Space systems design (spacecraft, satellites, space stations and their equipment)
Amirreza Kosari; Asad Saghari; Masoud Khoshsima
Volume 14, Issue 4 , December 2021, , Pages 1-9
Abstract
This article investigates an operational orbit's design and sensitivity analysis for Earth observation (EO) missions in non-sun-synchronous orbits. Sun-synchronous orbits are the primary choice for deploying EO satellites, but in the absence of access to such orbits, alternative options can be considered, ...
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This article investigates an operational orbit's design and sensitivity analysis for Earth observation (EO) missions in non-sun-synchronous orbits. Sun-synchronous orbits are the primary choice for deploying EO satellites, but in the absence of access to such orbits, alternative options can be considered, including multi-sun-synchronous orbits (MSSO) capable of repeating ground track (RGT).In this research, sets of such orbits are designed, taking into account the defined mission and considering the available altitude and inclination of the orbit. To achieve this, a constrained search problem is formulated, considering the constraints related to the characteristics of multi-sun-synchronicity and repeating ground tracks to search for orbit characteristics.Furthermore, to identify the allowable range of injection errors, a sensitivity analysis of the designed orbit's characteristics has been conducted to assess their sensitivity to uncertainties in injection accuracy during a case study investigation.
Space systems design (spacecraft, satellites, space stations and their equipment)
Hojat Taei; Amirhossain Adami; Mansour Hozuri
Volume 14, Issue 4 , December 2021, , Pages 85-98
Abstract
The need to improve the reliability and safety requirements, has led to increasingly utilization of reliability based design approaches. In this study, reliability based multidisciplinary design optimization for a bipropellant propulsion system has been investigated. The objective function is minimizing ...
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The need to improve the reliability and safety requirements, has led to increasingly utilization of reliability based design approaches. In this study, reliability based multidisciplinary design optimization for a bipropellant propulsion system has been investigated. The objective function is minimizing the total system mass and design constraints are the total impulse and the temperature of the wall of the combustion chamber. Monte Carlo simulation methodology is used to apply uncertainties in the problem and to show the reliability of the system under these uncertainties. The mass, functional and geometric results of the bipropellant propulsion system are differentiated for optimal design, reliability based design and optimal reliability based design. Then, considering the results, the concepts and definitions of design methods are compared and discussed and it is shown that the reliability based multidisciplinary optimization while having the desired mass, has high reliability.
Space subsystems design: (navigation, control, structure and…)
M. Navabi; H. Ghanbari
Volume 13, Issue 2 , June 2020, , Pages 79-86
Abstract
In this paper, attitude control of spacecraft in the presence of uncertainties and disturbances has been simulated. Access to rapid maneuver in spacecraft decreased accuracy. Therefore, to enhance the accuracy of spacecraft rapid maneuver and to resist uncertainties the adaptive control L1 is suggested. ...
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In this paper, attitude control of spacecraft in the presence of uncertainties and disturbances has been simulated. Access to rapid maneuver in spacecraft decreased accuracy. Therefore, to enhance the accuracy of spacecraft rapid maneuver and to resist uncertainties the adaptive control L1 is suggested. The controller is able to control the attitude of the spacecraft due to rapid adaptation and robustness against uncertainties simultaneously. In this paper, an adaptive control of L1 is compared with reference model. The dynamics of the multi-input-multi-output system. Simulation results show the desired performance of the L1 controller.
Space systems design (spacecraft, satellites, space stations and their equipment)
Hamed Hashemi Mehneh; amirreza Ghedamini Harouni
Volume 12, Issue 4 , December 2019, , Pages 1-17
Abstract
The robust multi-disciplinary, multi-objective shape optimization of re-entry capsule with aero-thermodynamic, trajectory, stability and the geometry considerations are presented in this paper. In this research, the results of maximizing the volumetric efficiency of the capsules while minimizing the ...
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The robust multi-disciplinary, multi-objective shape optimization of re-entry capsule with aero-thermodynamic, trajectory, stability and the geometry considerations are presented in this paper. In this research, the results of maximizing the volumetric efficiency of the capsules while minimizing the ballistic coefficient and the longitudinal stability derivative with considering uncertainties are discussed in presence of some constraints on geometry, heating load, and load factor. To reduce the time and cost of robust optimization, the Adaptive Monte Carlo Simulation technique is used which decreases the number of required evaluations within the robust optimization process. Utilizing the constrained multi-objective genetic algorithm will result in a collection of robust optimal solutions. The results show that the performance of obtained robust optimal configurations is in a way that the considered constraints aren’t violated with 99.8% of confidence level even in the presence of uncertainties.
Amirhossain Adami; Hojat Taei; Mansour Hozuri
Volume 12, Issue 1 , April 2019, , Pages 41-53
Abstract
Considering the importance of the presence of uncertainties in the design of complex engineering systems, in this research multidisciplinary design optimization process for a bipropellant propulsion system in the presence of uncertainties, which in addition to minimizing the system mass, has a high robust. ...
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Considering the importance of the presence of uncertainties in the design of complex engineering systems, in this research multidisciplinary design optimization process for a bipropellant propulsion system in the presence of uncertainties, which in addition to minimizing the system mass, has a high robust. Based on this, the multidisciplinary design view of the bipropellant propulsion system is expressed in both optimum design and optimum robust design. The continued with the application of uncertainties, the mass, operational and geometric results of the propulsion system are expressed in terms of optimum design, robust design and optimum robust design. According to the results, it is shown that the lowest mass occurs in optimum design mode. But with uncertainties, it is observed at this point that it has the least robust and reliability. It also attempts to explain the difference between the concepts of robust design and optimum design with the help of results
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.
atefeh hoseinzadeh; Amirhossain Adami; Asghar Ebrahimi
Volume 10, Issue 4 , March 2018, , Pages 29-40
Abstract
The atmospheric re-entry phase is one of the most significantmission steps in the space missions;hence, theguidance and control of reentry vehicles in this phase of mission is important. In this article, a reentry vehicle guidance algorithm has been proposed which has suitable robustness in the presence ...
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The atmospheric re-entry phase is one of the most significantmission steps in the space missions;hence, theguidance and control of reentry vehicles in this phase of mission is important. In this article, a reentry vehicle guidance algorithm has been proposed which has suitable robustness in the presence of initial reentry parameters uncertainties. Here,it has been tried to minimize the landing errors at terminal point using Nonlinear Quadratic Tracking (NQT) and chasing a reference trajectory. In order to define several trajectories with different initial states using evolutionary genetic algorithm with changes in weighting matrices Q and R, it hasbeen tried to reduce the errors of landing at terminal point. The reentry position of the reentry vehicles may be different from the desired ones with respect to several events. In this situation, reentry vehicles start to move in a new trajectory which is not suitable. Therefore, the reentry vehicles should be guided to come back into the desired trajectory or a new optimum trajectory needs to be redesignedto have the same target position on the ground. To do this, we need optimum weighting matrices R and Q for every new trajectory. In this article, this problem has been resolved using partial least squares regression; meanwhile, obtaining the optimal matrices by genetic algorithms needed many times. Also,it is shown that using this method, in the presence of reentry uncertainties, weighting matrices for each new initial condition hasbeen quickly derived. Additionaly,through the matrices obtained and the nonlinear quadratic tracking controller, reentry vehicle was directedto the target with a good accuracy. The Monte Carlo analysis has been used to evaluate the performance of the proposed algoritm. According to the results, the proposed algoritm has a suitable accuracy level and it can generate the online optimum trajectory.
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 ...
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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.
Mohammad Reza Mortazavi; Ali Reza Alikhani
Volume 8, Issue 1 , April 2015, , Pages 27-41
Abstract
This paper presents a suitable technique for nonlinear control of a flexible spacecraft in proximity operations. To do proximity operations well, the pursuer spacecraft must place itself in a pre specified location relative to target and align its docking port to target’s docking port while keeping ...
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This paper presents a suitable technique for nonlinear control of a flexible spacecraft in proximity operations. To do proximity operations well, the pursuer spacecraft must place itself in a pre specified location relative to target and align its docking port to target’s docking port while keeping their attitude compatible. This procedure usually needs large, fast and accurate manoeuvres which can cause flexible structure vibrations. In addition, external disturbances, actuator saturation and model uncertainties increase difficulties of achieving such a goal. Consequently it is necessary to utilize an effective and nonlinear controller design approach to overcome these challenges. To perform considered scenario successfully, in this paper we use a method in nonlinear optimal control called State Dependent Riccati Equation (SDRE). Simple formulation and tuning as well as good performance and satisfactory robustness are some advantages of this approach in unified control of the spacecraft position, attitude and flexible motion during a proximity operation. 6DoF simulations show good performance of controller in presence of structure flexibility, parametric uncertainties, input uncertainty and saturation and external disturbance.
Reza Mohsenipour; Mehrzad Nasirian; Abdol Reza Kashaninia; Mohsen Fathi
Volume 8, Issue 1 , April 2015, , Pages 61-71
Abstract
Increasing in dimensions of the satellites and using light movingstructures, causes flexibility and uncertainty in their models. Therefor to control the attitude of the satellites, should use those methods which resist against the plant’s model uncertainty and could reject the disturbance and the ...
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Increasing in dimensions of the satellites and using light movingstructures, causes flexibility and uncertainty in their models. Therefor to control the attitude of the satellites, should use those methods which resist against the plant’s model uncertainty and could reject the disturbance and the measurementnoise. One of these methods is the robust control. But due to the location of the poles in the dynamic equations of the satellite, the design of robust controllers faces some problems. In this paper, using aninternal feedback, the dynamic equations are changed so that the poles are located in a more proper place. And then,considering flexibility affects as uncertainty and also, uncertainty in inertia matrix of the satellite, a H∞ controller, and finally to improve the performance, a µ-controller will be designed for the new equations. But these two controllers will be analyzed and compared for the primary equations and not for the new equations.For comparison, a classical controller is also designed forthe primary system.
