scholarly journals Optimum Resolution Bandwidth for Spectral Analysis of Stationary Random Vibration Data

1993 ◽  
Vol 1 (1) ◽  
pp. 33-43 ◽  
Author(s):  
Allan G. Piersol
Keyword(s):  
Spectral Analysis ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Random Vibration ◽  
Damping Ratio ◽  
Frequency Resolution ◽  
Power Spectral ◽  
Averaging Time ◽  
Resolution Bandwidth

This article presents a methodology for selecting the frequency resolution bandwidth for the spectral analysis of stationary random vibration signals in an optimum manner. Specifically, the resolution bandwidth that will produce power spectral density estimates with a minimum mean square error is determined for any given measurement duration (averaging time), and methods of approximating the optimum bandwidth using practical spectral analysis procedures are detailed. The determination of the optimum resolution bandwidth requires an estimate for the damping ratio of the vibrating structure that produced the measured vibration signal and the analysis averaging time. It is shown that the optimum resolution bandwidth varies approximately with the 0.8 power of the damping ratio and the bandwidth center frequency, and the −0.2 power of the averaging time. Also, any resolution bandwidth within ±50% of the optimum bandwidth will produce power spectral density (PSD) estimates with an error that is no more than 25% above the minimum achievable error. If a damping ratio of about 5% for structural resonances is assumed, a constant percentage resolution bandwidth of 1/12 octave, but no less than 2.5 Hz, will provide a near optimum PSD analysis for an averaging time of 2 seconds over the frequency range from 20 to 2000 Hz. A simple scaling formula allows the determination of appropriate bandwidths for other damping ratios and averaging times.

scholarly journals Analysing Random Vibration of KLT Box during Transporting by Finite Element Method

10.29007/b1th ◽  
2022 ◽  
Author(s):  
Cong Hoa Vu ◽  
Ngoc Thien Ban Dang
Keyword(s):  
Finite Element ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Automotive Industry ◽  
Random Vibration ◽  
Element Model ◽  
Vibration Testing ◽  
Time Data ◽  
Power Spectral ◽  
The Impact

Today, freight is an extremely important industry for the world we are living. Fast transportation, large volume...will optimize the cost, time and effort. Besides, ensuring the products safety is a matter of concern. During transporting, it is inevitable that the vibration caused by the engine, rough road surface...the cargo inside can be damaged. Automobile industries have prime importance to vibration testing. Sine vibration testing is performed when we have been given with only one frequency at given time instant. Trend to perform random vibration testing has been increased in recent times. As random vibration considers all excited frequencies in defined spectrum at known interval of time, it gives real-time data of vibration severities. The vibration severity is expressed in terms of Power Spectral Density (PSD). KLT box is an industrial stacking container conforming to the VDA 4500 standard that was defined by German Association of the Automotive Industry (VDA) for the automotive industry. The aim of this paper is study about random vibration and power spectral density analysis, how it can be used to predict the impact of hash road to the KLT box on container / truck during transportation. Finite element model is developed in ANSYS, modal analysis and random vibration analysis were done.

scholarly journals Power spectral analysis of heart rate in hypothyroidism

2000 ◽  
pp. 327-333 ◽  
Author(s):  
V Cacciatori ◽  
ML Gemma ◽  
F Bellavere ◽  
R Castello ◽  
ME De Gregori ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Spectral Analysis ◽  
Spectral Density ◽  
Cardiovascular System ◽  
Power Spectral Density ◽  
Power Spectral Analysis ◽  
Control Subjects ◽  
Power Spectral ◽  
Hypothyroid Patients

OBJECTIVE: The aim of the present study was to evaluate the impact of hypothyroidism on the autonomic regulation of the cardiovascular system by analysing separately sympathetic and parasympathetic influences on the heart. DESIGN: In seven newly diagnosed untreated hypothyroid patients we analysed power spectral density of heart rate cyclic variations at rest, while lying, and while standing. The same protocol was repeated after the induction of stable euthyroidism by levothyroxine (L-T(4)) treatment. The results were also compared with those obtained from seven age-, sex- and body mass index-matched control subjects. METHODS: Heart rate variability was evaluated by autoregressive power spectral analysis (PSA). This method allows reliable quantification of low frequency (LF) and high frequency (HF) components of the heart rate power spectral density. These are considered to be under mainly sympathetic and purely parasympathetic control respectively. In addition, heart rate variations during deep breathing, lying to standing, and Valsalva's manoeuvre were assessed. RESULTS: PSA showed a sharp reduction in the HF (parasympathetic) component in hypothyroid subjects compared with controls (lying, 29.4+/-5.4 vs 47.7+/-6.3 normalized units (NU) (means +/- s.e.m.), P<0.05; standing, 14.0+/-3.5 vs 32.1+/-3.6NU, P<0.005). Conversely, the LF (mainly sympathetic) component was higher in hypothyroid subjects than in controls (lying, 61.6+/-6.4 vs 45.4+/-6.7 NU; standing, 71.7+/-8.0 vs 53.1+/-5.6NU), this difference being significant in the standing position. Hence, the LF/HF ratio, which is considered an index of sympathovagal balance, was increased in hypothyroid subjects while both lying (2.75+/-0.6 vs 1.16+/-0.3; P<0.05) and standing (10.0+/-3.7 vs 1.85+/-0.3; P<0. 02). Total heart rate variability, expressed as total power spectral density, was lower in hypothyroid patients than in control subjects, this difference being significant in the lying position (574+/-126 vs 2302+/-994ms(2), P<0.05). In patients re-examined after L-T(4) therapy, complete normalization of cardiovascular parameters was observed (LF/HF ratio, lying, 1.26+/-0.4; standing, 2.56+/-0.8, both P<0.01 vs baseline values). The response to conventional cardiovascular autonomic tests was not significantly different between hypothyroid patients and healthy controls, and did not change in patients after therapy. CONCLUSIONS: These results suggest that, contrary to the clinical picture, thyroid hormone deficiency is associated with an increased sympathetic influence on the autonomic cardiovascular system. The changes in sympathetic function could be explained by a secondary adaptation to an altered cardiovascular responsiveness.

Resolving the Issues of Capon and APES Approach for Projecting Enhanced Spectral Estimation

2016 ◽  
Vol 6 (2) ◽  
pp. 725
Author(s):  
Kantipudi MVV Prasad ◽  
H.N. Suresh
Keyword(s):  
Signal Processing ◽  
Spectral Analysis ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Simple Technique ◽  
Spectral Estimation ◽  
Research Work ◽  
Research Community ◽  
The Past ◽  
Power Spectral

There are various applications on signal processing that is highly dependent on preciseness and accuracy of the outcomes in spectrum of signals. Hence, from the past two decades the research community has recognized the benefits, significance, as well as associated problems in carrying out a model for spectral estimation. While in-depth investigation of the existing literatures shows that there are various attempts by the researchers to solve the issues associated with spectral estimations, where majority of teh research work is inclined towards addressing problems associated with Capon and APES techniques of spectral analysis. Therefore, this paper introduces a very simple technique towards resolving the issues of Capon and APES techniques. The outcome of the study was analyzed using correlational factor and power spectral density to find the proposed system offers better spectral estimations compared to existing system.

Random Vibration Analysis for Centrifugal Compressor Impellers With Unsteady Aerodynamic Excitations

2016 ◽  
Author(s):  
Yuefang Wang ◽  
Yan Liu ◽  
Xuejun Wang ◽  
Hongkun Li ◽  
Daren Jiang
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Centrifugal Compressor ◽  
Random Vibration ◽  
Pressure Field ◽  
Pseudo Excitation Method ◽  
Vibration Problem ◽  
Power Spectral ◽  
Pseudo Excitation ◽  
Excitation Method

Dynamic response of impeller of centrifugal compressor is studied considering pulsating pressure field on blades due to unsteady flow conditions. The aerodynamic forces on the blades are modeled as random load whose spectral characteristics are determined through computational fluid dynamic simulations in the time domain. The dynamical response in the unsteady case is solved as a random vibration problem in the frequency domain which provides useful power spectral density displacement and stress for early stage of impeller design. A semi-open impeller mounted with 19 blades is modeled using three dimensional solid finite elements. The random vibration problem of the impeller is solved through the Pseudo-Excitation Method considering spatial variance of the pressure field. A user-defined module is developed based on harmonic analysis to generate the auto power spectral density and variance of displacement and stress at 200 nodes. It is demonstrated that solving a random vibration problem through the Pseudo-Excitation Method is faster than the commonly adopted multiple-step transient analysis. It is concluded that evaluating the structural integrity of impeller solids in the regime of random vibration is a feasible and efficient approach at the early design stage of compressors.

Determination of the Wenzel roughness parameter by the Power Spectral Density of functional Alumina surfaces

2016 ◽  
Vol 606 ◽  
pp. 57-62 ◽  
Author(s):  
P.L.G. Jardim ◽  
F. Horowitz ◽  
N. Felde ◽  
S. Schröder ◽  
L. Coriand ◽  
...  
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Roughness Parameter ◽  
Power Spectral

scholarly journals Staggered-PRT Sequences for Doppler Weather Radars. Part I: Spectral Analysis Using the Autocorrelation Spectral Density

2017 ◽  
Vol 34 (1) ◽  
pp. 51-63 ◽  
Author(s):  
Sebastián M. Torres ◽  
David A. Warde
Keyword(s):  
Spectral Analysis ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Weather Radar ◽  
Real Data ◽  
Pulse Repetition ◽  
Spectral Processing ◽  
Weather Radars ◽  
Power Spectral ◽  
Repetition Time

AbstractThe autocorrelation spectral density (ASD) was introduced as a generalization of the classical periodogram-based power spectral density (PSD) and as an alternative tool for spectral analysis of uniformly sampled weather radar signals. In this paper, the ASD is applied to staggered pulse repetition time (PRT) sequences and is related to both the PSD and the ASD of the underlying uniform-PRT sequence. An unbiased autocorrelation estimator based on the ASD is introduced for use with staggered-PRT sequences when spectral processing is required. Finally, the strengths and limitations of the ASD for spectral analysis of staggered-PRT sequences are illustrated using simulated and real data.

scholarly journals Structural Damage Detection by Power Spectral Density Estimation Using Output-Only Measurement

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Eun-Taik Lee ◽  
Hee-Chang Eun
Keyword(s):  
Spectral Density ◽  
Damage Detection ◽  
Density Estimation ◽  
Power Spectral Density ◽  
Frequency Resolution ◽  
Noise Effect ◽  
Spectral Density Estimation ◽  
Power Spectral ◽  
Output Only ◽  
Power Spectral Density Estimation

Most damage detection methods have difficulty in detecting damage using only measurement data due to the existence of external noise. It is necessary to reduce the noise effect to obtain accurate information and to detect damage by the output-only measurement without baseline data at intact state and input data. This work imported the power spectral density estimation (PSE) of a signal to reduce the noise effect. By estimating the PSE to characterize the frequency content of the signal, this study proposes a damage detection method to trace the damage by the curvature of the PSE. Two numerical applications examine the applicability of the proposed method depending on a window function, frequency resolution, and the number of overlapping data in the PSE method. The knowledge obtained from the numerical applications leads to a series of experiments that substantiate the potential of the proposed method.

Power spectral density and probability analysis of electromyograms in shivering birds

1968 ◽  
Vol 46 (5) ◽  
pp. 703-706 ◽  
Author(s):  
George C. West ◽  
Edgar R. R. Funke ◽  
J. Sanford Hart
Keyword(s):  
Spectral Analysis ◽  
Spectral Density ◽  
Normal Distribution ◽  
Power Spectral Density ◽  
Species Differences ◽  
Probability Analysis ◽  
Frequency Of Occurrence ◽  
Power Spectral ◽  
Quiscalus Quiscula

The spectral analysis of electromyograms from evening grosbeaks, Hesperiphona vespertina, and common grackles, Quiscalus quiscula, revealed a statistically significant higher upper cut-off frequency during shivering in the former species. There was also a statistically significant decrease in the upper cut-off frequency with lowering of temperature in the evening grosbeak, but not in the grackle. The frequency of occurrence of various amplitudes during shivering followed the normal distribution closely in both species. The presence of frequencies in the range from 6 to 600 c.p.s. necessitates the use of wideband instrumentation for fidelity in measuring species differences.

Application of Power Spectral Density Method to Fatigue Life Estimation of the Axle Structure

2014 ◽  
Vol 487 ◽  
pp. 272-275
Author(s):  
Rui Feng Guo ◽  
Peng Li Wang
Keyword(s):  
Fatigue Life ◽  
Spectral Density ◽  
Density Function ◽  
Power Spectral Density ◽  
Random Vibration ◽  
Spectral Density Function ◽  
Power Spectral Density Function ◽  
Life Estimation ◽  
Power Spectral ◽  
Fatigue Life Estimation

Based on the random vibration theory, fatigue strength theory and Miner cumulative damage theory, the formulas for estimation of fatigue life which can be coped with narrowband and broadband random vibration was derived by the peak distribution function. The power spectral density function of axle structure is deduced after the power spectral density of standard road and the vibration model of wheel had studying. Combined the power spectral density function with broadband random vibration fatigue life estimation formula, the fatigue life of axle structure was obtained. This method is simple and has a strong engineering practicality.

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