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    Fault diagnosis in a yeast fermentation bioreactor by genetic fuzzy system

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 29, Issue 3 , 2010 , Pages 61-72 ; 10219986 (ISSN) Tayyebi, S ; Shahrokhi, M ; Bozorgmehry Boozarjomehry, R ; Sharif University of Technology
    Abstract
    In this paper, the fuzzy system has been used for fault detection and diagnosis of a yeast fermentation bioreactor based on measurements corrupted by noise. In one case, parameters of membership functions are selected in a conventional manner. In another case, using certainty factors between normal and faulty conditions the optimal values of these parameters have been obtained through the genetic algorithm. These two cases are compared based on their performances in fault diagnosis of a yeast fermentation bioreactor for three different conditions. The simulation results indicate that the fuzzy-genetic system is superior in multiple fault detection for the conditions where the minimum and... 

    A heuristic threshold policy for fault detection and diagnosis in multivariate statistical quality control environments

    , Article International Journal of Advanced Manufacturing Technology ; Volume 67, Issue 5-8 , July , 2013 , Pages 1231-1243 ; 02683768 (ISSN) Nezhad, M. S. F ; Niaki, S. T. A ; Sharif University of Technology
    2013
    Abstract
    In this paper, a heuristic threshold policy is developed to detect and classify the states of a multivariate quality control system. In this approach, a probability measure called belief is first assigned to the quality characteristics and then the posterior belief of out-of-control characteristics is updated by taking new observations and using a Bayesian rule. If the posterior belief is more than a decision threshold, called minimum acceptable belief determined using a heuristic threshold policy, then the corresponding quality characteristic is classified out-of-control. Besides using a different approach, the main difference between the current research and previous works is that the... 

    Satellite Attitude Actuator Fault Detection and Identification Using Adaptive Neuro-Fuzzy Inference System (ANFIS)

    , M.Sc. Thesis Sharif University of Technology Moosavi, Saba (Author) ; Asadian, Nima (Supervisor)
    Abstract
    This thesis focuses on the detection and estimation of faults occurring in one of the reaction wheel axes of a three-axis stabilized satellite. The wheel axes are aligned with the satellite's body axes, and the emphasis is on the attitude (rather than position) of the satellite. The primary goal of the subsystem is to determine and control the satellite's attitude, transitioning from its initial state to a desired Earth-pointing state. It is assumed that environmental disturbances, including gravitational disturbances and Drag related disturbances, are considered. Based on this, a PID controller is designed after modeling the nonlinear kinematics and dynamics of the satellite using Euler... 

    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
    Abstract
    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... 

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

    , Article International Journal of Control ; 2017 , Pages 1-11 ; 00207179 (ISSN) Khatibi, M ; Haeri, M ; Sharif University of Technology
    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 non-constant... 

    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... 

    Applications of soft computing in nuclear power plants: A review

    , Article Progress in Nuclear Energy ; Volume 149 , 2022 ; 01491970 (ISSN) Ramezani, I ; Moshkbar Bakhshayesh, K ; Vosoughi, N ; Ghofrani, M. B ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Soft Computing (SC) is defined as a group of computational techniques that solve complex problems independent of mathematical models. SC techniques including artificial neural networks (ANNs), fuzzy systems (FSs), evolutionary algorithms (EAs), etc., can solve problems that either cannot be solved by the analytical/conventional methods or require a long computation time. Due to their features, SC techniques are nowadays widely used in scientific and industrial researches. SC techniques have also been included in many types of research related to nuclear power plants (NPPs). In this paper, the applications of SC techniques in NPPs, according to published articles, are presented. The...