Analysis of the Positioning Process of Objects by the System of Oblique Friction Force Fields on the Example of the MSC Adams Model

2020 ◽  
Author(s):  
Tomasz Piatkowski ◽  
Miroslaw Wolski
Keyword(s):  
Numerical Simulations ◽  
Friction Force ◽  
Force Fields ◽  
Positioning Precision ◽  
Friction Models ◽  
The Cross ◽  
Sorting System ◽  
Theoretical Analyses

Abstract The paper concerns modelling of the rotational positioning process of cuboid objects with the system of oblique friction force fields produced by two conveyors. These conveyors are used when introducing streams of objects onto trays of the cross-belt sorting system. The purpose of positioning is to place the objects parallel to the edges of the trays with the greatest possible precision. The positioning precision depends on the choice of the conveyors’ motion velocities and conveyors’ position to each other, which can be determined on the basis of numerical simulations. During theoretical analyses, contact and friction models available in the MSC Adams environment were taken into account.

Hysteretic effects of dry friction: modelling and experimental studies

2007 ◽  
Vol 366 (1866) ◽  
pp. 747-765 ◽  
Author(s):  
Jerzy Wojewoda ◽  
Andrzej Stefański ◽  
Marian Wiercigroch ◽  
Tomasz Kapitaniak
Keyword(s):  
Numerical Simulations ◽  
Dry Friction ◽  
Experimental Studies ◽  
Friction Model ◽  
Hysteretic Effect ◽  
Motion Characteristic ◽  
Friction Models ◽  
Theoretical Analyses ◽  
Friction Modelling

In this paper, the phenomena of hysteretic behaviour of friction force observed during experiments are discussed. On the basis of experimental and theoretical analyses, we argue that such behaviour can be considered as a representation of the system dynamics. According to this approach, a classification of friction models, with respect to their sensitivity on the system motion characteristic, is introduced. General friction modelling of the phenomena accompanying dry friction and a simple yet effective approach to capture the hysteretic effect are proposed. Finally, the experimental results are compared with the numerical simulations for the proposed friction model.

Experimental Validation of Friction Models for Rotor-Rubbing

2019 ◽  
Author(s):  
Juan Jauregui ◽  
Oscar De Santiago Duran
Keyword(s):  
Friction Force ◽  
Cross Correlation ◽  
Tangential Force ◽  
Nonlinear Behavior ◽  
Experimental Results ◽  
Friction Forces ◽  
Rotating Speed ◽  
Friction Models ◽  
The Cross ◽  
Set Up

Abstract The work presented here is a continuation of a set of experiments that were designed for predicting friction forces during rotor rubbing. The experimental set up consisted of a rotor rubbing a fixed surface. The surface had two force sensors, one aligned with the tangential force, and the other aligned in the radial direction. This set up allowed us to measure the friction component and the normal force. The measurements were complemented with a couple of accelerometers mounted on the bearings, and the accelerations and the friction force were measured simultaneously. All the data were analyzed using the Continuous Wavelet Transform (CWT) and the cross-correlation function. The CWT produces a spectrogram that is useful for identifying the nonlinear behavior of the phenomenon. The cross-correlation is used to measure the similarities between the friction force and the acceleration measurements. At low friction levels, experimental results show a sub-synchronous vibration at half of the rotating speed. This pattern is always present regardless of the friction source, but it is impossible to reproduce this effect using current friction models. The experimental results were compared to numerical results, these results were computed with the Muszynska’s model that is based on the physics of the phenomenon, but their predictions differ significantly from the experimental results. One of the reasons for these discrepancies lay on the fact that rotor-rubbing models consider the friction as an external force instead of modifying the system parameters.

Regular and chaotic oscillations of friction force

2006 ◽  
Vol 220 (3) ◽  
pp. 273-284 ◽  
Author(s):  
A Stefański ◽  
J Wojewoda ◽  
M Wiercigroch ◽  
T Kapitaniak
Keyword(s):  
Theoretical Analysis ◽  
Numerical Simulations ◽  
Friction Force ◽  
Experimental Research ◽  
Friction Model ◽  
System Response ◽  
Chaotic Oscillations ◽  
Dynamical Nature ◽  
Friction Models

In this paper, several friction features and models are discussed in the context of the dynamical nature of friction force observed during experiments. On the basis of experimental and theoretical analysis, the authors show that such behaviour can be considered as a certain representation of the system dynamics. According to this approach, a classification of friction models with respect to their sensitivity on the system motion character is introduced. Next, the results of experimental research are reported. Friction characteristics reconstructed experimentally for various types of the system response, i.e. periodic, quasi-periodic, and chaotic, are demonstrated. Finally, these results are compared with numerical simulations using the proposed friction model.

An Improved MMSE Pre-Coding Method for the Downlink Multi-User MIMO System

2012 ◽  
Vol 457-458 ◽  
pp. 600-606
Author(s):  
Xian Kun Gao ◽  
Yan Cui ◽  
Ji Lai Ying ◽  
Yong Chang Yu
Keyword(s):  
Numerical Simulations ◽  
Mimo System ◽  
Multiple Antennas ◽  
Poor Performance ◽  
Inversion Method ◽  
Block Diagonalization ◽  
Coding Method ◽  
Diagonalization Method ◽  
Noise Ratio ◽  
Theoretical Analyses

Recently many practical downlink multi-user MIMO linear pre-coding methods have been proposed, such as the channel inversion method and the block diagonalization method (BD). Considering the channel inversion method based on MMSE criterion (MMSE-CI) which is confined to a single receives antenna case, the BD has more advantages in multiple antennas cases, however, it has poor performance at the low and medium SNR regime on account of no consideration on the noise. In this paper, an improved MMSE pre-coding method is proposed with multi receive antennas of each user. Based on MMSE-CI, the cooperation of multiple antennas is adopted to further suppress the residual interference during designing the pre-coding matrix, which could increase the signal-to- interference-plus-noise ratio (SINR) at each user’s receiver. The proposed method obtains a better performance than the MMSE-CI and the BD algorithms, and its effectiveness is validated by both theoretical analyses and numerical simulations.

Trapping patterns during capillary displacements in disordered media

2022 ◽  
Vol 933 ◽  
Author(s):  
Fanli Liu ◽  
Moran Wang
Keyword(s):  
Numerical Simulations ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Disordered Media ◽  
Pore Geometry ◽  
Control Parameters ◽  
Pore Throat ◽  
The Impact ◽  
Theoretical Analyses

We investigate the impact of wettability distribution, pore size distribution and pore geometry on the statistical behaviour of trapping in pore-throat networks during capillary displacement. Through theoretical analyses and numerical simulations, we propose and prove that the trapping patterns, defined as the percentage and distribution of trapped elements, are determined by four dimensionless control parameters. The range of all possible trapping patterns and how the patterns are dependent on the four parameters are obtained. The results help us to understand the impact of wettability and structure on trapping behaviour in disordered media.

scholarly journals Discussion on the Theoretical Basis for Cross-Over Method Applied to Downhole Wave Velocity Test

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Qing Dong ◽  
Zheng-hua Zhou ◽  
Su Jie ◽  
Bing Hao ◽  
Yuan-dong Li
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Wave Velocity ◽  
Theoretical Basis ◽  
Influence Factors ◽  
P Wave ◽  
Engineering Practice ◽  
S Wave ◽  
Simulation Results ◽  
The Cross

At engineering practice, the theoretical basis for the cross-over method, used to obtain shear wave arrival time in the downhole method of the wave velocity test by surface forward and backward strike, is that the polarity of P-wave keeps the same, while the polarity of S-wave transforms when the direction of strike inverted. However, the characteristics of signals recorded in tests are often found to conflict with this theoretical basis for the cross-over method, namely, the polarity of the P-wave also transforms under the action of surface forward and backward strike. Therefore, 3D finite element numerical simulations were conducted to study the validity of the theoretical basis for the cross-over method. The results show that both shear and compression waves are observed to be in 180° phase difference between horizontal signal traces, consistent with the direction of excitation generated by reversed impulse. Furthermore, numerical simulation results prove to be reliable by the analytic solution; it shows that the theoretical basis for the cross-over method applied to the downhole wave velocity test is improper. In meanwhile, numerical simulations reveal the factors (inclining excitation, geophone deflection, inclination, and background noise) that may cause the polarity of the P-wave not to reverse under surface forward and backward strike. Then, as to reduce the influence factors, we propose a method for the downhole wave velocity test under surface strike, the time difference of arrival is based between source peak and response peak, and numerical simulation results show that the S-wave velocity by this method is close to the theoretical S-wave velocity of soil.

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