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Total 131 records

    Design of a fault tolerated intelligent cntrol system for a nuclear reactor power control: Using extended Kalman filter

    , Article Journal of Process Control ; Vol. 24, issue. 7 , 2014 , pp. 1076-1084 ; ISSN: 09591524 Hatami, E ; Salarieh, H ; Vosoughi, N ; Sharif University of Technology
    Abstract
    In this paper an approach based on system identification is used for fault detection in a nuclear reactor. A continuous-time Extended Kalman Filter (EKF) is presented, which allows the parameters of the nonlinear system to be estimated. Also a fault tolerant control system is designed for the nuclear reactor during power changes operation. The proposed controller is an adaptive critic-based neuro-fuzzy controller. Performance of the controller in terms of transient response and robustness against failures is very good and considerable  

    Comparison of transfer functions using estimated rational functions to detect winding mechanical faults in transformers

    , Article Archives of Electrical Engineering ; Volume 61, Issue 1 , 2012 , Pages 85-99 ; 00040746 (ISSN) Bigdeli, M ; Vakilian, M ; Rahimpour, E ; Sharif University of Technology
    2012
    Abstract
    As it is found in the related published literatures, the transfer function (TF) evaluation method is the most feasible method for detection of winding mechanical faults in transformers. Therefore, investigation of an accurate method for evaluation of the TFs is very important. This paper presents three new indices to compare the transformer TFs and consequently to detect the winding mechanical faults. These indices are based on estimated rational functions. To develop the method, the necessary measurements are carried out on a 1.3 MVA transformer winding, under intact condition, as well as different fault conditions (axial displacement of winding). The obtained results demonstrate the high... 

    Control-flow checking using branch instructions

    , Article 5th International Conference on Embedded and Ubiquitous Computing, EUC 2008, Shanghai, 17 December 2008 through 20 December 2008 ; Volume 1 , January , 2008 , Pages 66-72 ; 9780769534923 (ISBN) Jafari Nodoushan, M ; Miremadi, S. G ; Ejlali, A ; IEEE Computer Society Technical Committee on Scalable Computing ; Sharif University of Technology
    2008
    Abstract
    This paper presents a hardware control-flow checking scheme for RISC processor-based systems. This Scheme combines two error detection mechanisms to provide high coverage. The first mechanism uses parity bits to detect faults occurring in the opcodes and in the target addresses of branch instructions which lead to erroneous branches. The second mechanism uses signature monitoring to detect errors occurring in the sequential instructions. The scheme is implemented using a watchdog processor for an VHDL model of the LEON2 processor. About 31800 simulation faults were injected into the LEON2 processor. The results show that the error detection coverage is about 99.5% with average detection... 

    Configurable ultrasonic flaw classification of oil pipelines

    , Article Nondestructive Testing and Evaluation ; Volume 23, Issue 2 , 2008 , Pages 77-88 ; 10589759 (ISSN) Ravanbod, H ; Jalali, A ; Sharif University of Technology
    2008
    Abstract
    These two papers present an innovative method of configurable flaw classification and volume estimation in oil pipelines. In part I, the ultrasonic image acquisition system is introduced and surface and volume of the flaw are estimated with fuzzy image processing. A number of real figures illustrate the system performance. The flops calculation reveals that this fuzzy estimator could be integrated in a real time flaw detection system. In part II, at first, the dynamic detection of interesting points, i.e. as feature points at different levels of images, is proposed using wavelet transform. Furthermore, a guided searching strategy is used for the best matching from the coarse level to a fine... 

    Error propagation analysis using FPGA-based SEU-fault injection

    , Article Microelectronics Reliability ; Volume 48, Issue 2 , 2008 , Pages 319-328 ; 00262714 (ISSN) Ejlali, A ; Miremadi, S. G ; Sharif University of Technology
    2008
    Abstract
    Error propagation analysis is one of the main objectives of fault injection experiments. This analysis helps designers to detect design mistakes and to provide effective mechanisms for fault tolerant systems. However, error propagation analysis requires that the chosen fault injection technique provides a high degree of observability (i.e., the ability to observe the internal values and events of a circuit after a fault is injected). Simulation-based fault injection provides a high observability adequate for error propagation analysis. However, the performance of the simulation-based technique is inadequate to handle today's hardware complexity. As an alternative, FPGA-based fault injection... 

    An efficient multi-band spectral subtraction method for robust speech recognition

    , Article 2007 9th International Symposium on Signal Processing and its Applications, ISSPA 2007, Sharjah, 12 February 2007 through 15 February 2007 ; 2007 ; 1424407796 (ISBN); 9781424407798 (ISBN) Safayani, M ; Sameti, H ; Babaali, B ; Manzuri Shalmani, M. T ; Sharif University of Technology
    2007
    Abstract
    In this paper we present a novel approach for adjusting a multi band spectral subtraction filter coefficients based on speech recognition system results. Currently most speech enhancement techniques are designed according to various waveform level criteria such as maximizing SNR or minimizing signal error. However improvement in these criteria does not necessarily result in increasing speech recognition performance. Only if these methods generate sequence of features that maximize or increase the likelihood of the correct transcription relative to other incorrect competing hypotheses, speech recognition performance will increase. Here we use an utterance with a known transcription and... 

    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  

    Static eccentricity fault diagnosis in wound-rotor resolvers

    , Article IEEE Sensors Journal ; Volume 21, Issue 2 , 2021 , Pages 1424-1432 ; 1530437X (ISSN) Lasjerdi, H ; Nasiri Gheidari, Z ; Tootoonchian, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Abstract
    In this paper static eccentricity (SE) fault diagnosis in wound rotor (WR) resolver is considered and a new noninvasive index is proposed. Using the proposed index not only leads to SE detection but also, helps to precisely determine the eccentricity level. Furthermore, the location of the fault is determined using two search coils. In this regard, a mathematical model based on the winding function method is proposed. In the proposed model the influence of non-uniform air-gap length on calculating the inductances is considered. Then, time-stepping finite element method (TSFEM) is used for approving the success of the proposed index. Finally, experimental tests are done to validate the... 

    Soft error mitigation in cache memories of embedded systems by means of a protected scheme

    , Article 2nd Latin-American Symposium on Dependable Computing, LADC 2005, Salvador, 25 October 2005 through 28 October 2005 ; Volume 3747 LNCS , 2005 , Pages 121-130 ; 03029743 (ISSN); 3540295720 (ISBN); 9783540295723 (ISBN) Zarandi, H. R ; Miremadi, S. G ; Sharif University of Technology
    2005
    Abstract
    The size and speed of SRAM caches of embedded systems are increasing in response to demands for higher performance. However, the SRAM caches are vulnerable to soft errors originated from energetic nuclear particles or electrical sources. This paper proposes a new protected cache scheme, which provides high performance as well as high fault detection coverage. In this scheme, the cache space is divided into sets of different sizes. Here, the length of tag fields associated to each set is unique and is different from the other sets. The other remained bits of tags are used for protecting the tag using a fault detection scheme e.g., generalized parity. This leads to protect the cache without... 

    Fast short circuit power switch fault detection in cascaded H-bridge multilevel converter

    , Article IEEE Power and Energy Society General Meeting ; 2013 ; 19449925 (ISSN); 9781479913039 (ISBN) Shahbazi, M ; Zolghadri, M. R ; Poure, P ; Saadate, S ; Sharif University of Technology
    2013
    Abstract
    Multilevel converters are being widely used in a large number of power electronics applications. Due to the increased number of switching devices, they are more likely to have faults in their switches than the conventional converters. In order to have a balanced operation after a short circuit power switch fault occurrence, it is necessary to detect the fault location. In this paper, a fast power switch fault detection method is presented to identify the fault location. This method only needs one additional voltage sensor per phase, and is faster compared to most of the existing methods. Also it is easy for implementation on a FPGA chip. The proposed method is verified by computer... 

    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... 

    An appropriate procedure for detection of journal-bearing fault using power spectral density, K-nearest neighbor and support vector machine

    , Article International Journal on Smart Sensing and Intelligent Systems ; Volume 5, Issue 3 , 2012 , Pages 685-700 ; 11785608 (ISSN) Moosavian, A ; Ahmadi, H ; Tabatabaeefar, A ; Sakhaei, B ; Sharif University of Technology
    2012
    Abstract
    Journal-bearings play a significant role in industrial applications and the necessity of condition monitoring with nondestructive tests is increasing. This paper deals a proper fault detection technique based on power spectral density (PSD) of vibration signals in combination with K-Nearest Neighbor and Support Vector Machine (SVM). The frequency domain vibration signals of an internal combustion engine with three journal-bearing conditions were gained, corresponding to, (i) normal, (ii) corrosion and (iii) excessive wear. The features of the PSD values of vibration signals were extracted using statistical and vibration parameters. The extracted features were used as inputs to the KNN and... 

    Performance improvement of steady-state and transient operation of offshore wind farm HVDC power transmission

    , Article 2015 IEEE 16th Workshop on Control and Modeling for Power Electronics, COMPEL 2015, 12 July 2015 through 15 July 2015 ; July , 2015 , Page(s): 1 - 7 ; 9781467368476 (ISBN) Safaeian, R ; Ebrahimi, S ; Parniani, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Wind power generation is increasing fast as a clean renewable energy resource. Offshore wind farms are popular due to advantages such as higher and smoother wind speeds, less farm site limitations, etc. High capacitive currents and need to expensive compensations, make use of high-voltage-direct-current (HVDC) power transmission indispensable for longdistance wind farm power generations. Steady-state and transient performance improvements of HVDC systems have always been an interesting industrial and academic research area. In this paper, a novel control method is proposed to improve the steady-state operation of HVDC system. Moreover, a new fault detection scheme is proposed to improve the... 

    Fast detection of open-switch fault in cascaded H-Bridge multilevel converter

    , Article 6th Annual International Power Electronics, Drive Systems, and Technologies Conference, PEDSTC 2015, 3 February 2015 through 4 February 2015 ; February , 2015 , Pages 538-543 ; 9781479976539 (ISBN) Shahbazi, M ; Zolghadri, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Cascaded H-Bridge converter has recently been utilized in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power switch fault detection method is presented to identify the fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is easy for implementation on an FPGA device, due to the use of simple math, relational and state machine blocks. The proposed method is verified by computer... 

    A fast and simple method to detect short circuit fault in cascaded H-bridge multilevel inverter

    , Article Proceedings of the IEEE International Conference on Industrial Technology, 17 March 2015 through 19 March 2015 ; Volume 2015-June, Issue June , 2015 , Pages 866-871 Ouni, S ; Rodriguez, J ; Shahbazi, M ; Zolghadri, M. R ; Schmeisser, U ; Oraee, H ; Lezana, P ; Ulloa Schmeisser, A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Abstract
    Fault detection is one of the most important tasks in fault tolerant converters. In this paper, a new method is proposed to detect the faulty cell in a cascaded H-bridge multilevel inverter. The detection technique is based on comparison of the output voltage with reference voltage made by using switching control pulses and DC-Link voltage. Because of the simplicity of this method, it is possible to use a single field-programmable gate array (FPGA) to implement this method and inverter control. The simulation and experimental results confirm the effectiveness of the proposed fault detection technique  

    Fast and simple open-circuit fault detection method for interleaved DC-DC converters

    , Article 7th Power Electronics, Drive Systems and Technologies Conference, PEDSTC 2016, 16 February 2016 through 18 February 2016 ; 2016 , Pages 440-445 ; 9781509003754 (ISBN) Shahbazi, M ; Zolghadri, M. R ; Ouni, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    Abstract
    Interleaved DC-DC boost converters are interesting choices in applications like fuel cells and photovoltaic systems. Although this converter offers low current ripple, but an open-circuit switch fault can lead to unacceptable current ripples. In this paper, a very fast and simple method is proposed to detect an open-circuit switch fault and its location. This method doesn't need any additional sensors, is efficient in CCM and DCM modes of operation, and can detect the fault in less than one switching period. Moreover, this method is suitable for implementation on an FPGA, due to the use of simple math and state machine blocks. Simulations are carried out to validate the effectiveness of this... 

    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... 

    Quick diagnosis of short circuit faults in cascaded H-bridge multilevel inverters using FPGA

    , Article Journal of Power Electronics ; Volume 17, Issue 1 , 2017 , Pages 56-66 ; 15982092 (ISSN) Ouni, S ; Zolghadri, M. R ; Rodriguez, J ; Shahbazi, M ; Oraee, H ; Lezana, P ; Schmeisser, A. U ; Sharif University of Technology
    Korean Institute of Power Electronics  2017
    Abstract
    Fast and accurate fault detection is the primary step and one of the most important tasks in fault tolerant converters. In this paper, a fast and simple method is proposed to detect and diagnosis the faulty cell in a cascaded H-bridge multilevel inverter under a short circuit fault. In this method, the reference voltage is calculated using switching control pulses and DC-Link voltages. The comparison result of the output voltage and the reference voltage is used in conjunction with active cell pulses to detect the faulty cell. To achieve this goal, the cell which is active when the Fault signal turns to “0” is detected as the faulty cell. Furthermore, consideration of generating the active... 

    Fast detection of open-switch fault in cascaded H-bridge multilevel converter

    , Article Scientia Iranica ; Volume 25, Issue 3D , 2018 , Pages 1561-1570 ; 10263098 (ISSN) Shahbazi, M ; Zolghadri, M. R ; Khodabandeh, M ; Ouni, S ; Sharif University of Technology
    Sharif University of Technology  2018
    Abstract
    Cascaded H-bridge converter has been utilized recently in different high-power applications due to its modular and simple structure. In order to have a balanced operation after a fault occurrence in this converter, it is necessary to detect the switch fault and its location. In this paper, a fast power-switch fault detection method is presented to identify a fault and its location. Only one voltage measurement per phase is required by this method, and the fault detection is faster compared to the existing methods. Moreover, it is suitable for implementation on an FPGA device due to the use of simple math, relational, and state machine blocks. The proposed method is verified by computer...