Frequency Domain Aspects Research Articles

DeepTool: A deep learning framework for tool wear onset detection and remaining useful life prediction

Milling tool availability and its useful life estimation is essential for optimisation, reliability and cost reduction in milling operations. This work presents DeepTool, a deep learning-based system that predicts the service life of the tool and detects the onset of its wear. DeepTool showcases a comprehensive feature extraction process, and a self-collected dataset of sensor data from milling tests carried out under different cutting settings to extract relevant information from the sensor signals. The main contributions of this study are:•Self-Collected Dataset: Makes use of an extensive, self-collected dataset to record precise sensor signals during milling.•Advanced Predictive Modeling: Employs hybrid autoencoder-LSTM and encoder-decoder LSTM models to estimate tool wear onset and predict its remaining useful life with over 95 % R2 accuracy score.•Comprehensive Feature Extraction: Employs an efficient feature extraction technique from the gathered sensor data, emphasising both time-domain and frequency-domain aspects associated with tool wear.

A new method for measurement of impulsive peak level attenuation of hearing protectors

ASA/ANSI S12.42-2010 contains the first standardized test method for measuring the performance of hearing protection devices (HPDs) with high-level impulsive noise. This standard defines the impulsive peak insertion loss (IPIL) as a time-domain metric that quantifies the reduction in peak sound pressure level provided by an HPD for impulsive noises. However, IPIL as defined in S12.42-2010 is dependent on the spectrum of the impulsive noise source used for measurements of HPDs. Recent studies of HPDs with impulsive noise have led to the investigation of frequency-domain metrics and calculation methods. Using frequency-domain calculations allows the impulsive peak level attenuation to be computed for a wide range of impulsive noises, not only those used for the measurement. Consequently, significant revisions to S12.42 are under consideration and a new standard, ISO 4869-7, is being developed in parallel with the ANSI revision. This presentation highlights key proposals and substantive changes including: measurement and calculation of the frequency-dependent impulsive insertion loss (IIL), incorporation of frequency-domain aspects such as real-ear attenuation at threshold (REAT) limits to attenuation, and a new impulsive peak level attenuation metric (IPLA) to be calculated from the REAT-bounded IIL.

ELM-based stroke classification using wavelet and empirical mode decomposition techniques

ABSTRACT Biomedical signal processing is crucial in many sectors that save lives. Artificial intelligence improvement in signal collection and conditioning boosted this application’s adaptability to varied bodily circumstances. In this study, a novel method is put forth for predicting the type of stroke in the human brain based on the observation of the Electroencephalography (EEG) signal. The signal is the first condition for removing undesirable frequencies by passing through a lowpass filter. To accurately extract the signal features, the signal is first transformed into a 1-second frame format and then normalised. Certain statistical and frequency domain aspects are highlighted to increase taxonomic accuracy. Under the wavelet packet transform, the empirical mode decomposition approach is utilised to recover the most information feasible from the signal. After training on extracted characteristics, the extreme learning machine is regarded to conduct classification. These work achieves 94.95 of Sensitivity, 84.95 of Specificity, 93.74 of Precision, 96.96 of Accuracy, 96.12 of F1 Score. Compared to the standard procedures, the proposed techniques have a greater accuracy rate of about 98%.

Proposed updates for ANSI/ASA S12.42 impulsive noise test methods

ANSI/ASA S12.42-2010 contains the first standardized test method for measuring the performance of hearing protection devices (HPDs) with high-level impulsive noise. This standard defines the impulsive peak insertion loss (IPIL) as a time-domain metric that quantifies the reduction in peak sound pressure level provided by an HPD for impulsive noises. However, IPIL as defined in S12.42-2010 is dependent on the spectrum of the impulsive noise source used for measurements of HPDs. Recent studies of HPDs with impulsive noise have led to the investigation of frequency-domain metrics and calculation methods. Using frequency-domain calculations allows IPIL to be computed for a wide range of impulsive noises, not only those used for the measurement. Consequently, significant revisions to S12.42 are under consideration. This presentation highlights select proposals including: definition and calculation of the frequency-dependent impulsive insertion loss, incorporation of frequency-domain aspects such as bone-conduction limits to attenuation, and redefinition of IPIL to be calculated from the impulsive insertion loss.

Fault Diagnosis System of Rolling Bearing Based on Ultrasonic Signal

The bearing of rotating machinery often fails due to the frictional forces of rolling element, in the early stages of the faults, a series of ultrasound can be generated in short time intervals, which occur at bearing characteristic frequencies. Since the frequencies of ultrasonic signal are very high, they will lead to much higher computing burden when using the common technique of Fast Fourier Transforms (FFT) directly. In this paper, envelope detection technology and heterodyne technology which integrated in an ultrasonic data collection system are used to reduce the frequency effectively. To allow for the easier detection of the bearing faults, these two techniques has been used together with FFT. A verification research with respect to vibration analysis is carried out to analyze the effectiveness and superiority of ultrasonic data collection in time domain and frequency domain aspects respectively. Extensive experiments have been performed in an Alternating Current (AC) motor system, and the results indicated that this ultrasonic data collection system is as useful as vibration analysis system in diagnosing the faults of bearings. In addition, it is more sensitive in fault diagnosis in the early stages of the bearing faults than vibration acquisition system.

Fault Diagnosis of Bearing Based on the Ultrasonic Signal

The bearing of rotating machinery often fails due to the frictional forces of rolling element, in the early stages of the faults, a series of ultrasound can be generated in short time intervals, which occur at bearing characteristic frequencies. Since the frequencies of ultrasonic signal are very high, they will lead to much higher computing burden when using the common technique of Fast Fourier Transforms (FFT) directly. In this paper, envelope detection technology and heterodyne technology which integrated in an ultrasonic data collection system are used to reduce the frequency effectively. To allow for the easier detection of the bearing faults, these two techniques has been used together with FFT. A verification research with respect to vibration analysis is carried out to analyze the effectiveness and superiority of ultrasonic data collection in time domain and frequency domain aspects respectively. Extensive experiments have been performed in an Alternating Current (AC) motor system, and the results indicated that this ultrasonic data collection system is as useful as vibration analysis system in diagnosing the faults of bearings. In addition, it is more sensitive in fault diagnosis in the early stages of the bearing faults than vibration acquisition system.

Time-Frequency Analysis of Aeroelastic Deflections of Flapping Wings

The flight dynamics of flapping-wing micro air vehicles result from a complicated relationship between aerodynamics and structural dynamics. This relationship has both frequency-domain aspects and time-domain aspects that are each critical. As such, analyzing data from a flapping wing requires techniques that can process information related to both of these domains. This paper introduces wavelet analysis as a tool that determine the frequency content of time-varying deflections. The resulting wavelet map presents a time-frequency domain representation that relates both the time-domain aspects and frequency-domain aspects. Data is analyzed using wavelet processing from a set of wings with different structural dynamics and different flapping parameters whose responses in the vertical and span-wise directions are recorded using digital image correlation. The resulting wavelet maps demonstrate the variations in energy content and temporal distribution associated with the deflections.

Cutting force and its frequency spectrum characteristics in high speed milling of titanium alloy with a polycrystalline diamond tool

In this paper, a series of experiments were performed by high speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) by use of polycrystalline diamond (PCD) tools. The characteristics of high speed machining (HSM) dynamic milling forces were investigated. The effects of the parameters of the process, i.e., cutting speed, feed per tooth, and depth of axial cut, on cutting forces were studied. The cutting force signals under different cutting speed conditions and different cutting tool wear stages were analyzed by frequency spectrum analysis. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The results indicate that a characteristic frequency in cutting force power spectrum does in fact exist. The amplitudes increase with the increase of cutting speed and tool wear level, which could be applied to the monitoring of the cutting process.

An Experimental Study of Cutting Forces in High-Speed End Milling and Implications for Dynamic Force Modeling

The characteristics of high-speed machining (HSM) dynamic milling forces was investigated. Recent studies in chip segmentation are discussed. A Mikron 700 High-Speed Machining Center was used in the end-milling of AISI H13 tool steel using PVD TiN coated two flute micrograin carbide tools. Dynamic force signals were studied using a real-time data acquisition system for spindle speeds from 3,750 to 31,500 rpm for a 6 mm dia tool. Frequency domain studies were also carried out for a larger tool of 12 mm dia for spindle speeds between 10,000 and 40,000 rpm. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The fundamental concept of modeling cutting forces based on chip morphology is revisited. A new basis for modeling dynamic forces from the static component and harmonic contributions is presented. This approach for modeling the dynamic HSM force signal accounts for secondary harmonics.

Computation of period sensitivity functions for the simulation of phase noise in oscillators

Accurate phase noise simulation of circuits for radio frequency applications is of great importance during the design and development of wireless communication systems. In this paper, we present an approach based on the Floquet theory for the analysis and numerical computation of phase noise that solves some drawbacks implicitly present in previously proposed algorithms. In particular, we present an approach that computes the perturbation projection vector directly from the Jacobian matrix of the shooting method adopted to compute the steady-state solution. Further, we address some problems that arise when dealing with circuits whose modeling equations do not satisfy the Lipschitz condition at least from the numerical point of view. Frequency-domain aspects of phase noise analysis are also considered and, finally, simulation results for some benchmark circuits are presented.

Tunable THz Sources and Their Applications

In this paper, the technology aspects of the THz laser and spectrometric devices, developed over the last decade are described and their applications in various fields of science and technology are explained. The THz sources of importance are the optically pumped lasers, solid state devices and the backward wave oscillator (BWO) based systems. The BWO system offers the electronic tuning and multiplexing facility like Fourier transform technology. The time resolved and frequency domain aspects with relative merits are discussed. Non-linear optical methods of production of monochromatic radiation using second harmonic generation (SHG) are also considered. The important areas of space applications are described in detail. Present status and future directions are indicated.

Some frequency domain aspects of wave propagation on nonuniform lines

Nonuniform line (NL) is the designation of a transmission line segment where the conductors are not parallel or where the sag is significant. In addition, transformers and also parts of metallic towers can be viewed as NLs. In this paper, the propagation characteristics of NLs are examined. They appear as generalizations of concepts from uniform transmission lines (ULs). It was found that an n-conductor NL has n pairs of modes and the forward and backward waves of a mode have the same propagation constants. However, the modeshapes defined by the voltages and currents of a given mode are different. For illustration, the variation with frequency of these propagation characteristics has been presented for the wide-span river crossing of an overhead transmission line.

Some Frequency Domain Aspects of Wave Propagation on Nonuniform Lines

Nonuniform line (NL) is the designation of a transmission line segment where the conductors are not parallel or where the sag is significant. In addition, transformers and also parts of metallic towers can be viewed as NLs. In this paper, the propagation characteristics of NLs are examined. They appear as generalizations of concepts from uniform transmission lines (ULs). It was found that an n-conductor NL has n pairs of modes and the forward and backward waves of a mode have the same propagation constants. However, the modeshapes defined by the voltages and currents of a given mode are different. For illustration, the variation with frequency of these propagation characteristics has been presented for the wide-span river crossing of an overhead transmission line.

Psychoacoustically informed spectrography and timbre

Pitch and loudness are subjective aspects of sound which can be described in terms of the observed abilities of subjects to rate them on a scale from ‘low’ to ‘high’. Timbre is a subjective aspect of sound for which there is no such scale and neither qualitative nor quantitative descriptions are generally found that are widely accepted. The purpose of this paper is to shed light on some frequency domain aspects of the nature of timbre by making use of the results obtained from an analysis system which is designed to take advantage of contemporary psychoacoustical knowledge relating to human peripheral hearing. Results are presented which illustrate the relationship between contemporary psychoacoustic ideas relating to timbre and ideas first discussed by Helmholtz and later taken up by other researchers. Analyses by the system of a selection of sounds from acoustic musical instruments with clear timbral differences are also presented in order to place these discussions in a musical context.

Some problems in voice source analysis

This is an overview of some recent studies of voice source acoustics and glottal flow analysis and modelling performed at the KTH. Time and frequency domain aspects of the production process are discussed with a view of relating glottal flow parameters from inverse filtering and vocal tract transfer functions to formant amplitudes and bandwidths. Alternative methods of determining the time constant T a = 1 (2πF a) in the return phase of glottal flow derivative after the instant of excitation, and thus of spectral tilt, are discussed. Selective inverse filtering, removing all but one formant, is potentially useful for this purpose. The influence of uncertainties in quantifying the vocal tract transfer function is exemplified by a calculation of the effects of introducing a finite baffle effect of the human head adding a high-frequency emphasis above the standard + 6 dB/octave. Particular attention has been paid to temporal variations within an utterance as derived from continuous inverse filtering. Aspects of breathy voicing and female-male differences in voice production are discussed. It is demonstrated that the temporal profile of the excitation amplitude, E e ( t), within an utterance derived from a male speaker can be approximated by the envelope of the negative part of the speech wave.

Industrial application of the frequency-domain aspects of the Kalman filter

Several classical industrial filtering applications have used notch filters to reject the unwanted dominant frequencies. For a class of industrial systems, it has been shown that the filter gain between the observations and the signal estimates is unity. While the gain between the observations and the disturbance state estimates is zero, the zeros of the Kalman filter are determined by the poles of the disturbance model. These results are generalised to a more representative case of a block-diagonal structure with feedback coupling.

Automated design of large-signal amplifiers for minimum distortion

A technique for the design of large-signal amplifiers for minimum distortion is presented. This technique takes advantage of the frequency-domain aspects of the problem by using the fast Fourier transform.