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Development of a Vision-Based Position and Attitude Estimation Algorithm for Close Proximity Operation of Small Satellite
, M.Sc. Thesis Sharif University of Technology ; Saghafi, Fariborz (Supervisor)
Abstract
One of the key technologies in the future space missions is the formation flight of small satellites. Currently, widespread research in this field is being carried out and remarkable developments have been achieved. In the mentioned laboratory researches, satellite navigation is performed by conventional sensors like infrared and ultrasonic. Both of these sensors are of active type and energy consuming. Also, use of the ultrasonic sensors is impractical in space missions (due to vacuum condition). Therefore, as an alternative for space missions, visual sensors are good candidates. The main goal of this research is to present a method for the relative navigation in proximity operations in an...
Modeling and Decentralized Control of Spacecraft Formation Flying
, Ph.D. Dissertation Sharif University of Technology ; Alasty, Aria (Supervisor) ; Assadian, Nima ($item.subfieldsMap.e) ; Salarieh, Hassan ($item.subfieldsMap.e)
Abstract
In this study, the distributed six degree-of-freedom (6-DOF) coordinated control of spacecraft formation flying in low earth orbit (LEO) has been investigated. For this purpose, an accurate coupled translational and attitude relative dynamics model of the spacecraft with respect to the reference orbit (virtual leader) is presented by considering the most effective perturbation acceleration forces on LEO satellites, i.e. the second zonal harmonic and the atmospheric drag. Subsequently, the 6-DOF coordinated control of spacecraft in formation is studied. During the mission, the spacecraft communicate with each other through a switching network topology in which the weights of its graph...
Autonomous temperature-based orbit estimation
, Article Aerospace Science and Technology ; Volume 86 , 2019 , Pages 671-682 ; 12709638 (ISSN) ; Kiani, M ; Pourtakdoust, H ; Sharif University of Technology
Elsevier Masson SAS
2019
Abstract
Orbit estimation (OE) is a required significant task in almost all space missions. Accordingly, a wide variety of sensors and estimation algorithms have been developed within the last few decades to this aim. However, the current study proposes a novel autonomous OE method that is purely based on temperature data of six orthogonal surfaces of a three-axis stabilized satellite as it orbits around the Earth. While the utility of satellite surface temperature data has been recently investigated for satellite attitude estimation (AE) assuming its navigational information, the present paper is focused on OE via only temperature data that has not been attended to in the related literature. To this...
Axis-switching and breakup of rectangular liquid jets
, Article International Journal of Multiphase Flow ; Volume 126 , May , 2020 ; Nasiri, M ; Amini, G ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
The behavior of low-speed liquid jets emerging from rectangular orifices into a quiescent air is studied numerically. After ejection, the rectangular cross-section transforms into an elliptical form along the jet and while axis-switching includes elliptical cross-sections only, the rectangular shape never establishes again. The optimum wavenumber, corresponding to the most dominant wave, is found to be greater in orifices with higher aspect ratios and, as a result, breakup length of the jet will be shorter. The breakup length decreases exponentially with the initial amplitude of disturbances. Moreover, it is observed that the form of final breakup leads to elimination of the satellite...
An accurate guidance algorithm for implementation onboard satellite launch vehicles
, Article Scientia Iranica ; Volume 17, Issue 2 D , JULY-DECEMBE , 2010 , Pages 175-188 ; 10263098 (ISSN) ; Mobed, M ; Sharif University of Technology
2010
Abstract
An algorithm for guiding a launch vehicle carrying a small satellite to a sun synchronous LEO is presented. Before the launch, a nominal path and the corresponding nominal control law for the entire journey are computed. For each sampling instant during the guided flight, a linear equation approximately relating the differences between the actual and nominal values is considered, and a LeastSquares formula using data from on-line state measurements is applied to compute the actual control. The coefficient matrices of the Least-Squares formula can be determined by off-line computations. The method enjoys simplicity of implementation by onboard computers, as well as robust accuracy against...
Quaternion based linear time-varying model predictive attitude control for satellites with two reaction wheels
, Article Aerospace Science and Technology ; Volume 98 , March , 2020 ; ISSN: 12709638 ; Nejat Pishkenari, H ; Salarieh, H ; Abdollahi, T ; Sharif University of Technology
Elsevier Masson SAS
2020
Abstract
Attitude control of a satellite having only two reaction wheels is a challenging issue. To address this problem, previously published researches considered some simplifying assumptions on the satellites such as diagonality of the moment of the inertia matrix. On the other hand, in some works, the total angular momentum of the satellite is assumed to be zero. In this paper, a linear time-variant model predictive control (LTV MPC) is designed to control a satellite with two reaction wheels. This control method can be applied to a satellite with a non-diagonal inertial matrix in the presence of external torques, to rotate the satellite toward the desired directions in the space and orbit. The...