ORCID Profile
0000-0002-7584-9637
Current Organisation
Iran University of Science and Technology
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Publisher: JVE International Ltd.
Date: 30-06-2016
Abstract: The vibrations of pantograph passing underneath the overhead system can be reduced by using droppers to place the contact wire in the designed curve. Nowadays, various software programs are used to estimate dynamic interaction of pantographs and overhead catenary system. In order to implement the software program, the necessary static force for each dropper should be estimated initially to place the contact wire in the designed curve. Unlike most available software programs, the implemented software program in this research consists of a heuristic analytical algorithm to estimate the static shape of the overhead catenary system. Accordingly, the variable separation and eigen function expansion method were used to calculate the static shape of contact wire and messenger cable under a given loading condition. At the next step, the stiffness matrix of contact wire in catenary was obtained and a procedure was defined to calculate the necessary static force for each dropper, which would then place the contact wire in the target curve. Finally, effort was made to examine the function of automatic tension device in OCS (Tension Wheel considering the Coulomb’s friction). Moreover, the deformations in the contact wire and messenger cable due to temperature changes were estimated and the results shows that allowable friction in the tension wheel can cause 27 % deviation in sag of the contact wire.
Publisher: Korean Society for Railway
Date: 30-09-2013
Publisher: SAGE Publications
Date: 16-11-2018
Abstract: The aim of this research is to propose and develop an analytical exact solution for finding the static equilibrium configuration of a catenary before and after incurring defects such as tension loss or a broken dropper. The procedure includes considering the steady-state solution of the dynamic motion equation of the contact wire and the messenger cable. The wire and the cable are considered as tensile Euler–Bernoulli beams. The stiffness matrix of the beam is configured and is used to calculate the dropper's dead load. Progressively, a novel method is proposed to find the equilibrium configuration of the same catenary after the defect. The results prove that the tension loss in the messenger cable is more precarious than the tension loss in the contact wire. The broken dropper causes a significant sag in the sub-span and increases the static forces of the adjacent droppers. A comparison with field measurements justifies the accuracy of the results of the proposed model.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Springer Science and Business Media LLC
Date: 28-02-2020
Publisher: SAGE Publications
Date: 10-01-2019
Abstract: Continuous and quality contact between the pantograph and the catenary system is one of the major challenges for increasing the speed of electric trains. Compared to other studies, this paper has considered the catenary system as the main system and has assumed the pantograph as an excitation factor. Based on this, a controller has been applied on the contact wire, once at the last span and another time near the contact point of the pantograph. Results were compared with the conventional controllers that exert control force on a collector's head. Based on this, two different objectives were considered for the controller including ‘improvement of contact quality’ and ‘minimisation of the vertical velocity of the overlap point’. For this purpose, a full analytical model of the catenary system was presented and was verified using the relevant standards, and then three types of linear quadratic optimal controllers were added to the model with the two objectives mentioned above. The results of the study show that if the model aims to reduce the overlap point vertical velocity, contact quality will be improved. However, in case it aims to enhance contact quality, the velocity of the overlap point will not necessarily be reduced. Moreover, the contact point controller aiming at reducing the overlap point velocity outperforms other controllers and makes 71% improvement in contact quality in comparison with the no-controller case.
Publisher: Hindawi Limited
Date: 27-12-2022
DOI: 10.1155/2022/4911952
Abstract: Rail welds are considered as the weak part of a railway track. Their defects and health can directly affect wheel-rail interaction, track safety, and reliability. Current practices for rail welds health assessment are based on 2D vertical and lateral wear measurement which needs time and track blocking. The development of inertia-based condition monitoring methods such as measuring axle box acceleration (ABA) comes with a crucial question on criteria or index for each rail track component health monitoring. In this study, an index for evaluation of rail weld health is proposed through integrated numerical and field experiment data within a metro line using the ABA technique. The relationship between the speed, wheel structural vibration, and acceleration litude is investigated using fast Fourier transformation (FFT) and a nonlinear neural network principal component analysis (PCA) model. An index is introduced to assess weld severity level based on the statistical method. This index is simple and applicable for maintenance practice.
Location: Iran (Islamic Republic of)
No related grants have been discovered for Habibollah Molatefi.