Hamid Kazemi
Volume 11, Issue 4 , December 2018, , Pages 51-64
Abstract
Because the lack of international regulations for exploiting the sources of celestial bodies, so some countries, such as the United States and Luxembourg, start to support the private sector, and to regulate and monitor their activities. , Have adopted a special national law that legislate that the appropriation ...
Read More
Because the lack of international regulations for exploiting the sources of celestial bodies, so some countries, such as the United States and Luxembourg, start to support the private sector, and to regulate and monitor their activities. , Have adopted a special national law that legislate that the appropriation of what is achieved by the private sector from natural sources of celestial bodies is not conflicting with international regulations. While the prevailing view is that the adoption of national laws on the use of celestial bodies as well as their sources contrary to the appearance of international on the Prohibition of Ownership and appropriation of the Moon and the celestial bodies and the principle of the common heritage of mankind. By analyzing current international space legal instruments such as the Outer Space Treaty 1967 and the Moon Agreement1979, the Article seeks to bring two perspectives together and propose an international regime governing the private sector's activity.
M. Jafari Nadoushan; M. Tivay
Volume 3, Issue 2 , January 2011, , Pages 53-58
Abstract
Effect of regularization on the solution of perturbed two body problem is investigated in this paper. Purposes of using this method are computational burden reduction and achieving desirable accuracy in the minimum time. In this regard the equations of motion are linearized and independent variable is ...
Read More
Effect of regularization on the solution of perturbed two body problem is investigated in this paper. Purposes of using this method are computational burden reduction and achieving desirable accuracy in the minimum time. In this regard the equations of motion are linearized and independent variable is changed from time to the true anomaly. These yield reducing run time, however increasing accuracy. The results of simulation confirm that utilizing this method in onboard computation or long term simulations is more suitable and efficient than other methods including general and special perturbation methods.
Mehran Nosrat Elahi; Ali Reza Basohbat Novinzadeh; Mostafa Zakeri
Volume 8, Issue 1 , April 2015, , Pages 53-60
Abstract
The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal ...
Read More
The design method presented in this paper is for utilizing, fast and easy system designing of orbital transfer block for transferring satellite from park orbit to destination orbit. The main purpose of this paper is system designing liquid propellant orbital transfer block with a new approach for ideal orbital transfer and presenting a simple interfered systematic method for designing aerospace products. Designing orbital transfer block consists of designing all subsystems and integrating all parts of design. Designing all subsystems can be achieved with a meaningful connection between all system and subsystem constraints. In addition to systematic design approach to each of the design sub algorithms, creating subsystem optimization environment according to physical performance of subsystem and also general integration of orbital transfer block system design in an optimized environment have been carried out. Final result of orbital transfer block design for a specific mission is through mass-dimension convergence of equations in integrated design. Design integration according to design matrix and optimizations and convergences of the design is discussed in the paper. According to presented method, which is scientific, functional and extensible to final design of the product, parametric process of results is briefly validated. So in this paper new method is provided for integrating the design in an optimized and collaborative convergence environment maintaining all systemic constraints and limitations to specify specifications of orbital transfer block systems and subsystems.
Y. Ghaderi-Dehkordi
Volume 3, Issue 1 , July 2010, , Pages 55-65
Abstract
In the present study, in order to choose the suitable heat shields a comprehensive investigation was performed. Therefore, different properties of each type of heat shields including ablative and thermo-physical properties were measured separately. Finally, the obtained properties were compared. The ...
Read More
In the present study, in order to choose the suitable heat shields a comprehensive investigation was performed. Therefore, different properties of each type of heat shields including ablative and thermo-physical properties were measured separately. Finally, the obtained properties were compared. The studied heat shields are phenolic resin composite reinforced by ceramic, asbestos AAA and C cloths. The experimental
investigations consist of oxyacetylene standard flame test, specific heat capacity, thermal analysis and thermal conductivity. In addition, in order to compare the thermal efficiency of mentioned heat shields, the temperature on the back surface of each sample subjected to constant heat flux was measured. The results showed that the specimen with 8 mm thickness reinforced with ceramic cloth, which was subjected to 2500 kW.m-2, reduced the temperature from 1550 to 100oC. Therefore, the phenolic composite containing ceramic cloth is the best option.
A. Esmaeilian; S. A. H Feghhi; H. Jafari; A. Pahlavan
Volume 6, Issue 3 , October 2013, , Pages 55-60
Abstract
Space radiation environment has concerned about proper performance of electronic systems and equipment used in the space due to a variety of space radiations. The radiation hardening techniques are required to all parts of the system in such environment. Therefore careful studies should be done on the ...
Read More
Space radiation environment has concerned about proper performance of electronic systems and equipment used in the space due to a variety of space radiations. The radiation hardening techniques are required to all parts of the system in such environment. Therefore careful studies should be done on the mechanism of radiation damage in these systems. Shielding is one of radiation hardening technique. The radiation effects on electronic components can be done using radiation simulating softwares. In this work, displacement damage, vacancies and ionization values in silicon and gallium arsenide with layers of metal as a shield have been calculated using TRIM software. The results showed that the more thickness and more elements with high atomic number of shield made more resistance to radiation. Thus, damage in electronic devices would be less. Also, the damages resulted from the incident beam of helium ions is much higher than that of hydrogen ions.
Alireza Rezaee; Niloofar Nobahari; Hakime Barghi Zanjani
Volume 10, Issue 1 , June 2017, , Pages 55-60
Abstract
This paper aims to propose the interference and also investigates the channel effect on power allocation issue. Here, the particle swarm optimization (PSO) method is employed in order to find the optimal solution. Because of the value of resources in the satellite telecommunication systems, optimizing ...
Read More
This paper aims to propose the interference and also investigates the channel effect on power allocation issue. Here, the particle swarm optimization (PSO) method is employed in order to find the optimal solution. Because of the value of resources in the satellite telecommunication systems, optimizing the use of power allocation is very important. In these systems, because of non-zero side lobe, there exists an interference between beams that affects the allocation problem. To assess the efficiency of PSO algorithm, the obtained results are compared with the Duality Theory. The analogy is conducted through three different scenarios: In the first scenario, it is supposed to have interference between each beam and the three adjacent beams. The second scenario assumes that the first beam interferes with other beams. Finally, in the third scenario, the analysis of channel conditions of each beam and its effect on the power allocation problem is provided. The objective functions for the proposed method are the total system capacity and sum of the square of difference between the requested traffic and the allocated beam power. The results indicate that the proposed algorithm improves the solution in each scenario and implements justice to the power allocation issue.
Vahid Bohlouri; S.H Jalali-Naini
Volume 10, Issue 4 , March 2018, , Pages 55-66
Abstract
his paper suggests arobust optimization algorithm for the design of the satellite attitude control system in order to increase the robustness of the performance under uncertainties. A single-axis on-off attitude control with rigid dynamics is considered using Schmitt-Trigger and PID controller. The model ...
Read More
his paper suggests arobust optimization algorithm for the design of the satellite attitude control system in order to increase the robustness of the performance under uncertainties. A single-axis on-off attitude control with rigid dynamics is considered using Schmitt-Trigger and PID controller. The model uncertainties include the moment of inertia, thrust level, thruster delay and theexternal disturbance amplitude.A weighted combination of expected value and standard deviation of pointing error is considered as an objective function for the robust optimization. The numerical solutions show that the robust optimization reduces the variations of the objective function, i.e. it increases the robustness of the system performance compared to the deterministic optimization.
Space subsystems design: (navigation, control, structure and…)
S. Hamid Jalali-Naini; omid Omidi Hemmat
Volume 14, Issue 1 , March 2021, , Pages 55-64
Abstract
This paper presents a modification to a type of Pulse-width Pulse-Frequency (PWPF) Modulator utilized an integrator block. In this modulator that called here as "Integral Pulse-Width Pulse-Frequency (IPWPF)," an integrator is used instead of the first-order low-pass filter. To improve the performance ...
Read More
This paper presents a modification to a type of Pulse-width Pulse-Frequency (PWPF) Modulator utilized an integrator block. In this modulator that called here as "Integral Pulse-Width Pulse-Frequency (IPWPF)," an integrator is used instead of the first-order low-pass filter. To improve the performance of the control system, the modulator is modified by using a logical circuit in order to reset the output of the integrator. In this logical circuit, if the error signal becomes less than a specified small value, the integrator will be reset, that is, "Small Error-Reset Integrator (SE-RI)." The modification is applied to the stabilization and pointing modes. In stabilization mode, the control gain is obtained analytically such that the angular rate of the satellite becomes zero or less than a specific percentage of its initial value by a single pulse. Simulation results show that the performance of the modified IPWPF is comparable with that of PWPF in pointing mode.
Space systems design (spacecraft, satellites, space stations and their equipment)
َAlireza Alikhani; Mohammad Reza Salimi
Volume 15, English Special Issue , May 2022, , Pages 55-64
Abstract
The cold gas thruster is one of the significant components of a satellite and its application possesses a marked impact on the entire system performance. The nonlinear function and order of magnitude, lead to increasing the importance of thruster function. Therefore, pre-mission performance assessment ...
Read More
The cold gas thruster is one of the significant components of a satellite and its application possesses a marked impact on the entire system performance. The nonlinear function and order of magnitude, lead to increasing the importance of thruster function. Therefore, pre-mission performance assessment has a considerable effect on the risk reduction of space missions. In this article, an uncomplicated and efficient pendulum scheme for development and implementation of a Thruster Test Stand (TTS), to measure the thrust produced at the end of the nozzle is proposed. The TTS is capable of measuring thrust levels in the range of 0.1Newtons to 3N with operating frequencies up to 50 Hz which is used by various satellite ranges. The experimental results demonstrate that although the designed device is less sophisticated than other test devices, it is capable of measuring the produced thrust very precisely and with less than 15mN.
T. Abdollahi; A. Jahangirian; A. Naghash
Volume 1, Issue 1 , September 2008, , Pages 57-66
Abstract
In this paper, the effects of future solar activities, drag coefficient and atmospheric wind on altitude loss and life time of a LEO satellite is investigated. For this purpose, an orbit propagator is used whose results have been verified by STK software. To analyze the satellite position, the effect ...
Read More
In this paper, the effects of future solar activities, drag coefficient and atmospheric wind on altitude loss and life time of a LEO satellite is investigated. For this purpose, an orbit propagator is used whose results have been verified by STK software. To analyze the satellite position, the effect of no spherical earth is also considered. In this investigation, simulation of the atmosphere, estimation of wind, and prediction of future solar activity have been implemented using MSIS-90, HWM-93, and 13-month Zurich smoothed models, respectively. Our investigation shows that the effect of future solar activity on satellite life time is a function of the predicted percentile. The effect of drag coefficient is almost linear while the effect of atmospheric wind is a function of inclination.
M. Navabi; R. Hamrah
Volume 6, Issue 1 , April 2013, , Pages 57-67
Abstract
In this paper, a precise propagation model which takes into account the effects of the atmospheric drag and gravitational harmonies is developed and presented using available Two Line Element (TLE) data. Moreover, the prediction of the trajectory of space objects (e.g. the operational and non-operational ...
Read More
In this paper, a precise propagation model which takes into account the effects of the atmospheric drag and gravitational harmonies is developed and presented using available Two Line Element (TLE) data. Moreover, the prediction of the trajectory of space objects (e.g. the operational and non-operational satellites and space debris) and their orbital data is performed. Then, the 2009 prominentcollisionbetween the Cosmos2251 and Iridium33 satellite is simulated and the maximum probability of their collision is computed by implementing the propagation algorithm and probabilities Theory, and finally the results are discussed. Therefore, the precise position and velocity of each space object at any time, as well as their collision probability will be determined, and if necessary, the time available to enact collision avoidance maneuver will be obtained. The success and accuracy of an avoidance maneuver is affected by the precision of the propagation model, the exact computation of collision probability, and finally the maneuver mechanism which are utilized.
M. Nasirian; S. ghaemi Sardroodi
Volume 8, Issue 2 , July 2015, , Pages 57-65
Abstract
In this paper a new method for satellite authomatic tracking presented by earth station via doppler frequency . This method done by calculating time diviation through difference between real dopper frequency by communication equipment and software Doppler frequency by theoretical TLE via ...
Read More
In this paper a new method for satellite authomatic tracking presented by earth station via doppler frequency . This method done by calculating time diviation through difference between real dopper frequency by communication equipment and software Doppler frequency by theoretical TLE via STK Software. Then Kepler parameters are chaned so this deviation limit to zero. By this action correct antenna direction to satellite and receiving signal without error. Method test was done by amature satellite in UHF frequency band & CW Modulaition.Â
A. H. Tavakkoli; A. Kalhor; S. M. M. Dehghan
Volume 5, Issue 2 , July 2012, , Pages 59-68
Abstract
In this paper the performance of a three Degrees Of Freedom simulator is evaluated. This platform is considered as an important instrument generally used in performance tests of spacecraft attitude determination and control subsystem on the ground. A hemispherical air bearing is used to provide micro ...
Read More
In this paper the performance of a three Degrees Of Freedom simulator is evaluated. This platform is considered as an important instrument generally used in performance tests of spacecraft attitude determination and control subsystem on the ground. A hemispherical air bearing is used to provide micro gravity condition. Reaction wheels produce required control torques and an integrated sensor is used for attitude determination. Commanding and visualization of the platform in monitoring station are provided by a wireless LAN. PD, QEF and LQR controllers are designed and implemented for slew maneuver to show the ability of the simulator. The desired attitude accuracy is obtained using these controllers. The test results verify the designed controllers and show the ability and functionality of the system, as a simulator for evaluating attitude controllers.
Ali Mehrabi; Fathallah Ommi
Volume 9, Issue 1 , May 2016, , Pages 59-72
Abstract
In this paper, an adaptive controller based on decentralized minimal control synthesis is designed n order to control an attitude of specific remote sensing satellite. The main design purposes are performing spinning, three axis and large angle maneuver as well as achieving a stable system and tracking ...
Read More
In this paper, an adaptive controller based on decentralized minimal control synthesis is designed n order to control an attitude of specific remote sensing satellite. The main design purposes are performing spinning, three axis and large angle maneuver as well as achieving a stable system and tracking the reference attitude trajectory in the presence of uncertainties. In the design process, the effects of internal and external disturbances, nonlinearities in the satellite dynamic and the accurate model of actuators are regarded. Four reaction wheels with pyramidal structure are modeled as the actuators to accomplish an attitude maneuver. So the exact reaction wheels’ model with regarding the maximum voltage, current, allowable angular velocities and power of wheels is developed. The simulation results show an acceptable performance of controller in the presence of exacts actuators’ model, external and internal disturbances and uncertainties in the satellite parameters.
M. Navabi; M.R. Hosseini
Volume 11, Issue 1 , June 2018, , Pages 59-71
Abstract
Using nonlinear control theories is common for the attitude control problem of spacecraft.Feedback linearization theory is a nonlinear control method which tries to transform nonlinear dynamics of system into linear.In this control theory, outputs choice will have a direct impact on the stability ...
Read More
Using nonlinear control theories is common for the attitude control problem of spacecraft.Feedback linearization theory is a nonlinear control method which tries to transform nonlinear dynamics of system into linear.In this control theory, outputs choice will have a direct impact on the stability of system.In order to control the spacecraft attitude by this method, parameters that describe the spacecraft attitude are considered as outputs.The aim of this study is to investigate the effect of using quaternion parameters as a conventional representation in the kinematic equations compared with modified Rodrigues parameters.According to designed controller and simulation results, it is evident that in maneuvers with zero scalar part of quaternion, the controller efficiency is reduced due to singularity in the calculations.This is while by using modified Rodrigues parameters, singularity does not occur and in this way the controller, in the same maneuvers as the previous method, is faster and more efficient with less effort.
Mohammad ghoharkhah; Behzad Alizadeh
Volume 13, Issue 4 , December 2020, , Pages 59-69
Abstract
In this numerical study, effect of magnetic field on the convective heat transfer of a magnetic fluid in an enclosure is investigated in the microgravity condition. Two cases of a single magnetic field source under the enclosure and two sources on the top and below the enclosure are considered and the ...
Read More
In this numerical study, effect of magnetic field on the convective heat transfer of a magnetic fluid in an enclosure is investigated in the microgravity condition. Two cases of a single magnetic field source under the enclosure and two sources on the top and below the enclosure are considered and the simulations are carried out for different magnetic field intensities and magnetic source distances from the enclosure. Results indicate that the heat transfer in the microgravity is much lower than that of natural condition due to the lack of the flow vortex. Applying the magnetic field and the induced vortex due to the magnetic body force cause a significant improvement of the heat transfer. Results show that the heat transfer rate in the microgravity condition can be increases up to 6.5 times. Moreover, placing two magnetic field sources improves the main vortex and leads to 19.7 times enhancement of the heat transfer rate compared to the case of single source.
S.H. Miri Roknabadi; M. Mirshams; A. A. Nikkhah
Volume 2, Issue 2 , July 2009, , Pages 61-68
Abstract
This paper presents a technical note of mathematic model, design and manufacturing steps of a Reaction Wheel, one of the most important active actuators of satellite. After that Reaction Wheels are tested for the satellite simulator of K.N.Toosi University of Technology, Iran. There were some requirements ...
Read More
This paper presents a technical note of mathematic model, design and manufacturing steps of a Reaction Wheel, one of the most important active actuators of satellite. After that Reaction Wheels are tested for the satellite simulator of K.N.Toosi University of Technology, Iran. There were some requirements and restrictions such as needed maximum torque and control accuracy for attitude maneuver, receivable power, voltage and current. Accordingly fundamental components of Reaction Wheel have been designed and selected. Wheel, motor, bearings and retentive are the significant components. At the rest of the paper, the substantial parameters of the Reaction Wheels are confirmed by a new test set. The results of test guarantee a satisfactory stabilization and accurate maneuver.
M. Naghikhani; H. R. Ali Mohammadi
Volume 4, Issue 1 , July 2011, , Pages 61-67
Abstract
Selection of the optimal tolerance for the components is one of the most important and complex issues in the design of the parts and products especially in sensitive and accurate industries (like as aerospace). Generally the design engineers tend to consider close tolerances in terms of product performances ...
Read More
Selection of the optimal tolerance for the components is one of the most important and complex issues in the design of the parts and products especially in sensitive and accurate industries (like as aerospace). Generally the design engineers tend to consider close tolerances in terms of product performances and high reliability, on the contrary to manufacturing engineers that used to open tolerances because of easier, cheaper and practicality of manufacturing processes. Study the balance between tolerance and other factors affecting it, such as quality, cost and production, is the most important issue in this case. In this regard, there are numerous articles and methods. In this paper we use the tools of statistics and mathematics as" response surface method", first method of diagnosis of the critical tolerances describes and then tolerance of the optimal allocation - in case the cost of production or quality characteristic is optimized- has been examined.
S. M. Hashemi Doulabi; H. Darabi; J. Roshnian
Volume 5, Issue 1 , April 2012, , Pages 61-72
Abstract
One of the most important problems that nowadays are common in aerospace societies in Iran and also around the world is how to optimize the designing of the flight objects. Since the flight objects like LVs, which are the subject of this paper, are composed of several subsystems that have influences ...
Read More
One of the most important problems that nowadays are common in aerospace societies in Iran and also around the world is how to optimize the designing of the flight objects. Since the flight objects like LVs, which are the subject of this paper, are composed of several subsystems that have influences to each others, the multidisciplinary design optimization methods(MDO) are commonly used for doing design optimization of them. In usage of the multidisciplinary design optimization methods for different objects, to select the proper optimization algorithm is one of the very important problems. In this research the conceptual design of a lightweight liquid propellant LV is done with the all at once (AAO) method. The object of optimization is to minimize gross launch weight and four disciplines of structure, aerodynamics, trajectory, and propulsion are considered. Performance of gradient based algorithm of SQP and heuristic algorithm of GA and traditional method (statistical method) by solving an example are compared and is shown that if the output of statistical method is used as start point of optimization using gradient based algorithm of SQP, the global answer will be derived.
hamed Alisadesghi; Hamed Ramezani-Najafi; Hossein Reza Abbasi
Volume 9, Issue 2 , September 2016, , Pages 61-76
Abstract
Base on space standards, the thermal design evaluations for satellites are performed using thermal balance tests. Regularly, the thermal model is used for the thermal balance test. This model is completely similar to the flight model of the satellite in terms of thermal characteristics. In this paper, ...
Read More
Base on space standards, the thermal design evaluations for satellites are performed using thermal balance tests. Regularly, the thermal model is used for the thermal balance test. This model is completely similar to the flight model of the satellite in terms of thermal characteristics. In this paper, the definition and implementation of thermal balance tests for Thermal model of AUTSAT Satellite is conducted. the evaluation of the TM and the procedure data Correlation of the numerical model have been focused. In order to increase the accuracy and feasibility of thermal mathematical model correlation, structural and complete models are considered for the balance test separately. In this study, the results of thermal balance test for the structural thermal model has been compared with the numerical analysis and the correlation procedure is illustrated. The results achieved by this procedure shows that all the requirements by the standard are satisfied in this level.
physiology and space medicine (astrobiology)
Zahra Hajebrahimi; Maryam Salavatifar
Volume 14, Issue 4 , December 2021, , Pages 61-66
Abstract
Studies have shown that simulated microgravity (SMG) affects tumor cell growth and metastasis. However, the underlying molecular basis is still not known. In recent years, due to the high expression of CD44 in invasive basal breast tumors, it has been the subject of many studies. The aim of present study ...
Read More
Studies have shown that simulated microgravity (SMG) affects tumor cell growth and metastasis. However, the underlying molecular basis is still not known. In recent years, due to the high expression of CD44 in invasive basal breast tumors, it has been the subject of many studies. The aim of present study was to investigate the gene expression of CD44 in MDA-MB-231cell line of breast cancer in microgravity conditioncell line was proliferated under normal gravity and microgravity (1 and 3 days) using 2-D clinostat. Gene expression was measured using real-time PCR technique. SMG increased gene expression (100%) after 1 day and decreased it (15%) during 3 days in comparison to the control samples. It seems that the response of cancer cells to microgravity is time dependent and simulated microgravity treatment for 3 days may have a positive effect on cancer characteristics of MDA-MB-231 cell line in order to decrease the expression of CD44.
Azadeh Hekmat; Bahar Hajati; Zahra Hajebrahimi
Volume 13, Issue 1 , March 2020, , Pages 61-70
Abstract
Amount of space exploration investigation has been done to understand the variations in biological structure and function of living organisms in microgravity condition. Nowadays, the investigation of the microgravity from a nanoscale viewpoint is encouraged. Silver nanoparticles have been involved in ...
Read More
Amount of space exploration investigation has been done to understand the variations in biological structure and function of living organisms in microgravity condition. Nowadays, the investigation of the microgravity from a nanoscale viewpoint is encouraged. Silver nanoparticles have been involved in large-scale production. In this research, the effect of simulated microgravity on DNA structure was studied. Additionally, the silver nanoparticles binding with DNA molecules under Earth gravity and simulated microgravity conditions by various spectroscopic instruments were investigated. The results displayed that microgravity simulation has created DNA structure variation. The binding affinity of silver nanoparticles to DNA altered. Microgravity initiated an alternation in size and surface charge of DNA and modified DNA structure from B to C-form. Consequently, based on our observation, microgravity can strictly affect the silver nanoparticles-DNA binding interaction. Our observations can open fascinating research lines in biology and biophysics.
M. Farhang; H. Dehghani
Volume 4, Issue 2 , January 2012, , Pages 63-70
Abstract
Automatic Modulation Recognition is an important task for intelligent receivers in modern communication systems, in which several modulation types are used. In order to improve the performance of modulation classification systems, the idea of multi-receiver recognition has been developed recently. In ...
Read More
Automatic Modulation Recognition is an important task for intelligent receivers in modern communication systems, in which several modulation types are used. In order to improve the performance of modulation classification systems, the idea of multi-receiver recognition has been developed recently. In this paper multiple receivers’ collaboration at different information levels is investigated for classification of signals used in DVB-S2 standard.Three methods are proposed for receivers’ cooperation at each one of signal, feature and decision levels. The proposed methods use cumulants and MLP neural network as signal features and classifier respectively. These methods are evaluated and compared through performance, complexity and equipment. The results show that receivers’ cooperation at signal level offers more accurate classification compared to feature and decision levels, in addition to less computational complexity.
A.H. Taghavi; A. Soleymani; T. Shojaee
Volume 7, Issue 2 , July 2014, , Pages 63-74
Abstract
Recently, new actuators known as fluidic momentum controllers (FMC) have been proposed for satellite attitude control. This actuator has many advantages such as high applied torque to weight ratio, easiness in assembly, low transmitted vibration and so on respect to the other momentum exchange devices ...
Read More
Recently, new actuators known as fluidic momentum controllers (FMC) have been proposed for satellite attitude control. This actuator has many advantages such as high applied torque to weight ratio, easiness in assembly, low transmitted vibration and so on respect to the other momentum exchange devices like momentum/reaction wheels or CMGs. However, one of the main problems in implementing such actuators is complexity in mathematic modeling of them. This issue makes many researchers to use a simplified model for control system designing without to consider uncertainty in this simplified model. In this paper for eliminating of this problem, an adaptive sliding mode control (SMC) has been used in this article. This control method is not also robust respect to uncertainties but also can estimate over threshold of them without necessity to use larger and heavier actuators to be sure of satellite stability. According to the results, we can observe that proposed control system is capable to reach satellite to the desire attitude in minimum time and without overshoot.
Seyed Mohammad Reza Mosavi; Narjes Rahemi; Satar Mirza Kuchaki
Volume 7, Issue 4 , January 2015, , Pages 63-72
Abstract
GPS is a satellite-based navigation system that is able to determine the exact position of objects on the Earth, sky, or space. By increasing the velocity of a moving object, the accuracy of positioning decreases; meanwhile, the calculation of the exact position in the movement by high velocities like ...
Read More
GPS is a satellite-based navigation system that is able to determine the exact position of objects on the Earth, sky, or space. By increasing the velocity of a moving object, the accuracy of positioning decreases; meanwhile, the calculation of the exact position in the movement by high velocities like airplane movement or very high velocities like satellite movement is so important. In this paper, two methods for positioning in very high velocities based on recursive least squares method and its combination with fuzzy logic are presented. Simulations on different data with different velocities show that proposed method can improve the accuracy of positioning more than 50%. In previous methods, the algorithm is quite dependent on the initial point, whereas in proposed method, this dependency is resolved.
