scholarly journals Effect of the Sound Source Position Error on Distribution Characteristics of Underwater Shock Wave Bunching Sound Field

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Xiaolong Liu ◽  
Hongbing Li ◽  
Ning Li ◽  
Kaizhuo Lei
Keyword(s):  
Shock Wave ◽  
Sound Source ◽  
Sound Field ◽  
Position Error ◽  
Distribution Characteristics ◽  
Source Position ◽  
Discharge Electrode ◽  
Finite Element Software ◽  
Position Errors ◽  
Effective Discharge

Curved reflection bunching technique of underwater plasma sound source (UPSS) uses the geometric characteristics of the curved reflector to reflect and bunching intense sound shock wave, so the center position error of the sound source is one of the important factors affecting the bunching performance of the shock wave. In this paper, the cause of the sound source position error is analyzed in detail, and nonlinear finite element software ANSYS/LS-DYNA (dynamic analysis software developed by LSTC) is used to establish the model of the shock wave bunching sound field. Through numerical simulations, the shock wave bunching sound field distribution characteristics under the influence of different position errors are comprehensively simulated, and the bunching performance of the shock wave and its influence law are deeply analyzed according to the simulation results. It provides guidance for reasonably controlling the machining error and installation error of the reflector and discharge electrode, estimating the effective discharge times of the discharge electrode, and formulating the design process.

Optimization of the Sound Source Position for Shaping Acoustically-Structurally Coupled Cavities

2001 ◽  
Author(s):  
Arzu Gonenc Sorguc ◽  
Ichiro Hagiwara ◽  
Qinzhong Shi ◽  
Haldun Akagunduz
Keyword(s):  
Sound Source ◽  
Sequential Quadratic Programming ◽  
Normal Modes ◽  
Sound Field ◽  
Source Strength ◽  
Source Position ◽  
Sound Sources ◽  
Coupled Cavities ◽  
Structural Loading ◽  
Initial Starting

Abstract In this study, sound field inside acoustically-structurally coupled rectangular cavity excited by structural loading and sound sources is shaped by optimizing the position of the sound source. In the optimization, Most Probable Optimal Design (MPOD) based on Holographic Neural Network is employed and the results are compared with Sequential Quadratic Programming (SQP). It is shown that source position, rather than source strength, is more effective in acoustically controlled modes. The nodal positions for in-vacuo acoustical normal modes are good candidates for initial starting points.

Analysis of Shock Wave Signals and Calculation of Trajectory Vector in Acoustic Positioning System

2014 ◽  
Vol 490-491 ◽  
pp. 1317-1321
Author(s):  
Song Lin Wu ◽  
Xiao Cheng Wang
Keyword(s):  
Shock Wave ◽  
Sound Source ◽  
Sound Field ◽  
Positioning System ◽  
Characteristic Parameters ◽  
Wavelets Analysis ◽  
Sensors Array ◽  
Ballistic Trajectory ◽  
Acoustic Positioning

Based on aerodynamics, this paper discussed the shock wave traits of ultrasonic bullet and studied the methods to calculate the position coordinate and ballistic trajectory vector in free sound field. Through experiments, the signals of shock wave from firing point and ballistic trajectory were decomposed and reconstructed, making use of wavelets analysis. The characteristic parameters were extracted to position the sound source and orientate the trajectory, based on the sensors array of right tetrahedron.

scholarly journals Consistency of the Empirical Distributions of Navigation Positioning System Errors with Theoretical Distributions—Comparative Analysis of the DGPS and EGNOS Systems in the Years 2006 and 2014

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 31
Author(s):  
Mariusz Specht
Keyword(s):  
Normal Distribution ◽  
Root Mean Square ◽  
Statistical Tests ◽  
Position Error ◽  
Positioning System ◽  
Navigation Systems ◽  
Mean Square ◽  
Positioning Systems ◽  
Position Errors ◽  
System Errors

Positioning systems are used to determine position coordinates in navigation (air, land and marine). The accuracy of an object’s position is described by the position error and a statistical analysis can determine its measures, which usually include: Root Mean Square (RMS), twice the Distance Root Mean Square (2DRMS), Circular Error Probable (CEP) and Spherical Probable Error (SEP). It is commonly assumed in navigation that position errors are random and that their distribution are consistent with the normal distribution. This assumption is based on the popularity of the Gauss distribution in science, the simplicity of calculating RMS values for 68% and 95% probabilities, as well as the intuitive perception of randomness in the statistics which this distribution reflects. It should be noted, however, that the necessary conditions for a random variable to be normally distributed include the independence of measurements and identical conditions of their realisation, which is not the case in the iterative method of determining successive positions, the filtration of coordinates or the dependence of the position error on meteorological conditions. In the preface to this publication, examples are provided which indicate that position errors in some navigation systems may not be consistent with the normal distribution. The subsequent section describes basic statistical tests for assessing the fit between the empirical and theoretical distributions (Anderson-Darling, chi-square and Kolmogorov-Smirnov). Next, statistical tests of the position error distributions of very long Differential Global Positioning System (DGPS) and European Geostationary Navigation Overlay Service (EGNOS) campaigns from different years (2006 and 2014) were performed with the number of measurements per session being 900’000 fixes. In addition, the paper discusses selected statistical distributions that fit the empirical measurement results better than the normal distribution. Research has shown that normal distribution is not the optimal statistical distribution to describe position errors of navigation systems. The distributions that describe navigation positioning system errors more accurately include: beta, gamma, logistic and lognormal distributions.

Consistency analysis of global positioning system position errors with typical statistical distributions

2021 ◽  
pp. 1-18
Author(s):  
Mariusz Specht
Keyword(s):  
Normal Distribution ◽  
Global Positioning System ◽  
Position Error ◽  
Statistical Distribution ◽  
Positioning System ◽  
Statistical Distributions ◽  
Position Errors ◽  
Global Positioning ◽  
Gps System ◽  
Best Fit

Abstract Research into statistical distributions of φ, λ and two-dimensional (2D) position errors of the global positioning system (GPS) enables the evaluation of its accuracy. Based on this, the navigation applications in which the positioning system can be used are determined. However, studies of GPS accuracy indicate that the empirical φ and λ errors deviate from the typical normal distribution, significantly affecting the statistical distribution of 2D position errors. Therefore, determining the actual statistical distributions of position errors (1D and 2D) is decisive for the precision of calculating the actual accuracy of the GPS system. In this paper, based on two measurement sessions (900,000 and 237,000 fixes), the distributions of GPS position error statistics in both 1D and 2D space are analysed. Statistical distribution measures are determined using statistical tests, the hypothesis on the normal distribution of φ and λ errors is verified, and the consistency of GPS position errors with commonly used statistical distributions is assessed together with finding the best fit. Research has shown that φ and λ errors for the GPS system are normally distributed. It is proven that φ and λ errors are more concentrated around the central value than in a typical normal distribution (positive kurtosis) with a low value of asymmetry. Moreover, φ errors are clearly more concentrated than λ errors. This results in larger standard deviation values for φ errors than λ errors. The differences in both values were 25–39%. Regarding the 2D position error, it should be noted that the value of twice the distance root mean square (2DRMS) is about 10–14% greater than the value of R95. In addition, studies show that statistical distributions such as beta, gamma, lognormal and Weibull are the best fit for 2D position errors in the GPS system.

scholarly journals Personnel Casualty Assessment for Explosion in the Subway Platform

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Jinju Zhang ◽  
Liqiong Wang
Keyword(s):  
Shock Wave ◽  
Explosive Charge ◽  
Assessment Method ◽  
Notch Effect ◽  
Distribution Characteristics ◽  
Wave Load ◽  
Spatial Distribution Characteristics ◽  
Injury Model ◽  
Personnel Safety ◽  
Casualty Assessment

The subway station is easy to be attacked by terrorist bombings, and it will cause heavy casualties. In this paper, a comprehensive casualty assessment method for personnel in the subway structure was established based on the existing personnel injury model. The spatial distribution characteristics of the shock wave suffered by the personnel in the subway platform were obtained. Combined with the comprehensive casualty assessment method, the personnel casualty area for the explosions in the subway platform was divided. The results show that for the same explosive charge, the maximum positive phase impulse generated by the explosion at the edge of the platform is smallest. The “notch effect” for the stair exit will increase the shock wave load. When the explosive is exploded in the center of the platform, the smaller the explosive charge is, the more obvious the “notch effect” is. When the explosive charge reaches 40 kg, the personnel safety area is reduced to a certain extent behind the stair except for the explosion happening at the stair. Also, the higher the shield door is, the larger the safety area behind the stair is.

scholarly journals Nonlinear Position Control Using Only Position Feedback under Position Errors and Yaw Constraints for Air Bearing Planar Motors

Mathematics ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 1354
Author(s):  
Wonhee Kim ◽  
Donghoon Shin ◽  
Youngwoo Lee
Keyword(s):  
Position Control ◽  
Position Error ◽  
Nonlinear Observer ◽  
Closed Loop System ◽  
Tracking Errors ◽  
Position Errors ◽  
Full State ◽  
Position Feedback ◽  
Position Controller ◽  
The Stability

In this paper, we propose a nonlinear position control using only position feedback to guarantee the tolerances for position tracking errors and yaw. In the proposed method, both mechanical and electrical dynamics are considered. The proposed method consists of the nonlinear position controller and nonlinear observer. The nonlinear position controller is designed by a backstepping procedure using the barrier Lyapunov function to satisfy the constraints of position error and yaw. The nonlinear observer is developed to estimate full state using only position feedback. The stability of the closed-loop system is proven using Lyapunov and input-to-state stabilities. Consequently, the proposed method satisfies the constraints of position error and yaw using only position feedback for the planar motor.

scholarly journals Analytical study of floating effects on load sharing characteristics of planetary gearbox for off-road vehicle

2020 ◽  
Vol 12 (7) ◽  
pp. 168781402094046
Author(s):  
Woo-Jin Chung ◽  
Joo-Seon Oh ◽  
Hyun-Woo Han ◽  
Ji-Tae Kim ◽  
Young-Jun Park
Keyword(s):  
Safety Factor ◽  
Planetary Gear ◽  
Load Sharing ◽  
Position Error ◽  
System Level ◽  
Load Factor ◽  
Road Vehicle ◽  
Design Modification ◽  
Planetary Gearbox ◽  
Position Errors

Uneven load sharing of a planetary gear set is the main cause of preventing the miniaturization and weight reduction of a planetary gearbox. Non-torque loads and carrier pinhole position errors are the main factors that worsen the load-sharing characteristics. However, their effects are seldom analyzed at a system level especially for an off-road vehicle. To make up this gap, some simulation models are proposed to investigate the effects of floating members on the load-sharing characteristics and the strength of a planetary gear set with non-torque load and carrier pinhole position error. When the error is not considered, the mesh load factor converges to unity irrespective of the type and number of floating members and the safety factors for pitting and bending are increased slightly. When the carrier pinhole position error is considered, the mesh load factor dramatically worsens. Although it is improved using the floating members, it does not converge to unity. However, the bending safety factor of the planet gear with the error is increased by 26%. This indicates that the design modification for the original planetary gearbox is needed to satisfy the safety factor requirement, but the problem is solved using only floating members.

Sound source separation using image signal processing based on sparsity of sound field

2016 ◽  
Vol 140 (4) ◽  
pp. 3058-3058 ◽  
Author(s):  
Masaaki Ito ◽  
Kenji Ozawa ◽  
Masanori Morise ◽  
Genya Shimizu ◽  
Shuichi Sakamoto
Keyword(s):  
Signal Processing ◽  
Sound Source ◽  
Source Separation ◽  
Sound Field ◽  
Sound Source Separation

scholarly journals An Optimized Symmetric WENO Method-Based Numerical Simulation of Intense Sound Field Generated by Underwater Plasma Sound Source

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Kaizhuo Lei ◽  
Xiaolong Liu ◽  
Ning Li ◽  
Xuchao Fan
Keyword(s):  
Euler Equations ◽  
Sound Source ◽  
Sound Field ◽  
Maximum Error ◽  
Numerical Examples ◽  
Weighted Essentially Nonoscillatory ◽  
The Third ◽  
Calculation Results ◽  
Pulse Sound ◽  
Fifth Order

The intensive pulse sound wave can be generated by the underwater plasma sound source (UPSS) based on the discharge of the underwater high voltage. The distribution of the sound field is prominently nonlinear. In this paper, the sound field of the intensive UPSS is described by the integral two-dimensional axisymmetric unsteady Euler equations firstly. In order to solve the Euler equations numerically, an optimized fifth-order symmetric WENO (weighted essentially nonoscillatory) method based on the three templates is proposed which is called WENO-SYM3. Without increasing the number of candidate templates, a new symmetric template structure can be obtained by expanding the second template and shifting the third one backwards for one space. The method is validated through numerical examples and experiments, and the results show that WENO-SYM3 has a high distinguished accuracy; meanwhile, its nonphysical oscillations are not obvious. The experimental results are basically the same as the calculation results, and the maximum error is around 3%.

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