Influence Of Sampling Frequency Research Articles

Fault Diagnosis Methodology of Redundant Closed-Loop Feedback Control Systems: Subsea Blowout Preventer System as a Case Study

In closed-loop feedback control systems, faults are propagated through the feedback link, which eventually leads to the abnormality of the entire system. Generally, it is very difficult to identify the faults of systems under the influence of the closed-loop feedback link. The existence of redundancy improves the reliability of the system. Meanwhile, it also poses new challenges to the fault diagnosis of multiple redundant systems. In this regard, a causality-based method is proposed for the fault diagnosis of closed-loop feedback control system with multiple modular redundancy. The dynamic Bayesian networks for fault diagnosis are established based on sensor data and system parameters. The networks consist of four layers, which are sensors, performances, monitors, and faults, respectively. Furthermore, the conditional probabilities of the fault nodes are calculated by Noisy-OR and Noisy-MAX models. The proposed method can dynamically evaluate system performance and integrate other monitoring information as evidence to assist faults diagnosis and location. A double modular redundant control system for a subsea blowout preventer is used as a case to demonstrate the proposed method, and the results show that the proposed method has high accuracy. The influence of sampling frequency, noise, and redundancy mode on diagnosis results is studied and discussed in the case study.

Influence of sampling frequency and estimation method on phosphorus load uncertainty in the Western Lake Erie Basin, Ohio, USA

Accurate estimates of nutrient loads are necessary to identify critical source areas and quantify the impact of management practices on pollutant export. Previous studies have investigated nutrient load estimate uncertainty, but they often focus on nutrient loads estimated using an interpolation method for large-scale watersheds with short-term datasets. The study objective was to quantify uncertainty in soluble reactive phosphorus (SRP), total phosphorus (TP), and suspended solids (SS) load estimates from two small (<103 km2) agricultural watersheds in the western Lake Erie Basin resulting from different sampling frequencies. Each watershed had high temporal resolution datasets of discharge (15 min) and nutrient concentration (1 to 3 samples per day) collected over a 30-year period (1990–2020). Firstly, SRP, TP, and SS loads were calculated using the high temporal resolution datasets, which was assumed as “true loads”. Secondly, the high temporal concentration data were decomposed to semiweekly, weekly, biweekly, and monthly sampling and annual loads were estimated using four common load estimation methods to assess the effect of sampling frequency and load estimation method on load estimate error. Across the four different methods, the composite method had the lowest relative root mean square and absolute bias, but the rectangular interpolation method was the most precise. However, even with semiweekly sampling, the composite method resulted in an unacceptable level of precision (average imprecision = 39 %), while the interpolation method resulted in an unacceptable bias (average absolute bias = 16 %). Because neither method could provide acceptable accuracy and precision at the lowest decrease in sampling (e.t. semiweekly sampling), continued daily sampling is recommended in these watersheds.

Influence of sampling frequency and laser pulse width on ranging accuracy of full-waveform LiDAR

Influence of sampling frequency and laser pulse width on ranging accuracy of full-waveform LiDAR

Time-domain distance protection of transmission lines based on the conic section general equation

This paper presents the development, implementation, and testing of a time-domain distance protection algorithm based on the behavior of voltage and current signals over time and on the conic section general equation that describes this behavior. The authors used six existing electrical systems modeled in ATP/EMTP to perform fault simulations varying the fault type, phases involved, fault resistance, inception angle, and fault location. Besides, the authors carried out a sensitivity analysis regarding the sampling frequency influence, noisy data, dynamic behavior of capacitor voltage transformers, power swings, and close-in faults. Finally, the authors tested the proposed method against an actual fault event on a 500 kV Brazilian transmission line. The results presented in this paper indicate that the proposed solution is robust, fast, accurate, secure, and dependable.

The influence of sampling frequency and interpolation on the bit error rate of GMSK signal

The sampling rate at a given bit rate is a requirement for the speed of digital signal processors. In this regard, it is necessary to strive to reduce it in the development of electronic devices, especially portable ones. However, this can lead to an increase in the bit error rate during signal detection. Therefore, it is important to determine the degradation of signal detection with decreasing sampling frequency and to develop practical recommendations to ensure the specified quality of communication. The aim of the article is to study the influence of sampling frequency and interpolation on the bit error rate of GMSK Signal. The article considers the incoherent detection of a GMSK signal in a channel with additive white Gaussian noise, taking into account the influence of the clock synchronization error. Numerical results are presented that characterize an increase in the bit error rate with a decrease in the signal sampling frequency. It is shown that when using the cubic Farrow interpolator, there is no significant degradation in the bit error probability. The minimum number of samples per symbol is determined, at which the bit error rate is close to the theoretical values in the absence of synchronization error. The presented results can be used in development of wireless data transmission systems.

The influence of quantization on level on an error of the digital voltmeter of alternating voltage

There are given the results of influence the level quantization to the accuracy of measured AC voltage by digital voltmeter. It is shown the influence of sampling frequency and the type of digital filter to effective digit capacity of conversion in case of synchronous and asynchronous sampling. There is obtained an estimate of error by representing the quantization error by centered noise with a uniform distribution. There are presented the results of modeling a digital voltmeter.

Influence of sampling frequency and number of strides on recurrence quantifiers extracted from gait data

In this study, the influence of the sampling frequency and number of strides on recurrence quantifiers extracted from gait data was investigated in order to provide baseline values and preserve the system's non-linear dynamical characteristics expressed by these recurrence quantifiers. Recurrence quantifiers were extracted from a recurrence plot (RP), which required the reconstruction of a high-dimensional state space capable of reproducing the dynamical characteristics of the analyzed system. In this study, the following quantifiers were extracted: rate of recurrence (RR), determinism (DET), average diagonal lines length (AVG), maximum diagonal lines length (MaxL), Shannon entropy (EntD), and measure of trend (TREND). Data collected during treadmill walking were statistically analyzed to compare the distribution characteristics (mean, median, and standard deviation) and the quantifiers' correlation with those obtained from a control time series with an acquisition time corresponding to 150 strides and a 100-Hz sampling frequency, which are common values used in gait studies. It was not possible to reduce the number of strides for the MaxL or TREND. However, for the RR, DET, AVG, and EntD, it was possible to reduce the number of strides by 60% when analyzed together. The minimum sampling frequency required to extract all quantifiers simultaneously was 100 Hz. This potential reduction in the number of strides is appropriate for evaluating fast gait events, with short temporal localization in the RP, by applying the sliding window method to the recurrence plot.

Novel traction control of electric vehicle based on single wheel dynamics

It is hard for traction control to ensure the stability of vehicles because of the non-linearity, uncertainty and parameters variation of vehicle dynamics. A novel traction control model is presented in this study to obtain the optimal traction performance by taking the advantage of fast torque response of electric vehicles (EVs) and dealing with driver operation properly. A new judgement unit is designed to combine the optimal slip ratio controller with driver operation, and the driver's input is kept when the slip ratio exceeds the reference value. Further, an engineering design method of the slip ratio controller is researched in terms of speed range and different work conditions. Two sets of controller parameters are designed since the vehicle time constant varies with wheel speed. The possibility of taking fix controller parameters value in one speed range is analysed and verified. Moreover, the stability of system and the influence of sampling frequency on system are analysed. Finally, the validity of the proposed control methodology is fully verified with simulation and experiments on the tire–road simulation test bench which adopts the asynchronous motor mechanical properties to simulate tire–road characteristics.

The higher, the closer, the better? Influence of sampling frequency and distance on the acoustic properties of short‐beaked common dolphins burst pulses in the Mediterranean Sea

Abstract When implementing conservation strategies involving passive acoustic monitoring, an accurate description of signal properties is crucial, especially when studying threatened and elusive vocalizing species. Misrepresentation of detected sounds can result in information loss or misclassification of species, thus compromising the management process. Distortion of the time–frequency features depends on the characteristics of acoustic propagation through sea water, sensitivity and sampling frequency of the acquisition system and distance between cetacean source and the receiving sensor (hydrophone). This study examined how the sampling frequency and the distance from the source affect the properties of burst pulsed sounds emitted by short‐beaked common dolphins in the Mediterranean Sea and how the signal is modified in relation to the recording scenarios. Burst pulses were collected at 300 000 samples/s, and down‐sampled at 192 000, 96 000, 48 000 and 44 100. Fifteen acoustic parameters were automatically measured. The median values were measured and compared among the signals sampled at different rates. Finally, a transmission loss model was applied to explore the variation of the power spectrum density during click propagation through seawater. The results showed that, even if higher sampling rates are a more accurate match with the original signal, some parameters (number of clicks, inter‐click‐interval and maximum peak) measured at 96 000 and 192 000 Hz did not display significant differences compared with 300 000 Hz, except for the frequency parameters. The transmission loss model also showed that the highest frequency components strongly attenuate within 800 m from the source. These results suggest that high recording distances and lower sampling rates do not allow an accurate analysis of burst pulsed signals. However, taking into account data storage limitations, recording at the highest frequency is not always required for an accurate description of signals and the outcomes of this study improve the accuracy of passive acoustic monitoring systems, thus enhancing the potential for conservation of short‐beaked common dolphins.

Influence of Sampling Frequency in DCPD Crack Monitoring

Due to the particularity of autoclave environment, it is difficulty to real-time monitor the crack growth state in the autoclave, and Direct Current Potential Drop method (DCPD) is widely in the crack propagate monitor in this kind experiment. The signal characterized by DCPD method is usually submerged by strong noise. In this paper, the extraction and filtering methods of crack characteristics in high temperature and high pressure environment are studied. The SINC filter is used to obtain crack initial data information and filter out the pulse interference signal, and the FIR filter is used to filter out high frequency interference. Finally, crack monitoring experiments at different sampling frequencies were studied. The experimental results show that the sampling frequency has a great influence on the stability and anti-interference ability of the data.

Time- and Frequency-Domain Fault Detection in a VSC-Interfaced Experimental DC Test System

The rapid discharge of a dc-link capacitor of the voltage-source converter (VSC)-based dc system is the primary indication of the fault condition. Apart from the time-domain analysis, frequency-domain analysis of the fault current could also be utilized for dc fault detection, as the rapidly rising fault current is expected to have high-frequency components. This paper proposes two fault detection methods and compares their performances with the wavelet transform. The first method is the time-domain analysis of the dc-link capacitor discharge and is termed as the capacitive discharge technique. The relationship between the dc line current and the behavior of the dc-link capacitor is measured in terms of a correlation coefficient, whose value can be used to establish a fault basis. The second method is the frequency-domain-based short-time Fourier transform, which is used for quantitative analysis of high-frequency components in the fault current. These methods are extensively analyzed and compared using a scaled-down VSC-based dc system experimental test setup. Comparison has been done based on fault detection time, sensitivity to fault parameters, influence of sampling frequency, and computation speed. Furthermore, the selectivity of the fault detection methods is studied on the multiterminal dc systems of two different topologies (ring and radial), modeled in PSCAD/EMTDC. The experimental and simulation results substantiate the applicability of all the methods to the dc system. Brief comparative analysis with the di/dt method is also presented to highlight the advantages of the proposed methods.

Research on the Influence of Sampling Frequency on Energy Measurement Precision of Electronic Instrument Transformer

Digital metering system, the electronic energy meter analog-to-digital conversion sampling function moved to the electronic instrument transformer, and electronic instrument transformer sampling frequency compared with the electronic energy meter is low, the sampling frequency will be insufficient in the analog-to-digital conversion process Introduce quantization error. In this paper, the measurement error model of electronic instrument transformer based on analog-to-digital conversion sampling principle is established, and the influence of sampling frequency on energy measurement error is quantitatively analyzed. The analysis shows that the accuracy of electronic instrument transformer measurement is related to oversampling rate.

Influence of sampling frequency and load calculation methods on quantification of annual river nutrient and suspended solids loads.

Better management of water quality in streams, rivers and lakes requires precise and accurate estimates of different contaminant loads. We assessed four sampling frequencies (2days, weekly, fortnightly and monthly) and five load calculation methods (global mean (GM), rating curve (RC), ratio estimator (RE), flow-stratified (FS) and flow-weighted (FW)) to quantify loads of nitrate-nitrogen (NO3--N), soluble inorganic nitrogen (SIN), total nitrogen (TN), dissolved reactive phosphorus (DRP), total phosphorus (TP) and total suspended solids (TSS), in the Manawatu River, New Zealand. The estimated annual river loads were compared to the reference 'true' loads, calculated using daily measurements of flow and water quality from May 2010 to April 2011, to quantify bias (i.e. accuracy) and root mean square error 'RMSE' (i.e. accuracy and precision). The GM method resulted into relatively higher RMSE values and a consistent negative bias (i.e. underestimation) in estimates of annual river loads across all sampling frequencies. The RC method resulted in the lowest RMSE for TN, TP and TSS at monthly sampling frequency. Yet, RC highly overestimated the loads for parameters that showed dilution effect such as NO3--N and SIN. The FW and RE methods gave similar results, and there was no essential improvement in using RE over FW. In general, FW and RE performed better than FS in terms of bias, but FS performed slightly better than FW and RE in terms of RMSE for most of the water quality parameters (DRP, TP, TN and TSS) using a monthly sampling frequency. We found no significant decrease in RMSE values for estimates of NO3-N, SIN, TN and DRP loads when the sampling frequency was increased from monthly to fortnightly. The bias and RMSE values in estimates of TP and TSS loads (estimated by FW, RE and FS), however, showed a significant decrease in the case of weekly or 2-day sampling. This suggests potential for a higher sampling frequency during flow peaks for more precise and accurate estimates of annual river loads for TP and TSS, in the study river and other similar conditions.

Influence of sampling frequency on detectability of fish community and fish species in a fishery-independent survey

Understanding the dynamics and regulation of a particular ecological process requires monitoring of the process at appropriate spatial and temporal scales. Information collected at an inappropriate spatio-temporal scale may be insufficient for capturing spatio-temporal dynamics of fish populations and community. In this study, a Monte Carlo method was developed to evaluate the detectability performances of different sampling frequencies, sampling timings and sampling intensities on fish community indices and fish species. Species richness indices tended to decrease with an increased sampling frequency, while species diversity indices had small changes in response to changes in sampling frequency. The diversity index was more likely to be influenced by the choice of sampling timing compared to the richness index. The total number of species, especially seasonal and rare species present in the simulated sampling, increased with sampling frequency. Although sampling frequency is more important than sampling intensity, sampling intensity is also important for the detectability of fish species. This study showed that sampling frequency and intensity could greatly influence the estimation of fish community. Choices of sampling timing, sampling frequency and intensity may result in different estimates of fish species compositions and community structure. It is very necessary to consider the importance of sufficient sampling frequency and intensity in a survey program.

Rolling bearing feature frequency extraction using extreme average envelope decomposition

The vibration signal contains a wealth of sensitive information which reflects the running status of the equipment. It is one of the most important steps for precise diagnosis to decompose the signal and extracts the effective information properly. The traditional classical adaptive signal decomposition method, such as EMD, exists the problems of mode mixing, low decomposition accuracy etc. Aiming at those problems, EAED(extreme average envelope decomposition) method is presented based on EMD. EAED method has three advantages. Firstly, it is completed through midpoint envelopment method rather than using maximum and minimum envelopment respectively as used in EMD. Therefore, the average variability of the signal can be described accurately. Secondly, in order to reduce the envelope errors during the signal decomposition, replacing two envelopes with one envelope strategy is presented. Thirdly, the similar triangle principle is utilized to calculate the time of extreme average points accurately. Thus, the influence of sampling frequency on the calculation results can be significantly reduced. Experimental results show that EAED could separate out single frequency components from a complex signal gradually. EAED could not only isolate three kinds of typical bearing fault characteristic of vibration frequency components but also has fewer decomposition layers. EAED replaces quadratic enveloping to an envelope which ensuring to isolate the fault characteristic frequency under the condition of less decomposition layers. Therefore, the precision of signal decomposition is improved.

The Influence of Sampling Frequency on the Results of Motion Analysis Performed by High-Speed Digital Image Correlation

The paper describes an experimental determination of kinematic quantities using high-speed digital image correlation system. It deals with the analysis of minimal sampling frequency needed for correctly performed high-speed correlation analysis. The authors also describe the influence of cameras sampling frequency on the quality of the obtained results. Mentioned analysis was performed using a rotational object. For the purposes of the results comparison the data obtained from correlation system in a form of displacements in three mutually perpendicular directions were processed in Matlab and in the paper are depicted in a form of graphical visualizations.

Measurement of carbonaceous aerosol with different sampling configurations and frequencies

Abstract. A common approach for measuring the mass of organic carbon (OC) and elemental carbon (EC) in airborne particulate matter involves collection on a quartz fiber filter and subsequent thermal–optical analysis. Although having been widely used in aerosol studies and in PM2.5 (fine particulate matter) chemical speciation monitoring networks in particular, this measurement approach is prone to several types of artifacts, such as the positive sampling artifact caused by the adsorption of gaseous organic compounds onto the quartz filter, the negative sampling artifact due to the evaporation of OC from the collected particles and the analytical artifact in the thermal–optical determination of OC and EC (which is strongly associated with the transformation of OC into char OC and typically results in an underestimation of EC). The presence of these artifacts introduces substantial uncertainties to observational data on OC and EC and consequently limits our ability to evaluate OC and EC estimations in air quality models. In this study, the influence of sampling frequency on the measurement of OC and EC was investigated based on PM2.5 samples collected in Beijing, China. Our results suggest that the negative sampling artifact of a bare quartz filter could be remarkably enhanced due to the uptake of water vapor by the filter medium. We also demonstrate that increasing sampling duration does not necessarily reduce the impact of positive sampling artifact, although it will enhance the analytical artifact. Due to the effect of the analytical artifact, EC concentrations of 48 h averaged samples were about 15 % lower than results from 24 h averaged ones. In addition, it was found that with the increase of sampling duration, EC results exhibited a stronger dependence on the charring correction method and, meanwhile, optical attenuation (ATN) of EC (retrieved from the carbon analyzer) was more significantly biased by the shadowing effect. Results from this study will be useful for the design of China's PM2.5 chemical speciation monitoring network, which can be expected to be inaugurated in the near future.

インバータ励磁下における磁気特性評価に対するサンプリング周波数の影響

インバータ励磁下における磁気特性評価に対するサンプリング周波数の影響

Study on the method of chaotic oscillator in weak signal detection

The feasibility of using Duffing chaotic oscillator to detect the weak sinusoidal signal is testified and the performance is analyzed. The method of using the pair of extreme values of the system output variance to detect the weak signal is proposed. The influence of sampling frequency on the results is analyzed based on the theory that the output variance value of the system will reach a maximum when the signal frequency is equal to the reference frequency. Experiments have indicated that the weak signal will be detected in the lower signal to noise ratio SNR =-45 dB by increasing the sampling frequency and the length of the data sequence in the meanwhile. Moreover, the signal which has a random phase difference with the reference signal can also be detected based on the above theory, the experiments results have verified that the variance still has a dramatic change when the signal frequency is approximately equal to the reference frequency, and there appears a maximum value and a minimum value. This new property is successfully applied to measuring the frequency of amplitude modulated signal produced by the signal generator.

Influence of Sampling Frequency on Estimation of Annual Total Phosphorus and Total Suspended Solids Loads1

Abstract: The determination of sediment and nutrient loads is typically based on the collection and analysis of grab samples. The frequency and regularity of traditional sampling may not provide representation of constituent loading, particularly in systems with flashy hydrology. At two sites in the Little Bear River, Utah, continuous, high‐frequency turbidity was used with surrogate relationships to generate estimates of total phosphorus and total suspended solids concentrations, which were paired with discharge to estimate annual loads. The high frequency records were randomly subsampled to represent hourly, daily, weekly, and monthly sampling frequencies and to examine the effects of timing, and resulting annual load estimates were compared to the reference loads. Higher frequency sampling resulted in load estimates that better approximated the reference loads. The degree of bias was greater at the more hydrologically responsive site in the upper watershed, which required a higher sampling frequency than the lower watershed site to achieve the same level of accuracy in estimating the reference load. The hour of day and day of week of sampling impacted load estimation, depending on site and hydrologic conditions. The effects of sampling frequency on the determination of compliance with a water quality criterion were also examined. These techniques can be helpful in determining necessary sampling frequency to meet the objectives of a water quality monitoring program.