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)
Ghasem Kahe; Mehdi Alemi Rostami
Volume 15, English Special Issue , May 2022, , Pages 45-53
Abstract
Diversity in both hardware and software plays an essential and unmatched role in increasing the reliability of redundant systems, especially in safety and mission critical applications. The onboard computer of satellites and the flight computer of spacecrafts, which are ultra-reliable systems, utilize ...
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Diversity in both hardware and software plays an essential and unmatched role in increasing the reliability of redundant systems, especially in safety and mission critical applications. The onboard computer of satellites and the flight computer of spacecrafts, which are ultra-reliable systems, utilize various hardware platforms for their redundant architecture to resolve a common cause failure (CCF) problem. Furthermore, the software is also developed by separate teams based on different software platforms to mitigate the specification and design flaws, and implementation mistakes. This paper focuses on modelling the diversity of redundant architectures in space systems using CCF modelling and Markov reliability analyzing. The proposed scheme is explored in two types of applications: mission critical applications (with long mission time) and safety critical applications (with short mission time). Analytical and simulation results show the effectiveness of diversity in increasing the reliability of these systems. Since a significant percentage of all failures appear as common cause failures, which restrict reliability improvement through similar redundant modules, achieving ultra-reliability necessitates considering diversity in these systems.
mehdi alemi rostami; Morteza Aghaei
Volume 11, Issue 1 , June 2018, , Pages 41-48
Abstract
In this paper, a high efficiency DC-DC converter for variable input voltage and high output voltage applications is presented. This converter is specially appropriate for driving travelling wave tube amplifier with a variable input source (i.e. solar panels). The proposed converter consists of a boost ...
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In this paper, a high efficiency DC-DC converter for variable input voltage and high output voltage applications is presented. This converter is specially appropriate for driving travelling wave tube amplifier with a variable input source (i.e. solar panels). The proposed converter consists of a boost converter to remove the variations of its input voltage and regulate its output voltage. Afterwards, a full bridge inverter controls the phase angle between the output inverter voltage and the current. Keeping the value of this angle at zero, the switching losses are reduced. A series-parallel resonant circuit uses the parasitic elements of the transformer as its elements and makes switches work in soft switching conditions. This reduces the converter power losses and increases the efficiency. Simulation results show the behavior of the proposed converter.
