Vibration Components Research Articles

Digital synchronous decomposition and period-N bifurcation size identification in dynamic systems: application to a milling process

Period-N bifurcation signal commonly contains the typical vibration and period-N bifurcation components. The period-N bifurcation size can be defined based on the period-N bifurcation component. It is challenging to extract the period-N bifurcation component with high accuracy in real-time since many frequencies may be contained in the period-N bifurcation signal. We proposed a digital synchronous decomposition (DSD) method to address this issue. Mathematical proof and numerical simulations validated that the DSD accurately decomposes the period-N bifurcation signal into the typical vibration and period-N bifurcation components in real-time. Moreover, an identification method and a bifurcation diagram were proposed to identify the period-N bifurcation size and depict period-N bifurcation evolution based on the DSD, respectively. We applied the proposed identification method to a benchmark milling process model and an actual milling process. Comparisons with the fast Fourier transform (FFT) highlight the proposed identification method's advantage. Besides, the proposed bifurcation diagram overcomes the limitation of the existing bifurcation diagrams and can quantitatively depict the period-N bifurcation severity and evolution.

Test and evaluation of driving comfort of rice combine harvester.

During the field operation of rice combine harvester, the vibration generated by vibration component will only reduce mechanical reliability and yield, but also cause resonance in the human body, leading to a decrease in driving comfort and even damage to the driver's health. To study the impact of combine harvester vibration on driving comfort, a certain type of tracked rice combine harvester was selected as the research object, and vibration tests were carried out based on vibration source analysis in the driving cab during field harvesting operations. The study showed that under the influence of field road conditions and crop flow, the operating speed of the engine, threshing rotor, stirrer, cutting blade, threshing cylinder, vibration sieve and conveyor were fluctuating, and their rotation and reciprocating motion would produce vibration excitation in the driving cab. A spectrum analysis was conducted on the acceleration signal of the driver's cab, and it was found that vibration frequencies at three measuring points, namely the pedal, control lever, and seat, can reach up to 36.7~43.3 Hz. These frequencies can cause resonance in various parts of the driver's body, such as the head and lower limbs, leading to symptoms such as dizziness, throat discomfort, leg pain, defecation anxiety, and frequent urination, and even affect vision of the driver. At the same time, a weighted root-mean-square acceleration evaluation method was used to evaluate the driving comfort of the harvester. The evaluation method showed that the vibration at the foot pedal (Aw1 = 4.4 m/s2>2.5 m/s2) caused extreme discomfort, while the vibration at the seat (0.5 m/s2< Aw2 = 0.67 m/s2<1.0 m/s2) and the control lever (0.5 m/s2< Aw3 = 0.55 m/s2<1.0 m/s2) caused relatively less discomfort. This research can provide some reference for the optimization design of the joint harvester driver's cab.

Health monitoring of the shaft bearings in a micro turbojet based on vibration analysis

In a recently implemented aerial target, the propulsion system consists of two JetCat micro turbojet engines. Due to the limited durability of the rotor support bearings, the engine operation time has been limited to two hours or two flights. In addition, after each flight, an engine bench test with vibration measurement is required. The adopted maintenance system is also labor-intensive and costly due to obligatory shaft bearing inspections performed frequently in the repair shop. These problems result from the limitations of the available high-speed bearing technology and the high rotor loads related to aircraft maneuvers in the air. The goal of the work is to develop a method for assessing the health of the main shaft bearings in the micro turbojet based on vibration signals. Methods known from full-scale jet engines were adapted for monitoring the health of the main shaft bearings. An accelerometer and rotational speed sensor were mounted on the engine. Vibration and other parameters of the engine were measured and analyzed, and then symptoms of damage were sought. The vibrations of seven JetCat engines were analyzed, selecting the one for further destructive testing. In all three axes X, Y and Z, the vibration components related to the rotational frequency and its orders are dominant, especially EO2 and EO3 related to rotor dynamics. Continuous engine vibration monitoring is a promising way of extending engine life and avoiding the deficiencies of microturbines related to their size and low-cost technology. The obtained results indicate that the tested JetCat engines have a life reserve, which has so far been used to a small extent.

Discomfort estimation for vertical whole-body vibration in the aircraft cabin considering the duration and static sitting comfort

This paper investigated the discomfort caused by vertical whole-body vibration (WBV) over 20 minutes using data recorded at the front, middle, and rear seats of the passenger cabin in civil aviation during a cruising flight. Twenty-four subjects experienced each stimulus at 0.5 ms−2 r.m.s. and judged discomfort at various moments (i.e., 1/6, 5, 10, 15, and 20 min) using a category-ratio method. The difference in discomfort due to high-frequency vibration components vanished after 10 min. Based on Stevens’ power law, a method is developed to estimate long-term vertical WBV discomfort by considering the static discomfort and an interaction coefficient between vibration and static discomfort as parameters. The proposed estimation method showed high accuracy with determination coefficients (R 2) higher than 0.97 and good linearity with values of growth rates 0.95, 1 and 0.95 for the vertical WBV discomfort at the front, middle and rear seat positions in the aircraft cabin.

Multimode Tip-Timing Analysis of Steam Turbine Rotor Blades

Presented in this paper is a multimode tip-timing analysis of steam turbine rotor blades using the Least Squares Technique. The rotor blade velocity obtained from the measured time of rotor blade arrival is used in the functional of the Least Square Technique, which is a novelty. The approach requires only two sensors in the casing for the algorithm to find blade multi-mode vibration components. For comparison, three and four sensors have also been used. An additional technique has been devised to determine the frequencies of blade vibration coupled modes, which is also a novelty. Verification of the algorithm is based on experimental and numerical analyses of steam turbine Low Pressure last stage rotor blades vibrating during run-down in a vacuum spin chamber, for synchronous vibrations, and during nominal work at 3000 rpm in a real working turbine for asynchronous vibrations. A multimode analysis is carried out for blade vibration at a nominal rotation speed of 3000 rpm. The considered steam turbine rotor blade is found to vibrate with two-mode shapes. This article considers the use of this method in BTT measurement uncertainties in the form of noise uniform distribution and noise normal distribution.

Increasing the accuracy of the process of automated counting of thin long products

Vibrating hopper feeders with an electromagnetic drive for automating the process of counting parts have become widely used. This process is necessary when transferring them to another workshop for the next technological operation. Also, it is necessary to count artificial products on the lot when packing them for packaging. Vibrating feeders are used to feed miniature, small, or medium-sized parts to the counting position of counting or packing machines. In this case, the parts supplied to these positions should be arranged in one layer. In addition, they should have a certain gap between them for reliable operation of the counting device. Basically, counters for such machines are made on the basis of photoelectric or inductive sensors. The disadvantage of inductive sensors is that they can only be used for metal objects. Photoelectric sensors are more versatile, so they have gained the most distribution for counting or filling machines. The principle of operation of the automatic counting position is that when the object to be counted is applied to it, it crosses the working area of the counting position and the sensor sends an impulse to the counting device. When using photoelectric sensors, parts or products cross the beam of the sensor and it supplies a counting pulse to the electronic counter at each crossing of the working beam. Basically, when using vibrating hopper feeders, the counting position is located either directly at the exit part of the transporting tray, or at the exit from it of the transported objects. The speed of transporting parts or products increases when moving up, because the amplitude of the horizontal component of oscillations increases when the diameter of the transporting tray increases. This is because the hopper of the vibratory feeder has a conical shape. This allows the parts to be refined in one layer. In addition, before the counting position, the parts must be separated from each other to create the necessary gap between them. This is necessary for the reliable operation of the photoelectric sensor. This system works reliably when the dimensions of the parts to be counted are larger than the diameter of the working beam of the sensor. But, when automating the counting of thin, long parts or products whose thickness is close to the size of the working beam of the sensor, the latter may cross it several times when passing through the zone of the counting position. This sharply reduces the accuracy of the counting process. This happens because the parts on the conveyor tray move with a small bounce due to the vertical component of the hopper's vibrations. Therefore, it became necessary to develop a new counting position system in order to increase the accuracy of the counting device for counting long thin parts or products (pins for electrical connectors, needles, matches, etc). The work considers a set of elements that affect the productivity and efficiency of counting devices based on vibrating hopper feeders with electromagnetic drives, for counting long thin parts or products of this shape.

Cause Analysis and Treatment of Abnormal Vibration of Hydraulic Generator Unit Caused by Coupling Defect

When a hydropower station 25MW hydropower unit is operated with load after overhaul, the upper bracket vibration will exceed the standard. To find out the cause of the problem and eliminate the fault, the mechanical, electromagnetic, and hydraulic aspects are mainly analyzed and checked. The results show that the excessive vibration of the upper bracket of the unit is caused by the incomplete pre-tightening force between the coupling bolts of the turbine and generator of the unit, as well as the improper location and thickness of the padding. It is characterized by a vibration component whose frequency is between the rotational frequency and twice the rotational frequency. By fully pre-tightening the coupling bolts and restoring the original padding position and thickness, the vibration of the upper bracket, upper guide swing, and other data are significantly improved, and the desired purpose is achieved. The cause analysis and fault treatment of the abnormal vibration of the hydro-generator unit can provide some reference for diagnosing other similar faults.

Orthogonalization of the measuring basis of triaxial vibration transducers by the method of successive approximations

The transversal sensitivity of tri-axial vibration transducers, which have found vast application in various vibration measuring and material testing systems, decreases the accuracy of measurements. We present a solution to the problem of eliminating the error attributed to the presence of the transverse sensitivity. The measurement error depends on many factors including the ratio of vibration components along the sensitivity axes, the width of the vibration spectrum, and the presence of intrinsic resonances of the vibration transducers in the main and transverse directions. The developed method provides almost complete compensation of the error. Analysis of the components of sensitivity vectors along the measuring directions showed that the transversal sensitivity vectors are in fact the parasitic penetrations from other directions, and can be decomposed along the measuring axes. To orthogonalize the sensitivity vectors during calibration, the sensitivity vectors should be rotated until they coincide with the orthogonal directions. A measuring basis with zero transverse sensitivities is thus obtained, and the sensitivity matrix is reduced to a diagonal form. With this approach the fundamentals and practical algorithm using successive approximations of triaxial transducer calibration with orthogonalization are outlined. Each orthogonalization step is illustrated by the current sensitivity matrix, showing the progress of transversal sensitivity reduction. The results of the developed tri-axial transducer coupled to a special preamplifier-converter with transversal sensitivities reduced to nearly zero values using the developed method are presented. Since calibration is carried out without dismantling of a vibration transducer, it can be carried out not only during its manufacture, but also during verification upon operation, which increases the service life. The use of the described technique not only improves the metrological parameters of vibration transducers, but also provides a significant reduction of the requirements for the accuracy of manufacturing their measuring system, thus reducing the production costs. The presented method is promising for the developing new precise multi-axis vibration transducers and measuring systems on their base.

TSCK guided parameter convex optimization tunable Q-factor wavelet transform and its application in wheelset bearing fault diagnosis

Wheelset bearing is a typical vulnerable structural component in high-speed trains and heavy haul vehicles. In addition to the typical nonlinear and nonstationary characteristics, the vibration signal of wheelset bearing also contains track subgrade vibration and transmission path coupling interference components. To solve this problem, this paper proposes a new feature extraction method for wheelset bearing faults. This method constructs the Teager energy spectrum correlation kurtosis, which is purposely sensitive to periodic fault impulse components, as the objective function. The Q-factor and redundancy of tunable Q-factor wavelet transform are selected by using the parameter convex optimization method, which makes the signal decomposition have better sparsity, so as to extract fault information accurately. Simulated analysis, experimental signal analysis of QPZZ-II test-bed, and experimental signal analysis of wheelset bearing test-bed show that the proposed method can suppress the influence of nonperiodic transient impulse components, harmonic components, and noise components in the signal and accurately extract the periodic impact characteristics of bearings.

Experimental Study on the Vibration Reduction Performance of the Spindle Rotor of a Rubbing Machine Based on Aluminium Foam Material

Larger vibration and noise often exist in agricultural machinery due to the harsh working environment and high power. The rubbing machine is one of the indispensable pieces of equipment in the agriculture and livestock industry, and it is affected by the vibration of large constraints on its promotion and use. To reduce the vibration of the rubbing machine, the vibration characteristics of the spindle rotor were first analysed by modal simulation, thus determining the larger contributions to the spindle rotor vibration. Second, aluminium foam material was installed in the large deformation part of the spindle rotor. Its vibration reduction and energy absorption characteristics were used to optimise the vibration reduction design by increasing the damping. Third, a steel ball impact test was conducted to analyse the vibration characteristics of the optimised spindle rotor. The results show that the maximum impact accelerations were reduced by 28.4% and 64.75% in the axial and radial directions, respectively, and the impact energies were reduced by 67.3% and 90.65% in the axial and radial directions within 2 s of impact collision, respectively, indicating that the optimised spindle rotor damping increased significantly. In addition, the vibration reduction effect of the optimised rubbing machine was verified by a bench test. By measuring the change degree of the static component of the spindle rotor vibration, the axial, radial, and vertical vibrations of the spindle rotor were improved by 5.78%, 10.32%, and 23.96%, respectively. Therefore, optimising the spindle rotor with aluminium foam material can reduce the vibration generated during the impact of the material on the spindle rotor. The rubbing machine’s vibration, damping, and energy absorption were also realised in real working conditions.

Compound faults diagnosis of rotating machinery via enhanced two-layer sliding correlated kurtosis

Compound faults identification from vibration signals is still a challenge for rotating machinery because the multiple periodic impulsive fault signals may oscillate with the same frequency. In this research, a method termed enhanced two-layer sliding correlated kurtosis (TLSCK) is presented for isolating and identifying the compound defects from the monitored data containing strong background noise and compound faults. The method contains two main steps: the dual-tree complex wavelet package transform (DTCWPT) based correlated kurtogram is conducted on the raw monitored data as a frequency filtering step; further, the enhanced TLSCK method is conducted to diagnosis the compound defects from above filtered signals. The output signal of the enhanced TLSCK could locate the occurrence of interested fault impulses, while the unwanted vibration components and residual noise are well eliminated. Both numerically simulated and experimentally measured vibration data of damaged rolling bearings are analyzed via the presented method to test its performance, and the analysis results validate that the proposed method is effective in detecting compound faults of rotating machinery.

A new ternary molybdenum phospho-silicide Mo3Si2P: Phase equilibria, structural, electronic, transport and thermal properties

Here we report the successful preparation and systematical characterization of a novel molybdenum compound Mo3Si2P. As the first genuine ternary molybdenum phospho-silicide, it augments the Mo–Si–P family and may be served as an innovative archetype to develop exotic electronic states. The phase-equilibrium relation of Mo–Si–P system was studied, which defines the phase-stability region of Mo3Si2P, and a phase diagram that makes reviews on the abundant material and electronic physics in the system was established. Mo3Si2P crystallizes in a non-centrosymmetric orthorhombic structure (space group: Ama2) that appears as alternately stacking flat (Mo1)3P3 sheets and buckled (Mo2)3Si3 double-layers along the a-axis direction. The Bloch-Grüneisen-Mott model is employed to describe the T-dependent multiband metallic-conduction which is principally governed by electrons at high temperatures. The thermal-conductivity components of charge carrier and lattice vibration were extracted from κtotal by following the extended Wiedemann-Franz law. Poor thermoelectric performance is evidenced by very low thermoelectric power factor and figure-of-merit that are ascribed to small Seebeck coefficient and high thermal conductivity. Sommerfeld coefficient (γ) and Wilson ratio (RW) demonstrate that the electron correlation is extremely weak. First-principles calculations predict significant contribution from Mo-4 dx2−y2 orbital electrons to the Fermi surface of Mo3Si2P which shows different band fillings from Mo3Ge2P where dz2 electrons take the maximal occupation. Electron-phonon coupling parameter λep was calculated as 0.74, which reveals a medium interaction strength.

Study on Typical Aerodynamic Faults of Variable Pitch Wind Turbine

The variable-speed variable-pitch wind turbine is an important part of China's power and energy systems, and is also the main conversion form of wind energy utilization. Aiming at the problem that the traditional blade element-momentum theory cannot achieve the modeling and simulation of wind turbine plane wind unbalance caused by wind shear and tower shadow effect, the modeling and simulation numerical calculation method of aerodynamic load of wind turbine actuation disk with different blade wind unbalance pitch angles is proposed, This method can derive the analytical expressions for solving the key variables of load calculation, axial induction factor and tangential induction factor, and realize the aerodynamic load solution. At the same time, it is also verified that the characteristic vibration component of 3 times the low speed shaft rotation frequency (3P) is a typical dynamic load feature of tower shadow effect, and is also the most important aerodynamic load fluctuation feature of variable-speed variable-pitch wind turbine, However, under normal conditions, the wind shear effect has little effect on the wind turbine load fluctuation.

Dynamic modeling and simulation analysis of inter-shaft bearing fault of a dual-rotor system

In order to study the vibration characteristics of inter-shaft bearing failures of a dual-rotor system, an eight-degree-of-freedom dynamic model of dual-rotor system containing inter-shaft bearings is established. The Newmark-β method is used to solve the proposed model equations. The dynamic characteristics of the rotor system when the inner ring and outer ring of the inter-shaft bearing has single-point failures or composite failures are analyzed. The comparison results show that the fault frequency distribution pattern in the envelope spectrum of the dynamic simulation results is consistent with that of the test results, which proves the effectiveness of the proposed dynamic model. It is found that when the inter-shaft bearing fails, a combination of rotor rotation frequency, multi-frequency, and fault frequency modulation frequency occurs in the fault characteristic frequency of the dual-rotor system. In addition to the speed-synchronized vibration components caused by the eccentricity, the rotor vibration signal is usually accompanied by a high-order harmonic vibration signal.

Real-Time Image-Based Vibration Extraction with Memory-Efficient Optical Flow and Block-Based Adaptive Filter

In this paper, we propose a real-time vibration extraction system, which extracts vibration component within a given frequency range from videos in real time, for realizing tremor suppression used in microsurgery assistance systems. To overcome the problems in our previous system based on the mean Lucas-Kanade (LK) optical flow of the whole frame, we have introduced a new architecture combining dense optical flow calculated with simple feature matching and block-based band-pass filtering using band-limited multiple Fourier linear combiner (BMFLC). As a feature of optical flow calculation, we use the simplified rotation-invariant histogram of oriented gradients (RIHOG) based on a gradient angle quantized to 1, 2, or 3 bits, which greatly reduces the usage of memory resources for a frame buffer. An obtained optical flow map is then divided into multiple blocks, and BMFLC is applied to the mean optical flow of each block independently. By using the L1-norm of adaptive weight vectors in BMFLC as a criterion, blocks belonging to vibrating objects can be isolated from background at low cost, leading to better extraction accuracy compared to the previous system. The whole system for 480p and 720p resolutions can be implemented on a single Xilinx Zynq-7000 XC7Z020 FPGA without any external memory, and can process a video stream supplied directly from a camera at 60fps.

Application of a thermo-biomechanical virtual manikin used In transient systems

In this paper is developed and applied a thermo-biomechanical virtual manikin used in transient systems. This numerical model, under transient conditions, is applied in the thermal and vibrations of the different sections of the human body. The thermal numerical model, based in energy and mass balance integral equations, considers the first order equations systems, while the vibration numerical model, based in Newton equation, considers the second order equations systems converted in first order equation system. The resolution of the numerical model is made through the Runge-Kutta-Fehlberg method with error control. The thermal numerical model is used in the study of the periodical and randomized airflow fluctuations applied to the human body section and the biomechanical numerical model is used in the study of the periodical and randomized vibrations applied to the feet, that a standing person is subjected. The signals of the stimuli, the power spectrum, the equivalent frequencies and the Draught Risk (DR) of the same signals will be presented. In accordance with the obtained results, is verified that: in the thermal component the DR is evaluated and in the vibration component the body structure reduces the power spectra energy frequency and the equivalent frequency analysis.

Combined analysis of acoustic emission and vibration signals in monitoring tool wear, surface quality and chip formation when turning SCM440 steel using MQL

With modern production, Minimum Quantity Lubricant (MQL) technology has emerged as an alternative to conventional liquid cooling. The MQLs is an environmentally friendly lubricant method with low cost while meeting the requirements of machining conditions. In this study, the experimental and analytical results show that the obtained acoustic emission (AE) and vibration signal components can effectively monitor various circumstances in the SCM440 steel turning process with MQL, such as surface quality and chip formation as cutting tool conditions. The AE signals showed a significant response to the tool wear processes. In contrast, the vibration signal showed an excellent ability to reflect the surface roughness during turning with MQL. The chip formation process through the cutting mode parameters (cutting speed, feed and depth of cut) was detected through analysis amplitude of the vibration components Ax, Ay and Az and the AE signal. Finally, Gaussian process regression and adaptive neuro-fuzzy inference systems (GPR-ANFIS) algorithms were combined to predict the surface quality and tool wear parameters of the MQL turning process. Tool condition monitoring devices assist the operator in monitoring tool wear and surface quality limits, stopping the machine in case of imminent tool breakage or lower surface quality. With the unique combination of AE and vibration analysis model and the training and testing samples established by the experimental data, the corresponding average prediction accuracy is 97.57 %. The highest prediction error is not more than 3.8 %, with a confidence percentage of 98 %. The proposed model can be used in industry to predict surface roughness and wear of the tools directly during turning

Gentle Driving of Piles (GDP) at a sandy site combining axial and torsional vibrations: Part I - installation tests

Gentle Driving of Piles (GDP) is a new technology for the vibratory installation of tubular (mono)piles. Its founding principle is that both efficient installation and low noise emission can be achieved by applying to the pile a combination of axial and torsional vibrations. Preliminary development and demonstration of the proposed technology are the main objectives of the GDP research programme. To this end, onshore medium-scale tests in sand have been performed on piles installed using both impact and vibratory driving methods (including GDP). After presenting the development of a purpose-built GDP driving device and the geotechnical characterisation of the site, this paper covers the execution of GDP installation tests. Focus is on the installation performance of GDP-driven piles, which is discussed with the aid of structural and ground monitoring data. The comparison between piling data associated with GDP and standard axial vibro-driving points out the potential of the proposed installation technology, particularly with regard to the beneficial effect of the torsional vibration component. The findings of this study encourage further development of the GDP method and its future extension to offshore full-scale conditions.

Numerical analysis and experimental research of vibration and noise characteristics of oil-immersed power transformers

Oil-immersed power transformers play a prominent role in power grid system, and its vibration and noise influence the operation of the power grid. In this paper, an electromagnetic–mechanical-acoustic coupled three-dimensional finite element method of oil-immersed transformer is established. On this basis, according to a noise and vibration experiment of product-level oil-immersed power transformer, it not only proves the effectiveness of the calculation model, but also explores the influences of the radiating grilles and input voltage on the vibration and noise characteristics of the oil immersion transformer quantitatively. Research shows that the main frequency components of transformer vibration and noise focus on 100 Hz and its higher and integer multiple frequencies. The errors of total vibration acceleration level and overall sound pressure levels between the simulation results and test results do not exceed 3 dB, which verify the effectiveness of the numerical method.

Research on the Electromagnetic Characteristics of an Integrated Multi-Winding Inductive Filtering Converter Transformer and Its Filter System

In this paper, the electromagnetic characteristics of a novel integrated multi-winding inductive filtering converter transformer, including two parallel-connected delta filter windings with zero impedance, are studied. First, based on Ansoft, a 3D FEM model of the novel converter transformer is built according to its structural parameters and material characteristics. Next, the external circuit connection based on the established 3D FEM model is realized so the corresponding field-circuit coupling model can be established under three different working conditions. On this basis, the electric field characteristics, magnetic field characteristics, winding electromagnetic force characteristics, and core loss characteristics of the novel converter transformer with different conditions are analyzed. The results show that because the harmonic current is effectively suppressed, the flux chain passing through the windings of the novel converter transformer is closer to the sinusoidal wave and the harmonic magnetic potential is effectively suppressed; the electromagnetic force received by each winding of the converter transformer and the high-frequency vibration component are significantly reduced; and the transformer core loss is also significantly reduced. The research on the internal electromagnetic characteristics of the integrated multi-winding inductive filter converter transformer reveals the mechanism of reducing vibration and noise.