Change search
Refine search result
1 - 49 of 49
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1. Bask, Michael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Analysis of least-squares state estimators for a harmonic oscillator2000In: Proceedings of the 39th IEEE Conference on Decision and Control: December 12 - 15, 2000, Sydney Convention and Exhibition Centre, Sydney, Australia, Piscataway, NJ: IEEE Communications Society, 2000, Vol. 4, p. 3819-3824Conference paper (Refereed)
    Abstract [en]

    The concept of least-squares observer is revisited. Robustness properties of this class of observers with respect to norm-bounded measurement noise are investigated and shown to be very much dependent on the operator chosen for the observer implementation. For the case of a harmonic oscillator, an explicit observer parameterization in terms of the implementation operator and the oscillator frequency is obtained, and observer's existence conditions are proven and analyzed

  • 2. Bask, Michael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    External model repetitive controller for active vibration isolation1999In: Proceedings of Active 99: International Symposium on Active Control of Sound and Vibration : an international INCE symposium, Fort Lauderdale, Florida, USA, 1999 December 02-04 / [ed] Scott Douglas, Washington, DC: Institute of noise control engineering , 1999, p. 177-188Conference paper (Refereed)
    Abstract [en]

    This paper deals with the External Model Repetitive Controller, a structure that combines the classical repetitive disturbance model (in the form of a time delay with a unit feedback) with a feedback of a disturbance estimate. The latter is often termed the External Model Controller and has a broad spectrum of technical applications, e.g., active vibration control. By analyzing the controller performance under the assumption of a disturbance period modeling error, it is shown that an unacceptable performance degradation might occur even for very small values of the modeling error

  • 3.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Arvanitidis, Ioannis
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Physical modeling and control of dynamic foaming in an LD-converter process2001In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 37, no 4, p. 1067-1073Article in journal (Refereed)
    Abstract [en]

    This paper deals with physical modeling and control of dynamic foaming in the LD-converter process. An experimental setup consisting of a water model, digital signal processor, and PC hardware is built and shown to be useful for studying dynamic foaming. Furthermore, a foam height estimation algorithm is presented and validated through experiments. Finally, sound signals from the LD-converter and water model are compared and similarities between them are found.

  • 4.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Arvanitidis, Ioannis
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jönsson, Pär
    Kungliga tekniska högskolan, KTH.
    Foam level control in a water model of the LD converter process2003In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 11, no 1, p. 49-56Article in journal (Refereed)
    Abstract [en]

    This paper deals with estimation and control of foam level in dynamic foaming. An improved foam level estimation methodology from a microphone signal and its automatic calibration is presented. The dynamical reaction of the foam level on air lance movements is modelled using system identification. Based on the resulting mathematical model, a controller for foam level stabilisation is designed and applied to a water model, representing the LD converter process. It is shown that the foam level can be controlled using a microphone as the measurement device and air lance movement as the actuator.

  • 5.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Pressure and flow control of a pulverized coal injection vessel1997In: Proceedings of the 1997 IEEE International Conference on Control Applications: October 5 - 7, 1997, Sheraton Hartford Hotel, Hartford, Connecticut, USA, Piscataway, NJ: IEEE Communications Society, 1997, p. 127-132Conference paper (Refereed)
    Abstract [en]

    Deals with model-based pressure and flow control of a fine coal injection vessel for the use of the blast furnace injection process. By means of system modeling and identification, the structure and behavior of the coal injection vessel are analyzed. It is shown that by use of model-based design, the control goals can be reached and the control performance can be significantly improved compared to the conventional PI-controllers. Several dynamic models of the plant are developed. A number of control strategies are presented and compared by means of practical tests. The LQG design method is used to design the controllers. All the controllers are validated through experiments on the coal injection plant at SSAB Tunnplat in Lulea, Sweden

  • 6.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Pressure and flow control of a pulverized coal injection vessel2000In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 8, no 6, p. 919-929Article in journal (Refereed)
    Abstract [en]

    This paper deals with model-based pressure and flow control of a fine coal injection vessel for the use of the blast furnace process. A control system should be in place to maintain a constant coal mass flow from the injection vessel to the blast furnace, since irregularities in the coal mass flow cause significant variations in the hot metal quality. By means of system modeling, the structure and behavior of the coal injection vessel are analyzed. It is shown that by use of a model-based design, the control objectives can be reached and the control performance can be significantly improved compared to the proportional integral (PI) controllers. Alternative control strategies are discussed and compared with the conventional design. The linear quadratic Gaussian (LQG) design method is used to design a multi-input multi-output (MIMO) controller which is validated through experiments on the coal injection plant at SSAB Tunnplat, Lulea, Sweden.

  • 7.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sensitivity analysis of an LQ optimal multivariable controller for a fine coal injection vessel1999In: Conference record of the 1999 IEEE Industry Applications Conference: fourth IAS annual meeting, 3 - 7 October 1999, Hyatt Regency, Phoenix, Arizona, USA, Piscataway, NJ: IEEE Communications Society, 1999, p. 1322-1328Conference paper (Refereed)
    Abstract [en]

    This paper deals with a sensitivity analysis of an LQ optimal multivariable controller for a fine coal injection vessel used in the blast furnace process. The multivariable controller from a previous work is briefly presented and the closed loop system is studied by means of a sensitivity analysis. Effects of disturbances and uncertainty on the closed loop system are studied based on analysis of the singular values of the sensitivity and the complementary sensitivity functions, the relative gain array and the minimized condition numbers. Finally, the sensitivity analysis is validated by the use of logged data from test operation at the coal injection plant at SSAB Tunnplat Lulea, Sweden

  • 8.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sensitivity analysis of an LQ optimal multivariable controller for a fine coal injection vessel2000In: IEEE transactions on industry applications, ISSN 0093-9994, E-ISSN 1939-9367, Vol. 36, no 3, p. 871-876Article in journal (Refereed)
    Abstract [en]

    This paper deals with a sensitivity analysis of a linear quadratic optimal multivariable controller for a fine coal injection vessel used in the blast furnace process. The multivariable controller from a previous work is briefly presented and the closed-loop system is studied by means of a sensitivity analysis. Effects of disturbances and uncertainty on the closed-loop system are studied based on analysis of the singular values of the sensitivity and the complementary sensitivity functions, the relative gain array, and the minimized condition numbers. Finally, the sensitivity analysis is validated by the use of logged data from test operation at the coal injection plant at SSAB Tunnplat AB, Lulea, Sweden

  • 9. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    L2 time delay estimation by means of Laguerre functions1999In: Proceedings of the 1999 American Control Conference :: June 2 - 4, 1999, Hyatt Regency San Diego, San Diego, California, USA, Piscataway, NJ: IEEE Communications Society, 1999, p. 455-459Conference paper (Refereed)
    Abstract [en]

    A straightforward method for the estimation of continuous time delays in narrowband signals is proposed. Delay estimation is especially of interest for those areas in signal processing that deal with the time delay of arrival (TDOA). The new method involves a parameterization of the identification problem in the Laguerre functions. This formalism is chosen due to the nature of the signals. Then the delay is obtained from a finite number of input/output Laguerre coefficients by using l2 norm optimal estimation. Estimation bounds are given and experiments from ultrasonic applications are presented

  • 10. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Laguerre domain estimation of time delays in narrowband ultrasonic echoes1999In: Proceedings of the 14th World Congress: International Federation of Automatic Control : Beijing, P.R. China, 5 - 9 July 1999 / [ed] Han-Fu Chen, Kildington: Publ. for the International Federation of Automatic Control by Pergamon, , 1999, p. 361-366Conference paper (Refereed)
    Abstract [en]

    The time delay of arrival (TDOA) is required in many areas in signal processing. In this paper we propose a novel and straightforward method to estimate small continuous time delays in narrowband signals out of a sampled sequence of the input and output signals. It is based on the parameterization of the identification problem in the Laguerre functions. An lp norm optimal estimator is then applied to estimate the delay. Furthermore, estimation bounds are studied and experiments from ultrasonic applications are presented to highlight the performance of the method

  • 11. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Laguerre domain estimation of time delays in narrowband ultrasonic echoes1999In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 32, no 2, p. 4129-4134Article in journal (Refereed)
    Abstract [en]

    The time delay of arrival (TDOA) is required in many areas in signal processing. In this paper we propose a novel and straightforward method to estimate small continuous time delays in narrowband signals out of a sampled sequence of the input and output signals. It is based on the parameterization of the identification problem in the Laguerre functions. An lp norm optimal estimator is then applied to estimate the delay. Furthermore, estimation bounds are studied and experiments from ultrasonic applications are presented to highlight the performance of the method

  • 12. Fischer, Britta
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Laguerre shift identification of a pressurized process1998In: Proceedings of the 1998 American Control Conference, ACC, June 24 - 26, 1998, Philadelphia, Pennsylvania, USA, Piscataway, NJ: IEEE Communications Society, 1998, p. 1933-1937Conference paper (Refereed)
  • 13.
    Johansson, Andreas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Model-based leakage detection in a pulverized coal injection vessel1999In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 7, no 6, p. 675-682Article in journal (Refereed)
    Abstract [en]

    A method for detecting and isolating incipient leakages in the valves of a pulverized coal injection vessel for a blast furnace process is presented. Nonlinear physical gray-box models of the plant are developed. Values of the unknown parameters are estimated by identification. Observers are constructed for these models and the residuals are used in a generalized likelihood ratio test. The method is successfully tested with real leakages intentionally introduced in the plant.

  • 14.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A guaranteed performance flux observer for induction machines1997In: Proceedings of the 36th IEEE Conference on Decision and Control: December 10 - 12, 1997, Hyatt Regency San Diego, San Diego, California, USA / IEEE Control Systems Society, Piscataway, NJ: IEEE Communications Society, 1997, p. 229-232Conference paper (Refereed)
    Abstract [en]

    By making use of a second-order complex-valued model of the induction machine dynamics, two observer design methods providing a guaranteed estimation error convergence rate at any, probably time-varying, rotor angular velocity are introduced. The design algorithms are based on eigenvector-eigenvalue assignment, alternatively matrix measure assignment and demonstrated to work well in an experiment

  • 15.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Continuous least-squares observers with applications1995In: Proceedings of the 34th IEEE Conference on Decision and Control: December 13 - 15, 1995, New Orleans Hilton Riverside, New Orleans, Louisiana, USA, Piscataway, NJ: IEEE Communications Society, 1995, p. 321-326Conference paper (Refereed)
    Abstract [en]

    A wide class of continuous least-squares (LS) observers is treated in a common framework provided by the pseudodifferential operator paradigm. It is shown that for the operators whose symbols satisfy certain conditions, the continuous LS-observer always exists provided observability of the plant. The general result is illustrated by an LS-observer stemmed from a sliding-window convolution operator. Applications to state feedback control and fault detection are discussed. A wide class of continuous least-squares (LS) observers is treated in a common framework provided by the pseudodifferential operator paradigm. It is shown that for the operators whose symbols satisfy certain conditions, the continuous LS-observer always exists provided observability of the plant. The general result is illustrated by an LS-observer stemmed from a sliding-window convolution operator. Applications to state feedback control and fault detection are discussed. A wide class of continuous least-squares (LS) observers is treated in a common framework provided by the pseudodifferential operator paradigm. It is shown that for the operators whose symbols satisfy certain conditions, the continuous LS-observer always exists provided observability of the plant. The general result is illustrated by an LS-observer stemmed from a sliding-window convolution operator. Applications to state feedback control and fault detection are discussed.

  • 16.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Continuous least-squares observers with applications1996In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 41, no 10, p. 1530-1537Article in journal (Refereed)
    Abstract [en]

    A wide class of continuous least-squares (LS) observers is treated in a common framework provided by the pseudodifferential operator paradigm. It is shown that for the operators whose symbols satisfy certain conditions, the continuous LS observer always exists, providing observability of the plant. The general result is illustrated by an LS observer stemming from a sliding-window convolution operator. Applications to state feedback control and fault detection are discussed

  • 17.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Disturbance attenuation enhancement in continuous Parity Space Methods1997In: 4th European Control Conference: ECC 1997, Brussels, Belgium 1 - 4 July 1997, 1997, p. 2529-2534Conference paper (Refereed)
    Abstract [en]

    This paper presents a generalization of the Parity Space Method (PSM) for fault detection and isolation by means of pseudodifferential operators. It is shown that a number of recently suggested Parity Space approaches in continuous time can be treated within a generic framework. Disturbance rejection properties of the parity checks written as polynomials in a pseudodifferential operator are studied in terms of 2- and ∞-norms. A consequent analysis demonstrates superior performance of the sliding-window convolution operator-based PSM

  • 18.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Disturbance attenuation in finite spectrum assignment controllers1996In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 29, no 1, p. 1620-1625Article in journal (Refereed)
    Abstract [en]

    Two finite-spectrum-assignment controllers for continuous linear dynamic systems with multiple time delays in input signal are introduced. The controllers are shown to comprise least-squares state estimators. Disturbance attenuation properties stipulated by the choice of shift operator in the observers are studied.

  • 19.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Disturbance attenuation in finite spectrum assignment controllers1997In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 33, no 6, p. 1163-1168Article in journal (Refereed)
    Abstract [en]

    Two finite-spectrum-assignment controllers for continuous linear dynamic systems with multiple time delays in input signal are introduced. The controllers are shown to comprise least-squares state estimators. Disturbance attenuation properties stipulated by the choice of shift operator in the observers are studied.

  • 20.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fault detection and isolation by a continuous parity space method1995In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 31, no 7, p. 1039-1044Article in journal (Refereed)
    Abstract [en]

    The well-known parity space method for fault detection and isolation is generalized to a continuous-time case. As in the discrete-time case, it is shown that the parity space equations can be implemented using a number of time delays, and are equivalent to a continuous deadbeat observer. Algorithms for isolation of sensor and actuator faults are derived and illustrated by a numerical example. (

  • 21.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fault detection and isolation by functional continuous deadbeat observers1996In: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 64, no 3, p. 425-439Article in journal (Refereed)
    Abstract [en]

    A continuous deadbeat observer estimating a linear combination of the state variables is introduced and applied to the problem of detecting and isolating faults in a linear time-invariant system. The existence conditions for the deadbeat observer are shown to be the same as for the functional Luenberger observer.

  • 22.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fault detection by continuous deadbeat observation1994In: Fault detection, supervision, and safety for technical processes: IFAC Symposium, Helsinki University of Technology, Espoo, Finland, 13 - 16 June 1994 / [ed] Tuula Ruokonen, Oxford: Pergamon Press, 1994, p. 28-33Conference paper (Refereed)
  • 23.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fault Detection by Continuous Dead-Beat Observation1994In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 27, no 5, p. 28-33Article in journal (Refereed)
    Abstract [en]

    An application of continuous-time deadbeat observation to fault analysis in linear dynamic systems is discussed. A finite memory residual chosen as a difference of two deadbeat state vector estimates is shown to be independent of both the state vector and control signal. The mapping of the fault mode to the residual is proven to be intrinsically BIBO-stable. Exploiting a decomposition of the “sliding-window” convolution operator, an upper bound for residual norm is derived and a fault detectability condition is obtained. Due to its simple structure, the deadbeat observer does not create a hard computational burden and can be easily implemented in real-time applications.

  • 24.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On robust stability of two flux observers for induction machines1999In: Proceedings of the 1999 IEEE International Conference on Control Applications: IEEE International Conference on Control Applications held together with IEEE International Symposium on Computer Aided Control System Design, August 22 - 27, 1999, Hapuna Beach Prince Hotel, Kohala, Coast-Island of Hawai'i, Hawai'i, USA, Piscataway, NJ: IEEE Communications Society, 1999, p. 962-967Conference paper (Refereed)
    Abstract [en]

    Deals with stability properties of two known flux observers for induction machines. It is shown that an arbitrary fast convergence rate in one of the observers is achieved at the expense of its robustness against uncertainty in the rotor angular velocity. Another observer is proven to retain stability notwithstanding any error in the angular velocity measurements, but its estimation error convergence rate is limited by the rotor time constant

  • 25.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Parity space method: a continuous time approach1994In: Proceedings of 1994 American Control Conference: the Stouffer Harborplace Hotel, Baltimore, Maryland, June 29 - July 1, 1994, Piscataway, NJ: IEEE Communications Society, 1994, Vol. Vol. 1, p. 662-665Conference paper (Refereed)
    Abstract [en]

    In this paper, the well-known parity space method is generalized to a continuous-time case both in deterministic and stochastic frameworks. As in the discrete-time case, it is shown that the parity space equations are equivalent to a continuous deadbeat observer or, taking into account measurement/process noise, to a finite-memory smoother. Both structures are infinite-dimensional by nature and can be implemented using a number of time delays. In the deterministic setting there is a significant liberty in choosing the delays. In the stochastic setting, to achieve optimality of the resulting parity equations, the delays are to be computed from the properties of noise.

  • 26.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    State estimation and fault detection by a bank of continuous finite-memory filters1996In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 29, no 1, p. 6542-6547Article in journal (Refereed)
    Abstract [en]

    A continuous observer estimating the state vector of a linear time-invariant system from the measurements of the system's inputs and outputs passed through a bank of finite-memory filters is introduced. System observability is shown to guarantee the existence of the observer. An application of the observer to the problem of detecting and isolating sensor and actuator faults is discussed

  • 27.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    State estimation and fault detection by a bank of continuous finite-memory filters1998In: International Journal of Control, ISSN 0020-7179, E-ISSN 1366-5820, Vol. 69, no 4, p. 499-517Article in journal (Refereed)
    Abstract [en]

    A continuous observer estimating the state vector of a linear time-invariant system from the measurements of the system's inputs and outputs passed through a bank of finite-memory filters is introduced. System observability is shown to guarantee the existence of the observer. An application of the observer to the problem of detecting and isolating sensor and actuator faults is discussed

  • 28.
    Medvedev, Alexander
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Toivonen, Hannu
    Department of Chemical Engineering, Åbo Akademi.
    Continuous-time deadbeat observation problem with application to predictive control of systems with delay1994In: Kybernetika (Praha), ISSN 0023-5954, E-ISSN 1805-949X, Vol. 30, no 6, p. 669-688Article in journal (Refereed)
    Abstract [en]

    A continuous-time deadbeat observation paradigm is discussed. Two observers are shown to estimate the state of a linear dynamic system in continuous time with respectively finite and infinite memory. Among other properties, BIBO-stability is proved for both structures. Based on the theory devised, deadbeat and asymptotic predictors for plants with delayed control are developed and shown to give rise to predictive feedback controllers assigning finite spectrum to the closed-loop system

  • 29.
    Medvedev, Alexander
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Toivonen, Hannu
    Department of Chemical Engineering, Åbo Akademi.
    Feedforward time-delay structures in state estimation: finite memory smoothing and continuous deadbeat observers1994In: IEE Proceedings - Control Theory and Applications, ISSN 1350-2379, E-ISSN 1359-7035, Vol. 141, no 2, p. 121-129Article in journal (Refereed)
    Abstract [en]

    The paper investigates the possibilities of using a feedforward time-delay structure for state estimation and smoothing in linear continuous dynamic systems. A fixed-lag finite-memory smoother and a continuous deadbeat observer are shown to be described by a linear combination of delayed measurements of the system inputs and outputs. To facilitate implementation of the observer-based controllers an infinite-memory deadbeat observer is introduced. Design methods are illustrated by numerical examples.

  • 30.
    Medvedev, Alexander
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Toivonen, Hannu T.
    Department of Chemical Engineering, Åbo Akademi.
    A systematic synthesis of a neural network-based smoother1992In: Proceedings of the 1992 IEEE International Symposium on Intelligent Control: 11 - 13 August, Forte Crest Glasgow Hotel, Glasgow, Scotland, U.K., New York: IEEE Communications Society, 1992, p. 147-151Conference paper (Refereed)
    Abstract [en]

    A feedforward neural network (FNN) implementation of a finite-memory smoother (FMS) is proposed. For a linear time-invariant dynamic system with measurement and process white noise, a single-layer FNN with delayed inputs is found to possess the same structure as the FMS designed by the least-squares method. The FNN-based FMS features definite speed advantages over conventional approaches and intrinsically finite process memory. Due to its parallel structure and absence of state vector integration, the FNN suffices for real-time applications. A numerical example illustrates the design procedure

  • 31.
    Medvedev, Alexander
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Toivonen, Hannu T.
    Department of Chemical Engineering, Åbo Akademi.
    Continuous finite-memory deadbeat observer1992In: Proceedings of the 1992 American Control Conference: the Westin Hotel, Chicago, Illinois, June 24 - 26, 1992, IEEE Communications Society, 1992, p. 1800-1806Conference paper (Refereed)
    Abstract [en]

    A significant class of model-based control approaches uses Kalman filters or Luenberger observers to estimate the plant state vector. Infinite dynamic observer memory inflicts a phenomenon generally referred to as divergence. To overcome this drawback, a structure that intrinsically has finite process memory and does not need state vector integration is proposed in this paper. The observer uses a finite number of delayed input/output measurements to reconstruct the state vector with zero error being provided with a process history over its largest time-delay. This property resembles the deadbeat observer performance for discrete time systems. Moreover, the largest time-delay value puts a natural limit to the observer memory. The Luenberger observer analogy proved to be a useful tool for the observer analysis and paves the way toward observer optimization.

  • 32.
    Medvedev, Alexander
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Zell, Caj
    Designing a flux observer for induction machines1994In: The proceedings of the third IEEE Conference on Control Applications: August 24th - 26th, 1994, venue the University of Strathclyde, Glasgow. Scotland, UK, Piscataway, NJ: IEEE Communications Society, 1994, p. 453-458Conference paper (Refereed)
  • 33.
    Stenlund, Benny
    et al.
    Luleå tekniska universitet.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Level control of cascade coupled flotation tanks2002In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 33, no 22, p. 185-190Article in journal (Refereed)
    Abstract [en]

    At the Boliden's concentrator in Aitik, bulk flotation constitutes an important part of the process for extracting valuable minerals from the ore. A series of flotation cells consists of five tanks connected in cascade with control valves between the tanks and a slowly varying flow of mineral slurry into the first tank. This paper deals with a comparative study of control strategies for level control in a flotation series in Aitik. The aim is to show the potential performance improvements taking into account couplings between the process state variables. Two control strategies are considered; a decoupling controller and a linear quadratic (LQ) optimal multivariable controller. Experiments with both structures show a significant enhancement of the level control performance as compared to the original SISO design

  • 34.
    Stenlund, Benny
    et al.
    Luleå tekniska universitet.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Level control of cascade coupled flotation tanks2002In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 10, no 4, p. 443-448Article in journal (Refereed)
    Abstract [en]

    At the Boliden's concentrator in Aitik, bulk flotation constitutes an important part of the process for extracting valuable minerals from the ore. A series of flotation cells consists of five tanks connected in cascade with control valves between the tanks and a slowly varying flow of mineral slurry into the first tank. This paper deals with a comparative study of control strategies for level control in a flotation series in Aitik. The aim is to show the potential performance improvements taking into account couplings between the process state variables. Two control strategies are considered; a decoupling controller and a linear quadratic (LQ) optimal multivariable controller. Experiments with both structures show a significant enhancement of the level control performance as compared to the original SISO design

  • 35. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimation of induction machine parameters at start-up using current envelope2002In: Conference record of the 2002 IEEE Industry Applications Conference: 37th IAS annual meeting ; 13 - 18 October 2002, Pittsburgh, Pennsylvania, USA, Piscataway, NJ :: IEEE Communications Society, 2002, p. 1163-1170Conference paper (Refereed)
    Abstract [en]

    A new method for estimation of electrical parameters in Induction Machines (IM) is presented. Evaluation of the parameters is performed by considering the envelope of the stator currents under motor start-up, thus avoiding the high sampling rates necessary for logging the actual currents. The use of start-up data makes the method attractive in the IM control and monitoring applications where the parameter estimates can be used for adjusting the control law or evaluating the motor condition. It is also demonstrated that the use of a simplified decoupled dynamic model of the IM in the estimation algorithm does not significantly worsen the quality of the obtained parameter estimates. Both simulations and experiments show fast convergence of the suggested algorithm.

  • 36. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Guaranteed convergence rate for linear-quadratic optimal time-varying observers2006In: Proceedings of the 45th IEEE Conference on Decision and Control: San Diego, CA, 13 - 15 December 2006, Piscataway, NJ: IEEE Communications Society, 2006, p. 181-188Conference paper (Refereed)
    Abstract [en]

    A well-known method by Anderson and Moore for optimal quadratic feedback design with guaranteed convergence rate for linear time-invariant systems is generalized to linear complex-valued time-varying systems and convergence rates. The resulting method is applied to observer design and illustrated by solving the problem of flux estimation in induction machines. A pre-assigned time-varying convergence rate is shown to improve the observer's transients in comparison with a constant one. The suggested design technique can be readily utilized for nonlinear state-affine systems

  • 37. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Linear-quadratic optimal time-varying observers with time-varying guaranteed convergence rate2009In: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 3, no 2, p. 181-188Article in journal (Refereed)
    Abstract [en]

    well-known method by Anderson and Moore for optimal quadratic feedback design with guaranteed constant convergence rate for linear time-invariant systems is generalised to linear complex-valued time-varying systems and time-varying convergence rates. The resulting method is readily applicable to observer design for state-affine systems and unifies methods developed there with the classical quadratic optimal state estimation and control. A pre-assigned time-varying convergence rate is shown to significantly improve the observer's transients in comparison with a constant one being employed for flux estimation in induction machines.

  • 38. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On observability and controllability of faulty induction machines2006In: American Control Conference: Mineapolis, Minnesota, USA, June 14-16, 2006, Piscataway, NJ: IEEE Communications Society, 2006, p. 4399-4405Conference paper (Refereed)
    Abstract [en]

    In this paper an analysis of observability and controllability of the electrical part of faulty (non-symmetric) induction machines (IMs) is performed. A two-axis model of healthy or faulty IM is studied and the conditions under which it does not degenerate to a descriptor system are obtained. When degeneration does not occur and stator voltages, stator currents and the rotational angle/speed of the rotor are measured, a fault in the IM does not, in general, render the motor neither unobservable nor uncontrollable. However, it turns out that when the rotor resistance is very small, problems with observability and controllability still may arise.

  • 39. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On-line estimation of all electrical parameters in induction machines subject to stator fault2007In: IEEE International Conference on Control Applications, 2007 : CCA 2007: 1 - 3 Oct. 2007, Singapore ; [part of IEEE Multi-Conference on Systems and Control, MSC], Piscataway, NJ: IEEE Communications Society, 2007, p. 527-532Conference paper (Refereed)
    Abstract [en]

    Identification of all the electrical parameters of Induction Machines (IMs) is a prerequisite for successful model-based control and/or fault detection. Most of the existing identification methods of symmetrical IMs are, strictly speaking, valid only at stationary conditions, which limitation results in either poor dynamics excitation or gross approximation errors, depending on the working conditions of the motor. In this paper, the topic of identification of all electrical parameters of faulty IMs is addressed for the first time. A method for on-line observer-based estimation of all electrical parameters of IMs with faulty stator is presented aiming primarily at fault tolerant control and fault detection. The approach does not rely on any assumptions regarding the rotor angular speed and/or acceleration.

  • 40. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    On-line estimation of all electrical parameters in symmetrical and faulty induction machines: stator fault case2006Report (Other academic)
    Abstract [en]

    Identification of all the electrical parameters of Induction Machines (IMs) is a prerequisite for successful model-based control and/or fault detection. Various approaches have been proposed previously: off-line experiments under alternating stationary conditions, least squares batch and on-line estimation, to name only a few. Both continuous and discrete time have been considered, all of them utilizing models for symmetrical IMs. Existing methods for identification of the electrical parameters of the IM are strictly speaking valid only at stationary conditions, which limitation results in either poor dynamics excitation or gross approximation errors, depending on the working conditions of the motor. Unrealistic assumptions about the rotor's angular acceleration are also often employed. The topic of identification of all electrical parameters of faulty IMs has not been addressed so far. In this paper, a method for on-line observer-based estimation of all electrical parameters of symmetrical IMs as well as IMs with faulty stator is presented aiming primarily at fault tolerant control and fault detection. The approach does not rely on any assumptions regarding the rotor's angular speed and/or acceleration.

  • 41. Stocks, Mikael
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Open loop stabilization of the rotor angular speed in the induction machine2002In: Proceedings of the 2002 IEEE International Conference on Control Applications: September 18 - 20, 2002, Scottish Exhibition and Conference Centre, Glasgow, Scotland, U.K., Piscataway, NJ: IEEE Communications Society, 2002, p. 108-113Conference paper (Refereed)
    Abstract [en]

    The stationary conditions for an induction machine (IM) fed by a voltage source containing more than one frequency are studied. Furthermore, it is shown that given one: harmonic input signal, it is possible to stabilize the angular speed of the IM at a beforehand chosen level, by a special choice of frequency and amplitude of a second signal. A generalization to a broader class of feeding signals is provided. The theoretical results suggest that conventional linear time-invariant identification of electrical parameters of the IM become applicable, since using two different symmetrical signals at once will guarantee sufficiently rich excitation for successful identification. Moreover, the method may be used for a new kind of control, where some control algorithm changes the amplitude and/or frequency of the two symmetrical signals.

  • 42. Stocks, Mikael
    et al.
    Rodjukov, Fedor
    Faculty of Mathematics and Mechanics, Saint-Petersburg State University.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Experimental validation of idealized two-axis models of faulty induction machines2006In: 2006 American Control Conference: Minneapolis, MN, 14 - 16 June 2006, Piscataway, NJ: IEEE Communications Society, 2006, p. 1845-1850Conference paper (Refereed)
    Abstract [en]

    In this paper, two dynamical models of the induction machine (IM) subject to electrical faults in the stator and rotor respectively are validated against experimental data. The considered stator faults are inter-turn short circuit in one of the phases and increased phase winding resistance. The rotor model is validated against an IM with one broken rotor bar, but otherwise healthy. The model parameters are estimated by the Gauss-Newton method and the obtained estimates are compared and discussed. The validation results show, for each of the considered faults, very good agreement between simulations and experiments. This makes the models promising in various applications involving asymmetric IM such as fault tolerant motor drives and motor condition monitoring.

  • 43. Stocks, Mikael
    et al.
    Rodjukov, Fedor
    Faculty of Mathematics and Mechanics, Saint-Petersburg State University.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Idealized two-axis model of induction machines under stator fault2006In: 2006 1st IEEE Conference on Industrial Electronics and Applications: Singapore, 24 - 26 May 2006, Piscataway, NJ: IEEE Communications Society, 2006, p. 1-7Conference paper (Refereed)
    Abstract [en]

    In this paper, a low differential order model describing the dynamics of IMs with faulty stator is developed. The modelling is performed under well established idealizing assumptions regarding the magnetic and electrical properties of the motor. Typical motor faults as inter-turn short circuit and increased winding resistance are taken into account. The resulting model can be handled analytically and serve as a ground for fault detection and fault tolerant control of the IM. For each of the considered faults, very good agreement between simulations and experimental data collected from mass-produced industrial IMs is observed.

  • 44. Stocks, Mikael
    et al.
    Rodjukov, Fedor
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Idealized two-axis models of faulty induction machines2005Report (Other academic)
    Abstract [en]

    In this report a general framework for developing two-axis models for Induction Machines (IMs) with electrical faults is presented. It produces models that are of reasonably low differential order, suitable for mathematical analysis and can serve as a ground for fault detection and fault tolerant control of the IM. The modelling is performed by applying well established idealizing assumptions regarding the magnetic and electrical properties of the motor. In particular, models describing the IM subject to electrical faults in the stator and rotor are derived. Typical motor faults as inter-turn short circuit, increased winding resistance and broken rotor bars are taken into account. The models are validated against data collected from mass-produced industrial IMs. The validation shows very good agreement between simulations and experiment, for each of the considered faults. Finally, a stability proof for the derived models is presented enabling their use in control and monitoring applications.

  • 45.
    Widlund, Daniel
    et al.
    Department of Metallurgy, Royal Institute of Technology.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gyllenram, Rutger
    Kobolde AB.
    Towards Model-Based Closed-Loop Control of the Basic Oxygen Steelmaking Process1998In: Elsevier IFAC Publications / IFAC Proceedings series, ISSN 1474-6670, Vol. 31, no 23, p. 69-74Article in journal (Refereed)
    Abstract [en]

    Model-based closed-loop control of the basic oxygen steelmaking process will give an opportunity to increase process operation performance. By using control algorithms that interact with thermodynamical and physical models capable of making real-time predictions of the effects of control actions, the time delays in order to wait for process response will be eliminated. Existing limitations like pre-set lance programs can be avoided. This paper outlines the concept of a recently started project aiming at model-based closed-loop control as well as present the initial work that has been made on the subject.

  • 46. Zell, Caj
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Fault detection and isolation in processes involving induction machines1997In: COMADEM '97 / [ed] Erkki Jantunen; Kenneth Holmberg; Raj B.K.N. Rao, Espoo: Valtion teknillinen tutkimuskeskus. Tie- ja liikennelaboratorio , 1997, Vol. 1, p. 223-232Conference paper (Refereed)
  • 47. Zell, Caj
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Reduced-order flux observers with arbitrary convergence rate1995In: Proceedings of the 4th IEEE Conference on Control Applications: The Desmond Hotel, Albany, New York, September 28 - 29, 1995, Piscataway, NJ: IEEE Communications Society, 1995, p. 793-798Conference paper (Refereed)
    Abstract [en]

    This paper describes a method of designing reduced-order observers in the space-phasor flux description of the induction machine. By making use of the second-order complex model of the induction machine, two reduced-order observer structures with time-invariant feedback gains are derived and shown to possess arbitrary convergence rate. Experimental runs facilitate comparison of the suggested reduced-order observers with the well-known full-order time-variant feedback gain observer.

  • 48. Zell, Caj
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Robust detection and isolation of mechanical faults in processes driven by induction machines1998In: Proceedings of the 1998 American Control Conference, ACC, June 24 - 26, 1998, Philadelphia, Pennsylvania, USA, Piscataway, NJ: IEEE Communications Society, 1998, p. 3307-3311Conference paper (Refereed)
    Abstract [en]

    A robust model-based technique for fault detection and isolation in electro-mechanical systems comprising induction machines is introduced. A state observer for reconstructing the magnetic flux components of the induction machine and thereby the electrical torque is used in combination with a robust state estimator for the mechanical load torque based on a model with structured uncertainties. The fault detection and isolation problem is reduced to validation/invalidation of the models representing different fault hypotheses. The practical applicability of the method is demonstrated in a simulation example

  • 49. Zell, Caj
    et al.
    Medvedev, Alexander
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sampled-data flux estimation in induction machines1996In: Proceedings of the 1996 IEEE International Conference on Control Applications, Piscataway, NJ: IEEE Communications Society, 1996, p. 1102-1107Conference paper (Refereed)
    Abstract [en]

    This paper proposes a discrete-time flux observer for the induction machine. The observer is based on a discretization of the continuous-time space-phasor flux description facilitated by a Jordan factorization of the system matrix. The proposed observer requires no assumption of stepwise constancy of the input voltage and can be modified to be especially well suited for the case of sinusoidal inputs. This makes the observer an effective tool in, for example, monitoring applications where the proposed observer is shown to yield accurate flux estimates at considerably lower sampling rates than has been possible with conventional methods. Numerical examples, as well as experimental runs, show comparisons of the proposed observer and a well-known discrete-time observer

1 - 49 of 49
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf