space sciences and exploration
Iman Shafieenejad
Articles in Press, Accepted Manuscript, Available Online from 25 July 2023
Abstract
The aim of this research is to optimize the trajectory of a low-trust spacecraft carrying biological cargo. Reducing the radiation stresses of the Van Allen belt is the optimal criterion of the optimal control problem of the orbital transfer from the low orbits to the high orbits. Since the minimum radiation ...
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The aim of this research is to optimize the trajectory of a low-trust spacecraft carrying biological cargo. Reducing the radiation stresses of the Van Allen belt is the optimal criterion of the optimal control problem of the orbital transfer from the low orbits to the high orbits. Since the minimum radiation stress criterion introduced in this article is not among the conventional optimality criteria, solving the above optimal control problem will be complicated and the honey bee optimization method has been used. The optimization of the path in this article is done by rewriting the motion equations based on the control variable and solving the new motion equations with the help of bee optimization. The main advantage of the method used in this problem is the use of optimal control theory and population-based optimization methods with a global approach. In the presented new method, the optimal control problem is simplified by redefining the differential equation system, and the results show the accuracy and ease of solution. Results of the optimal criterion of the minimum time and the minimum radiation stresses presented in this article, the criterion of the minimum radiation causes an increase of 8.89% in the transfer time.
Space systems design (spacecraft, satellites, space stations and their equipment)
Hojat Taei; Pourya Shokrolahi
Volume 13, Issue 2 , June 2020, , Pages 87-96
Abstract
The final phase of orbital rendezvous and docking has been studied in this article. The main objective is to control the position of a chaser that can reach the target in the minimum time, or in other words, bypassing the optimal path. Another important objective of this paper is the minimum energy consumption. ...
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The final phase of orbital rendezvous and docking has been studied in this article. The main objective is to control the position of a chaser that can reach the target in the minimum time, or in other words, bypassing the optimal path. Another important objective of this paper is the minimum energy consumption. In the dynamic simulation, the equations of the linear form of Clohessy-Wiltshire (CWH) equations have been utilized. In linear CWH equations, the change in either direction of X or Y will result in the change in another direction and will affect the orbital docking operation. In order to achieve the objectives of this paper, the design variables should be optimized; To optimize the design variables, two methods, i.e. genetic algorithm (GA) and particle swarm optimization (PSO), have been used. Finally, to evaluate the real conditions, the results will be investigated by applying uncertainty in the outputs of thrusters.
atefeh hoseinzadeh; Amirhossain Adami; Asghar Ebrahimi
Volume 11, Issue 1 , June 2018, , Pages 1-12
Abstract
The atmospheric reentry phase is one of the most important mission steps in space missions, therefore, the guidance and control of reentry vehicles in this phase of mission is important. In this article, a reentry vehicle guidance algorithm is proposed which has suitable robustness in the presence of ...
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The atmospheric reentry phase is one of the most important mission steps in space missions, therefore, the guidance and control of reentry vehicles in this phase of mission is important. In this article, a reentry vehicle guidance algorithm is proposed which has suitable robustness in the presence of initial reentry parameters uncertainty. To use any conductive method, first the motion equations must be obtained. In this paper, quadratic nonlinear control method is used to guide the vehicle. In this regard, the equations of motion of reentry vehicles are developed in form of state space and the system and control matrices depending on the state and control variables are extracted. In this article, it is tried to minimize the landing errors at terminal point using Nonlinear Quadratic Tracking (NQT) and chasing a reference trajectory. In order to define a trajectory with different initial states using evolutionary genetic algorithm with changes in weighting matrices Q and R, it is tried to reduce the errors of landing at terminal point. Monte Carlo analysis is used to evaluate the performance of the proposed algorithm. According to the results, the proposed algorithm can reduce the errors more than 90% in the presence of reentry initial parameter uncertainties.
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 ...
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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.
M. H. Korayem; M. Nazemizadeh; H. N. Rahimi
Volume 5, Issue 2 , July 2012, , Pages 25-34
Abstract
Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space ...
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Flexible manipulators have plentiful applications in Aero-Space fields, due to their less weight and maneuverability. In fact, the ratio of their load carrying capacity to their weight, make them more excellent over their rigid ones. Moreover, these manipulators are known as good candidates in Aero-Space applications because of their less energy consumption, and smaller actuators. In this paper, the dynamic modeling of the flexible manipulators are performed using Finite Element Method (FEM), and optimal control of point-to-point motion of robot is done via optimal control method. To dynamic modeling of flexible manipulator, each link of the robot is divided into sufficient elements, and total displacement of the element is presumed as summation of a rigid displacement and a displacement because of flexibility. By means of Lagrange’s principle, dynamic equations of the flexible robot are derived, and the effect of number of the on dynamic motion of the robot is considered. Also, for the optimal point-to-point motion planning of the elastic manipulator, the nonlinear dynamic equations of the robot is assumed as constraints of optimal control problem, and a proper cost function is defined including torque and speed terms. Then, variation of calculus and Pontryagin’s minimum principle are employed and optimality conditions are resulted in a set of nonlinear differential equations, which is solved numerically. The priority of the optimal control method on the optimal motion planning of the flexible manipulator is discussed, and simulations for a single-link elastic robot illustrate the applicability of the method.
M. Mortazavi; D. Abbasi-Moghadam
Volume 3, Issue 2 , January 2011, , Pages 69-76
Abstract
هدف اصلی مقاله حاضر، هدایت بهینه و برخط اجسام بازگشتی به زمین است. روند دستیابی به این مهم مبتنی بر روش بسط مجانبی هماهنگ است که یکی از روشهای خانوادة اغتشاشات تکین است ...
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هدف اصلی مقاله حاضر، هدایت بهینه و برخط اجسام بازگشتی به زمین است. روند دستیابی به این مهم مبتنی بر روش بسط مجانبی هماهنگ است که یکی از روشهای خانوادة اغتشاشات تکین است و به کمک روش تغییر اکسترمالها تقویت شده است. روش جدید حاصل MAEOGکه مخفف کلمات مربوط به هدایت بهینة مبتنی بر بسط مجانبی هماهنگ است ضمن ارائة راه حل با دقت قابل قیاس با روشهای دیگر، بسیار سریع مسئله را به جواب میرساند و زمان حل را کاهش میدهد. به علاوه، این امکان را میدهد که چه برا و چه زاویة رول به عنوان متغیرهای کنترل در نظر گرفته شوند. ویژگیهای روش جدید برای توسعة الگوریتم هدایتی بازگشت به زمین کاملاً مناسب به نظر میرسند.
S. H. Jalali-Naini
Volume 2, Issue 3 , December 2009, , Pages 1-12
Abstract
In this paper, a closed-loop optimal guidance with final position and velocity constraints is obtained by applying time-varying weighting coefficient in the performance index in order to shape the commanded acceleration. The control system is assumed to be linear, time-varying, and of arbitrary order ...
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In this paper, a closed-loop optimal guidance with final position and velocity constraints is obtained by applying time-varying weighting coefficient in the performance index in order to shape the commanded acceleration. The control system is assumed to be linear, time-varying, and of arbitrary order with a throttleable engine. The acceleration due to drag is also modeled as a linear function with respect to velocity vector multiplied by a given function of time. In addition, different weighting functions are suggested for different acceleration constraints, such as maximum dynamic pressure, separation of stages, and zero acceleration at the final time. Finally, the performance of the guidance law for a combined weighting function is evaluated and discussed.
R. Jamilnia; A. Naghash
Volume 1, Issue 2 , December 2008, , Pages 35-42
Abstract
In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is ...
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In this paper, a new approach is proposed for solving the problem of optimal low thrust orbit transfer. In this approach, the problem of trajectory optimization of optimal orbit transfer is defined by modified equinoctial orbital elements. For solving this problem, direct collocation method, that is an efficient numerical method for solving optimal control problems, is used. By using this method, the problem of trajectory optimization is fully discretized and converted to a nonlinear programming problem. This discrete problem with large numbers of variables and constraints is solved by a powerful nonlinear programming solver (IPOPT). Finally, optimal state and control variables are achieved for optimal orbit transfer with minimum fuel consumption.
S. A. Fazelzadeh; Gh. A. Varzandian
Volume 1, Issue 2 , December 2008, , Pages 43-50
Abstract
In this study, optimal low-thrust spacecraft trajectories are obtained by time-domain finite element method. Equations of motion are expressed in state-space form. The performance index is considered as minimum time. The problem has been formulated through the variational approach. The time-domain finite ...
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In this study, optimal low-thrust spacecraft trajectories are obtained by time-domain finite element method. Equations of motion are expressed in state-space form. The performance index is considered as minimum time. The problem has been formulated through the variational approach. The time-domain finite element discretized form of the performance index, state equation constraints and the related boundary conditions are presented. By setting out the discrete equations, a set of nonlinear algebraic equations is generated and by using Newton–Raphson method, optimum answer is attained. The effects of the number of time segments on the performance index are examined. Furthermore, the influences of effective exhaust velocities on the optimal trajectory are demonstrated.
