Space subsystems design: (navigation, control, structure and…)
hamid reza ali mohamadi; Hassan Naseh
Articles in Press, Accepted Manuscript, Available Online from 25 September 2023
Abstract
Achieving to new technologies with high reliability, along with reducing the cost and time of the design cycle, is one of the most important challenges in complex systems. In this paper, reliability based design of a space system is discussed in the conceptual design phase. Normally, there are eight ...
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Achieving to new technologies with high reliability, along with reducing the cost and time of the design cycle, is one of the most important challenges in complex systems. In this paper, reliability based design of a space system is discussed in the conceptual design phase. Normally, there are eight steps in the design for reliability. The first step, planning, and the next seven steps that applied for the liquid propellant engine with electro-pump technology included: determination of failure modes; reliability modeling; reliability allocation; propagation of uncertainty; Implementation of the chosen method in reliability analysis; reliability prediction and reliability evaluation. Therefore, in this research has been performed to achieved method and implementation steps of reliability design in the conceptual design phase of a space system.
Space subsystems design: (navigation, control, structure and…)
Milad َAzimi
Articles in Press, Accepted Manuscript, Available Online from 07 April 2022
Abstract
This paper deals with semi-analytical modeling and stability analysis of a coupled slosh-tank dynamics as a multibody system using the Homotopy Perturbation Method (HPM). The sloshing motion of the liquid inside the tank is considered as the equivalent pendulum model. The nonlinear equations of the motion ...
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This paper deals with semi-analytical modeling and stability analysis of a coupled slosh-tank dynamics as a multibody system using the Homotopy Perturbation Method (HPM). The sloshing motion of the liquid inside the tank is considered as the equivalent pendulum model. The nonlinear equations of the motion under lateral and longitudinal excitations (compressive oscillations) are derived using the Lagrangian approach. In this model, the effects of essential parameters such as viscous damping, amplitude, and frequency of the excitation are studied for two typical points inside and outside the stability regions. It has been shown that viscous damping, compared to other principle parameters, brings the points located in the unstable region closer to the stable region. The simulations in terms of stability diagrams, phase portraits, and time histories of sloshing amplitude are achieved using HPM and compared to the numerical Runge-Kutta method to follow the stability phenomena and highlight the analytical approach's validity.
Space subsystems design: (navigation, control, structure and…)
Moslem Karim Abadeh; Morteza Tayefi
Articles in Press, Accepted Manuscript, Available Online from 09 April 2024
Abstract
In this study, the control of a space capsule during the re-entry phase is examined. Re-entry is one of the most important phases of a spacecraft's mission because when the spacecraft enters the Earth's atmosphere, aerodynamic forces and moments will disturb the angles of attack and side slip. These ...
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In this study, the control of a space capsule during the re-entry phase is examined. Re-entry is one of the most important phases of a spacecraft's mission because when the spacecraft enters the Earth's atmosphere, aerodynamic forces and moments will disturb the angles of attack and side slip. These disturb angles, if not controlled, can cause serious injuries to the spacecraft and its passengers. To eliminate the disturbances, moving mass controllers have been used as an operator. Moving mass controllers (MMC) control the flying device by creating an internal force. The main advantage of moving mass controllers compared to other operators such as aerodynamic surfaces and thrust jets is the non-production of turbulent aerodynamic force (which can disrupt the controller's performance) due to the creation of internal force. Another important factor is the mechanism of moving mass controllers. In this research, in addition to the cross mechanism, which is a more common mechanism, the radial mechanism has also been examined. A non-linear controller is needed in order to use the radial mechanism, and in this research, a non-linear proportional-integral-derivative controller is suggested.
Space subsystems design: (navigation, control, structure and…)
Amir Labibian
Volume 17, Issue 1 , March 2024, , Pages 11-20
Abstract
IIn high resolution remote sensing satellites, meeting stability and pointing requirements are very crucial in mission’s success. In this regard, usually, very accurate gyroscopes are utilized as one of the main attitude sensors. In order to avoid decreasing attitude estimation accuracies, gyroscopes ...
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IIn high resolution remote sensing satellites, meeting stability and pointing requirements are very crucial in mission’s success. In this regard, usually, very accurate gyroscopes are utilized as one of the main attitude sensors. In order to avoid decreasing attitude estimation accuracies, gyroscopes data should be calibrated in appropriate time intervals. In this research an Extended Kalman Filter (EKF) based approach is investigated for gyro calibration. Therefore, at first, a model which contains main gyro parameters, namely, biases, scale factors and misalignments is proposed. Then, an EKF based algorithm for gyro parameters estimation is presented. Next, a Multiplicative Quaternion Extended Kalman Filter (MQEKF) which uses star sensor data as measurement is applied for attitude estimation. Finally, in order to evaluate the performance of the proposed gyro calibration method in attitude control loop, a quaternion feedback controller is implemented. The simulation results show that satellite’s stability and pointing are maintained with accuracies better than 0.005 deg/second and 0.15 deg which demonstrate the proposed method will be beneficial for missions with tight control requirements.
Space subsystems design: (navigation, control, structure and…)
Arian Zakiani; Seyed Hassan Sedighy; Razieh Narimani
Volume 17, Issue 1 , March 2024, , Pages 73-79
Abstract
Due to the limited communication time between LEO satellites and the ground station and large volume of satellite image data, it is necessary to establish a high transmission rate connection. Therefore, the use of a high-efficiency satellite antenna is inevitable. In order to use the limited viewing ...
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Due to the limited communication time between LEO satellites and the ground station and large volume of satellite image data, it is necessary to establish a high transmission rate connection. Therefore, the use of a high-efficiency satellite antenna is inevitable. In order to use the limited viewing time of the satellite, it must be possible to communicate with the ground station at low angles and change the main beam direction of satellite antenna to the direction of the ground station. The proposed array is composed of 8 antenna elements with a compact microstrip feed network. Low profile structure, circular polarization, high gain and low cost specifications of this proposed antenna array, candidate it for conformal array antenna in satellite applications.
Space subsystems design: (navigation, control, structure and…)
Valiollah Shahbahrami; Milad َAzimi; َAlireza Alikhani
Volume 16, Issue 4 , December 2023, , Pages 1-13
Abstract
In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates ...
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In this paper, a robust adaptive hybrid control approach based on a combination of super-twisting and non-singular terminal sliding mode control (STNSMC) approaches for vibration and attitude control of a flexible spacecraft with fully coupled dynamic is developed. The proposed adaptation law eliminates the need for bounds knowledge of external disturbances and uncertainties. Then an ST-based NSMC generates a continuous control signal to reject the Chattering phenomenon, the non-singular terminal switching control law with the ability to generate continuous control commands to eliminate the chattering phenomenon. Moreover, finite-time convergence is achieved, and the singularity problem has been avoided. The overall stability of the system has been demonstrated using the Lyapunov theory. One of the essential features of the proposed control algorithm is to prevent overestimation of control gains and faster convergence rates comparing to conventional ST and non-singular terminal SMC approaches. The simulations in the form of a comparative study for large-angle maneuver reveal the advantage of the proposed approach.
Space subsystems design: (navigation, control, structure and…)
Mohammad Haji Jafari; Afshin ValiMohammad; Mahsa Mahdavi
Volume 16, Issue 4 , December 2023, , Pages 41-56
Abstract
In this research, the dynamic response of a U-12 CubeSat (20x20x30 cm) is investigated for three configurations during the launch conditions. Despite the existence of a successful design for this satellite, adding a mount to install on a standard adapter, the structural design of the satellite has been ...
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In this research, the dynamic response of a U-12 CubeSat (20x20x30 cm) is investigated for three configurations during the launch conditions. Despite the existence of a successful design for this satellite, adding a mount to install on a standard adapter, the structural design of the satellite has been modified for modal computability with the launcher., which is based on 3 general approaches: to apply geometric changes to the structure, changing the extent of the points to improve the limitations of connecting to the launcher, and rearranging the internal system components regarding the standards and principles of compatibility and proximity. Therefore, more than the addition of the adapter mount and a few changes in the separating plates, a spire has been added to the structure, which has caused a change in the internal arrangement, including the halving of the fuel tank (by reducing the capacity of 595 cubic centimeters). Despite the increase of 370 grams of total mass, the natural frequencies of the system have been increased enough without the need for redesign and there will be no frequency interference with the frequency spectrum of the launcher.
Space subsystems design: (navigation, control, structure and…)
Ali Kasiri; Farhad Fani Saberi; Vahid Joudakian
Volume 16, English Special Issue , November 2023, , Pages 1-23
Abstract
Many studies have investigated the problem of external disturbance rejection and also increasing the attitude control system's robustness against the parametric uncertainties. Due to stochastic properties, noise effect minimization becomes an interesting and challenging problem in the field of spacecraft ...
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Many studies have investigated the problem of external disturbance rejection and also increasing the attitude control system's robustness against the parametric uncertainties. Due to stochastic properties, noise effect minimization becomes an interesting and challenging problem in the field of spacecraft attitude control that has been underestimated, while control actuators and attitude sensors themselves are important sources of noise generation., the main purpose of this paper is to (i)control the satellite’s attitude and (ii)minimize the variance of output, simultaneously. The Minimum Variance controller, which is considered the simplest type of model predictive controller, has a powerful capability for minimizing the effects of output noise. This feature makes it a suitable control scheme for space-based high-resolution photography missions. so,, we described the conventional Minimum Variance regulator method at first, then an Incremental version of the regulator has been presented to solve the tracking problem. Finally, the generalized minimum variance controller which can control both minimum-phase and non-minimum-phase systems is derived for a high pointing accuracy spacecraft. The simulation results show the efficiency of the proposed controller to restrain the noise effects in a high-resolution tri-stereo imaging mission.
Space subsystems design: (navigation, control, structure and…)
Abbas Dideban; Alireza Ahangarani Farahani
Volume 16, English Special Issue , November 2023, , Pages 25-38
Abstract
This paper presents a new control methodology based on Continuous Time Delay Petri Nets (CTDPN) tool for the attitude control of satellite simulator. The graphical and mathematical features of this tool help the expert designer to design an appropriate controller using graphical model easily, and then ...
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This paper presents a new control methodology based on Continuous Time Delay Petri Nets (CTDPN) tool for the attitude control of satellite simulator. The graphical and mathematical features of this tool help the expert designer to design an appropriate controller using graphical model easily, and then apply the necessary changes to the mathematical model. In this approach, the controller gains are derived from the states and some other variables. Thus, the system states and variables must be available. The new gain tuning algorithm consists of three stages. First, A simulation environment is made for mathematical modeling based on the CTDPN tool and controller design. Secondly, using optimal methods, the controller gains are calculated at any given time and the data are collected. Finally, using the database, a relationship between the set of variables and the gains are derived. Experimental results indicate the promising performance of the controller in comparison to the conventional controller applied to the satellite simulator platform. The results indicate that the designed controller is robust against variation of parameters, as the controller gains are tuned based on the system state and variables.
Space subsystems design: (navigation, control, structure and…)
Arash Abarghooei; Hassan Salarieh; Pedram Hosseiniakram
Volume 16, English Special Issue , November 2023, , Pages 51-64
Abstract
Linear algorithms are the most widely used method for satellite attitude control using reaction wheels because of their simplicity and low computational cost. The first part of the paper introduces different attitude determination and control algorithms, and reviews resources that utilized optimal linear ...
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Linear algorithms are the most widely used method for satellite attitude control using reaction wheels because of their simplicity and low computational cost. The first part of the paper introduces different attitude determination and control algorithms, and reviews resources that utilized optimal linear and nonlinear control methods (such as LQR and SDRE). Next, dynamic equations for the control of the satellite using reaction wheels have been extracted, then the satellite controller has been designed by using optimal linear and nonlinear methods, which are robust against noise and disturbance, as an alternative for the PD controller. Finally, the designed control algorithms have been implemented for different satellite pointing scenarios, and by simulating these methods in MATLAB software, their performance has been studied and compared.
Space subsystems design: (navigation, control, structure and…)
Milad َAzimi; Samad Moradi
Volume 16, Issue 3 , September 2023, , Pages 15-26
Abstract
This paper deals with form-finding and free vibration analysis of a pre-stressed class-one triplex tensegrity structure. The form-finding is performed via a two-step procedure, the nodal coordinates connectivity matrix, and structural element force density determination. Accordingly, the possible states ...
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This paper deals with form-finding and free vibration analysis of a pre-stressed class-one triplex tensegrity structure. The form-finding is performed via a two-step procedure, the nodal coordinates connectivity matrix, and structural element force density determination. Accordingly, the possible states for the nodal coordinates and the structural force density of the triplex prism have been determined by trial and error (based on topology and member type knowledge) to satisfy the force density, and equilibrium matrices rank requirements. Based on different structural topologies, the equation of the motion in the frequency domain for free vibration analysis of the system is derived using the spectral element approach and dynamic shape functions. Simulations are provided for different system heights and the top-bottom aria ratios and compared with the FEM. The numerical simulations in the form of a comparative study of the natural frequencies of triplex tensegrity prism with different heights and cross-sections represent the system’s robustness with different topologies for single or multi-stage applications.
Space subsystems design: (navigation, control, structure and…)
Hamed Kashani
Volume 16, Issue 3 , September 2023, , Pages 27-36
Abstract
Aerospace systems and subsystems are subjected to impulsive loads due to several reasons like engine start and burnout, separation, and so on. These loads may make temporary or permanent failures in some sensitive components or subsystems. To avoid these failures some constraints should be consider in ...
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Aerospace systems and subsystems are subjected to impulsive loads due to several reasons like engine start and burnout, separation, and so on. These loads may make temporary or permanent failures in some sensitive components or subsystems. To avoid these failures some constraints should be consider in design mechanical process. Another approach can be reducing the load level in transmission path without any change in the source of load and without adding any new component and only with design optimization of available components i.e, structural joints destructive effects of impulsive loads. This paper uses analytical results of joints behavior to present practical solution for minimizing load transmission through the joint
Space subsystems design: (navigation, control, structure and…)
Alireza Ahangarani Farahani; Amirhossain Adami; Hamed Arefkhani
Volume 16, Issue 3 , September 2023, , Pages 79-89
Abstract
In this article, a new approach has been presented in the design of a satellite's status controller using reaction wheels. First, a non-linear controller whose gains depend on the state variables at any moment is proposed. In the first step, the process of extracting control coefficients using the GA ...
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In this article, a new approach has been presented in the design of a satellite's status controller using reaction wheels. First, a non-linear controller whose gains depend on the state variables at any moment is proposed. In the first step, the process of extracting control coefficients using the GA optimizer is described. Then, using the results of a number of tests, sufficient data for meta-modeling of the system is extracted and the relevant control gain functions are optimized using the data bank. The input of the mentioned function is the system states and its output is the control coefficients. Finally, a simulator platform was used to determine and control the position of the satellite based on the air bearing to evaluate the proposed approach. Laboratory test results show that the performance of the proposed method is up to 30% better than the classical PID controller with fixed coefficients.
Space subsystems design: (navigation, control, structure and…)
M. Navabi; M. Salehi
Volume 16, Issue 2 , June 2023, , Pages 63-77
Abstract
In a flying system, attitude control is one of the essential subsystems. In this subsystem, estimating the current state is very important to control the state, which is achieved by considering the attitude sensors. Comprehensive research is being done today to reduce the cost of Attitude sensors in ...
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In a flying system, attitude control is one of the essential subsystems. In this subsystem, estimating the current state is very important to control the state, which is achieved by considering the attitude sensors. Comprehensive research is being done today to reduce the cost of Attitude sensors in applications such as drones, satellite simulation platforms, etc. For this purpose, sensors based on Micro-electromechanical Systems have received much attention due to their small size and low energy consumption. This model of sensors, despite its many advantages, has various noises and disturbances that require the application of fusion and estimation algorithms to obtain an acceptable output. In this research, to determine the attitude of the test platform, data fusion algorithms including complementary filter, Kalman filter, and Extended Kalman filter are implemented on a low-cost sensor. The mentioned estimation methods were implemented on the test platform and by determining the effective parameters in the estimation algorithms, the desired accuracy was obtained. The module obtained in these experiments is comparable to more expensive sensors.
Space subsystems design: (navigation, control, structure and…)
Masoud Khoshsima; Mehran Shahryari ; Sajjad Ghazanfarinia; Shiva Emami; yaser saffar
Volume 16, Issue 2 , June 2023, , Pages 79-91
Abstract
The results show that the lidar in cold orbital conditions has a temperature increase of about 38 degrees Celsius due to thermal design. Also, the range of temperature fluctuations before applying thermal design in the cold state of temperature changes in a circuit is about 14 degrees and after designing ...
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The results show that the lidar in cold orbital conditions has a temperature increase of about 38 degrees Celsius due to thermal design. Also, the range of temperature fluctuations before applying thermal design in the cold state of temperature changes in a circuit is about 14 degrees and after designing these fluctuations have been reduced to about 5 degrees. In hot conditions, the temperature conditions have improved a lot after the design and the maximum operating temperature is about 27 degrees the average temperature has decreased by about 22 degrees, while the temperature fluctuations have also decreased by 21 degrees. A significant temperature increase has occurred in the receiver after applying the thermal design in cold conditions, which is still within the allowed range. This is despite the fact that in hot conditions, after applying the thermal design, there was no significant change in the temperature of the receiver. In the case of the reflector, the conditions are completely different, so the minimum temperature in cold conditions has increased by 42 degrees and the maximum temperature has decreased by 7 degrees in hot conditions. In addition, temperature changes have become more uniform in both cases.
Space subsystems design: (navigation, control, structure and…)
Hamed Ramezani Najafi; S.M.Hossein Karimian; Mohammad Reza Pakmanesh
Volume 16, Issue 1 , March 2023, , Pages 11-21
Abstract
One of the passive components of the satellite Thermal control subsystem is multilayer insulation. In order to prevent air from being trapped between the multilayer insulation layers, which causes the thin layers to inflate and disintegrate during satellite launches, holes are made in the layers. These ...
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One of the passive components of the satellite Thermal control subsystem is multilayer insulation. In order to prevent air from being trapped between the multilayer insulation layers, which causes the thin layers to inflate and disintegrate during satellite launches, holes are made in the layers. These holes in different layers may not be aligned due to heat transfer problems as well as manufacturing constraints. For maximum thermal efficiency of thermal insulation, gas outlets must be designed to have the least resistance to exhaust gas flow, because the air trapped between the layers will greatly reduce the insulation efficiency by leaving a convective heat transfer path between them. In this article, different perforation matrix that have been used in articles are reviewed. By analyzing the computational fluid dynamics of gas outflow from these insulators, the effect of various parameters has been studied.
Space subsystems design: (navigation, control, structure and…)
Mahdi Rivandi; Mehran Mirshams; Mohammad Zarourati
Volume 16, Issue 1 , March 2023, , Pages 75-88
Abstract
To test the Attitude Determination and Control Subsystem of a satellite, it is necessary to have an attitude dynamics simulator, and the simulator must be in a balance condition. Disturbances on the balance system in the simulation include deviations caused by the difference between the center of mass ...
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To test the Attitude Determination and Control Subsystem of a satellite, it is necessary to have an attitude dynamics simulator, and the simulator must be in a balance condition. Disturbances on the balance system in the simulation include deviations caused by the difference between the center of mass and rotation, as well as the movement of two horizontal actuators. The movement of two horizontal actuators is a factor for rotational and vortex motion. In the simulation of experimental models, PID control coefficients are also used to control three axes. The balance system actuators include moving masses and reaction wheel that are installed around the horizontal and vertical axes, respectively. To validate the results, a hardware sample has been developed for laboratory tests. Using the sampling time, models and experimental coefficients, the hardware reaches the accuracy of 0.2 and 0.5 degrees in 25 seconds, respectively, which indicates a suitable accuracy for balancing the simulator of the CubeSat attitude.
Space subsystems design: (navigation, control, structure and…)
Amirhossein Mirzaei; S. Hamid Jalali-Naini; Ali Arabian Arani
Volume 15, Issue 4 , December 2022, , Pages 1-18
Abstract
The miss distance analysis of the first-order explicit guidance law (EGL) is carried out using linearized equation of motion in the normalized form in order to obtain normalized miss distance curves. The initial heading error, constant target, acceleration limit, radome refraction error, and fifth-order ...
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The miss distance analysis of the first-order explicit guidance law (EGL) is carried out using linearized equation of motion in the normalized form in order to obtain normalized miss distance curves. The initial heading error, constant target, acceleration limit, radome refraction error, and fifth-order binomial control system are considered. Moreover, body rate feedback is added to the explicit guidance law as a well-known classical compensation method of the radome effect as in proportional navigation. The analysis is performed for different values of the power of the alpha function, defined as the time decrease rate of the zero-effort miss to unit control input. As a special case, the EGL with unit power gives the first-order optimal guidance strategy for minimizing the integral of the square of the commanded acceleration during the total flight time. For the performance/stability analysis, the rms miss distance versus turning rate time constant and radome slope can be plotted for different values of the power of alpha function.
Space subsystems design: (navigation, control, structure and…)
Morteza Tayefi; Ramin Kamali Moghadam
Volume 15, Issue 3 , September 2022, , Pages 1-9
Abstract
To create drag and reduce the speed of space payloads in the phase of entering the atmosphere, the payload body itself can be used as brake mechanisms without using additional tools. The approach analyzed in this paper is the separation of the nose and then the stability of the cylindrical body in horizontal ...
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To create drag and reduce the speed of space payloads in the phase of entering the atmosphere, the payload body itself can be used as brake mechanisms without using additional tools. The approach analyzed in this paper is the separation of the nose and then the stability of the cylindrical body in horizontal or vertical mode. First, by numerical solution, the cylindrical body is aerodynamically simulated in the flight conditions entering the atmosphere, and the location of the center of mass is designed to achieve static stability. Then, by developing the equations of motion of atmospheric reentry using aerodynamic coefficients and derivatives calculated by DATCOM, the flight parameters for both modes are compared and evaluated. The simulation results show that the horizontal flight is more efficient and is able to create better conditions for opening the parachute and landing. Another advantage of atmospheric reentry flight in horizontal mode is the proper distribution of aerodynamic heating and reduction of heat load in certain points of the payload.
Space subsystems design: (navigation, control, structure and…)
Mohsen Ebrahimi; Amir Farhad Ehyaei
Volume 15, Issue 3 , September 2022, , Pages 11-22
Abstract
In this paper, in addition to investigation and analyzing the dynamic model of a maneuver target, a new method based on the Interaction Multiple Model (IMM) method is presented to solve the tracking problem in presence of measurement noise. In this procedure, two models are used along with an extended ...
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In this paper, in addition to investigation and analyzing the dynamic model of a maneuver target, a new method based on the Interaction Multiple Model (IMM) method is presented to solve the tracking problem in presence of measurement noise. In this procedure, two models are used along with an extended Kalman filter for each model, for estimation of the states related to stochastic target model. To this end, a specific weight is calculated adaptively for each model and the final estimation of the target is obtained from the weighted sum of the modes related to each model. In this paper, second order Markov models are used to better describe the system behavior which leads to a decrease in the number of required motion models. This means that the previous two models are used to decide on the next model, and a much better algorithm is provided than the first-order IMM algorithm.
Space subsystems design: (navigation, control, structure and…)
Seyyed Rashad Rouholamini; Mohammad Ali Amirifar; Alireza Rajabi; Nooredin Ghadiri Massoom
Volume 15, Issue 3 , September 2022, , Pages 33-47
Abstract
In this paper, by creating and developing a code based on thermodynamics and gas dynamics equations, the performance characteristics of a 1N hydrazine monopropellant thruster such as thrust force, specific impulse, characteristic exhaust velocity, and propellant mass flow rate have been studied theoretically ...
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In this paper, by creating and developing a code based on thermodynamics and gas dynamics equations, the performance characteristics of a 1N hydrazine monopropellant thruster such as thrust force, specific impulse, characteristic exhaust velocity, and propellant mass flow rate have been studied theoretically in terms of reaction chamber temperature. In this regard, by taking into account the adiabatic assumption, the reaction chamber temperature of monopropellant thruster has been analyzed zero-dimensionally using the ammonia dissociation rate as an independent variable under equilibrium and non-equilibrium conditions and it has been analyzed one-dimensionally using the hydrazine and ammonia homogeneous and heterogeneous reaction rate constants. Also, the effect of nozzle throat thermal expansion on reaction chamber pressure, thrust force, and propellant mass flow rate and the effect of reaction chamber pressure on ammonia dissociation rate and consequently on reaction chamber adiabatic temperature under thermodynamic equilibrium conditions have been studied.
Space subsystems design: (navigation, control, structure and…)
Mahsa Javaheripour; Ahmad Reza Vali; Vahid Behnam Gol; Firouz Allahverdizadeh
Volume 15, Issue 3 , September 2022, , Pages 67-78
Abstract
Proportional navigation is one of the most widely used methods in guiding flying objects. This method requires the rotation rate of the line between the interceptor and the target to calculate the guidance command. For a variety of reasons, including cost savings, simple sensors are used to measure tracking ...
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Proportional navigation is one of the most widely used methods in guiding flying objects. This method requires the rotation rate of the line between the interceptor and the target to calculate the guidance command. For a variety of reasons, including cost savings, simple sensors are used to measure tracking information, including line of sight angle. Therefore, some non-measurable information such as the angular velocity of the line of sight must be estimated using mathematical equations. Due to the noise and other problems, the use of derivatives is not desirable in this situation. Therefore, in this paper, an extended nonlinear observer is used to estimate the angular velocity of the line. Due to the nonlinear dynamics of the intercepting of flying objects, a nonlinear type of observer has been selected. By performing a computer simulation, the correct operation of the proposed observer is shown.
Space subsystems design: (navigation, control, structure and…)
Milad َAzimi; Samad Moradi
Volume 15, Issue 2 , June 2022, , Pages 1-13
Abstract
This paper presents a study concerning active vibration control of a smart flexible spacecraft during attitude maneuver using thrusters and reaction wheels (RW) in combination and piezoelectric (PZT) sensor/actuator patches. The large-angle maneuver and residual vibration of the spacecraft are controlled ...
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This paper presents a study concerning active vibration control of a smart flexible spacecraft during attitude maneuver using thrusters and reaction wheels (RW) in combination and piezoelectric (PZT) sensor/actuator patches. The large-angle maneuver and residual vibration of the spacecraft are controlled using an extended Lyapunov-based design (ELD) and strain rate feedback (SRF) theory for a two-mode mission. The single-axis fully coupled nolinear rigid-flexible dynamic of the system is derived applying a Lagrangian approach and Finite Element Method (FEM). The overall stability of the system including energetic terms covering a hub and two flexible appendages, torsional spring, RW, and PZT dynamics, has been proved and the control law has been derived accordingly. A pulse-width pulse-frequency (PWPF) modulation is used to alleviate the excitations of high-frequency flexible modes. However, due to the fast maneuver, there are still residual vibrations in the system. Hence, the SRF algorithm using PZT is applied to prepare further vibration suppression. A great feature of the proposed hybrid actuator system is the switching time of the thrusters and RW, which is based on total system energy. The numerical results for a flexible spacecraft with large-angle, agile, and precise maneuver requirements through a comparative study verify the merits of the proposed approach.
Space subsystems design: (navigation, control, structure and…)
M. Navabi; F. Malekpour
Volume 15, Issue 2 , June 2022, , Pages 15-25
Abstract
In the variable parameter linear method, which is used to express systems with time-varying state-space matrices, the stability and performance of the feedback system are guaranteed, and there is a significant potential for improving efficiency. The dynamics of these systems depend on a variable parameter ...
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In the variable parameter linear method, which is used to express systems with time-varying state-space matrices, the stability and performance of the feedback system are guaranteed, and there is a significant potential for improving efficiency. The dynamics of these systems depend on a variable parameter with time, considered in this research as the angular velocity of the reaction wheel. The values of this parameter are during an unknown period but can be measured by system performance. Using the tabulation gain technique, the stability of the variable parameter system is checked, and the tabulation parameter is selected for estimating practical control factors. The convex algorithm can solve the extracted sufficient conditions converted into linear matrix inequality conditions. By solving these controlling conditions, the tabulated gain is obtained to guarantee the stability and performance of the variable parameter system. Numerical simulation results show the success of the proposed method.
Space subsystems design: (navigation, control, structure and…)
Fatemeh Asdaghpour; Fatemeh Sadeghikia; Mohammad Ali Farsi
Volume 15, Issue 2 , June 2022, , Pages 103-113
Abstract
Antennas, which are usually installed on the outer shell of these systems, are therefore always exposed to the thermal fluctuations of the space environment. Thermal fluctuations cause the antenna surfaces to expand, contract and distort and can cause the antenna to malfunction. In this paper, the effects ...
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Antennas, which are usually installed on the outer shell of these systems, are therefore always exposed to the thermal fluctuations of the space environment. Thermal fluctuations cause the antenna surfaces to expand, contract and distort and can cause the antenna to malfunction. In this paper, the effects of thermal expansion and contraction due to an LEO orbital mission on the radial characteristics of two X-band reflective antennas, one broadband antenna and the other narrowband, And the resulting radiation characteristics are compared with the characteristics of equivalent sample antennas at ambient temperature. Analyses show that narrowband antennas are very vulnerable to thermal fluctuations and, therefore, it is necessary to choose the material of the antennas from materials whose thermal expansion coefficient is very small. In addition, choosing the appropriate protection method to maintain the optimal performance of the antenna is one of the most essential activities in the construction of space antennas.