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    Failure detection and isolation in robotic manipulators using joint torque sensors

    , Article Robotica ; Volume 28, Issue 4 , 2010 , Pages 549-561 ; 02635747 (ISSN) Namvar, M ; Aghili, F ; Sharif University of Technology
    Reliability of any model-based failure detection and isolation (FDI) method depends on the amount of uncertainty in a system model. Recently, it has been shown that the use of joint torque sensing results in a simplified manipulator model that excludes hardly identifiable link dynamics and other nonlinearities such as friction, backlash, and flexibilities. In this paper, we show that the application of the simplified model in a fault detection algorithm increases reliability of fault monitoring system against modeling uncertainty. The proposed FDI filter is based on a smooth velocity observer of degree 2n where n stands for the number of manipulator joints. No velocity measurement and... 

    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 diagnosis in robot manipulators in presence of modeling uncertainty and sensor noise

    , Article Proceedings of the IEEE International Conference on Control Applications, 8 July 2009 through 10 July 2009, Saint Petersburg ; 2009 , Pages 1750-1755 ; 9781424446025 (ISBN) Mohseni, S ; Namvar, M ; Sharif University of Technology
    In this paper, we introduce a new approach to fault detection and isolation for robot manipulators. Our technique is based on using a new simplified Euler-Lagrange (EL) equation that reduces complexity of the proposed fault detection method. The proposed approach isolates the faults and is capable of handling the uncertainty in manipulator gravity vector. It is shown that the effect of uncalibrated torque sensor measurement is asymptotically rejected in the detection process. A simulation example is presented to illustrate the results. © 2009 IEEE  

    A geometric approach to fault detection and isolation in a grid-connected inverter

    , Article IEEE Transactions on Control Systems Technology ; November , 2020 , Pages: 1-8 Mashreghi, A ; Namvar, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    We present a nonlinear geometric approach to fault detection and isolation (FDI) in a grid-connected inverter system. Open-switch faults in inverter power transistors together with faults in grid voltages and source current sensors are detected and isolated in the presence of disturbance. The detection process is based on dynamic model of an inverter, including a dc-bus capacitor and an output RL filter. The proposed FDI system does not rely on balanced or zero-sum conditions in the grid point and is functional under nonsinusoidal voltages and currents. IEEE  

    Proposal of a fault-tolerance technique for 1-ph open circuit fault in resolvers

    , Article IEEE Sensors Journal ; Volume 21, Issue 14 , 2021 , Pages 15987-15992 ; 1530437X (ISSN) Bahari, M ; Tootoonchian, F ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2021
    Due to their cost-effective manufacturing and robust structure, an electromagnetic sensor called resolver is being applied in a wide range of applications, especially in those which high reliability is particularly essential. Since resolvers are usually chosen as position detector units in harsh environments, their chronic exposure to high temperature and mechanical shocks is unpreventable and accordingly, performance failure as a result of output signal winding open circuit fault (OCF) is inevitable. In this paper, a new technique is proposed to keep the performance of the resolver within an acceptable range of position error while one of the output signals (SIN/COS) is inaccessible. To... 

    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... 

    FPGA-based fault tolerant scheme with reduced extra-sensor number for WECS with DFIG

    , Article Proceedings - ISIE 2011: 2011 IEEE International Symposium on Industrial Electronics, 27 June 2011 through 30 June 2011 ; 2011 , Pages 1595-1601 ; 9781424493128 (ISBN) Shahbazi, M ; Gaillard, A ; Poure, P ; Zolghadri, M. R ; Sharif University of Technology
    Fast fault detection and converter reconfiguration is necessary for fault tolerant doubly fed induction generator (DFIG) in wind energy conversion systems (WECS) to prevent further damage and to make possible the continuity of service. Extra sensors are needed in order to detect the faults rapidly. In this paper, a very fast FPGA-based fault detection scheme is presented that minimizes the number of additional voltage sensors. A fault tolerant converter topology for this application is studied. Control and fault detection system are implemented on a single FPGA and Hardware in the Loop experiments are performed to evaluate the proposed detection scheme, the digital controller and the fault... 

    Sensor fault-tolerant scheme for IPM synchronous motor drives via nonlinear observer

    , Article AUPEC'09 - 19th Australasian Universities Power Engineering Conference: Sustainable Energy Technologies and Systems, 27 September 2009 through 30 September 2009, Adelaide ; 2009 ; 9780863967184 (ISBN) Nademi, H ; Farshidnia, A ; Keivanian, R ; Sharif University of Technology
    This paper describes a control scheme that allows an IPMS motor drive system to operate in the event of current and speed sensor faults. This task can be achieved by two control strategies: a nominal performance controller and a fault detection part. The nominal controller combines field oriented control and addresses fault tolerance scheme. Fault-tolerant strategy will operate in parallel with the system until a fault is detected. This approach is based on the adaptive backstepping observer. Stator resistance as possible source of system uncertainty is taken into account under different operating conditions. Sensors failure are detected and developed observer is used to estimate currents...