A Launch Vehicle Tracker Design Based on On-Line Linearization
A.
Madadkar
Department of New Sciences and Technologies, Tehran University
author
A.
Kalhor
School of Electrical and Computer Engineering, Tehran University
author
A.R.
Kosari
Department of New Sciences and Technologies, Tehran University
author
text
article
2016
per
In order to overcome the nonlinear terms in the flight equations of a launch vehicle, an appropriate control strategy has to be designed. In this paper, the fundamentals of designing a simple controller in order to control a typical launch vehicle for tracking the optimum launch vehicle path is presented. The principals of this strategy are based on on-line linearization of the nonlinear equations in each sampling interval during the flight and eventually representing system equations as extended Jacobean equations. It is important to note that equations linearization does not work in some areas and equilibrium points of the system but in each sampling interval is trying the system of nonlinear equations can be transformed into linear equations and then by using the pole placement theory, a good tracking controller proposed for the system. Design and simulation results show good accuracy and proper convergence of the reference signals (speed and pitch angle signals) and eventually, the success of the mission.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
1
9
http://jsst.ias.ir/article_44267_27271be6809a685d7edbdfcb83d7fad9.pdf
Design, Construction, Test and Modeling of Triaxial Helmholtz Coil for Magnetic Tests of Satellite
S.M.S
Mosvi
Department of Aerospace Engineering, Amirkabir University of Technology
author
M.
Mortazavi
Department of Aerospace Engineering, Amirkabir University of Technology
author
text
article
2016
per
In order to be sure from true function of satellite’s Attitude determination and Control Subsystem (ADCS) and its parts, some tests are needed to be done in part or subsystem level. One of the useful tools for doing these tests is Helmholtz Coil. This tool is usable in functional tests and calibration of satellite’s magnetic sensors and actuators, in Hardware In the Loop (HIL) tests of ADCS subsystem, and also in related tests to residual magnetic of satellite’s part. In this paper, we study mathematical equations of Helmholtz coil, propose design procedure and requirements, also introduce set of functional and identification tests for evaluating the constructed Helmholtz Coil. By obtaining results and finding the mathematical model of Helmholtz Coil, preparations for designing closed loop control system to eliminate environmental magnetic disturbances and create desired magnetic field by Helmholtz coil are provided.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
11
24
http://jsst.ias.ir/article_44271_dd798c6bd0565a16d5e700161c055d6d.pdf
Satellite Spin Stabilization by Magnetic Torquers and Validation with Air-Bearing Simulator
H.
Arefkhani
Department of Aerospace Campus, Malek Ashtar University
author
M.
Mehdi-Abadi
Department of Aerospace Campus, Malek Ashtar University
author
S.M.M.
Dehghan
Department of Aerospace Campus, Malek Ashtar University
author
text
article
2016
per
In this paper, magnetic spin control using Spin and B-dot control laws have been studied in a lab environment. Evaluation of this control laws is done by a "three degrees of freedom air-bearing simulator". Due to the inherent simulator limitations, laboratory test results are visible only on one axis. Therefore, to evaluate these three-axis laws precisely, evaluation modeling is discussed by comparing the simulator dynamic and kinematic equations with the results of laboratory experiments. After evaluation of the modeling process, simulation of three-axis control law is conducted. Since the validated model shares same basis with satellite model equations except the torque disturbances caused by the distance between the center of the mass and the center of the rotation, it can be assured that these control laws are suitable for three-axis control of a satellite. Test results indicate appropriate performance of control laws.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
25
34
http://jsst.ias.ir/article_44273_3d235819a6a4e3f2b14355248b06ac92.pdf
Atmospheric Doppler Modelling for Open Loop Tracking in GPS-RO Receivers
L.
Mohammadi
Department of Institute for Communication Technology, ICT Research Institute
author
Sh.
Amiri
Department of Institute of Electrical and Information Technology, Iranian Research Organization for Science and Technology (IROST)
author
Gh.
Mohammadkhani
Department of Institute of Electrical and Information Technology, Iranian Research Organization for Science and Technology (IROST)
author
text
article
2016
per
One of the main challenges of the Open-Loop Signal Tracking method in GPS-RO space receivers, is Doppler prediction. Almost in all satellite communication systems, accurate carrier phase tracking under difficult conditions is depend on Doppler prediction accuracy. Obviously, there are several methods for producing a predicted Doppler model, and one of the earliest is Sokolovskiy. In this paper, we are analyzing the typical and operational atmospheric Doppler prediction models for the Open-Loop Signal Tracking of radio occultation, in satellite communications. A summary and comparison between these methods will be concluded in the end of this paper. finally we propose a prediction method can be used in national GPS-RO payloads for predicting atmospheric doppler based on combination of Sokolovsky and C.O. Ao methods.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
35
46
http://jsst.ias.ir/article_44274_62ce787a6e50dd056ebc4d84f909a6b3.pdf
Evaluation of Magnetic Attitude control with Air-Bearing simulator
H.
Arefkhani
Department of Aerospace University Camplex, Maleke Ashtar University of Technology
author
S.M.M.
Dehghan
Department of Aerospace University Camplex, Maleke Ashtar University of Technology
author
A.H.
Tavakoli
Department of Aerospace University Camplex, Maleke Ashtar University of Technology
author
text
article
2016
per
In this paper, the three-axis magnetic attitude control using PD and LQR control laws have been studied in a lab environment. Evaluation of the magnetic attitude control with this control laws is done by a "three degrees of freedom air-bearing simulator". Developed dynamic and kinematic equations to be used in actual simulator are evaluated by open loop test. Then control laws evaluated by comparing close loop simulation and laboratory test. Due to the inherent simulator limitations, magnetic attitude control only possible in the yaw axis. Laboratory test results indicate the improved and accurate performance of LQR control law for most satellite missions. Therefore by generalized LQR controller, three-axis simulation was performed for a satellite.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
47
60
http://jsst.ias.ir/article_44275_cd45384b7ca198b92161eae8884b61e8.pdf
Design and Manufacture of Thermal Model of AUTSAT Satellite and Its Thermal Balance Test
H.
Alisadeghi
Department of Aerospase Engineering, K.N Toosi of Technology
author
H.
Ramezani-Najafi
Department of AUTSAT Satellite Project, Amirkabir University of Technology
author
H.R.
Abbasi
Department of AUTSAT Satellite Project, Amirkabir University of Technology
author
text
article
2016
per
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.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
61
76
http://jsst.ias.ir/article_44277_f8b4a9890d0c1691c585a6456249ebbe.pdf
Determining orbital element on Earth Observation Repeat-Ground-Track orbit
P.
Torabi
Department of Aerospace Engineering, Amirkabir University of Technology
author
A.
Naghash
Department of Aerospace Engineering, Amirkabir University of Technology
author
text
article
2016
per
This paper presents a new methodology for a quick and efficient numerical determination of the condition for repeat ground tracks to be employed in an orbital optimization design methodology. This methodology employs the simplicity and reliability of the epicyclical motion condition for a repeat ground track to find a semimajor axis for a given repetition cycle and inclination. Then the semimajor axis is re fined for application to any elliptical motion. This methodology was discovered by comparing two recent methods in addition to a new proposed method offered in this paper investigating both nonlinear algebraic and polynomial formulations of the governing repeat-ground-track condition relationship. A lesser known simplified method is used for preliminary solution refinement. The advantages and disadvantages of each approach are weighed with each method ’s reliability, performance, and computational ease based on a case study. From these criteria, one method is recommended for use in repeat-ground-track orbit design optimization methodology.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
77
83
http://jsst.ias.ir/article_44278_0bb9f04b6c65e75b451f04fb30d19e47.pdf
(Technical Note)
Design and Construction of Star Tracker Platform in Order to Satellite Attitude Determination Based on Star Tracking Algorithm
Malihe
Hashemi
دانشکدة مهندسی برق، دانشگاه علم و صنعت ایران
author
s.Kamaleddin
Mosavi Mashhadi
دانشکدة مهندسی برق، دانشگاه علم و صنعت ایران
author
S. Majid
Esmaeilzadeh
دانشکدة مهندسی برق، دانشگاه علم و صنعت ایران
author
Mohammad
Fiuzy
دانشکدة مهندسی برق، دانشگاه علم و صنعت ایران
author
text
article
2016
per
Attitude Determining is one of the major and critical satellites space missions. In this study, a new method to Attitude determination of satellites is presented. Such that, based on the proposed method search space will be more limited then accuracy and speed of attitude determination in the proposed method has risen. At first in this method, implementation and the test algorithms will be discussed, after these some algorithms, such as navigation, pattern recognition and ultimately attitude determination will be reviewed. In order to implement these algorithm. High quality images of stars which must provided by the star tracker camera requires to implement. Really these images to perform the necessary processing sent to the processor so the processor based on designed algorithms, determines the attitude of camera and satellite in all three axes. This means that some features considered for star tracker and based on them begins the designing process. The range of accurately determination for star tracker is one of these features. In this article, the ranges of two axes of Yao and Pitch less than 20 seconds on the scale of degree are considered and in the roll axis less than 100 seconds is intended. Can show in the results, much better accuracy and less than initial assumptions have been achieved. It also carried out by an adaptive identified algorithm so that the brighter stars are identified and based on their attitude determination, the sensor accuracy have increased. Because of according research, the clearer stars, have more accurate in calculation. The other important feature is the speed of attitude detection which performed by 1 GHz processor, and correct identification of pyramidal algorithm where have reached less than 15 milliseconds. Due to the duration, the desire update rate gained. Other important parameters which influence the accuracy of the attitude determination is knowing the exact coordinates of the intersection point vector of focal length lens with image sensors. By Land calibration for camera with a good accuracy, these parameters were estimated.
Journal of Space Science and Technology
پژوهشگاه هوافضا و انجمن هوافضای ایران
2008-4560
9
v.
2
no.
2016
85
90
http://jsst.ias.ir/article_44553_0d858b07d9f338266f45d93e6dcf8f9e.pdf