Search for: fault-tolerant-control
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    Post Fault Vector Control of CHB Driven Induction Motor

    , M.Sc. Thesis Sharif University of Technology Fathi, Manochehr (Author) ; Zolghadri, Mohammad Reza (Supervisor)
    Multilevel converters are considered recently as one of the industrial solutions for high-power and power quality demanding applications. Casacade H-Bridge (CHB) converter is one of the well known topologies among multilevel converters. CHB converter is characterized by its high modularity allowing its power to be easily increased. Modularity also allows any faulty cell to be isolated, so the load can be fed by the remaining operative cells, which leads to an unbalanced output voltage of the CHB converter. To avoid the unbalanced operation, recently a solution based on modifying the phase and the magnitude of the voltage refereces has been proposed. This thesis presents a method to control... 

    Fault Tolerant Control Considering Actuator Saturation and External Disturbances

    , Ph.D. Dissertation Sharif University of Technology Khatibi, Mahmood (Author) ; Haeri, Mohammad (Supervisor)
    A control system capable of tolerating system malfunctions while maintaining an acceptable level of performance is referred as fault tolerant control system. The constraints on the amplitude of input control signals limit the domain of attraction even for linear models. Ignoring this fact may lead to an unsatisfactory performance and even closed loop instability. Designing the controller such that the domain of attraction is maximized has been an attractive topic for researchers. On the other hand, persistent disturbances always play an essential role in the real word systems. Designing the controller in a way such that the effect of such disturbances is attenuated is another challenging... 

    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)
    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... 

    Post-Fault Control of Fault-Tolerant Multi Module Converters

    , M.Sc. Thesis Sharif University of Technology Kazemi, Hossein (Author) ; Zolghadri, Mohammad Reza (Supervisor)
    Nowadays, multilevel converters are significantly developed in industrial applications as well as energy transmission systems regarding proper quality of output waveforms and fault tolerant operation ability. Among the different topologies of multilevel converters, modular multilevel converter (MMC) due to its modularity feature it more accepted in high voltage direct current (HVDC) transmission systems. Fast fault detection in power electronics converters is necessary to bypass the defected part in order to prevent failure propagation to other Submodules and to provide continues servicing. On this basis, different researches are reported in literature for MMCs fault tolerant operation. In... 

    Fault Tolerant Model Predictive Control of Tethered Satellite System

    , M.Sc. Thesis Sharif University of Technology Ramezani, Mahya (Author) ; Asadian, Nima (Supervisor)
    In this thesis, a control method to cope with the fault in the two-satellite two-tether satellite systems has been proposed to avoid failing the mission in the case one tether is torn. A new model for the tethered satellite system with two tethers has been developed to show the effects of tethers’ tension forces in the attitude dynamics. One of the main features of this model is the ability of changing the tethers’ connection points to the co-satellite for attitude control purposes. As a result, tethers’ tension forces are used as control actions to reduce the fuel consumption. The introduced coupled tethered satellite system has been controlled using the model predictive control method.... 

    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.... 

    Actuator Failure-Tolerant Predictive Control of an All-Thruster Satellite in Coupled Translational and Rotational Motion using Neural Networks

    , Ph.D. Dissertation Sharif University of Technology Tavakoli, Mohammad Mahdi (Author) ; Asadian, Nima (Supervisor)
    In this thesis, the problem of failure-tolerant control of the satellite in coupled orbital and rotational motion is investigated. All of the actuators of the satellite are thrusters and only the failure of the actuators is considered. At first, the equations of coupled relative translational-rotational motion of the satellite are derived. Then, the required specifications of the approapriate control method for the problem is explored with the conclution that the controller must be able to predict the behavior or planning the future trajectory of the satellite. In the next step, model predictive control, which has the required specifications, is used to control the coupled... 

    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... 

    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)
    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... 

    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)
    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)
    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... 

    Model Predictive Control Applications in Turbocompressor Control System

    , Ph.D. Dissertation Sharif University of Technology Sheikhbahaei, Reza (Author) ; Alasty, Aria (Supervisor) ; Vossoughi, Gholamreza (Supervisor)
    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... 

    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
    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
    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... 

    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
    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... 

    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
    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... 

    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
    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,... 

    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
    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  

    Fault-Tolerant control of uncertain linear systems in the presence of L∞ disturbances and actuator saturation

    , Article 4th International Conference on Control, Instrumentation, and Automation, 27 January 2016 through 28 January 2016 ; 2016 , Pages 307-312 ; 9781467387040 (ISBN) Khatibi, M ; Haeri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc 
    In this paper the fault-Tolerant control problem for uncertain linear systems in the presence of L, disturbances and actuator saturation is studied. The conflict between enlarging the domain of attraction and attenuating the effect of L, disturbances is tackled by proposing a non-constant state feedback controller. The feedback gains are calculated off-line by using linear matrix inequalities. In addition, the proposed method is capable of tolerating time-varying faults. The suggested approach is implemented on a sample model and the result is compared with other works  

    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
    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