amir reza kosari

This paper investigates solar activities and its phenomena from the perspective of risks to the earth's environment, human health, and space weather risks to space systems. In this article, in addition to a brief explanation about the physics of the sun and space weather phenomena, the effects of these phenomena on human health have been investigated. moreover the results of international researches have been studied and analyzed to determine the relationship between heart diseases, brain diseases, cancer, birth rates, health of astronauts, and animal life with space weather phenomena. The results of this article help to predict these events during the occurrence of solar events and by taking the correct actions in addition to preserving biological health, possible damages can also be minimized.

This paper investigates solar activities and its phenomena from the perspective of risks on the functioning of urban infrastructures, industrial systems and economic structure affected by such phenomena. Also, according to the existing analyzes and results, basic requirements have been introduced to prevent the severity of the resulting injuries. Space weather events can cause disruptions in the power grid, telecommunications and radio communications, airlines, railways, and in addition cause damage to pipelines, oil and mining industry. Also, these phenomena can cause damage and dysfunction in satellites that are used for global positioning, communication and weather forecasting. Considering the importance of the items mentioned in this article, an attempt has been made to investigate the research done in some other countries regarding the impact of space weather phenomena on socio-economic systems and to study the disruptions and failures caused by this impacts in the industries and socio-economic infrastructures of the society. This studies can help in the formation of the necessary fields and preventive actions in facing the dangers of space weather in order to lead the scientific community to investigate similar cases in the country in order to create related management and technological measures.

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.

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.

In this paper, attitude control of a rigid satellite in the presence of external perturbations and considering the parametric uncertainties with the fractional order controller is investigated. To control the attitude of the satellite, a reaction wheel actuator with a first-order dynamic model is used and uncertainty is considered in the parameters of the satellite’s moment of inertia, the actuator model and external perturbations. For comparative purposes, in addition to the fractional order controller, the integer order controller is also used. Numerical solution is performed by Euler method and Granwald-Letinkov definition is used to solve the fractional order integral and derivative. The coefficients of the integer order and fractional order controllers were extracted by the particle swarm optimization method with the performance criterion of mean of absolute value of error. Fractional order controllers have more degree of freedom than integer order controllers due to their more design parameters. Therefore, according to the results, the appropriate performance of fractional order controllers can be seen in overshoot, settling time and against of perturbations and uncertainty in the satellite attitude control.

Very High Resolution Passive Scan Agile Earth Observation Satellites are able to maneuver around all their three body axes and scan the target area in different directions, simultaneously. The most stringent mid-level requirements which dominate their attitude determination and control subsystem performance are applied in detumbling and fine pointing modes. These performance requirements are maneuverability, agility, accuracy and stability. In this research, first, we derive the analytical and statistical relationships between quantitative criteria of mid-level requirements and spatial resolution as a high-level mission requirement, next the design drivers of reaction wheels are extracted consequently. Then the size, mass and consuming power of an operational satellite and the reaction wheels torque authority and momentum capacity is guesstimated based on its imaging payload size and specifications.

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.

In order to reduce the weight and increase the efficiency of thermal control subsystem of the small satellites, employing efficient equipment is necessary. Smart radiator is one of the useful equipment in this field. Emission coefficient of these radiators change as a function of temperature or voltage. These variations cause heaters consumption power to be decreased in satellites. In this study, smart radiator is simulated and used in a thermal control subsystem of a small satellite. The result is compared to a conventional radiator. Non-linear proportional-integral method is employed to control the temperature. In this method, each part temperature is considered as state variable and heaters are considered as operators. Simulation results show that non-linear proportional-integral control method has better performance in decreasing the overshoot and settling time in comparison with the linear proportional-integral control method. Besides, smart radiators cause heaters consumption power to be declined. In a way that for the battery about 7% and for the top plate about 27% of the heater power consumption has been reduced.

Due to the unique characteristics of the geo-synchronous orbit and the importance of establishing a satellite in this flying corridor, it is necessary to investigate the effect of environmental disturbances on the orbital elements and to maintain the satellite orbital elements in order to increase the longevity and operation of a satellite in this orbit. A satellite in earth orbit is also always exposed to various environmental disturbances such as earth gravity gradient force, gravity of the moon and sun, solar radiation pressure, and so on. For this reason, it is constantly deviating from its original path and needs to study the effect of environmental disturbances on the orbital elements in order to properly correct the disturbed orbital parameters. To achieve the above goals, in this paper, we try to investigate the effect of the environmental perturbations on the orbital characteristics by simulating the satellite translational dynamic behavior in the presence of environmental disturbances. Then, utilizing the genetic algorithm and fuzzy logic approach, an attempt was made to modify the compensation logic of the orbital elements correction, so that, the satellite may be forced to remain in its limited operational orbital window during the mission lifetime. The proposed method could improve the problem-solving operational effectiveness to maintain the position of the satellite with the criterion of minimizing fuel consumption. The case study simulation results may indicate the capability of the proposed approach in satisfying the performance requirements of the satellite station-keeping maneuver.

The study was done to identify periodic Lyapunov orbits in the presence of the primaries oblateness applying Poincaré map at the restricted three-body. Governing equations of the PRTBP orbital motion were derived using principles of the Lagrangian mechanics. Since the governing equations have no closed-form solution, so the numerical method must be applied. So the problem can have different periodic or non-periodic responses to the initial conditions. The proper initial conditions were obtained from combining the third-order approximation of the Unperturbed Restricted Three-Body Problem and the orbital correction algorithm in previous researches. This method required complex and time-consuming mathematical calculations. Therefore, in this paper, the suitable initial conditions of periodic Lyapunov orbit are suggested to identify with the Poincaré map. Poincaré maps are a valuable tool for capturing the dynamical structures of a system, such as periodic solutions via a discrete and lower-dimensional representation of the dynamical flow. The center and boundaries of the islands created in this map are considered as suitable initial conditions to meet the periodic responses. To validate the proposed method, the perturbed Lyapunov orbits family is plotted. Also, in order to illustrate the effect of perturbations, the initial conditions of the perturbed and unperturbed models are compared due to the same initial guess vectors.

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.

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.

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.

In this paper, a new methodology to develop an optimum flying law using model predictive control algorithm for a third order non-minimum phase system is presented. The guidance law of the optimum line of sight strategy may be extracted for an ideal non-minimum phase control model of first, second and third order. Optimization algorithm of controller has been introduced and the simulation results for the non-minimum phase system is provided. The results indicate efficiency of the proposed controller in alleviating the adverse effect of the non-minimum phase system and the proposed method could be extended to use in other systems with higher order and complexity in online applications.

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.

In this paper, a new methodology has been proposed to enhance the conformal mapping applications in the process of optimum trajectory planning in Terrain Following (TF) and Terrain Avoidance (TA) Flights. The new approach uses the conformal mapping concept as a flattener tool to transform the constrained trajectory-planning problem with flight altitude restrictions due to the presence of obstacles into a regenerated problem with no obstacle and minimal height constraints. In this regard, the Schwarz–Christoffel theorem has been utilized to incorporate the height constraints into the aircraft dynamic equations of motion. The regenerated optimal control problem then is solved employing a numerical method namely the direct Legendre-Gauss-Radau pseudospectral algorithm. A composite performance index of flight time, terrain masking, and aerodynamic control effort is optimized. Furthermore, to obtain realistic trajectories, the aircraft maximum climb and descent rates are imposed as inequality constraints in the solution algorithm. Several case studies for two-dimensional flight scenarios show the applicability of this approach in TF/TA trajectory-planning. Extensive simulations confirm the efficiency of the proposed approach and verify the feasibility of solutions satisfying all of the constraints underlying the problem

The main goal of this research is the conflict resolution and collision avoidance between multi low altitude aircraft using differential game theory. The conflict resolution is investigated as a cooperative differential game using a non-inferior method. In this study, the problem is considered as a constrained nonlinear differential game and is transformed into a single objective function using the weighted combination of aircraft objective functions. The objective function obtained along with all functional and environmental constraints will be solved in nonlinear programming using the pseudo-spectral method. The three degrees of freedom with performance constraints are used to model the problem. Also for the validation, the problem of conflict resolution will be solved in four different examples using the performance characteristics of a real aircraft based on low altitude flight rules. In these examples, the impact of priority coefficients on the flight path, the impact of the presence and constraint of the flight space on two-dimensional and three-dimensional space will be examined. The results show that in order to resolution of conflict base on the flight priority, it affects the control effort and flight path of each of the conflicting aircraft. This flight priority can be based on the need for airlines, flight delay, number of passengers or etc.

The design structure matrix (DSM) is a potent tool in the management of product design processes. Although the compactness and ability to represent design cycles are the main advantages of DSMs over existing traditional tools, the intact whole DSM is not always an understandable piece of information. To overcome this shortcoming, certain analyses have been proposed for a better understanding of the matrix in which partitioning and tearing have significant importance. There are several algorithms for these two analyses that mainly focus on a few rules of thumb. Although partitioning and tearing were originally developed for binary DSMs, they can be extended to numerical variants in which the work transformation matrix (WTM) is of the highest fame and application. In this paper, the authors have proposed an algorithm inspired by the formation of sugar crystals in saturated syrup for reordering the activities in a coupled block of activities (CBAs) based on their level of coupling. To implement this approach, a code was developed to achieve pseudo-optimum solutions. By using a discrete-time simulation, which was applied to an aerospace case study, it was demonstrated that the method produces restructured schemes of the WTM that are comparable/superior to the classical methods.

Developing aerospace products in the shortest possible time is one of the most important market competitive parameters. Meanwhile, inherent complexity of these products leads to large information cycles that increase completion time, significantly. As a result, the shortest completion time beside acceptable quality becomes an inevitable necessity. In this paper, “Minimum-Risk Execution Plan (MREP)” is used to improve the conceptual design process of EH101 utility helicopter as the case study. The plan is formed around iteration management and reducing completion time in framework of Work Transformation Matrix (WTM). MREP is a work policy based on beginning with tasks with the highest couplings and by progressing the design process, adding the others in a gradual manner. The method can be described as the art of effective arrangement of design tasks while observing rework risk. Discrete-time simulation results show the supremacy of the proposed method over existing models in regard of completion time while the rework risk is maintained in the lowest possible level.

The main goal of controlling urban wastewater treatment plants is to adopt an algorithm in which the process works in optimal operating conditions. For this purpose, we need to use the process mathematical model. In this study, the steps of building the enchmark Simulation Model No. 1 (BSM1) were presented step by step. Appropriate numerical methods were proposed for solving the simulation model, and the most effective parameter of the process was determined to provide control strategies. Finally, behavior of the process was examined against different weather conditions. The initial values inside the reactors and the clarifier layers were calculated by solving the state equations of each reactor. Using the Euler and Range Kutta hybrid numerical approach, the BSM1 simulating model was created in MATLAB environment. By applying different weather conditions, the behavior of the treatment process was investigated. Findings: Applying more than one numerical solution to solve the simulation model reduced significantly the amount of additional calculus and time, as a very important item in predictive controlling systems. Make use of different control strategies, necessarily do not improve the quality of all process parameters. Nitrogen-containing parameters, especially ammonia nitrogen, are the most effective control parameters in activated sludge process. This process complies effluents standard limits of chemical oxygen demand (COD), 5- day biological oxygen demand (BOD5), and total suspended solids (TSS) with significant difference. Only in nitrogen parameter, we see some violations of the standard. The model that is created for the first time in the country can be used for different purposes in the fields of process recognition and operation.

In this paper, the combination of reaction wheels and thrusters is applied to attitude control of a satellite. First, governing equations of satellite attitude dynamics are given using quaternion and PID controller is designed based on the satellite quaternion to determine the applied control torque. By applying the reaction wheels physical constraints such as its maximum torque, its maximum momentum and maximum power on the desired torque, reaction wheels angular momentums and torques are found. The obtained results show that the unsaturated reaction wheels capabilities in attitude control. Results also show that the wheels saturation leads to error in control and increases the Euler angles and quaternions. Satellite thrusters are utilized to reaction wheels de-saturation and attitude control simultaneously. Three different strategies are proposed in this paper for wheels de-saturation using thrusters. Two well known methods, pulse width modulator (PWM) and pulse width pulse frequency (PWPF) modulator are used to attitude control using thrusters. All methods are compared together and the optimal method is proposed for the satellite attitude control. This paper results can be useful in design and control of different class of satellites.

In the present paper the problem of designing a flying vehicle trajectory to avoid the collision with Terrain by limiting the flight range in a flight corridor influenced by the shape of the terrain has been investigated. In order to improve the traceability of the designed trajectory, considering the performance characteristics of the aircraft, the effect of two performance parameters including of the maximum rate of climb and the maximum increasing rate of the flight path angle, are considered in the solution algorithm. In this regard, the quantification of the system performance, has been implemented during the definition of different cost functions to minimize the operating time, control effort and vertical acceleration imposing on the aircraft. Mathematical modeling of the terrain which is considered as the route location of the threat, has been implemented using a power polynomial solution for smoothing. Finally, optimal control theory and nonlinear programming approach are utilized to solve the defined problem. The evaluation of case studies and numerical simulations confirmed the effectiveness of the proposed approach to solve the planning problem in flying maneuvers with low altitude requirements for follow and avoidance of direct and indirect environmental hazards.

This paper investigates effect of coupling of satellite translational dynamics and rotational kinematic aiming to design of geosynchronous satellite formation flying at drift phase to the determined operational nominal position at the orbital window in the geosynchronous orbit. Firstly, dynamical and kinematical equations of satellite, and then, the interaction of translational and rotational motion at drifting to the final position at the target orbit by considering satellite as a rigid object have been studied. Despite of similar studies utilized simplifications such as circular assumption of target orbit or various linearization methods, presented analysis of this paper are based on the general form of nonlinear translational equations. According to acquired results of investigating the coupled dynamics at the drift phase to the determined position at the orbital window by considering different attitudinal situations, drift considerations and procedure in presents of other satellites at the orbital window have been presented. Position and attitude of satellite have been controlled by utilization of PD control law associated with the optimized gains based of PSO optimization algorithm aiming to minimizing control effort and fuel and consequently minimizing fuel consumption and increasing satellite operational life. Acquired results from simulations represent effectiveness of the proposed methodology.

In this paper, minimum-time low-thrust planar orbit transfer problem is solved by fuzzy optimal control. Trajectory dynamic restricting assumptions and using analytical averaging method, the governing equations of orbit transfer problem in its desired form with constant acceleration magnitude is achieved. Then, using Euler discretization method, the whole differential dynamic equations, performance function and transversality conditions are represented in a discrete form. Calling membership function concept of fuzzy environment, this algorithm transfers classical optimal control including performance index and trajectory transversality conditions associated with uncertanities to fuzzy environment. Thereafter, introducing slack variables all the inequalities change to equality conditions. Applying Bellman-Zadeh approach, optimal control problem turns to parameter optimization problem which then is solved by Lagrange multipliers technique. Finally, solving the set of nonlinear algebraic equations made by optimality necessary conditions simultaneously is achieved by nonlinear programming method. Numerical fuzzy optimal control results are validated with available analytical results which show the priorities of this method in orbit transfer trajectory optimization in presence of uncertainities. FOC approach is categorized into direct methods for solving optimal control problems, while it is far from their defects e.g. curse of dimensionality and burdensome computational load so that it applies fuzzy approach and expert knowledge to simply solve the problems.