Vibroacoustic Signals Research Articles

Designing the technology of express diagnostics of electric train's traction drive by means of fractal analysis

The object of this study was the development of technology of the express diagnostics of the traction drives of electric trains. Its base was obtaining, processing and fractal analysis of vibroacoustic signals, which makes it possible to forecast the period of service of this unit in between planned maintenance works. We carried out the research into the failures of equipment of electric trains in operation, which showed that the share of defects in the traction reducers is the most significant and amounts to 41,2 % of the total number of failures in the carriage part. The method of selection of acoustic components (samples) was created, which makes it possible to separate them from the complete vibroacoustic signal. Its characteristic peculiarity is initial link to the time interval, determining final duration, as well as selection of a number of cyclically repeated components with each rotation of the large gear of the traction drive. Based on the wavelet conversion of detailing coefficients with high content of noise components, we used the method of denoising vibroacoustic samples with the help of soft thresholding. As the diagnostic parameter, the fractal Hurst index is proposed. The process of its determining is described and the maximum ranges of its change from the point of view of persistence are found. Accordingly, the Hurst index's matching one or another range makes it possible to tell the presence or absence of defect in the traction drive, which can be later on, during a regular maintenance, categorized and removed. Thus, the application of the comprehensive technology of the express diagnostics makes it possible to promptly assess the technical condition of the traction drives of electric trains and to forecast their working capacity in between the planned types of repairs.

Joint Motion Quality in Chondromalacia Progression Assessed by Vibroacoustic Signal Analysis

BackgroundBecause of the specific biomechanical environment of the patellofemoral joint, chondral disorders, including chondromalacia, often are observed in this articulation. Chondromalacia via pathologic changes in cartilage may lead to qualitative impairment of knee joint motion. ObjectiveTo determine the patellofemoral joint motion quality in particular chondromalacia stages and to compare with controls. DesignRetrospective, comparative study. SettingVoivodship hospitals, university biomechanical laboratory. PatientsA total of 89 knees with chondromalacia (25 with stage I; 30 with stage II and 34 with stage III) from 50 patients and 64 control healthy knees (from 32 individuals). MethodsVibroacoustic signal pattern analysis of joint motion quality. Main Outcome MeasurementsFor all knees vibroacoustic signals were recorded. Each obtained signal was described by variation of mean square, mean range (R4), and power spectral density for frequency of 50-250 Hz (P1) and 250-450 Hz (P2) parameters. ResultsDifferences between healthy controls and all chondromalacic knees as well as chondromalacia patellae groups were observed as an increase of analyzed parameters (P < .001) with only one exception. No statistically significant difference between control group and stage I of chondromalacia patellae was found. All chondromalacia groups were differentiated by the use of all analyzed parameters (P < .01), whose values correspond to the progress of chondromalacia. ConclusionsChondromalacia generates abnormal vibroacoustic signals, and there seems to be a relationship between the level of signal amplitude as well as frequency and cartilage destruction from the superficial layer to the subchondral bone. Level of EvidenceIV

Diagnostic features for the condition monitoring of hypoid gear utilizing the wavelet transform

The present paper contributes to the development of new efficient solutions aimed at improving vehicle functional safety through the implementation of new transmission diagnostic methods. The study focuses on a new perspective of the diagnostic frequency range for hypoid gear condition monitoring, using acoustic emission and vibro-acoustic signal measurements and the Discrete Wavelet Transform for data analysis. The identification of the most sensitive diagnostic parameters and determination of frequency intervals using the Discrete Wavelet Transform, in which the most significant increase in the values of diagnostic parameters can be seen, has been presented. In addition, the identification of the sensitivity of the above-introduced non-destructive methods is presented. Diagnostic results in the extended frequency range were compared with the results of the classical method, and it was found that the selected parameter in the proposed measuring range could better characterize the condition of the gear unit.

Usage of Characteristic Function as Informative Diagnostic Feature

The statistic analysis of instantaneous values of vibration and acoustic signals showed that in particular the form of probability density function of instantaneous vibroacoustic signal values changes depending on the condition of the device under vibration- based diagnostics. The shape of the probability density curve can be described by the characteristic function. With regard to the diagnostics of reciprocating compressors the hypothesis had been put forward that the characteristic function of the vibroacoustic signal of reciprocating compressor is an informative diagnostic parameter of the technical condition of the unit. The article presents the results of a study of the statistical moments of the characteristic function parameters obtained for the different conditions of the test device. The studies revealed that the module of the characteristic function is the informative diagnostic symptom of reciprocating compressors faults and allows to assess the state of their units and parts.

Defining the Parameters of Loading of Concrete Bridges Superstructures Basing on the Level of Vibroacoustic Emission Signals

The technique and experimental equipment for remote monitoring of concrete bridge superstructures by vibroacoustic emission signals method was developed. The transducers are mounted on concrete beams for measuring the oscillation energy of moving vehicles within the two frequency ranges. Deflections of beams are measured by low-frequency vibrations and the intensity of degradation processes in the beams is determined by high-frequency vibrations. It is proposed to use the ratio of vibrations intensity indicators within the specified frequency ranges for the diagnostics of the technical state of reinforced concrete beams of superstructures and forecasting residual operational life. The industrial testing of experimental equipment for different traffic volume was held.

ANALYSIS OF VIBROACOUSTIC SIGNALS RECORDED IN THE PASSENGER LIFT CABIN

ANALYSIS OF VIBROACOUSTIC SIGNALS RECORDED IN THE PASSENGER LIFT CABIN

Selection of Coherent Frequency Components of Vibroacoustic Signals from Assemblies of Rotor Machinery

The purpose of this article is to determine optimal conditions for rotor machinery operation in order to evaluate its condition using coherent function. The coherent function is an analogue of the correlation factor in frequency domain. The function reflects the linear relationship levels of harmonic components of parallel signals covered in the article. The conditions are considered optimal when the coherence function is expressed the most evidently. In other words, the coherent components are close to one.

Application of bispectral analysis of vibroacoustic signals for diagnosis blades cracks in aircraft engines

Background . The work is devoted to vibroacoustical diagnosis of the crack-like damages of the gas-turbine engines (GTE) blades at the steady-state modes of GTE. Objective . The effectiveness of the usage bispectrum analysis is investigated for signal processing at the vibroacoustical diagnostic of the blades cracks of aviation gas-turbine engines. Methods . Bispectral analysis is used for diagnostic information processing. Bispectrum can be found using Fourier transform third-order autocorrelation functions: \[S_{3x}(f_{1},f_{2})=\sum_{k,l=-\infty }^{\infty}C_{3x}(k,l)\textrm{exp}(-j2\pi f_{1}k)\textrm{exp}(-j2\pi f_{2}l).\] Results . Simulation bispectrum analysis vibroacoustical signals, radiated by models blades of working wheels without crack and with crack at the stationary vibrating excitations are carried out and investigated. It demonstrates that appearence and evolution of the fatigue crack in a blade increases intensity of bispectral modules. Conclusions . Application of a modern signal processing methods allows to detect fault features, which are sensitive to small crack-like damages. The receive results can be used to create a vibroacoustical monitoring system for aircraft engine rotor components.

Evaluation of diagnostic thresholds dependability for tribologic signals received in the environment disturbed by vibroacoustic and functional signals

Abstract Determination of dependable diagnostic thresholds for tribologic signals received e.g. from antifriction bearings (in particular for insufficient number of measurements, only 4÷5) is a really difficult task due to complexity of working environment where such bearings are operated. Typical working environment for such objects must take account for operation time under various working conditions and accompanying (and disturbing) signals, e.g. vibroacoustic ones. The sought assessment of the relationship between diagnostic signals and environmental noise can be determined from convolution of both diagnostic and environments signals that make up the complete set of received information. The convolution of these two series of signals can be obtained from an algorithm based on the Cauchy product. Then one has to find the coherence factor and the square of amplitude gain for the set of diagnostic signals with reference to various sets of signals received from environment, which makes it possible to evaluate cohesion of the investigated series of signals, thus their suitability to determine diagnostic threshold for tribologic signals intended for the analysis.

Improvement of machining by the vibroacoustic diagnostics of electrophysical processes

The use of vibroacoustic signals in the diagnostics and control of electrospark machining is investigated.

Significant damages of core diamond bits in the process of rocks drilling

Technology of rotary drilling with diamond bits requires expert knowledge and experience. Drilling modes i.e. combination of pressure on the bit, the rotational speed of the bit, and the quantity and quality of lavage has a decisive influence to achieve maximum drilling speed with minimum consumption drilling bits with diamonds. Optimal setting of the operating mode of technological parameters pressure force, speed and lavage is a fundamental prerequisite to achieving maximum productivity and overall streamlining of the drilling. When talking about the use of diamond bits the careful handling is necessary since assembly operations till drilling process. The shedding of diamonds from the cutting rim and related premature wear, destruction of the entire drilling tool results in inefficient drilling and high cost of labor and drilling tools. This paper deals with the dynamic faults of diamond core bits in drilling of selected rock. We analyze the causes and consequences of developing these faults. The frequency spectra of vibro-acoustic signal of drilling tool with water flush, without water flush, with the bit for drilling of the rock and without bit no-load are presented. Obtained knowledge about the failure causes contributes to the prediction of possible emergency conditions, to the prevention of the operating mode faulty setting. The paper points out possibilities for efficient use of the drilling process from both energetic and economic point of view.

Adaptive noise cancellation based on EMD in water-supply pipeline leak detection

In water-supply pipeline leak detection and location, both the leak signals and blurred noises are closely related to the pipeline states and surroundings and most of the conventional noise-cancellation methods have to depend on the empirical parameters of either signals or noises. EMD (Empirical Mode Decomposition) is an adaptive signal decomposition method and is exclusive of base functions. A signal is decomposed into several IMFs (Intrinsic Mode Functions) in EMD, then the noise in a signal can be cancelled through removing uncorrelated IMFs. The existing EMD noise cancellation methods need to know the characteristics of either the wanted signal or the noise for rebuilding the noise-removed signal. However the characteristics of leak signals and noises are not fixed in various pipeline conditions, so the existing EMD noise cancellation methods can’t be directly applied in water-supply pipeline leak detection. This paper proposes an adaptive noise cancellation method based on EMD, in which the IMFs that don’t or less contain the components related to the leak can be removed through the cross-correlation between the IMFs and another signal collected at the either side of a suspect leak. In simulation analysis, the adaptive noise cancellation method can increase the SNRs (Signal to Noise Ratios) of leak signals as high as 16dB. In processing practical pipeline vibro-acoustic signals, with the proposed method the peak of adaptive time delay estimate of leak signals, which determines the location of a leakage, becomes more distinguished, and thus the error of leakage location is improved.

Diagnostics and Control of Ceramic Tools During High-Speed Milling of Tempered Steels on CNC Machine Tools

The operating principles of an algorithm for integrated diagnostics and control of ceramic tools during milling of tempered steel are discussed. The algorithm for detection of wear of the tool is based on the use of force parameters and chipping is identified from vibro-acoustic signals. The generalized structure of the subsystem for diagnostics and control of the state of a ceramic tool in a computer numerical controlled milling machine is described.

Investigation of monitoring perspectives for electroerosion processes by vibration parameter variation

The aim of investigations presented is the improvement of electroerosion (EE) machining stability, quality of product surface being obtained as well as the level of automation for the complete technological process. It is shown that in this case, the processing data from a working area in the form of vibroacoustic (VA) signals can be successfully used.

Vibroacustical Method for Measuring the Effect of Cavitation Erosion

One of the most harmful effects of cavitation, with strong influence on the life of the hydraulic machines is the destruction caused by erosion Since its discovery, over 150 years ago, evaluating the degradation is achieved by mass of material removed by erosion in a given time, which in the case of rotors and blades of hydraulic machines and marine propeller blades are equivalent by amount of electrode consumption for filling the voids left by the removal of material. Laboratory research on cavitation, from the beginning until now, evaluates the intensity of cavitation erosion rate, defined as a mass of material removed by erosion at a certain time of attack.The purpose of this paper is to develop and validate a technique based on vibroacoustic signal analysis of corroded samples, and that through their natural frequencies deviations to emphasize mass loss.The experimental measurement of the vibroacustic response of corroded specimens is carried out by using a condenser microphone. The vibration responses, in free-free conditions of the specimens, are analyzed using algorithm based on Fast Fourier Transform (FFT). The results are compared with other indicators of cavitation corrosion, such as lost mass and mass loss rate.

The Operating Diagnostics in the Computer Aided Systems of Production Processes

The paper presents the operational diagnostic problems in production systems. It briefly discusses the estimation of vibroacoustic signal characteristics used in diagnostic systems, the possibility of applications have been pointed out. Basing on the elements of the fuzzy logic, decision-making system in the areas of ambiguity during machining has been presented.An initial structure of the integrated supporting system of manufacturing processes dedicated to small and medium-sized enterprises in the metal industry have been shown. Future directions of authors’ research work have been indicated.

Wykorzystanie sygnału wibroakustycznego do diagnozowania stanu wierteł ze stali HS 2-5-1 przy wierceniu stali konstrukcyjnych

Wykorzystanie sygnału wibroakustycznego do diagnozowania stanu wierteł ze stali HS 2-5-1 przy wierceniu stali konstrukcyjnych

Automatic cough episode detection using a vibroacoustic sensor.

Cough monitoring is an important element of the diagnostics of respiratory diseases. The European Respiratory Society recommends objective assessment of cough episodes and the search for methods of automatic analysis to make obtaining the quantitative parameters possible. The cough "events" could be classified by a microphone and a sensor that measures the vibrations of the chest. Analysis of the recorded signals consists of calculating the features vectors for selected episodes and of performing automatic classification using them. The aim of the study was to assess the accuracy of classification based on an artificial neural networks using vibroacoustic signals collected from chest. Six healthy, young men and eight healthy, young women carried out an imitated cough, hand clapping, speech and shouting. Three methods of parametrization were used to prepare the vectors of episode features - time domain, time-frequency domain and spectral modeling. We obtained the accuracy of 95% using artificial neural networks.

Identification of Engine Operation States Using Advanced Signal Analysis Methods

The article provides a discussion concerning the potential for applying advanced methods of vibroacoustic signal processing for the purposes of identification of a combustion engine state. It contains example results of vibration measurements on the passenger car combustion engine in three directions. The research was conducted on stopping vehicle, for different pre-set values of the engine rotational speed. The results of preliminary tests focused on the potential use in the diagnostics of engine operation.

The Choice of Vibroacoustic Signal Measures in Mechanical Fault Diagnosis of Diesel Engines

The use of diesel engines as a basic power unit of electric generators in big ship crafts and as a power unit in smaller ship crafts is very common. Low fuel consumption, high resistance to overload and long life span are the basic features which made these engines so commonly used. The development of electronic control of high pressure injection systems of the engine made the service of such an engine not so simple any more. What is more, control systems are directed at reducing fumes toxicity, which does not have to go hand in hand with early detection of engine damages. It happens in the case of a particular group of mechanical damages of the engine, which are undetectable by an onboard diagnostic system in the early stage of the development. The injection system is able to choose regulation parameters in such a way so that the composition of the air fuel mixture is in optimal range, and as a result it hides the information about the damage.This paper presents the results of analysis of the usefulness of the chosen vibroacoustic signal measures in the process of detecting damages of this type.