communications
Peyman Mohammadi; Mehdi Alemi Rostami
Volume 17, Issue 1 , March 2024, , Pages 37-48
Abstract
One of the most important issues related to the power supply of TWTA lamps in satellites is to have low ripple, high efficiency, high reliability and optimal volume and weight,. In this article, the efficiency and reliability of high voltage DC/DC electronic-power converter is optimized for use in satellite ...
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One of the most important issues related to the power supply of TWTA lamps in satellites is to have low ripple, high efficiency, high reliability and optimal volume and weight,. In this article, the efficiency and reliability of high voltage DC/DC electronic-power converter is optimized for use in satellite and TWTA lamps. The goal of optimization using multi-objective genetic algorithm (NSGA-II) in this article is to minimize the objective function, which includes efficiency and reliability. Markov model is used to evaluate reliability, in which short-circuit and open-circuit errors are considered for circuit switches and diodes, and short-circuit errors are considered for passive circuit elements. for optimization, first, the input variables of the algorithm are determined as the input of the objective function, so that with the help of sensitivity analysis, the parameters that have low sensitivity and their changes do not have a major impact on the objective function are eliminated. parameters of NSGA-II algorithm, including the number of iterations, the number of populations, and the probability have been determined for the accurate calculation of circuit variables. the results section this method, in addition to maintaining high efficiency, with the optimal selection of elements, high reliability can be achieved .
Space systems design (spacecraft, satellites, space stations and their equipment)
Hojat Taei; Amirhossain Adami; Mansour Hozuri
Volume 14, Issue 4 , December 2021, , Pages 85-98
Abstract
The need to improve the reliability and safety requirements, has led to increasingly utilization of reliability based design approaches. In this study, reliability based multidisciplinary design optimization for a bipropellant propulsion system has been investigated. The objective function is minimizing ...
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The need to improve the reliability and safety requirements, has led to increasingly utilization of reliability based design approaches. In this study, reliability based multidisciplinary design optimization for a bipropellant propulsion system has been investigated. The objective function is minimizing the total system mass and design constraints are the total impulse and the temperature of the wall of the combustion chamber. Monte Carlo simulation methodology is used to apply uncertainties in the problem and to show the reliability of the system under these uncertainties. The mass, functional and geometric results of the bipropellant propulsion system are differentiated for optimal design, reliability based design and optimal reliability based design. Then, considering the results, the concepts and definitions of design methods are compared and discussed and it is shown that the reliability based multidisciplinary optimization while having the desired mass, has high reliability.
Ashkan Mahmoud-Aghdami; Farhad Farhang Laleh; Mohammad Ghahramani
Volume 9, Issue 3 , December 2016, , Pages 37-51
Abstract
In this article the design and the development of spool type pin puller mechanism from concept model to engineering model was expressed. At first, present models and designs were investigated and the conceptual design was based on positive aspects of these models and in order to better study the operation ...
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In this article the design and the development of spool type pin puller mechanism from concept model to engineering model was expressed. At first, present models and designs were investigated and the conceptual design was based on positive aspects of these models and in order to better study the operation of mechanism, the concept model was built 5 times bigger than the real model. After this model the pre-engineering model with 350N pulling force was designed and built. It was tried to reduce the operational defects of concept model like fuse operation and the rupture of warping wire, in the pre-engineering model. Assembling of the model was carried out with special tools and operation test carried out in room temperature. In the engineering model pulling force was increased to 500 N and the material of inside parts was changed due to special electrical and mechanical conditions. Temperature and atmospheric test conditions were considered in the last model and the model was prepared to pass all qualification tests. Vibration tests and also Temperature tests were performed in vacuum chamber with respect to space standards. Reliability calculations were done on each pin puller parts and at last reliability of whole pin puller system were obtained.
S. M. M. Sharifi; H. Gholami Mazinan; K. Shahanaghi; M. Karbasian
Volume 5, Issue 1 , April 2012, , Pages 73-80
Abstract
Failures identification of vital and sensitive products and their reliability estimation, before applying affects design improvement of them. On the other hand, because of lack of data,reliability estimation of some systems such asspace products is hard and sometimes impossible. Bayesian networks method ...
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Failures identification of vital and sensitive products and their reliability estimation, before applying affects design improvement of them. On the other hand, because of lack of data,reliability estimation of some systems such asspace products is hard and sometimes impossible. Bayesian networks method is a graphical model with high efficiency for reliability estimation of complex systems and it can also eliminate problem of data shortage. Accordingly, at this paper, first, fault tree related to structure of launch vehicle with liquid fuel has been designed and then mapped into Bayesian networks. Finally using expert decision of system and estimation of model conditional parameters with Monte Carol Markov Chain, reliability of launch vehicle structure has been estimated.
M. Karbasian; A. Bagheri
Volume 2, Issue 2 , July 2009, , Pages 69-73
Abstract
Recognition of any type of failures in systems and prediction of its reliability have important role in improvement of design of systems. Fault Tree Analysis (FTA) is one of the best techniques in analysis and improvement of complex systems. In this paper first, we show reliability block diagram (RBD) ...
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Recognition of any type of failures in systems and prediction of its reliability have important role in improvement of design of systems. Fault Tree Analysis (FTA) is one of the best techniques in analysis and improvement of complex systems. In this paper first, we show reliability block diagram (RBD) of Rocket Engine and then its fault tree is analyzed. Finally based on FTA, reliability of combustion of rocket engine is calculated.
