GPS and navigation GPS)، GLONASS، GALILEO
Mona Zahednamazi; Alireza Toloui
Volume 16, Issue 4 , December 2023, , Pages 57-70
Abstract
One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the ...
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One of the attitude sensors for the spacecraft is the star sensor. The attitude calculation by the star sensor includes several steps: image processing, star identification, database search, and implementation of the attitude determination algorithm. This paper presents analysis and improvements on the star identification algorithm based on singular value decomposition. To improve the identification results, modifications have been made to the algorithm. Also, analysis and simulation are presented to investigate the effect of field of view dimensions and the number of stars used on the identification results, and the rate of duplicate sets in the database. In addition, identification has been considered a two-step process based on singular values and vectors. The results show the superiority of the improved algorithm in increasing the identification rate and reducing the rate of duplicate sets in the database. The identification rate of the improved algorithm in 〖10〗^°×〖10〗^° and 〖12〗^°×〖12〗^° fields of view dimension is always more the %97. The simulations were performed based on the Hipparcos star catalog for stars brighter than magnitude 6.5 and using MATLAB software.
Space New Technologies
Sadjad Samipour; Alireza Toloei; Vladimir Batrakoff
Volume 15, Issue 4 , December 2022, , Pages 31-43
Abstract
Development in the aerospace industry is linked to the continuous pursuit of lightweight designs. Open-architecture composite structures are a new and novel use of composites for minimal-weight component design. It is reasonable to use efficient and advanced techniques such as radial braiding in the ...
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Development in the aerospace industry is linked to the continuous pursuit of lightweight designs. Open-architecture composite structures are a new and novel use of composites for minimal-weight component design. It is reasonable to use efficient and advanced techniques such as radial braiding in the manufacturing of composite lattice tubular structures. In this article, an aerospace composite lattice tubular structure with a braided reinforcement system is studied. A method is developed to determine the parameters of the preform reinforcement. A new process has been created for the manufacture of lattice structures with a braided reinforcement system. A methodology has been developed for determining the technological parameters of radial braiding. A sample structure is manufactured and tested. Experimental studies of lattice structure samples were carried out in order to verify the methods for determining mechanical, structural, and technological parameters.
Space systems design (spacecraft, satellites, space stations and their equipment)
Mostafa Jafari; Alireza Toloei
Volume 15, English Special Issue , May 2022, , Pages 35-44
Abstract
A numerical dynamic-aerodynamic interface for simulating the separation dynamics of constrained strap-on boosters jettisoned in the atmosphere is presented. Two commercial solvers: a 6DOF multi-body dynamic solver and a numerical time-dependent flow solver are integrated together with an interface code ...
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A numerical dynamic-aerodynamic interface for simulating the separation dynamics of constrained strap-on boosters jettisoned in the atmosphere is presented. Two commercial solvers: a 6DOF multi-body dynamic solver and a numerical time-dependent flow solver are integrated together with an interface code to constitute a package that presents real-time dynamic/aerodynamic coupled analysis. Dynamic unstructured mesh approach is employed using local remeshing methods in respect of bodies motion with a second-order upwind accurate 3D Euler solver. This interface can simulate multi body separation dynamics interaction with aerodynamic effects to complete separation mechanisms like springs, thrusters, joints and so on. The flow solver is validated by the Titan IV launch vehicle experimental data. The separation integration is used for a typical launch vehicle with two strap-on boosters using spring ejector mechanism and spherical constraint joints acting in the dense atmosphere. Hence, the aim of the presented interface is to facilitate the integration of complicated separation mechanisms with a full numerical CFD aerodynamic solver.
Space systems design (spacecraft, satellites, space stations and their equipment)
Alireza Toloei; Mohammad Fatehi; Behrooz Keshtegar
Volume 14, Issue 3 , September 2021, , Pages 1-14
Abstract
In this paper, a design of a hydrazine monopropellant system is proposed based on the maximum likelihood for the presentation of uncertainties, without any specific assumptions about the type of distribution and even uncertainty in distribution parameters by the johnson distributions family. The maximum ...
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In this paper, a design of a hydrazine monopropellant system is proposed based on the maximum likelihood for the presentation of uncertainties, without any specific assumptions about the type of distribution and even uncertainty in distribution parameters by the johnson distributions family. The maximum likelihood method for the combination of spars point and interval data has been added to a separate formulation for design variables and parameters. This formulation is also suitable for both epistemic and aleatory uncertainty with three presentation types of spars points, single interval, and multi-interval.
H. Sedaghat; A. R. Toloei; H. Ghanbarpoor
Volume 4, Issue 2 , January 2012, , Pages 83-92
Abstract
A current method by which star trackers identify stars is to match the angles between stars within its field of view to angles stored in a catalog. If an angle can be matched to one pair of stars, the attitude of the star tracker can be determined. However, the measurement of the angle will include error, ...
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A current method by which star trackers identify stars is to match the angles between stars within its field of view to angles stored in a catalog. If an angle can be matched to one pair of stars, the attitude of the star tracker can be determined. However, the measurement of the angle will include error, and so the true angle can only be known to lie within a certain measured range. The result is, after comparing the measured angle to the catalog of angles, more than one pair of stars can be the correct solution. A method for narrowing down to one solution involves employing many angles within the field of view in a certain order, called “pivoting,” which can be time consuming and does not always yield a solution. another method presented here matches planar triangles made from sets of three stars within the field of view to planar triangles stored within a catalog. By using both the area and polar moment properties of the planar triangle, the range of possible solutions is very quickly narrowed, fewer pivots to other planar triangles are required, and the method is more likely to yield the correct solution than the angle method. New method presented here use these two methods simultaneously, first, by angle method candidate some stars to identification. In this level reduces stars in FOV. Second, by triangle method in fewer time identification completed, because FOV is smaller. So this new method is faster than triangle and more accurate than angle method and we do not pivoting the same as each method. In addition, Simulation results show the performance of the new method as well as its robustness with respect to including false stars.
