Search for: attitude-control
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    Optimal tracking neuro-controller in satellite attitude control

    , Article IEEE International Conference on Industrial Technology, IEEE ICIT 2002, 11 December 2002 through 14 December 2002 ; Volume 1 , 2002 , Pages 54-59 ; 0780376579 (ISBN) Sadati, N ; Meghdari, A ; Tehrani, N. D ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2002
    In this paper, a new control strategy for optimal attitude tracking control of a multivariable satellite system has been presented. The approach is based on Radial Basis Function Neural Network (RBFNN) and classical PD Controller for its initial stabilization. It is shown how the network can be employed as a multivariable self- organizing and self learning controller in conjunction with a PD controller for attitude control of a satellite. By using four reaction wheels and quaternion for kinematics representation, the attitude dynamics of the satellite has been presented. In contrast to the previous classical approaches, it is shown how this controller can be carried out in an on-line manner... 

    Multivariable adaptive satellite attitude controller design using RBF neural network

    , Article Conference Proceeding - 2004 IEEE International Conference on Networking, Sensing and Control, Taipei, 21 March 2004 through 23 March 2004 ; Volume 2 , 2004 , Pages 1189-1194 ; 0780381939 (ISBN) Sadati, N ; Tehrani, N. D ; Bolandhemmat, H. R ; Sharif University of Technology
    In this paper a new control strategy for adaptive attitude control of multivariable satellite system has been presented. The approach is based on radial basis function neural network (RBFNN). By using four reaction wheels and Modified Rodrigues Parameters (MRPs) for attitude representation, the attitude dynamic of satellite has been considered. The Lyapunov stability theory has been used to achieve a stable closed loop system. Also to enhance the robustness of the controller, the RBF neural network has been employed to estimate the model base terms in control law. The control objective is the plant to track a reference model. Simulation results illustrate the performance of the on-line... 

    Magnetic attitude control using fuzzy logic

    , Article Proceedings of the IEEE International Conference on Control Applications, 8 July 2009 through 10 July 2009 ; 2009 , Pages 456-460 ; 9781424446025 (ISBN) Heydari, A ; Pourtakdoust, S. H ; Heydari, H ; Sharif University of Technology
    A fuzzy controller has been suggested for attitude control of magnetic actuated satellites in order to calculate the desired mechanical torque based on the attitude error including error in the angles and their rates. The problem of selecting proper magnetic dipole based on the known desired mechanical torque has been investigated, two different methods for the purpose has been suggested and the performance of the attained fuzzy magnetic attitude controllers has been shown under two different simulated conditions. © 2009 IEEE  

    Attitude Estimation and Control of Satellite Using Noisy Measurements

    , M.Sc. Thesis Sharif University of Technology Firoozi, Dena (Author) ; Namvar, Mehrzad (Supervisor)
    Satellite attitude determination means specifying its rotation relative to a known reference. To determine satellite attitude, gyroscope is used to measure angular velocity and attitude sensors such as sun sensor, magnetometer, star tracker and earth horizon scanner are used in order to obtain vector measurements. In kinematic control, satellite angular velocity is determined in a way that its attitude converges to desired attitude. Usually, gyroscope and attitude sensors measurements are contaminated by noise which leads to errors in satellite attitude estimation and control. In the literature, gyroscope and at least two vector meaurements are used to estimate and control the... 

    Satellite Attitude Control by Limiting Velocity of Reaction Wheels

    , M.Sc. Thesis Sharif University of Technology Shayestehmanesh, Saeed (Author) ; Namvar, Mehrzad (Supervisor)
    The satellite attitude control problem is to determine the torque that is produced by actuators in such a way that, the satellite reaches to a desired final state from an initial state. If we do not consider the structural and dynamical equations of actuators and its effects in the system’s equations, the control problem is simple and can be solve easily. But, when the dynamic of the actuators and practical constraints associated with them and the equations of the system are to be considered, due to the dependence of these equations, solving the satellite attitude control is not simple like before. That is why, no effective method is presented to solve it. One of the most widely used... 

    Satellite Attitude Determination and Control in Presence of Time Delay

    , Ph.D. Dissertation Sharif University of Technology Bahrami, Somayeh (Author) ; Namvar, Mehrzad (Supervisor)
    Attitude determination and control system (ADCS) design is usually based on using measurements provided by rate gyros or attitude sensors such as Sun, Earth-magnetic, Earthhorizon and star trackers. In many practical scenarios, vector measurements provided by attitude sensors and the corresponding reference vectors are available with time delay while the angular velocity is measured by Gyro without significant delay. Time delay can cause ADCS performance degradation and even instability of the closed-loop system. Due to the nonlinearity of satellite dynamics and kinematics, controller and observer design in presence of measurement delays has its own complexity. Hence, despite its... 

    Robust attitude control of an agile aircraft using improved Q-Learning

    , Article Actuators ; Volume 11, Issue 12 , 2022 ; 20760825 (ISSN) Zahmatkesh, M ; Emami, S. A ; Banazadeh, A ; Castaldi, P ; Sharif University of Technology
    MDPI  2022
    Attitude control of a novel regional truss-braced wing (TBW) aircraft with low stability characteristics is addressed in this paper using Reinforcement Learning (RL). In recent years, RL has been increasingly employed in challenging applications, particularly, autonomous flight control. However, a significant predicament confronting discrete RL algorithms is the dimension limitation of the state-action table and difficulties in defining the elements of the RL environment. To address these issues, in this paper, a detailed mathematical model of the mentioned aircraft is first developed to shape an RL environment. Subsequently, Q-learning, the most prevalent discrete RL algorithm, will be... 

    Design of Nonlinear Observer and Controller for Satellite Attitude Estimation and Control

    , M.Sc. Thesis Sharif University of Technology Khosravian, Alireza (Author) ; Namvar, Mehrzad (Supervisor)
    The goal of the attitude determination is to determine the orientation of a satellite with respect to a reference frame. For this purpose, gyroscopes are used to measure the satellite’s angular velocity. Also, the attitude sensors such as magnetometers, Sun sensors, Earth sensors or star trackers are employed to collect vector measurements. The aim of the attitude control is to calculate the torque which is needed to be applied to the satellite such that its orientation and angular velocity converge to their desired values. It is usual to determine the attitude of satellite first and then use it in the attitude control algorithms. When multiple independent vector measurements are available,... 

    Fault-Tolerant Attitude Control of Satellite with Thrusters Using μ-synthesis

    , M.Sc. Thesis Sharif University of Technology Taheri, Abdolreza (Author) ; Assadian, Nima (Supervisor)
    In this project, a fault-tolerant attitude control system is developed for thruster-driven satellites. The proposed method has the advantage over current state-of-the-art approaches in that it does not require a fault detection and isolation system. Generalized moments are generated by a robust controller that is designed using mixed sensitivity H_∞ and μ-synthesis by DK-iteration. Moreover, a pulse-width modulation technique with quadratic programming optimization is tuned to map the controller outputs to thruster on-off commands as efficiently as possible. The controller is designed to tolerate up to ±30% perturbations in inertia properties and thrust degradations up to 90% of the nominal... 

    Multi-objective optimization in graceful performance degradation and its application in spacecraft attitude fault-tolerant control

    , Article Aerospace Science and Technology ; Volume 69 , 2017 , Pages 465-473 ; 12709638 (ISSN) Moradi, R ; Alikhani, A ; Fathi Jegarkandib, M. F ; Sharif University of Technology
    Reducing the burden of the remaining actuators through decreasing the performance gracefully is an important field in active fault tolerant control. According to the literature, two important points have been identified in the works considering graceful performance degradation: 1) using single-objective optimization, 2) assuming an engineering insight into the performance of the faulty system. This paper has two contributions: First, it is shown that in some cases, single-objective optimization may not be able to provide a satisfactory solution for the problem. Second, a new systematic and general method is proposed to remove the need for the engineering insight. The proposed method is based... 

    Attitude control of an underactuated satellite in presence of disturbance torque with optimal motion planning

    , Article Aerospace Science and Technology ; Volume 121 , 2022 ; 12709638 (ISSN) Mehrparwar Zinjanabi, A ; Nejat Pishkenari, H ; Salarieh, H ; Abdollahi, T ; Sharif University of Technology
    Elsevier Masson s.r.l  2022
    The failure of mechanical components is a common phenomenon in satellites. This failure can happen in the satellite attitude control system, which causes that the control system of the satellite becomes underactuated. There have been many attempts to control the orientation of underactuated satellites. However, in most studies, the inertia matrix of the satellite is assumed to be diagonal with respect to the body coordinate system, and no limitations on the amount of torque applied by the reaction wheels have been considered. In this paper, at first, it is attempted to control the satellite using the motion planning method. The satellite control inputs are assumed to be cubic spline with... 

    Geometric Control of Tethered Satellite Formations by Controlling the Tether Length

    , M.Sc. Thesis Sharif University of Technology Makarem, Hadi (Author) ; Alasty, Aria (Supervisor)
    Satelites formation which is a specic spatial conguration of satellites, is of great importance in design and control of satellite systems. Reducing the required power to maintain that conguration, while imposing complicated dynamics on the system, connecting satelites through tethers has recently attracted researchers' attention. Developing a new model based on which the motion of the satellite formation will be expressed through simple equations, followed by the study of how the tether length control participates in the orientation control of the system, are the principal aims of current research. First, a new model is proposed for a group of tethered satellite for- mations, and based on... 

    Controlling the attitude of linear time-varying model LEO satellite using only electromagnetic actuation

    , Article 2002 IEEE Aerospace Conference, Big Sky, MT, 9 March 2002 through 16 March 2002 ; Volume 5 , 2002 , Pages 2221-2230 ; 1095323X (ISSN); 078037231X (ISBN); 9780780372313 (ISBN) Jafarboland, M ; Momeni, H. R ; Sadati, N ; Baclou, H. G ; Sharif University of Technology
    Recently small satellites are used more commonly because of the low launching cost and development of microelectronics. Also lower weight, size, cost and the power consumption of magnetorquer, has made the application of them in controlling attitude of the satellites common. Intensive changes and non-ability of geomagnetic field are some of the problems, which have limited the efficiency of magnetorquers. In this paper a new control method is presented that keeps the attitude of satellite in desired condition only by electromagnetic coils. The distinction of this method is its abilities in comparison with other methods. In this analytic method a direct relation between design parameters,... 

    Quaternion based linear time-varying model predictive attitude control for satellites with two reaction wheels

    , Article Aerospace Science and Technology ; Volume 98 , March , 2020 ; ISSN: 12709638 Golzari, A ; Nejat Pishkenari, H ; Salarieh, H ; Abdollahi, T ; Sharif University of Technology
    Elsevier Masson SAS  2020
    Attitude control of a satellite having only two reaction wheels is a challenging issue. To address this problem, previously published researches considered some simplifying assumptions on the satellites such as diagonality of the moment of the inertia matrix. On the other hand, in some works, the total angular momentum of the satellite is assumed to be zero. In this paper, a linear time-variant model predictive control (LTV MPC) is designed to control a satellite with two reaction wheels. This control method can be applied to a satellite with a non-diagonal inertial matrix in the presence of external torques, to rotate the satellite toward the desired directions in the space and orbit. The... 

    Coupled Trajectory and Attitude Control of an Exoatmospheric Interceptor

    , M.Sc. Thesis Sharif University of Technology Farvardin Ahranjani, Fatemeh (Author) ; Nobahari, Hadi (Supervisor)
    In this thesis, coupled trajectory and attitude control of an exoatmospheric interceptor is investigated. The interceptor is considered to track and intercept orbital targets in its terminal phase using an infrared strapdown seeker. Attitude control system uses its thrusters in order to keep permanently the detector toward the target in both elevation and azimuth directions. Detector is attached to the body. Divert thrusters generate acceleration perpendicular to the longitudinal axis of the interceptor to correct the trajectory. It is assumed that the interceptor has mass asymmetries. Transltional and rotational dynamics are coupled. Therefore, in order to improve the performance of... 

    Attitude Control of Flexible Satellite using CMG in Slew Maneuver Considering Bending and Torsion Deflections

    , M.Sc. Thesis Sharif University of Technology Faghihi Nia, Ali (Author) ; Asadian, Nima (Supervisor)
    In this thesis the attitude dynamics, simulation and control of a flexible satellite with CMG (Control Moment Gyro) actuator in three-dimensional slew and rest-to-rest maneuvers have been studied. The flexible satellite is modeled as a rigid hub and two flexible appendages. The bending and torsion of the flexible panels have been considered. The equations of motion have been derived using the Lagrange method and assumed-modes approach is utilized for converting the partial differential equations of structural dynamics into an ordinary differential equation set. The MATLAB and SIMULINK software has been used for simulation and validation of the equations of motion. The simulation and control... 

    Adaptive Attitude and Position Control of a Rigid Body Insect-Like Flapping Wing

    , M.Sc. Thesis Sharif University of Technology Taymourtash, Neda (Author) ; Banazadeh, Afshin (Supervisor)
    In this study, adaptive control of attitude and position of a rigid body insect-like flapping wing is investigated. For this purpose, a non-linear dynamic and time varying modeling and simulation is carried out initially with six degrees of freedom, and then the accuracy of the simulation is evaluated during different test cases. In order to design the controller, non-linear and time varying dynamic is transformed into non-linear and time-invariant dynamic using theory of averaging. Then, a non-linear controller is designed based on Lyapunov stability theory. Due to the inefficiency of the aforementioned controller under disturbances and unknown uncertainties in the model, an adaptive... 

    Development of a Fall Risk Assessment Method Based on COP Data in Parkinson’s Disease

    , M.Sc. Thesis Sharif University of Technology Shokouhi, Shabnam (Author) ; Behzadipour, Saeed (Supervisor)
    In recent years, there has been an increasing interest in posturography methods as an objective quantitative tool for assessing balance and indicating patient with high risk of fall. Although many posturographic studies tried to describe balance deficiencies in PD, little success has been achieved in utilizing static posturography as a tool for discriminating faller and non-faller PD patients. Furthermore, Dynamic posturography studies have delivered valuable insight into the potentiality of these methods for assessing balance, but these devices are very high in price and cumbersome to move that can limit the feasibility of their use in the clinical settings. The aims of this study were: 1)... 

    Model Predictive Control of Satellite Attitude Using Reaction Wheels

    , M.Sc. Thesis Sharif University of Technology Khoshrooz Azad, Reza (Author) ; Pourtakdoust, Hossein (Supervisor)
    This project discusses designing and implementing a model predictive controller for attitude control of a satellite with reaction wheels as actuator. Deriving a predictive model and designing the controller is performed based on linear model of rigid satellite attitude dynamics. The designed controller is utilized to control both a constrained and a nonlinear problem by using optimization method such as quadratic programming. The controller performance and its robustness, in case of uncertainties in model parameters and encountering external disturbances, are studied and compared with those sliding mode controller  

    Fault-tolerant Attitude Control of Sattelite Using Neural Networks

    , M.Sc. Thesis Sharif University of Technology Sepehr, Firoozeh (Author) ; Asadian, Nima (Supervisor)
    This research aims to introduce a new integrated fault tolerant attitude control system of satellites based on the neural networks. First, a linear controller and an optimal controller are designed assuming that no fault occurs in the reaction wheels of the satellite. It is obvious that these controllers are not able to respond properly when a fault occurs. Therefore, artificial neural networks are employed in the fault tolerant controller design. Neural networks are well-known for their adaptiveness and the ability to learn the dynamics of a system. Therefore, they can be used to predict the faulty conditions. In this research two approaches are examined to deal with the faulty conditions....