Hossean Bolandi; Mohammad Hassan Ashtari; Ghodratollah Barati; Jafar Kochaki; Mohammad Sadegh Zayghami; Majed Esmaeilzadeh
Volume 8, Issue 3 , October 2015, , Pages 65-70
Abstract
In the mission of satellites, instantaneous positioning and estimation of the future position are necessary. In the communication satellite, this matter is so important. Thus in the Tadbir satellite, for the first time in the country, we consider an orbit determination subsystem that equipped with a ...
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In the mission of satellites, instantaneous positioning and estimation of the future position are necessary. In the communication satellite, this matter is so important. Thus in the Tadbir satellite, for the first time in the country, we consider an orbit determination subsystem that equipped with a spaceborne GPS receiver and contains appropriate algorithms in order to achieve satellite position data during the lunch period and in the orbit. In this paper a brief review of the software and hardware parts of this subsystem is presented. In additional the process of testing to achieve good performance, including functional tests of ODS processor board and functional test of GPS receiver with GPS simulator, environmental condition tests, mechanical tests, thermal vacuum cycle tests, electromagnetic compatibility test and finally integrated satellite tests are stated. This paper, in addition to a description of the Tadbir satellite orbit determination subsystem, an implementation testing of a satellite subsystem is demonstrated, which can be useful to other space field researchers. Â
H. Bolandi; M. H. Ashtari; M. Esmaeilzadeh; M. Haghparast
Volume 6, Issue 3 , October 2013, , Pages 27-37
Abstract
In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion ...
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In this paper predicting of position of satellite based on extended kalman filter with considering hardware implementation consideration and simultaneously maintaining desired accuracy is investigated. For this purpose, first, effective forces on orbital dynamic and nonlinear equation of orbital motion are presented. In order to increasing accuracy of prediction in position of satellite, J2, J3 and J4 harmonics of potentialfunction of the earth are considered and future position of satellite is predicted using linearized dynamic model and applying EKF on this model. Here Measurement data are position and velocity vector of satellite which are extracted by GPS receivers. Since in this paper systematic satellite design is considered, scenario of “ON TIME” of GPS receivers based on power consumption considerations is discussed. Finally simulation results for a LEO satellite and comparing these results with STK results, shows accuracy of presented modeling and equations.
H. Bolandi; M. H. Ashtari; M. Nadi; M. Esmaeelzade
Volume 6, Issue 2 , July 2013, , Pages 29-42
Abstract
In this article by analyzing the TLE data of Navid satellite from IranUniversityofScienceand Technology the effects of these data on tracking operation of ground station has been studied. Then the prediction accuracy of satellite position, the error rate of antenna ground station, the error rate of satellite ...
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In this article by analyzing the TLE data of Navid satellite from IranUniversityofScienceand Technology the effects of these data on tracking operation of ground station has been studied. Then the prediction accuracy of satellite position, the error rate of antenna ground station, the error rate of satellite rise time and the sensitivity survey of these toward the variation of drag term () of TLE data has been investigated. The results show that the accuracy of TLE data, the intervals of updating them and the time elapsed the epoch related to TLE data directly effected on accuracy prediction of thesatellite position and atracking operation. In some cases such as the limitation of ground antenna beam, tracking satellite is not succeeded. Therefore it has been suggested that tracking operation of satellite is done by ground station and independent of the TLE data and using TLE data as a reserve state has been considered. In this case TLE data must be updated daily.
H. Bolandi; M. Abedi; M. Haghparast
Volume 6, Issue 1 , April 2013, , Pages 31-46
Abstract
This paper presents robust fault detection based on adaptive thresholds for a three axis satellite. For this purpose, first we described the attitude control system (ACS) as a quasi linear parameter model. Next, an interval observer has been designed that based on, effect of the satellite parameter uncertainties ...
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This paper presents robust fault detection based on adaptive thresholds for a three axis satellite. For this purpose, first we described the attitude control system (ACS) as a quasi linear parameter model. Next, an interval observer has been designed that based on, effect of the satellite parameter uncertainties has been propagated into the alarm limits and so the adaptive thresholds are generated. In this paper, it is shown that the developed method minimizes the missing alarm rates; also this approach detects small or incipient faults more effectively than the classical fault detection algorithms with constant thresholds. In the next part of paper, we propose an isolation algorithm using the fault tree approach. Also, an accommodation system has been designed based on reconfiguration of available actuators. Accordingly, after isolation of faulty reaction wheels, the accommodation system turns them off and replaces the suitable magnetic tourqers instead of the faulty reaction wheels and so the attitude control error is maintained limited.
S. S. Nasrolahi; H. Bolandi; M. Abedi
Volume 5, Issue 2 , July 2012, , Pages 1-13
Abstract
In this study, a fault tolerant Attitude Determination System (ADS) has been designed which provides fault detection, isolation and tolerant abilities in this system. Suggested approach is based on derivation of all possible rotations between body and orbital frames and comparison of Euler angles provided ...
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In this study, a fault tolerant Attitude Determination System (ADS) has been designed which provides fault detection, isolation and tolerant abilities in this system. Suggested approach is based on derivation of all possible rotations between body and orbital frames and comparison of Euler angles provided by them. In this regard, significant changes in the variance of Euler angles set are considered as criteria for fault detection. Moreover, fault isolation and tolerant mechanisms are based on classification of rotation matrices which are not affected by faulty components. The above features present a quite analytical and computational approach which does not impose additional mass, power consumption and cost in the satellite. Also, designed diagnosis and fault correction algorithms are model-free basedmechanisms which always provide tolerated attitude angles for the attitude control subsystem. The mentioned abilities combined with the model based FDI mechanisms utilized in the attitude control system, provide an advanced decision support system capable of isolation of faults which have been simultaneously occurred in the satellite sensors and actuators. Finally, performance of the designed algorithm is approved by simulation results.
H. Bolandi; M. Haghparast; M. Abedi
Volume 5, Issue 1 , April 2012, , Pages 29-40
Abstract
A Fault Tolerant attitude control system has been designed in this paper, which provides abilities of fault detection, identification and recovery. For this purpose, nonlinear dynamics of satellite is modeled based on Takagi-Sugeno method, which enables us to extend advantages of linear adaptive observer ...
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A Fault Tolerant attitude control system has been designed in this paper, which provides abilities of fault detection, identification and recovery. For this purpose, nonlinear dynamics of satellite is modeled based on Takagi-Sugeno method, which enables us to extend advantages of linear adaptive observer for nonlinear dynamics of satellite. In the designed adaptive observer, occurrence of fault in satellite reaction wheels are estimated based on an adaptive law which provides abilities of fault detection and identification in these actuators. Also, a back stepping feedback linearization control law has been applied for recovery which uses estimated fault term provided by adaptive observer as a compensation term in control law. So, bounded error of attitude control has been guaranteed even in faulty conditions. Finally, fault detection, identification and recovery algorithms have been verified by simulation results.
H. Bolandi; A. M. Gheitaghy; B. Ghorbany Vagheii; S. M. Smailzadeh; M. R. Talaee
Volume 5, Issue 1 , April 2012, , Pages 81-90
Abstract
The responsibility of the satellite thermal control system is to maintain equipments temperature in all external environments and under operational modes within an allowable temperature range. The geometric math model of satellite with available relations in references is obtained and certified with ...
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The responsibility of the satellite thermal control system is to maintain equipments temperature in all external environments and under operational modes within an allowable temperature range. The geometric math model of satellite with available relations in references is obtained and certified with Thermal Desktop software. The outputs of geometric math model are external heating rates and radiation interchange factors. In this paper, the electrical simulation method is proposed as a tool for thermal math model of rotating satellite as equipments and structure of satellite are divided into several nodes and each term of thermal balance equation is simulated with equivalent electrical elements (capacitor, resistance, current source and etc.) and obtained circuit is solved fast and easily with HSPICE code. The values of voltage and current in each node are equivalent to temperature and heat flux, respectively. The results are illustrated the low run time with exact temperature responses of electrical simulation method in thermal modeling of satellite. By using the semi active thermal control, the thermal requirements are achieved and the effect of radiator paint is investigated.
H. Bolandi; F. Fani-Saberi
Volume 2, Issue 2 , July 2009, , Pages 17-26
Abstract
In this paper, a novel and highly accurate attitude estimation method for a LEO satellite is designed. The method is based on multiple model adaptive estimation (MMAE) structure. In this method, the satellite dynamic equation is linearized in a few points in order to increase the computational rate compared ...
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In this paper, a novel and highly accurate attitude estimation method for a LEO satellite is designed. The method is based on multiple model adaptive estimation (MMAE) structure. In this method, the satellite dynamic equation is linearized in a few points in order to increase the computational rate compared with extended Kalman filter (EKF) method. The attitude determination and control system of the satellite is consists of a star sensor, gyroscope and reaction wheels. As known, star sensor is a very power consuming sensor in attitude determination of the satellite; therefore, a lesser power consuming method, using the dynamic model of the satellite along with angular momentum of the reaction wheels, is proposed to estimate the satellite attitude. This method assures the proper operation and the attitude estimation of the satellite in eclipse mode as well. By applying this method, the star sensor is used for a short period of time which reduces power consumption considerably. The performance and effectiveness of the proposed algorithm are investigated through numerical simulations and is compared with extended Kalman filter.
H. Bolandi; F. Fani- Saberi; B. Ghorbani-Vaghei
Volume 1, Issue 2 , December 2008, , Pages 9-15
Abstract
In this paper, the main stereo-imaging methods by high resolution satellites, including Along-Track and Across-Track, have been evaluated and then we will combine the two main stereo-imaging configurations of along track and across track as a new idea to obtain the advantages of both methods. In the ...
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In this paper, the main stereo-imaging methods by high resolution satellites, including Along-Track and Across-Track, have been evaluated and then we will combine the two main stereo-imaging configurations of along track and across track as a new idea to obtain the advantages of both methods. In the proposed stereo-imaging scenario, fast and simultaneous large maneuvers of the satellite around pitch and roll axes is one of the versatile methods. So, highly nonlinear characteristics of the governing equations because of large angle slewing maneuvers are very effective on pointing accuracy and stability and should be considered to design control laws. The purpose of this paper is to design a nonlinear control method using four reaction wheels based on PD controller that can be used to perform a spacecraft large angle maneuver using quaternion attitude variables. The configuration of reaction wheels in the simulated spacecraft has been arranged as a skewed four-wheel reaction. Reaction wheels unloading is also accomplished through the use of three magnetic torquers to prevent the speeds of the reaction wheels exceeding their designed limits, largely as a result of the action of secular components of disturbing torque. Simulation study has verified the performance and effectiveness of the proposed algorithm to achieve the proposed stereo-imaging scenario.
H. Bolandi; B. Ghorbani-Vaghei; F. Fani- Saberi
Volume 1, Issue 2 , December 2008, , Pages 27-33
Abstract
Attitude control system of satellite with Gravity Gradient stabilization requires high moments of inertia ratio for providing stability and continuous orientation toward Earth. Although, this high ratio causes satellite has small body and reduce mission capability. In this paper, moments of inertia ratio ...
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Attitude control system of satellite with Gravity Gradient stabilization requires high moments of inertia ratio for providing stability and continuous orientation toward Earth. Although, this high ratio causes satellite has small body and reduce mission capability. In this paper, moments of inertia ratio is reduced using a closed form formula based on our previous work, in such a way that it could be provided more missions by augmented solar panels to satellite. Solar orientation could be yielded by rotating satellite about gravity gradient boom (yaw rotation). Interaction between yaw rotation and satellite rotation around Earth causes biased-attitude error in roll axis. To overcome this problem, it is necessary to reduce yaw rotation by adding a reaction wheel toward boom direction. To realization this method, stability criteria of gravity gradient is developed and control law for small and large angles rotation is designed in such a way that angular momentum and moment constraints of reaction wheel to be satisfied. Finally, fine performance of attitude control system will be illustrated with simulation based on specification of an on-orbit satellite and actual consideration
H. Bolandi; B. Ghorbani Vaghei
Volume 1, Issue 1 , September 2008, , Pages 11-19
Abstract
In this paper, attitude control system of an axisymmetric satellite will be designed in such a way that required stability is provided with slow spinning about yaw axis. In this regard, dynamic of motion and coupling between satellite’s axes is modeled. As a result, a closed form formula is yielded ...
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In this paper, attitude control system of an axisymmetric satellite will be designed in such a way that required stability is provided with slow spinning about yaw axis. In this regard, dynamic of motion and coupling between satellite’s axes is modeled. As a result, a closed form formula is yielded included moment of inertia ratio, angular velocity about yaw axis and pointing accuracy of control system. Then, magnetic control is designed for providing capture range of gravity gradient stabilization and requirements of pointing accuracy. Finally, fine performance of designed control system will be illustrated with simulation based on specification of a near axisymmetric satellite.
