Search for: fault-tolerant-control
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    Robust adaptive fault-tolerant control for leader-follower flocking of uncertain multi-agent systems with actuator failure

    , Article ISA Transactions ; Volume 71 , 2017 , Pages 227-234 ; 00190578 (ISSN) Yazdani, S ; Haeri, M ; Sharif University of Technology
    In this work, we study the flocking problem of multi-agent systems with uncertain dynamics subject to actuator failure and external disturbances. By considering some standard assumptions, we propose a robust adaptive fault tolerant protocol for compensating of the actuator bias fault, the partial loss of actuator effectiveness fault, the model uncertainties, and external disturbances. Under the designed protocol, velocity convergence of agents to that of virtual leader is guaranteed while the connectivity preservation of network and collision avoidance among agents are ensured as well. © 2017 ISA  

    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... 

    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
    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... 

    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... 

    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... 

    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... 

    Design of a fault tolerated intelligent control system for load following operation in a nuclear power plant

    , Article International Journal of Electrical Power and Energy Systems ; Volume 78 , 2016 , Pages 864-872 ; 01420615 (ISSN) Hatami, E ; Vosoughi, N ; Salarieh, H ; Sharif University of Technology
    Elsevier Ltd 
    Fault detection has always an important role in maintaining the system stability and assuring satisfactory and safe operation. In this paper a method based on system identification is used for fault detection on a nuclear reactor. The combination of Extended Kalman Filter and recursive Least Square are used to identify the system parameters. Another goal of this paper is design of a fault tolerant control system for a nuclear reactor during power change operation. The proposed controller is an adaptive neuro-fuzzy controller based on emotional learning. Performance of the controller in term of transient response and robustness against failure is very good and outstanding  

    Reducing the effects of inaccurate fault estimation in spacecraft stabilization

    , Article Journal of Aerospace Technology and Management ; Volume 9, Issue 4 , 2017 , Pages 453-460 ; 19849648 (ISSN) Moradi, R ; Alikhani, A ; Fathi Jegarkandi, M ; Sharif University of Technology
    Reference Governor is an important component of Active Fault Tolerant Control. One of the main reasons for using Reference Governor is to adjust/modify the reference trajectories to maintain the stability of the post-fault system, especially when a series of actuator faults occur and the faulty system can not retain the pre-fault performance. Fault estimation error and delay are important properties of Fault Detection and Diagnosis and have destructive effects on the performance of the Active Fault Tolerant Control. It is shown that, if the fault estimation provided by the Fault Detection and Diagnosis (initial “fault estimation”) is assumed to be precise (an ideal assumption), the... 

    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 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,... 

    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
    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... 

    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...