Structure
Zahra Daneshjoo; Faezeh Shokri
Abstract
The layout design of satellite components is a key method to improve the overall performance of the satellite; So that proper placement design has been a common feature in most of the successful satellites. In this research, the layout and configuration design of a remote sensing satellite will be discussed. ...
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The layout design of satellite components is a key method to improve the overall performance of the satellite; So that proper placement design has been a common feature in most of the successful satellites. In this research, the layout and configuration design of a remote sensing satellite will be discussed. This design is done using the requirements given to the structural subsystem by other subsystems. The difference between the layout of this satellite and other satellites is that in this satellite the elements are placed on the main structure of the satellite, which includes Honeycomb plates (honeycomb core and an aluminum shell), instead of a layered arrangement. For this purpose, in the first step, the satellite structure along with all the elements of different subsystems will be modeled in Solidworks Software. Next, according to the given requirements, the layout of elements will be done. After that, the results of the center of mass and moments of inertia in two open and closed states of the solar panels are obtained. These results show that the cross moments of inertia are insignificant (close to zero) compared to the moments around the coordinate axes; therefore, it can be stated that the considered coordinate axes are consistent with the main axis of the satellite; This is a proof of a suitable layout and configuration design.
Control
Sevil M. Sadigh; Narges Talebi Motlagh; Hossein Behesgti; Sahand Moharrami; Moharram Shameli
Abstract
In this paper, an adaptive fault-tolerant control based on modified nonsingular fast terminal sliding mode control is developed for attitude tracking of a satellite with three magnetorquers and one reaction wheel. The proposed approach is designed to be robust in the presence of actuator faults, external ...
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In this paper, an adaptive fault-tolerant control based on modified nonsingular fast terminal sliding mode control is developed for attitude tracking of a satellite with three magnetorquers and one reaction wheel. The proposed approach is designed to be robust in the presence of actuator faults, external disturbances, and inertia uncertainties and preserve the acceptable performance of system. The adaptive law is designed to estimate the upper bound of uncertain expressions, increase the tracking accuracy, and improve the performance of system. This parameter with a coefficient of sliding surface variable are used in the reaching phase of control law to achieve the chattering-free phenomenon. Stability and finite-time convergence of attitude variables is proved by the extended Lyapunov condition. To increase the tracking accuracy and compensate the required torque, a reaction wheel is used as a redundancy. Also, for increasing the control accuracy, the dynamics of this actuator is considered as well as the constraints of magnetorquers and reaction wheel. The simulations are performed and compared with the similar control method under the mentioned conditions to evaluate the performance of the proposed method. The results show the finite-time convergence, increasing the tracking accuracy, smoothing of satellite attitude changes, and generating the chattering-free control signals.
Telecommunication
hossein soleimani; mohammad mashayekhi; Iman Aryanian
Abstract
In this article, the synthesis of the two-dimensional radiation pattern of multi-beams in the time-modulated planar antenna array is discussed. With the aim of reducing the time of numerical calculations of multi-beam synthesis and eliminating the traditional and optimization approaches, which are mostly ...
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In this article, the synthesis of the two-dimensional radiation pattern of multi-beams in the time-modulated planar antenna array is discussed. With the aim of reducing the time of numerical calculations of multi-beam synthesis and eliminating the traditional and optimization approaches, which are mostly complicated and time-consuming, the convolutional neural network approach has been investigated. In this study, the simultaneous shaping of multiple beams as desired in the time modulated antenna array is presented for the first time. By using the method of switching elements and their time modulation, which is based on the Chabi-Sheff distribution, to use and realize multi-beams such as the fundamental beam and the first and second harmonics with low side lobe level and steering at different spatial angles, create various random data. After that patterns and modulations like them are stored. After that, by presenting and designing a model of the convolutional neural network, learning the model for the relationship between the main beam pattern and the first two harmonic patterns with the time modulation of each element has been done. The presented neural network has been able to learn the relationship between the time modulation parameters of the antenna array elements with the main beam patterns and the first and second harmonics with a mean square error of about 0.03. In order to evaluate this model, a random sample of data has been selected to give its patterns to the input of the network. The output of the network has estimated the time modulation sequence of each element. Finally, the modulation pattern of the estimated elements is compared with the main patterns of the comparison and shows the closeness of the original pattern to the estimated pattern. This method provides a good capability for arbitrary control of multiple beams for applications that require establishing multiple connections.
