Aerospace Science and Technology
Fatemeh Amozegary; Amir reza Kosari; Mahdi Fakoor
Abstract
The ever increasing demand for placing satellites in the geostationary orbit has caused the revision and change of the conventional mechanism of allocating orbital slots. Therefore, collocation approaches and station keeping of several satellites with a common position have been developed to improve ...
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The ever increasing demand for placing satellites in the geostationary orbit has caused the revision and change of the conventional mechanism of allocating orbital slots. Therefore, collocation approaches and station keeping of several satellites with a common position have been developed to improve the utilization of the capacity of the geostationary orbit. This, in turn, leads to an increase in the complexity and sensitivity of the modeling, guidance, and control processes. However, new restrictions are added to the problem of maintaining a common location, such as maintaining the minimum separation distance between satellites to prevent possible interference. Employing a collocation strategy is essential, especially for effective control of high-demand orbital regions that will lead to space congestion.Controlling the relative motion of satellites by maintaining a safe distance between them is the main rule in collocation. This article investigates the problem of the relative motion of satellites corresponding to collocation strategies. Then, the results are implemented and compared using a solution based on geometrical modeling of relative orbit and the concepts of spherical geometry. In this regard, the relative orbital elements of the two satellites are calculated using the presented relative motion modeling. Also, the relative position of the satellites is obtained. The case studies and evaluations confirmed that the inclination and eccentricity separation strategies are suitable options for meeting the fuel consumption requirements and providing more space for collocated satellites than other strategies.
Aerospace Science and Technology
Amir reza Kosari; Elahe Khatoonabadi; Vahid Bohlouri
Abstract
In this paper, the control of a three-axis rigid satellite attitude control system with a fractional order proportional-integral-derivative (PID) controller is investigated in the presence of disturbance and parametric uncertainties. The reaction wheel actuator with the first-order dynamic model is used ...
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In this paper, the control of a three-axis rigid satellite attitude control system with a fractional order proportional-integral-derivative (PID) controller is investigated in the presence of disturbance and parametric uncertainties. The reaction wheel actuator with the first-order dynamic model is used to control the attitude of the satellite. Uncertainties are considered on satellite moment inertia, actuator model and amplitude and frequency of external disturbances. External disturbances are modeled with two fixed and periodic parts and uncertainty is also considered on the disturbances model. The integer order controller is also used for the same conditions to compare the results with the fractional order controller. The usual Granwald-Letinkov definition is used to solve integrals and fractional order derivatives. The mean absolute of the pointing error of the satellite pointing maneuver has been selected as an objective function of the optimization problem. The controller gains in integer and fractional order are obtained by particle swarm evolution algorithm (PSO) optimization method. The performance criterion has been studied in terms of the controller time response and also in terms of the standard deviation of the mentioned uncertainties and external disturbance. The results show that the fractional order controller performs more accurate and robustness than the integer order controllers in the face of uncertainty and disturbance.
Aerospace Science and Technology
Amir reza Kosari; Ehsan Abbasali; Majid Bakhtiyari; Hamed Golpour
Abstract
The main purpose of this article is to examine the periodic coupled orbit-attitude of a satellite at restricted three body problem considering both primaries oblateness perturbations. The proposed model was based on a simplified coupled model meaning that the time evolution of the orbital state variables ...
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The main purpose of this article is to examine the periodic coupled orbit-attitude of a satellite at restricted three body problem considering both primaries oblateness perturbations. The proposed model was based on a simplified coupled model meaning that the time evolution of the orbital state variables was not a function of the attitude state variables. Since, the problem has no closed-formed solution, and the numerical methods must be used, so the problem can have different periodic or non-periodic responses to the initial conditions. The initial guess vector of the coupled model’s states was introduced to achieve the optimal initial conditions leading to the periodic responses, and then the P-CR3BP coupled orbit-attitude correction algorithm was proposed to correct this initial guess. Since, the number of periodic solutions is restricted; the suitable initial guess vector as the inputs of the coupled orbit-attitude correction algorithm increases the chances of achieving more accurate initial conditions. The initial guess of orbital states close to the initial conditions of the P-CR3BP periodic orbit, along with initial guess vector of attitude dynamics states with Poincaré mapping was suggested as the suitable initial guess vector of the coupled model.
Aerospace Science and Technology
Mahdi Fakoor; Hamidreza Heidari; Behzad Moshiri; Amir reza Kosari
Abstract
In this study, Adaptive Network-Based Fuzzy Inference System (ANFIS) is presented with sensor data fusion approach to estimate satellite attitude. The active sensors are sun and earth sensors. Satellite attitude dynamic, including attitude quaternion and angular velocities are estimated simultaneously ...
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In this study, Adaptive Network-Based Fuzzy Inference System (ANFIS) is presented with sensor data fusion approach to estimate satellite attitude. The active sensors are sun and earth sensors. Satellite attitude dynamic, including attitude quaternion and angular velocities are estimated simultaneously utilizing the measured values by the sensors. The Extended Kalman Filter (EKF) is employed to verify and evaluate the efficiency of the presented method. Additionally, the neural networks with Radial Basis Function (RBF) and Multi-Layer Perceptron (MLP) are also designed to prove the superiority of the proposed ANFIS network among the smart methods of sensor data fusion for satellite attitude estimation. Root Mean Square Error (RMSE) as a numerical criterion and graphical analysis of residues are utilized to evaluate the simulation results. The simulations confirm that the obtained estimations from ANFIS network have more accuracy in modeling of nonlinear complex systems compared to EKF, MLP and RBF networks. In general, using intelligent data fusion, especially ANFIS, reduces attitude estimation error and time in comparison to the classical EKF method.
Aerospace Science and Technology
Amir reza Kosari; Alireza Akbar Attar; Peyman Nikpey
Abstract
In this study, the performance requirements influencing the orbital and attitude control system of a geostationary satellite in the station-keeping flight mode considering the coupling effect of both attitude and orbital motion is determined. Controlling and keeping the satellite in its orbital window ...
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In this study, the performance requirements influencing the orbital and attitude control system of a geostationary satellite in the station-keeping flight mode considering the coupling effect of both attitude and orbital motion is determined. Controlling and keeping the satellite in its orbital window have been done using a set of four thrusters located on one side of the satellite body, with considering the coupling effect of the attitude motion on orbital motion. The satellite’s orbital motion could be disturbed by the attitude motion in the allowable orbital window. The main factors conducting this behavior are derived utilizing the satellite attitude and orbital dynamic equations of motion. In the mathematical analysis of this study, the effects of environmental perturbations originating from the oblateness of Earth, third mass gravity like sun and moon, and solar radiation pressure on the satellite dynamic behavior are also considered. Afterward, the condition of using four installed thrusters on one side of the satellite and the reaction wheels in order to control the satellite orbital and attitude motion is investigated. To reduce the satellite attitude’s error, a proportional-derivative controller is employed to activate the reaction wheels properly. The satellite positions in north-south and east-west directions are controlled by a specific array of thrusters in order to maintain in its predefined orbital window. The required amount of velocity variations for a duration of one year via some simulation may demonstrate the effectiveness of the proposed approach in enhancing the orbital maintenance procedure of the satellite.
Aerospace Science and Technology
Asad Saghari; Amirreza Kosari; Masoud Khoshsima
Abstract
This paper deals with the problem of optimal selection of orbital parameters for an Earth observation mission in the absence of the possibility of injection into sun-synchronous orbit by considering the requirements and limitations of the mission and the satellite platform. By modeling the existing relationships ...
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This paper deals with the problem of optimal selection of orbital parameters for an Earth observation mission in the absence of the possibility of injection into sun-synchronous orbit by considering the requirements and limitations of the mission and the satellite platform. By modeling the existing relationships between each of the three areas of orbit, mission and platform, the effects of changes in each of the parameters have been analyzed and tracked. One of the important advantages of the proposed solution is that in the process of optimal selection of relevant parameters, all aspects of the orbit, mission and platform are considered simultaneously. This, in turn, can lead to an implementable and operational option for accomplishing the mission. In evaluation of effects of changing orbital parameters on the mission characteristics and requirements of the satellite platform, a developed computer code has been used.
Aerospace Science and Technology
Ehsan Abbasali; Amir reza Kosari; Majid Bakhteiari
Abstract
In this paper, the effect of perturbations of oblate primaries in the Circular Restricted Three-Body Problem is studied, and the equations of satellite orbital motion in the Circular Restricted Three-Body Problem are developed by employing Lagrangian mechanics. Since the equations have no closed-form ...
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In this paper, the effect of perturbations of oblate primaries in the Circular Restricted Three-Body Problem is studied, and the equations of satellite orbital motion in the Circular Restricted Three-Body Problem are developed by employing Lagrangian mechanics. Since the equations have no closed-form solution and numerical methods must be applied, the problem can have different periodic or quasi-periodic solutions depending on the equation's initial conditions of orbital state parameters. For this purpose, an algorithm named “orbital correction algorithm” is proposed to correct the initial conditions of orbital state parameters. The limited number of periodic orbits in the study environment indicates the algorithm’s need for suitable initial guesses as input. In the present paper, suitable initial guesses for orbital state parameters are selected from the third-order approximation of the Unperturbed Circular Restricted Three-Body Problem’s periodic solutions, increasing the chance of obtaining desired periodic solutions. The obtained perturbed and unperturbed periodic orbits are compared in order to understand the effect of perturbations. Adding the perturbations brings the study environment closer to the real environment and helps understand satellites' natural motion.
Aerospace Science and Technology
Amir reza Kosari; Masoud Mirzaei Tashenizi
Abstract
This article is aimed to investigate the interference elimination between multiple aircraft using game theory. A differential game is used to eliminate the interference if all the interfering aircraft cooperate to eliminate the interference or if each makes a rational decision based on their own interests. ...
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This article is aimed to investigate the interference elimination between multiple aircraft using game theory. A differential game is used to eliminate the interference if all the interfering aircraft cooperate to eliminate the interference or if each makes a rational decision based on their own interests. All interfering aircraft calculate the interference elimination route in cooperative mode by defining the flight priority. In the non-cooperative state, the problem of eliminating the interference is investigated using the Nash equilibrium, and then the new path is calculated. A point mass model has been used to implement this problem, which is converted into a linear model by changing the control variable. The above problem is solved using the quasi-spectral numerical solution method. In order to validate the presented method, the problem of eliminating the interference between several aircraft in two-dimensional space has been studied, and the results show the appropriate performance of the presented method.
Amirreza Kosari; Javad Bahremandjouy
Abstract
In this paper, a Force Control Solution on Space Docking is proposed providing low impact and safe connection between space modules in different missions. In this solution, the force control concept has been employed along with traditional position control in space docking process because the interaction ...
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In this paper, a Force Control Solution on Space Docking is proposed providing low impact and safe connection between space modules in different missions. In this solution, the force control concept has been employed along with traditional position control in space docking process because the interaction forces between those parties involved (the chaser spacecraft and the target) in this phase are quite significant. Among the available methods in the force control field, Position Based Impedance Control strategy has been used as this strategy controls neither position nor force but the dynamic relationship between relative positions and interaction forces which is used widely in robotic science; however, other methods exhibit instability problems at the connection stage due to change between the position controller and the force controller. As we know, there are different kinds of space vehicles with particular connection scenarios and various connection latches; in order that, each vehicle demands specific interaction force in the connection phase; therefore, Position Based Impedance Control combined with Hill's Equations, which is used for space docking in circular orbit as relative position, is presented to be applied to different docking strategies and mechanisms. For the position controller that lies into Position Based Impedance Control structure, a nonlinear-PID Controller has been utilized possessing an anti-windup property and good capability to track the reference signal. The results show that we can ensure low impact connection by modifying target impedance coefficients in addition to precise position control.