scholarly journals Fuzzy Identification of The Reliability State of The Mine Detecting Ship Propulsion System

2019 ◽  
Vol 26 (1) ◽  
pp. 55-64 ◽  
Author(s):  
Michał Pająk ◽  
Łukasz Muślewski ◽  
Bogdan Landowski ◽  
Andrzej Grządziela
Keyword(s):  
Vibration Measurement ◽  
Dynamic State ◽  
Mutual Correlation ◽  
Shaft Line ◽  
Current State ◽  
Signal Characteristics ◽  
Rotational Systems ◽  
Turbine Shaft ◽  
State Changes ◽  
The Time Domain

Abstract The study presents the evaluation and comparative analysis of engine shaft line performance in maritime transport ships of the same type. During its operation, a technical system performs functions for which it was designed. It goes through different states. Dynamic state changes of a rotational system can be identified by means of its vibration measurement. For this purpose, a research was carried out which involved recording vibrations of the analysed rotational systems. The recordings were used for calculating selected characteristics in the time-domain, where one of the most unique is the value of the normalized mutual correlation function. On the basis of the concentration values, the characteristics which unambiguously determine the ability state were selected for further studies. Then an identification method for rotational system non-coaxiality was proposed. The method involves using fuzzy clustering. According to this method the values of input signal characteristics were used to formulate fuzzy clusters of system ability and inability states. The method can be used for identifying the current state of the system. The study presents the results of the application of this method in engine turbine shaft lines of minesweepers, with the rotational system selected as an example. It needs to be noted that the efficiency of identifying the operating state of the system with this method is higher than with other methods described in the literature by authors who deal with this issue. The research results have a significant impact on the evaluation of mechanical properties of the studied objects and directly affect operational states of mechanical systems, including those installed in minesweepers, thus determining their reliability.

Assessment of delamination location in composite laminates based on a chaotic oscillator method

2021 ◽  
Vol 263 (2) ◽  
pp. 4709-4716
Author(s):  
Xuan Li ◽  
Dunant Halim ◽  
Xiaoling Liu
Keyword(s):  
Material Properties ◽  
Composite Laminates ◽  
Damage Index ◽  
Vibration Signal ◽  
Harmonic Excitation ◽  
Vibration Measurement ◽  
Chaotic Oscillator ◽  
Signal Characteristics ◽  
High Level ◽  
Delamination Damage

The work aims to study the assessment of delamination location in composite laminates using vibration measurement with a chaotic oscillator method. Delamination is a type of damage that commonly occurs in composite laminates, which can cause a severe degradation of their material properties. The traditional vibration-based methods can encounter difficulties in detecting and locating these delamination-type damages especially when the size of delamination is relatively small and there is a significant level of noise in its vibration measurement. With this particular consideration, a vibration-based method using a non-linear chaotic oscillator was used in this study due to its sensitivity to the change in vibration signal characteristics. A numerical model of composite laminates with delamination damage under harmonic excitation was developed and the vibration signal obtained from composite laminates was processed using the chaotic oscillator method. A feature named Lyapunov Exponent (LE) was used as a delamination damage index to describe the characteristics of the chaotic oscillator for cases with delamination at varying structural locations. The effects of delamination locations on the developed damage index were analyzed in this work. The results showed that there was a strong correlation between the delamination location and the LE feature, even for the case with a relatively high level of measurement noise. The results demonstrated the effectiveness of the method to identify delamination in composite laminates, which has also the potential to be used to detect other types of damages.

Control of First Order Systems With Bounded Input by Asymptotic Output Tracking With Fractional Regulators

2007 ◽  
Author(s):  
Rube´n Marti´nez ◽  
Israel Mazaira ◽  
Vicente Feliu
Keyword(s):  
State Feedback ◽  
Dynamic State ◽  
Control Input ◽  
Bounded Control ◽  
First Order ◽  
Output Tracking ◽  
The Time Domain ◽  
Rational Order ◽  
Bounded Input ◽  
System Time

In this paper, the control of first order systems by applying fractional regulators in the time domain with bounded input is presented. The design of the proposed fractional regulator, is based in the local asymptotic output tracking of linear systems with bounded control input by linear dynamic state feedback and the reduction of the system time response by the expansion of integer-order models to rational-order one.

On the Evaluation of Dynamic Stresses in Pipelines Using Limited Vibration Measurements and FEA in the Time Domain

1999 ◽  
Vol 121 (1) ◽  
pp. 37-41 ◽  
Author(s):  
W. A. Moussa ◽  
A. N. AbdelHamid
Keyword(s):  
Time Domain ◽  
Minimum Distance ◽  
Exciting Force ◽  
Vibration Measurement ◽  
Dynamic Stresses ◽  
Vibration Measurements ◽  
Pipe Model ◽  
Related Risk ◽  
The Time Domain

A practical technique is investigated for the determination of dynamic stresses in pipelines through the use of finite element method (FEM) and field measurement vibrations at selected points. Numerical simulation of a randomly loaded pipeline structure is used to establish the validity of the technique in the time domain. The analysis is carried out for a fixed-hinged pipe model. The results show that lack of coincidence between the vibration measurement points (VMPs) and the exciting force, or the use of only translational vibration measurements (TVMs) produce an approximate stress picture. The extent of the “error” in these cases is found to depend on the density of the VMPs and the proximity between these points and the exciting force location. A safety-related risk assessment is applied to find the minimum distance between measuring points that is needed to meet design codes reliability specifications.

Understanding Dynamic State Changes in Temporal Lobe Epilepsy

2001 ◽  
Vol 18 (3) ◽  
pp. 246-258 ◽  
Author(s):  
Robert Savit ◽  
Dingzhou Li ◽  
Weiping Zhou ◽  
Ivo Drury
Keyword(s):  
Temporal Lobe Epilepsy ◽  
Temporal Lobe ◽  
Dynamic State ◽  
State Changes

Financial Index Prediction Based on Wavelet Analysis and SVM

2013 ◽  
Vol 303-306 ◽  
pp. 1114-1118
Author(s):  
Xian Tan
Keyword(s):  
Wavelet Analysis ◽  
Frequency Domain ◽  
Time Domain ◽  
Financial Time Series ◽  
Support Vector ◽  
Frequency Domain Method ◽  
Signal Characteristics ◽  
Vector Machines ◽  
Financial Index ◽  
The Time Domain

The analysis of the time sequence can be two ways in the time domain and frequency domain. But many financial time series exhibit strong non-stationary and long memory, which makes many traditional individually focused on the research and analysis of the time domain or frequency domain method is no longer applicable. In this paper, wavelet analysis and support vector machines for use in the time domain and frequency domain have the ability to characterize the local signal characteristics, location and mutation of the singular points and irregular mutation analysis, these mutations detected the degree of significance.

scholarly journals Blade Serial Number Identification Based on Blade Tip Clearance without OPR Sensor

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Liang Zhang ◽  
Qidi Wang ◽  
Huiqun Yuan ◽  
Xin Li
Keyword(s):  
Rotation Speed ◽  
Tip Clearance ◽  
Vibration Measurement ◽  
Dynamic State ◽  
Measurement Technology ◽  
Static State ◽  
Identification Method ◽  
Serial Number ◽  
Blade Tip ◽  
Blade Tip Clearance

Blade serial number identification is one of the key issues in blade tip-timing vibration measurement without once-per-revolution (OPR) sensor. In order to overcome the shortcomings of the existing blade serial number identification methods without OPR sensor, a new identification method of blade serial number based on blade tip clearance is proposed in this paper. The relationship between blade tip-timing data and blade serial number can be identified by the matching relationship between blade tip clearance under static state and dynamic state. According to the finite element simulation and experimental data, the accuracy of the blade serial number identification method based on blade tip clearance is verified by using the OPR sensor method. The results show that in the nonresonant rotation speed region, the method can identify the blade serial number, and the identification result is consistent with the result of the OPR sensor method. In the resonance rotation speed region, when the blade tip clearance change caused by the blade circumferential bending vibration is less than the dispersion of initial blade tip clearance, the method in this paper can accurately identify the blade serial number. Otherwise, the inference method can be used. It provides theoretical support and technical basis for the engineering application of blade tip-timing vibration measurement technology without OPR sensor.

scholarly journals ANALYSIS OF THE BMA K2400 VERTICAL CENTRIFUGE TURBINE IN TERMS OF BALANCING AND VIBRATION DIAGNOSTICS

2021 ◽  
Vol 297 (3) ◽  
pp. 71-80
Author(s):  
MIKOŁAJ SZYCA
Keyword(s):  
Load Transfer ◽  
Dynamic Condition ◽  
Friction Pair ◽  
Vibration Signal ◽  
Vibration Measurement ◽  
Dynamic State ◽  
Material Surface ◽  
Physical Damage ◽  
Technological Defect ◽  
Acceleration Sensors

Physical damage to a material is a diffuse defect in the form of vacancies, microcracks, micro-voids or damaged micro-volumes, which reduce the effective or load-bearing part of the material. Surface fatigue defects, such as deformation and cracks, occur in the bearing during the load transfer. Imbalance is a practical problem in the operation of many rotating machines, causing not only increased vibration of the machine, but also leading to accelerated wear of the rotor bearings. The subject of this work is the analysis of the dynamics of the BMA K2400 centrifuge in terms of the possibility of correcting the balance in the given dynamic state. The paper describes the individual stages of solving the problem of excessive machine vibrations, assuming that its bearings were replaced before the diagnostic test. As a result of the lack of effects after replacing the motor bearings and after analyzing the vibration measurement results presented in article, a decision was made to inspect the centrifuge bearings. The diagnostics was performed again, but it concerned only the bearing node No. 1 with the disassembled basket. The measurements were performed using the DIAMOND 401 AX device, equipped with Wilcoxon 780B acceleration sensors with a sensitivity of 100mV/g. The appearance of a technological defect on the outer ring of the bearing, which is a friction pair with a housing, is not a typical damage for this type of machines and was an interesting problem. The consequence of the occurrence of bearing defects may be an increase in statistical values of the vibration signal and the appearance of new amplitudes in the FFT spectra. A vicious circle is created here, where bearings in poor dynamic condition increase the transmission of vibrations through the machine, and high vibrations accelerate the degradation of the bearings. The poor condition of rolling bearings may also prevent dynamic balancing of the rotor, and thus – lead to further propagation of bearing damage caused by an increased level of the machine’s own vibrations.

Implementation of GRACE and GRACE-FO observation covariance estimates at JPL

2020 ◽  
Author(s):  
Matthias Ellmer ◽  
David Wiese ◽  
Christopher McCullough ◽  
Dah-Ning Yuan ◽  
Eugene Fahnestock
Keyword(s):  
Gravity Field ◽  
Time Domain ◽  
Stochastic Models ◽  
Carrier Phase ◽  
State Of The Art ◽  
Water Storage ◽  
Laser Ranging ◽  
Least Squares Estimate ◽  
Current State ◽  
The Time Domain

<p class="Standard">Developing meaningful uncertainty quantifications for GRACE or GRACE-FO derived products, e.g. water storage anomalies, requires a robust understanding of the information and noise content in the observables employed in their estimation.</p> <p class="Textbody">The stochastic models for GRACE and GRACE-FO K-Band, and GPS carrier phase and pseudorange observables employed in upcoming JPL solutions will be presented. Within these models, the time-domain correlations for each of the observations are estimated, and then applied in the least squares estimate of monthly gravity field solutions. Reproducing results from other groups, the resulting formal errors of monthly solutions are improved.</p> <p class="Standard">We compare this approach to the current state of the art at JPL, and show that noise content in the determined gravity field solutions is reduced. We further demonstrate the application of this method to data from the GRACE-FO Laser ranging interferometer.</p>

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