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    Fault-tolerant control of flexible satellite with magnetic actuation and reaction wheel

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 236, Issue 6 , 2022 , Pages 1222-1238 ; 09544100 (ISSN) Hajkarim, M. H ; Assadian, N ; Sharif University of Technology
    SAGE Publications Ltd  2022
    Abstract
    The attitude fault-tolerant control of a flexible satellite actuated by reaction wheels and magnetic torquer bars is investigated in this article. A low earth orbit is considered for moment perturbations such as drag and gravity gradient. Furthermore, the flexible panels attached to a rigid central body are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using Lagrange’s equation, and the resulting dynamical model is validated by comparing its simulation results to the NX Siemens software results. Finally, a fault-tolerant controller based on sliding mode control is suggested and... 

    Fault-tolerant control of flexible satellite with magnetic actuation and reaction wheel

    , Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; 2021 ; 09544100 (ISSN) Hajkarim, M. H ; Assadian, N ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Abstract
    The attitude fault-tolerant control of a flexible satellite actuated by reaction wheels and magnetic torquer bars is investigated in this article. A low earth orbit is considered for moment perturbations such as drag and gravity gradient. Furthermore, the flexible panels attached to a rigid central body are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using Lagrange’s equation, and the resulting dynamical model is validated by comparing its simulation results to the NX Siemens software results. Finally, a fault-tolerant controller based on sliding mode control is suggested and... 

    Fault-tolerant predictive trajectory tracking of an air vehicle based on acceleration control

    , Article IET Control Theory and Applications ; Volume 14, Issue 5 , 2020 , Pages 750-762 Emami, S. A ; Banazadeh, A ; Sharif University of Technology
    Institution of Engineering and Technology  2020
    Abstract
    A novel fault-tolerant model predictive control (MPC)-based trajectory tracking approach for an aerial vehicle is presented in this study. A generalised online sequential extreme learning machine is introduced first to identify the corresponding coefficients of actuator faults. Subsequently, a robust trajectory tracking control is developed based on MPC, where the system constraints can be effectively considered in the designed control scheme. Trajectory tracking control is achieved by controlling only the acceleration of the aerial robot in the MPC structure. This leads to less computational burden and faster closed-loop dynamics. In addition, an effective disturbance observer is employed,... 

    Intelligent trajectory tracking of an aircraft in the presence of internal and external disturbances

    , Article International Journal of Robust and Nonlinear Control ; Volume 29, Issue 16 , 2019 , Pages 5820-5844 ; 10498923 (ISSN) Emami, A ; Banazadeh, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2019
    Abstract
    This research deals with developing an intelligent trajectory tracking control approach for an aircraft in the presence of internal and external disturbances. Internal disturbances including actuators faults, unmodeled dynamics, and model uncertainties as well as the external disturbances such as wind turbulence significantly affect the performance of the common trajectory tracking control approaches. There are several fault-tolerant control approaches in the literature to overcome the effects of specific actuator or sensor faults during the flight. However, trajectory tracking control of an air vehicle in the presence of unexpected faults and simultaneous presence of wind turbulence is... 

    Post fault vector control of an induction motor fed by a chb inverter

    , Article 10th International Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2019, 12 February 2019 through 14 February 2019 ; Pages 149-154 , 2019 ; 9781538692547 (ISBN) Fathi, M ; Zolghadri, M ; Ouni, S ; Babaloo, R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2019
    Abstract
    In this paper, a new post-fault vector control of an induction motor, fed by a faulty Cascaded H-Bridge (CHB) inverter, is presented. Among fault tolerant control methods, waveform based methods are suitable for closed-loop control and provide higher output voltage. In order to control the speed of the motor, a rotor field oriented control (RFOC) is used. During the fault, the FOC is modified to decrease the fault impact on the motor as low as possible. The proposed method is validated by means of simulation results for different loads and faults. The results show an improvement in both the final operating point and the transient response of the motor  

    A unified framework for passive–active fault-tolerant control systems considering actuator saturation and L ∞ disturbances

    , Article International Journal of Control ; Volume 92, Issue 3 , 2019 , Pages 653-663 ; 00207179 (ISSN) Khatibi, M ; Haeri, M ; Sharif University of Technology
    Taylor and Francis Ltd  2019
    Abstract
    This paper presents a unified passive–active fault-tolerant control strategy to compensate the loss of actuators’ effectiveness. The proposed approach is capable of handling the system in pre- and post-fault diagnosis intervals by passive and active approaches, respectively. The stability of the designed system is independent of the accuracy of information provided by the fault detection and diagnosis unit, however, a precise estimation could improve the conservation. Actuator saturation and L ∞ disturbances effects are considered in the design stage. The trade-off between maximising the domain of attraction and minimising the effects of L ∞ disturbances is tackled by developing a... 

    Fault-tolerant control considering time-varying bounds on faults

    , Article Transactions of the Institute of Measurement and Control ; Volume 40, Issue 10 , 2018 , Pages 2982-2990 ; 01423312 (ISSN) Khatibi, M ; Haeri, M ; Sharif University of Technology
    SAGE Publications Ltd  2018
    Abstract
    This paper presents a novel fault-tolerant control strategy to compensate the time-varying loss of actuators’ effectiveness. It considers intermediate situations where the fault is not determined precisely (unlike active approaches) but overall estimations about its rate and final value are available through the previous experiences and/or experiments. Based on the estimations, two upper and lower time-varying bounds on the actuators’ effectiveness are established to be exploited in the procedure of controller design. In a special case, where these bounds are constant, the method will be reduced to the conventional passive approach. Also, actuator saturation and the effects of (Formula... 

    Comparing the performance of reference trajectory management and controller reconfiguration in attitude fault tolerant control

    , Article 2017 Asia Conference on Mechanical and Aerospace Engineering, ACMAE 2017, 29 December 2017 through 31 December 2017 ; Volume 151 , 2018 ; 2261236X (ISSN) Moradi, R ; Alikhani, A ; Jegarkandi, M. F ; Sharif University of Technology
    EDP Sciences  2018
    Abstract
    Reference trajectory management is a method to modify reference trajectories for the faulty system. The modified reference trajectories define new maneuvers for the system to retain its pre-fault dynamic performance. Controller reconfiguration is another method to handle faults in the system, for instance by adjusting the controller parameters (coefficients). Both of these two methods have been considered in the literature and are proven to be capable of handling various faults. However, the comparison of these two methods has not been considered sufficiently. In this paper, a controller reconfiguration mechanism and a reference trajectory management are proposed for the spacecraft attitude... 

    Predictive fault-tolerant control of an all-thruster satellite in 6-DOF motion via neural network model updating

    , Article Advances in Space Research ; Volume 61, Issue 6 , March , 2018 , Pages 1588-1599 ; 02731177 (ISSN) Tavakoli, M. M ; Assadian, N ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    The problem of controlling an all-thruster spacecraft in the coupled translational-rotational motion in presence of actuators fault and/or failure is investigated in this paper. the nonlinear model predictive control approach is used because of its ability to predict the future behavior of the system. The fault/failure of the thrusters changes the mapping between the commanded forces to the thrusters and actual force/torque generated by the thruster system. Thus, the basic six degree-of-freedom kinetic equations are separated from this mapping and a set of neural networks are trained off-line to learn the kinetic equations. Then, two neural networks are attached to these trained networks in... 

    Adaptive integrated guidance and fault tolerant control using backstepping and sliding mode

    , Article International Journal of Aerospace Engineering ; Volume 2015 , September , 2015 ; 16875966 (ISSN) Jegarkandi, M. F ; Ashrafifar, A ; Mohsenipour, R ; Sharif University of Technology
    Hindawi Publishing Corporation  2015
    Abstract
    A new method of integrated guidance and control for homing missiles with actuator fault against manoeuvring targets is proposed. Model of the integrated guidance and control system in the pitch plane with actuator fault and some uncertainty is developed. A control law using combination of adaptive backstepping and sliding mode approaches is designed to achieve interception in the presence of bounded uncertainties and actuator fault. Simulation results show that new approach has better performance than adaptive backstepping and has good performance in the presence of actuator fault  

    Wind energy conversion system based on DFIG with open switch fault tolerant six-legs AC-DC-AC converter

    , Article Proceedings of the IEEE International Conference on Industrial Technology, Cape Town ; February , 2013 , Pages 1656-1661 ; 9781467345699 (ISBN) Shahbazi, M ; Zolghadri, M. R ; Poure, P ; Saadate, S ; The Institute of Electrical and Electronics Engineers (IEEE); IEEE Industrial Electronics Society (IES); IEEE Technology Management Council; IEEE Region 8; IEEE South Africa Section IE/IA/PEL Joint Chapter ; Sharif University of Technology
    2013
    Abstract
    Continuity of service of wind energy conversion systems as well as their reliability and performances are some of the major concerns in this power generation area. Six-legs AC/DC/AC converters are normally used in modern wind energy systems like as in the system with a doubly-fed induction generator (DFIG). A sudden failure of the converter can lead to the total or partial loss of the control of the phase currents and can cause serious system malfunction or shutdown. Therefore, to prevent the spread of the fault to the other system components and to ensure continuity of service, fault tolerant converter topologies associated to quick and effective fault detection and compensation methods... 

    Fault-tolerant five-leg converter topology with FPGA-Based reconfigurable control

    , Article IEEE Transactions on Industrial Electronics ; Volume 60, Issue 6 , 2013 , Pages 2284-2294 ; 02780046 (ISSN) Shahbazi, M ; Poure, P ; Saadate, S ; Zolghadri, M. R ; Sharif University of Technology
    2013
    Abstract
    Fast fault detection and reconfiguration of power converters is necessary in electrical drives to prevent further damage and to make the continuity of service possible. On the other hand, component minimized converters may provide the benefits of higher reliability and less volume and cost. In this paper, a new fault-tolerant converter topology is studied. This converter has five legs before the fault occurrence, and after fault detection the converter continues to function with four legs. A very fast fault detection and reconfiguration scheme is presented and studied. Simulations and experimental tests are performed to evaluate the structure requirements, the digital reconfigurable... 

    A sensor fault tolerant drive for interior permanent-magnet synchronous motors

    , Article 2008 IEEE 2nd International Power and Energy Conference, PECon 2008, Johor Baharu, 1 December 2008 through 3 December 2008 ; January , 2008 , Pages 283-288 ; 9781424424054 (ISBN) Tahami, F ; Nademi, H ; Rezaei, M ; Sharif University of Technology
    2008
    Abstract
    The study reported in this paper deals with the problem of developing a controller with tolerance to current sensor faults. To achieve this goal, two control strategies are considered. In the first method, field oriented control and a developed observer are used in case of no fault. The second approach is concerned with fault tolerant strategy based on an observer for faulty conditions. Current sensors failures are detected and the current will be estimated successfully in order to allow continuous operation of the vector control. Based on the motor model, currents can be estimated using a nonlinear observer. A decoupling current vector control strategy is developed to ensure high... 

    A diversity based reconfigurable method for fault tolerant control of induction motors

    , Article International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2006. SPEEDAM 2006, Taormina, 23 May 2006 through 26 May 2006 ; Volume 2006 , 2006 , Pages 66-71 ; 1424401941 (ISBN); 9781424401949 (ISBN) Tahami, F ; Shojaei, A ; Ahmadi Khatir, D ; Sharif University of Technology
    2006
    Abstract
    AC motor drive systems are sensitive to faults occurring at the power inverter, or at the control system. A novel fault tolerant Field Oriented Control system for induction motors is introduced. The system maintains speed control in the event of sensors malfunction and adverse signal conditions, providing enhanced reliability. The system comprises four different flux estimators which are fused by a Fuzzy aggregation system in order to give a reliable estimate of motor flux. The proposed control system is an effective and easy to implement method giving a potential for motor drive reliability enhancement. © 2006 IEEE  

    Design of an Adaptive Controller for Uncertain Fractional-order Systems Subject to Actuator Failure

    , M.Sc. Thesis Sharif University of Technology Dolatabadi, Shayesteh (Author) ; Shahrokhi, Mohammad (Supervisor)
    Abstract
    The objective of this research is to design an adaptive controller for a class of fractional-order nonlinear systems in the strict-feedback form with unmodeled dynamics. Actuator saturation and actuator fault are also considered. All of the system states are assumed to be measurable, and all the sensors can be faulty. Fractional-order systems are chosen because, in the modeling of physical systems, the fractional-order calculus is often preferable to the classical integer-order calculus. The controller is designed by using the backstepping design technique. The fuzzy logic systems are used to eliminate the problem of "explosion of complexity" in the conventional backstepping method and also... 

    Fault-tolerant Control of Formation Flying Satellites Using Machine Learning

    , M.Sc. Thesis Sharif University of Technology Farhang Fallah, Raouf (Author) ; Assadian, Nima (Supervisor)
    Abstract
    In this thesis, a fault-tolerant method for controlling the relative position and attitude between two satellites in a leader and follower formation is proposed. The follower satellite is equipped with twelve thrusters which are installed on the satellite in a particular pattern. These thrusters are assumed to be afflicted by faults. The satellites are subject to external disturbances – such as the ellipsoidal gravity of Earth (J2), drag force, solar radiation pressure, and the third body, and a controller is designed to attain the desired formation under these disturbances.For this purpose, six separated neural networks are trained, one for each of the position or attitude channels. Since... 

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

    , M.Sc. Thesis Sharif University of Technology Taheri, Abdolreza (Author) ; Assadian, Nima (Supervisor)
    Abstract
    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... 

    Fault Tolerant Control of Flexible Launch Vehicle Using Fractional-Order Controller

    , M.Sc. Thesis Sharif University of Technology Salehi Abari, Akbar (Author) ; Fathi Jegarkandi, Mohsen (Supervisor)
    Abstract
    In this research the attitude control of a flexible launch vehicle using fractional order proportional-integral-derivative controller in the presence of actuators failures is described. Other work done in this study is the investigation of on-line fault detection and diagnosis effects in the attitude control of flexible launch vehicle in the presence of actuator failures. Rigid-elastic equations of motion and assumed modes have been used to simulate dynamics of launch vehicle in the Simulink environment of MATLAB software using two elastic bending modes. The performance of fractional order controller has been compared with conventional proportional-integral-derivative and adaptive augmented... 

    Model Predictive Control Applications in Turbocompressor Control System

    , Ph.D. Dissertation Sharif University of Technology Sheikhbahaei, Reza (Author) ; Alasty, Aria (Supervisor) ; Vossoughi, Gholamreza (Supervisor)
    Abstract
    The purpose of this study is to develop model predictive control approach to control a turbocompressor. The turbocompressor which is consisted of a gas turbine and a centrifugal compressor is manufactured for providing the necessary pressure for gas transport via the gas transmission network. The turbocompressor control system regulates the compressor outlet pressure by controlling the rotational speed of the gas turbine, while preventing the surge phenomenon in the compressor. Surge is a serious instability in the compressor that is associated with periodic fluctuations in system variables and can cause heavy damage to expensive machine parts.In this research, model predictive control has... 

    Fault-Tolerant Control of Flexible Satellite with Magnetic Actuation and Reaction Wheel

    , M.Sc. Thesis Sharif University of Technology Hajkarim, Mohammad Hossein (Author) ; Assadian, Nima (Supervisor)
    Abstract
    The primary goal of this thesis is to develop a Fault Tolerant Control (FTC) system for a flexible satellite in presence of actuators fault and failure. The actuators of the satellite are including three magnetorquers and three reaction wheels on each principal axis. At first, the three-degree-of-freedom rotational motion of a rigid satellite with two flexible solar panels is modeled. The flexible panels are modeled through the assumed mode approach by a finite set of bending modal motion. The ordinary differential equations of their generalized coordinates are found using the Lagrange’s equation. Then, the dynamic model is validated by comparing the simulation results of the model to the NX...