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.
Space subsystems design: (navigation, control, structure and…)
Maziar Shefaee Roshan; Mahdi Ghobadi; Mahdi jafari Nadoushan
Volume 13, Issue 1 , March 2020, , Pages 71-82
Abstract
Using linear programming method in control allocation for attitude control subsystem of spacecraft with redundant thrusters is studied in this paper. The simplex algorithm is utilized as a solver and the Direction Preserving and Bodson’s Reduced size Direction preserving approaches are used as ...
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Using linear programming method in control allocation for attitude control subsystem of spacecraft with redundant thrusters is studied in this paper. The simplex algorithm is utilized as a solver and the Direction Preserving and Bodson’s Reduced size Direction preserving approaches are used as optimal approaches to deal with non admissible solutions. Also, proper functioning of these approaches against thrusters fault phenomenon is evaluated. The results show that the Direction Preserving approache has less computational time and less fuel consuming. However, the Bodson’s Reduced size Direction preserving approache has more computational time and more fuel consuming but less tri-axis tracking error. It should be noted that the PD controller has been used as a spacecraft control rule, and simulations have been made for the number and configuration of the specific thrusters.
