressor stage is simulated and the data compared with reference numerical methods. Finally, to validate the method a single stage transonic axial compressor with casing treatments is simulated and the results are compared with previously published time-domain simulations as well as experimental data based on particle image velocimetry measurements in the blade tip region.

Flutter Analysis Using Quasi-Steady Time-Domain Flutter Derivatives

2019 ◽  
Author(s):  
Sébastien Maheux ◽  
Sébastien Langlois ◽  
Frédéric Légeron
Keyword(s):  
Time Domain ◽  
Forced Vibration ◽  
Bridge Deck ◽  
Domain Model ◽  
Vibration Tests ◽  
The Time Domain ◽  
Development And Validation ◽  
Derivatives Of ◽  
Great Belt ◽  
Flutter Derivatives

<p>To be able to perform nonlinear flutter analyses for bridges, time‐domain approaches should be used instead of Scanlan’s formulation of self‐excited forces. Thus, this paper addresses the development and validation of a modified quasi‐steady time‐domain model similar to Scanlan’s approach that is based on the velocity and acceleration of the bridge deck. In this formulation, quasi‐steady time‐domain flutter derivatives measured in the wind tunnel through forced‐vibration tests at absolute constant velocity and acceleration are used. For this, a unique test rig, which can be used either for free‐ or forced‐vibration tests, was utilized. By measuring the time‐domain flutter derivatives of the Great Belt Bridge, their nondimensionalization with respect to the bridge‐deck width, velocity and acceleration of the deck is validated. Then, time‐domain flutter analyses are performed using this new model. They agree with the experimental critical speed and the prediction using Scanlan’s model.</p>

Numerical analysis of the effects on a floating structure induced by ship waves

2011 ◽  
Vol 55 (02) ◽  
pp. 124-134
Author(s):  
L. Sun ◽  
G.H Dong ◽  
Y. P. Zhao ◽  
C. F. Liu
Keyword(s):  
Time Domain ◽  
Equation Of Motion ◽  
Offshore Structures ◽  
Floating Body ◽  
Kutta Method ◽  
Floating Structure ◽  
Ship Waves ◽  
Runge Kutta Method ◽  
Frequency Domain Methods ◽  
The Time Domain

Ship-generated waves can make bad effects on offshore structures. A numerical model is presented for evaluating the forces exerted on a nearby floating structure by ship generated waves. The ship waves were modeled using Michell thin-ship theory (Wigley waves), the forces were computed using a boundary element method in the time domain, and the motions of the offshore structures were evaluated using the equation of motion of the floating body, and predicted using the fourth-order Runge-Kutta method. The numerical method was validated by comparing its results to those of frequency-domain methods reported in the literature. It was then applied to calculate the force of ship waves on a floating box. The ship's speed, dimensions, and distance were varied. The numerical results indicate some useful rules for varying these factors.

A Comparison of Time Domain and Frequency Domain Approaches for the Fully Coupled Analysis of Deepwater Floating Systems

2006 ◽  
Author(s):  
Ying Min Low ◽  
Robin S. Langley
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Coupled Analysis ◽  
Integration Scheme ◽  
Global Coordinate System ◽  
Mooring Lines ◽  
Frequency Domain Methods ◽  
The Time Domain ◽  
Fully Coupled ◽  
Fully Coupled Analysis

The recognition of the need for a fully coupled analysis of deepwater floating production systems has led to the research and development of several coupled analysis tools in recent years. Barring a handful of exceptions, these tools and available commercial packages are invariably in the time domain. This has resulted in a much better understanding and confidence in time domain coupled analysis, but less so for the frequency domain approach. In this paper, the viability of frequency domain coupled analysis is explored by performing a systematic comparison of time and frequency domain methods using computer programs developed in-house. In both methods, a global coordinate system is employed where the vessel is modeled with six degrees-of-freedom, while the mooring lines and risers are discretized as lumped masses connected by extensional and rotational springs. Coupling between the vessel and the mooring lines is achieved by stiff springs, and the influence of inertia and damping from the lines are directly accounted for without the need for prior assumptions. First and second order wave forces generated from a random environment are applied on the vessel, as well as drag and inertia loading on the lines. For the time domain simulation, the Wilson-theta implicit integration scheme is employed to permit the use of relatively large time steps. The frequency domain analysis is highly efficient despite being formulated in global coordinates, owing to the banded characteristics of the mass, damping and stiffness matrices. The nonlinear drag forces are stochastically linearized iteratively. As both the time and frequency domain models of the coupled system are identical, a consistent assessment of the error induced by stochastic linearization can be made.

Research on the Equivalent Circuit Modeling of Oil-Paper Insulation of Transformer by Analyzing the Dielectric Spectra

2012 ◽  
Vol 260-261 ◽  
pp. 408-413
Author(s):  
Yong Qing Liu ◽  
Jin Ding Cai ◽  
Yan Xue Guo
Keyword(s):  
Equivalent Circuit ◽  
Time Domain ◽  
Equivalent Circuit Model ◽  
Debye Model ◽  
Dielectric Polarization ◽  
Dielectric Spectra ◽  
Equivalent Circuit Modeling ◽  
Frequency Domain Methods ◽  
The Time Domain ◽  
Paper Insulation

To assess the oil-paper insulation of transformer, it is necessary to establish the equivalent circuit for it regardless of using the time domain methods or frequency domain methods. Based on the principle of dielectric polarization, the extended Debye model is always adopted for the equivalent circuit of oil-paper insulation in transformer in most cases; however, it is usually difficult to determine the number of relaxation mechanisms in the model. This paper presents a method to determine it by the time domain dielectric spectra, namely, conduct differential operation for the depolarizing current of transformer’s oil-paper insulation to obtain the time domain dielectric spectra, and the number of spectrum peaks is equal to that of relaxation mechanisms. Thereby, the extended Debye model of the equivalent circuit of the oil-paper insulation of transformer can be built. This paper describes the analytical procedures of the time domain dielectric spectra method in detail and presents examples to validate its feasibility and rationality in determining the equivalent circuit model of transformer’s oil-paper insulation.

scholarly journals Filters, Waves and Spectra

Econometrics ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 35 ◽  
Author(s):  
D. Pollock
Keyword(s):  
Frequency Response ◽  
Frequency Domain ◽  
Time Domain ◽  
Econometric Analysis ◽  
Frequency Domain Methods ◽  
The Time Domain ◽  
Filtering Techniques

Econometric analysis requires filtering techniques that are adapted to cater to data sequences that are short and that have strong trends. Whereas the economists have tended to conduct their analyses in the time domain, the engineers have emphasised the frequency domain. This paper places its emphasis in the frequency domain; and it shows how the frequency-domain methods can be adapted to cater to short trended sequences. Working in the frequency domain allows an unrestricted choice to be made of the frequency response of a filter. It also requires that the data should be free of trends. Methods for extracting the trends prior to filtering and for restoring them thereafter are described.

Vibration Test and Fault Diagnosis for Main Hoist Gearbox of Heavy Casting Crane

2014 ◽  
Vol 532 ◽  
pp. 374-377
Author(s):  
Zhang Li ◽  
Xing Dong Wang ◽  
Chang Yi Hu ◽  
Chi Zhong Chen ◽  
Li Ming
Keyword(s):  
Fault Diagnosis ◽  
Time Domain ◽  
Planetary Gear ◽  
Vibration Signal ◽  
Vibration Test ◽  
Signal Characteristic ◽  
Engineering Software ◽  
Fault Type ◽  
The Time Domain ◽  
Main Hoist

In view of the structure and running characteristics of gearbox of large and special crane, we have respectively carried out vibration test of fault and free-fault gearbox containing planetary gear in the work. With the help of Matlab engineering software, we can read and process the collected vibration signal of gearbox and draw the time-domain and frequency-domain graph. Through the comparative analysis of vibration information of gearboxes, we can determine the link between fault type and signal characteristic value, effectively realize the fault diagnosis of gearbox.

scholarly journals Modeling the Gas price data Using Periodogram and Fourier Series Analysis: استخدام التحليل في مجال التردد لنمذجة بيانات مبيعات الغاز الطبيعي في الولايات المتحدة الأمريكية بواسطة شكل الدورة وتحليل سلسلة فورير

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Safia Abdullah Al Fadhel, Amal Al-Ser Al-khadir, Obeid Mahmo
Keyword(s):  
Fourier Series ◽  
Frequency Domain ◽  
Time Domain ◽  
Domain Analysis ◽  
The United States ◽  
Frequency Domain Method ◽  
Series Analysis ◽  
Frequency Domain Methods ◽  
The Time Domain ◽  
Fourier Series Analysis

:   This paper takes into account the application of the Periodogram and the Fourier Series Analysis. It is one of the non-parametric methods of Frequency domain analysis or spectral analysis of time series using Gas sales data in the United States of America from 1993-2014. In order to achieve these objectives، the data were obtained and then the Periodogram and the Fourier series methods were used to analyze the data. Based on the analysis، the cycle of variability within the period under study was 135 months، and a high Accuracy data model was estimated for the Fourier series which included trend، seasonal and error components. The RMSE، MASE and MAE standards were used to confirm the efficiency of the model and the model was then used to predict gas sales for six months، and we have 90% 95% confidence intervals for predictions. In addition، a time domain analysis was provided for the data series using Bok Jenkins method to obtain the appropriate ARMA model and to generate Predictions. Finally، a comparison was made between the accuracy measures of the time domain and frequency domain methods The frequency domain method competed with the time domain and the slight difference in efficiency.

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