Track Defects Recognition Based on Axle-Box Vibration Acceleration and Deep- Learning Techniques

As an important component of load transfer,various fatigue damages occur in the track as the rail service life and train traffic increase gradually,such as rail corrugation,rail joint damage,uneven thermite welds,rail squats fas-tener defects,etc.Real-time recognition of track defects plays a vital role in ensuring the safe and stable operation of rail transit.In this paper,an intelligent and innovative method is proposed to detect the track defects by using axle-box vibration acceleration and deep learning network,and the coexistence of the above-mentioned typical track defects in the track system is considered.Firstly,the dynamic relationship between the track defects(using the example of the fastening defects)and the axle-box vibration acceleration(ABVA)is investigated using the dynamic vehicle-track model.Then,a simulation model for the coupled dynamics of the vehicle and track with different track defects is established,and the wavelet power spectrum(WPS)analysis is performed for the vibra-tion acceleration signals of the axle box to extract the characteristic response.Lastly,using wavelet spectrum photos as input,an automatic detection technique based on the deep convolution neural network(DCNN)is sug-gested to realize the real-time intelligent detection and identification of various track problems.Thefindings demonstrate that the suggested approach achieves a 96.72%classification accuracy.

A Study on the Vibration of the Charging Belt in an Electrostatic Accelerator

The vibration of the charging belt in an electrostatic accelerator has intense influ- ences on the accelerator operation. A calculating model was set up in this paper to study the belt vibration. The results show that the belt tension, belt velocity and belt current all contribute to the belt vibration. There is an optimal relationship among the three factors by which the belt would run most smoothly. There exists a minimum value of optimal tension for various belt velocities. The vibrating frequency of the is generally around several Hz.

Wireless Self-Powered Vibration Sensor System for Intelligent Spindle Monitoring

In recent years,high-end equipment is widely used in industry and the accuracy requirements of the equipment have been risen year by year.During the machining process,the high-end equipment failure may have a great impact on the product quality.It is necessary to monitor the status of equipment and to predict fault diagnosis.At present,most of the condition monitoring devices for mechanical equipment have problems of large size,low precision and low energy utilization.A wireless self-powered intelligent spindle vibration acceleration sensor system based on piezoelectric energy harvesting is proposed.Based on rotor sensing technology,a sensor is made to mount on the tool holder and build the related circuit.Firstly,the energy management module collects the mechanical energy in the environment and converts the piezoelectric vibration energy into electric energy to provide 3.3 Vfor the subsequent circuit.The lithium battery supplies the system with additional power and monitors’the power of the energy storage circuit in real-time.Secondly,a three-axis acceleration sensor is used to collect,analyze and filter a series of signal processing operations of the vibration signal in the environment.The signal is sent to the upper computer by wireless transmission.The host computer outputs the corresponding X,Y,and Z channel waveforms and data under the condition of the spindle speed of 50∼2500 r/min with real-time monitoring.The KEIL5 platform is used to develop the system software.The small-size piezoelectric vibration sensor with high-speed,high-energy utilization,high accuracy,and easy installation is used for spindle monitoring.The experiment results show that the sensor system is available and practical.

Field measurement and evaluation of vibration in different areas of a metro depot

This paper presents a study of the characteristics of a railway vibration at three key sections containing different track structures in a metro depot.The results show that the vertical and horizontal vibration acceleration levels are proportional to train speed.The Z-weighted vertical acceleration levels obtained showed that the vibration source strengths at the ballast foot of the testing line and the throat area were very close.The vibration attenuation at the repair line was larger than that of the testing line.In the throat area,the peak frequency of vibration obtained at the ballast foot(2.5 m)could be shifted to a lower frequency band by using polyurethane sleepers instead of standard concrete sleepers.Polyurethane sleepers can help to reduce vertical vibration in a frequency band of 0-10 Hz.The vibration levels would satisfy the limits given in the ISO2631-2-2003(2013)for any location more than 5 m away from the source at the testing line and 2.5 m away from the source at the repair line and throat area.

Various performance-enhancing effects from the same intensity of whole-body vibration training

Purpose:The purpose of this study was to compare the effects of an 8-week whole-body vibration training program in various frequency and amplitude settings under the same acceleration on the strength and power of the knee extensors.Methods:Sixty-four young participants were randomly assigned to 1 of 4 groups with the same acceleration(4 g):high frequency and low amplitude(n = 16,32 Hz,1 mm) group,medium frequency and medium amplitude(n = 16,18 Hz,3 mm) group,low frequency and high amplitude(n = 16,3 Hz,114 mm) group,and control(n = 16,no vibration) group.All participants underwent 8 weeks of training with body mass dynamic squats,3 sessions a week.Results:The results showed that the high frequency and low amplitude group increased significantly in isometric contraction strength and 120°/s isokinetic concentric contraction strength;the medium frequency and medium amplitude group increased significantly in 60°/s and 120°/s isokinetic strength of both concentric and eccentric contraction;and the low frequency and high amplitude group increased significantly in 60°/s and 120°/s isokinetic eccentric contraction strength.Conclusion:All frequency and amplitude settings in the 8-week whole-body vibration training increased muscle strength,but different settings resulted in various neuromuscular adaptations despite the same intensity.

Experimental and numerical studies on vibration characteristics of a railway embankment

In order to study the dynamic response of the rail embankment under different speeds and moving load of following vehicles,a model experiment with a ratio of 1:10 is established to test the time history of acceleration and the earth pressure of the embankment at various train speeds.Using the ABAQUS finite element calculation software,a train load is applied through the FORTRAN subroutine,thereby establishing a three-dimensional finite element model with the same size as the model experiment.The data and conclusions of the finite element method model are verified by the model experiment.The model also makes some supplements to the model experiment.The experimental results show that with the increase of speed,the peak acceleration and earth pressure of the embankment also increase.By analyzing the experimental data,it can also be found that the vertical acceleration of the embankment is much greater than the axial acceleration and the lateral acceleration.In addition,the elastic modulus of the soil and the sleeper pitch also have some influence on the acceleration.

Field monitoring of railroad embankment vibration responses in seasonally frozen regions

To investigate the vibration characteristics of a railway subgrade in different seasons, three field experiments were carried out in the seasonally frozen Daqing area of China during spring, smnmer, and winter. The vibration characteristics and attenuation rates of the subgrade induced by passing trains were investigated, and the influences of the season, train speed, train type, train load, and number of train compartments are described in this paper. The results show that： （1） near the rail track the vibration in the vertical direction was more significant than in the lateral and longitudinal directions, and as the distance from the railway track increased, the acceleration amplitudes and the attenuation rates all decreased in all three directions; （2） the acceleration amplitudes and at- tenuation rates decreased in the three different study seasons as the distance from the railway track increased, and the attenuation rates in the freezing period were the largest; and （3） the acceleration amplitude induced by a freight train was greater than that by a passenger train, and the subgrade vibration increased with increasing passenger train speeds when the number of train compart- ments was similar. These results have great significance for enhanced understanding of the characteristics of wain-induced vibra- tion embankment response in seasonally frozen regions, and provide essential field monitoring data on train-induced vibrations in order to improve the performance criteria of railroading in seasonally frozen regions.

Experimental Study of Structure Shock Vibration in Soil Caused by Explosion of Conventional Weapons

When hitting underground structures directly or exploding in rock-soil media near underground structures, the conventional weapons with large charge weight will make underground structures be subjected to strong shock vibration and cause personal casualty and damage of precision electronic equipments. The shock vibration has become one of the cardinal killing means of weapons. However, the existing methods of predicting structure shock vibration are limited evidently. In this paper the coupling coefficient of acceleration in clayey soil is obtained firstly. Subsequently based on repeated experiments of chemical explosion, after dimension analysis and by using method of multivariate stepwise regression, the calculation formulae of shock vibration acceleration for the underground structure are obtained finally. The formulae consider top and side explosion respectively, taking into account the effects of penetration depth, charge weight, distance to explosion center, rock-soil media, size of structure and buried depth. They are easy to use with high practicability and degree of confidence, and can provide credible evidence for prediction of shock vibration and vibration isolating design of underground structure.

An Investigation of Vibration Reducing on a Machine Tool

In order to reduce the vibration on a machine tool, more orthogonal experiment schemes have been designed, which are based on the steel balls vibration reducing principle. After experiments the optimal reducing vibration scheme was determined. This kind of vibration reducing scheme is used in steel balls vibration absorber, which can be used to reduce vibration magnitudes of a machine tools under the working conditions, whereby improving machining precision. The suggested experiment method is of useful reference in reducing vibrations on other machine tools too.

Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

STUDY ON SENSOR-BASED CONTROL METHOD FOR HARMONIC DRIVE SYSTEM

A new type of robust traje ctory tracking control for harmonic using joint torque sensor and joint acceleration sensor information is concerned with.Joint torque sensor information is used to compensate the uncertainty of link and load parameters. Joint acceleration feedback control will enhace the robustness of the driving system, resist the dynamic uncertainties and disturbing torque acted on the joint axis within definite bandwidth, improve the joint tracking performance, and resist the vibration of the load side of the harmonic drive system. Experimental studies are carried out and comparison of several controllers , such as PD and sensor- based control, the experimental results clearly illustrate the effectiveness of the proposed methods.

Dynamic analysis of wave slamming on plate with elastic support

Experiments are conducted to investigate the dynamic response of a plate with elastic support under a regular wave slamming. The statistical analysis results obtained in different model testing cases are presented. The theoretical analysis of the plate vibrations(including the forced and free vibrations) is performed. Four characteristic stages of the plate vibration accelerations between two consecutive wave impacts are identified. The submergence durations of the plate during the wave action and the hydro-elastic effects are discussed. Finally, some useful conclusions are drawn.