scholarly journals Experimental Study on Characteristics of Short Wave Irregularity in Urban Rail Transit

2020 ◽  
Author(s):  
Jian Fang ◽  
Wenwen Zheng ◽  
Xiaoyan Lei
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Amplitude Distribution ◽  
Short Wave ◽  
Point Of View ◽  
Rail Transit ◽  
Track Structure ◽  
Power Spectral ◽  
Surface Irregularities ◽  
Maximum Entropy Spectrum

Based on the measured irregularity data of Shanghai rail transit 11# line, firstly from the angle of time domain the amplitude stability and amplitude distribution characteristics of the rail surface short wave irregularity whose wavelengths are in the range of 0.01 ∼ 1 m are analyzed. Secondly from the point of view of frequency domain by using the maximum entropy spectrum method the short wave power spectral density is estimated. Then the power spectral density curves are compared with the short spectrum of Wang Lan and Sato and the different track structure effects on the states of the rail surface irregularities are also analyzed. The research show that the amplitude distribution of track surface short wave irregularity is close to the normal distribution. And the maximum amplitudes of some sections in Jiading Xincheng – Malu and Nanxiang – Taopu saemaul undong exceed 2.0mm. In the section of Liziyuan-Shanghai West Railway Station, the power spectral density curves of track structure with the supporting block, DTIII-2 type fasteners and with the conventional integral track bed are also similar to that of Sato spectrum. And it is obviously superior to that of other track structures in this section.

The Response of Rotating Machinery to External Random Vibration

1974 ◽  
Vol 96 (2) ◽  
pp. 477-489 ◽  
Author(s):  
J. M. Tessarzik ◽  
T. Chiang ◽  
R. H. Badgley
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
High Speed ◽  
Thrust Bearing ◽  
Dynamic Environment ◽  
Amplitude Distribution ◽  
Random Vibrations ◽  
Mass Model ◽  
Power Spectral ◽  
Rotor Axis

A high-speed turbogenerator employing gas-lubricated hydrodynamic journal and thrust bearings was subjected to external random vibrations for the purpose of assessing bearing performance in a dynamic environment. The pivoted-pad type journal bearings and the step-sector thrust bearing supported a turbine-driven rotor weighing approximately twenty-one pounds at a nominal operating speed of 36,000 rpm. The response amplitudes of both the rigid-supported and flexible-supported bearing pads, the gimballed thrust bearing, and the rotor relative to the machine casing were measured with capacitance type displacement probes. Random vibrations were applied by means of a large electrodynamic shaker at input levels ranging between 0.5 g (rms) and 1.5 g (rms). Vibrations were applied both along and perpendicular to the rotor axis. Response measurements were analyzed for amplitude distribution and power spectral density. Experimental results compare well with calculations of amplitude power spectral density made for the case where the vibrations were applied along the rotor axis. In this case, the rotor-bearing system was treated as a linear, three-mass model.

scholarly journals Simulation of a vehicle movement on a roadway with stochastic irregularities prescribed by the power spectral density

2021 ◽  
Vol 1199 (1) ◽  
pp. 012070
Author(s):  
J Dižo ◽  
M Blatnický ◽  
O Kravchenko ◽  
V Mamrai ◽  
D Barta ◽  
...  
Keyword(s):  
Spectral Density ◽  
Mechanical System ◽  
Power Spectral Density ◽  
Ride Comfort ◽  
Vertical Direction ◽  
Driving Safety ◽  
Vertical Movements ◽  
Power Spectral ◽  
Surface Irregularities ◽  
On The Road

Abstract A vehicle represents a mechanical system, which consists of bodies interconnected by joints, force elements, constraints and other coupling elements. When a vehicle moves on a roadway, it is excited due to roadway surface irregularities. It results to vibration of the vehicle mainly in the vertical direction. These vertical movements are known as a vertical dynamics of vehicles. The level of vibrations characterized by their frequency and amplitudes considerably effects two main phenomena, i.e. driving safety and ride comfort for passengers. Therefore, it is necessary to investigate and analyse response of vehicles to the vertical excitations. This article is aimed at evaluation and research of driving properties of a vehicle by means of simulation computations. In case of analysing vehicle’s mechanical system using a virtual model, it is necessary to define in a proper way not only parameters of an investigated vehicle, but also parameters of the excitations due to a roadway surface irregularities. In the reality, roadway surface irregularities have a stochastic behaviour. These fact is processed using statistical methods and it results to the power spectral density of the roadway surface irregularities. A presented research is focused on evaluation of selected output quantities of a vehicle, which moves on the road at various speeds and on various road qualities. An evaluated vehicle uses independent front wheels suspension, which design comes from the utility model. The rear axle is a rigid axle. Dynamic analyses and assessment of the resulting parameters were performed in the Simpack multibody software package. Based on reached results it is obvious, that vertical dynamics of the vehicle is affected by road quality and driving speed. Moreover, the performed analyses have proven, that the used independent front wheels suspension improves driving properties of the vehicle, contributes to better ride comfort and ensures required driving safety.

Fuzzy Modeling of Multi-Degree-of-Freedom Power Spectral Density Systems

2009 ◽  
Vol 2 (1) ◽  
pp. 40-47
Author(s):  
Montasser Tahat ◽  
Hussien Al-Wedyan ◽  
Kudret Demirli ◽  
Saad Mutasher
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Fuzzy Modeling ◽  
Degree Of Freedom ◽  
Power Spectral

scholarly journals Noise power spectral density scaled SNR response estimation with restricted range search for sound source localisation using unmanned aerial vehicles

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Benjamin Yen ◽  
Yusuke Hioka
Keyword(s):  
Spectral Density ◽  
Noise Reduction ◽  
Power Spectral Density ◽  
Sound Source ◽  
Processing Algorithm ◽  
Post Processing ◽  
Time Frequency ◽  
Distance Error ◽  
Rotor Noise ◽  
Power Spectral

Abstract A method to locate sound sources using an audio recording system mounted on an unmanned aerial vehicle (UAV) is proposed. The method introduces extension algorithms to apply on top of a baseline approach, which performs localisation by estimating the peak signal-to-noise ratio (SNR) response in the time-frequency and angular spectra with the time difference of arrival information. The proposed extensions include a noise reduction and a post-processing algorithm to address the challenges in a UAV setting. The noise reduction algorithm reduces influences of UAV rotor noise on localisation performance, by scaling the SNR response using power spectral density of the UAV rotor noise, estimated using a denoising autoencoder. For the source tracking problem, an angular spectral range restricted peak search and link post-processing algorithm is also proposed to filter out incorrect location estimates along the localisation path. Experimental results show the proposed extensions yielded improvements in locating the target sound source correctly, with a 0.0064–0.175 decrease in mean haversine distance error across various UAV operating scenarios. The proposed method also shows a reduction in unexpected location estimations, with a 0.0037–0.185 decrease in the 0.75 quartile haversine distance error.

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