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  • 1.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Dudarenko, Natalia
    Saint-Petersburg National Research University of Information Technologies, Mechanics and Optics.
    Reconfiguration of the air control system of a bark boiler2016In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 24, no 2, p. 565-577Article in journal (Refereed)
    Abstract [en]

    In this paper the problem of reconfiguration of controllers in the air control system of a bark boiler is addressed. The air control system of a bark boiler is considered as an interconnected multivariable system and the configuration of the controllers is adapted with the perspective to improve the closed loop performance of the system. The paper proposes a generic procedure for the reconfiguration of controllers using a combination of established theories together with rather recently proposed methods. The procedure is applied to a model of the air flow system, which is derived in this study. The results indicate that a significant performance improvement can be achieved by reconfiguring the control system instead of re-design the process. The improvement is quantified through theoretical assessment, simulation studies, and performance assessment of pilot tests at the bark boiler at SCA Obbola Sweden. It can be concluded that the proposed procedure is both efficient and easy to apply.

  • 2.
    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.

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  • 3.
    Fresk, Emil
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nikolakopoulos, George
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Gustafsson, Thomas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Generalized Reduced-Complexity Inertial Navigation System for Unmanned Aerial Vehicles2017In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 25, no 1, p. 192-207Article in journal (Refereed)
    Abstract [en]

    In this paper, a generic approach to attitude and position estimation, suited for any type of unmanned aerial vehicle, is presented. This will be achieved by establishing a generic framework, which can be extended using adaptive methods to determine the thrust properties of the engines and the mass of the aircraft, while keeping the overall computational complexity of the system low. Furthermore, the effect of magnetic disturbances will be reduced in a novel way by confining the magnetic errors to affect only heading, without compromising the pitch and roll estimation of the system with error-based estimation. The efficacy of the proposed framework will be evaluated through extended simulations and experimental validations on a multirotor. Finally, guidelines will be provided toward: 1) an implementation with a reduced computational complexity and 2) the utilization of the square-root formulations of the extended Kalman filter for extending the dynamic range of the filter.  

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  • 4.
    Hartland, N.R.
    et al.
    Department of Mechanical Engineering, University of Auckland.
    Mace, B.R.
    Institute of Sound and Vibration Research, University of Southampton.
    Jones, Richard W.
    Luleå tekniska universitet.
    Adaptive-passive control of vibration transmission in beams using electro/magnetorheological fluid filled inserts2001In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 9, no 2, p. 209-220Article in journal (Refereed)
    Abstract [en]

    A method for the control of the transmission of bending vibrations in beams is described. A composite beam (a structural insert) is inserted into a part of the structure to affect the transmission there. The insert comprises two elastic face plates and a central core of tunable fluid such as an electrorheological (ER) or magnetorheological (MR) fluid. By adjusting the applied electric or magnetic field the rheological properties of the fluid can be controlled and hence so too can the vibration transmission properties of the insert. Theoretical results concerning the transmission of vibrations in beam-like structures are reviewed. Numerical results are presented for the transmission through ER and MR fluid filled inserts, with experimental results for an ER case. The transmission is seen to show a pass/stopband structure with the stopbands being tunable.

  • 5.
    Hillerström, Gunnar
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Adaptive suppression of vibrations: a repetitive control approach1996In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 4, no 1, p. 72-78Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to present an adaptive solution to suppression of vibrations. Adaptation is appropriate whenever the fundamental frequency is unknown or drifting, e.g., when the vibration is caused by a rotational machine with unknown rotational speed. The approach presented here has its roots in repetitive control based on models of isolated frequencies rather than the commonly used delay model. The relationship between different modeled frequencies is fixed by the model structure, and the fundamental frequency is obtained by gradient descent or Newton's method. To show the feasibility of this approach, it was used to reduce the vibrations on a lever that were caused by a motor with imbalance in its rotation. As an actuator, a standard loudspeaker was used, and the vibration was sensed by an accelerometer.

  • 6.
    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.

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  • 7.
    Lucchese, Riccardo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Birk, Wolfgang
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A study of fine and coarse actuation capabilities in air-cooled server racks: control strategies and cost analysis2019In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865Article in journal (Refereed)
  • 8.
    Lucchese, Riccardo
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Controlled Direct Liquid Cooling of Data Servers2019In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865Article in journal (Refereed)
  • 9.
    Norlander, Torbjörn
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Mäkilä, Pertti
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Defragilization in optimal design and its application to fixed structure LQ controller design2001In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 9, no 4, p. 590-598Article in journal (Refereed)
    Abstract [en]

    In this work, we present a general methodology to address the recently debated fragility issue in optimization-based modern control systems design. Based on this methodology we have developed a defragilization procedure which is applied to fixed structure linear quadratic (LQ) control design. Issues regarding computational efficiency of the procedure and the relationship between controller fragility and controller parameterization are discussed via two examples taken from practical applications. The first example is based on a rotary cement kiln control application and the latter example on a wing flutter control application. The procedure could also be used in design problems with specifications which are related to controller nonfragility requirements, e.g., so as to allow some degree of controller online tuning.

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  • 10.
    Saradagi, Akshit
    et al.
    Indian Institute of Technology System (IIT System), Dept Elect Engn, Madras 600036, Tamil Nadu, India.
    Muralidharan, Vijay
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Krishnan, Vishaal
    University of California San Diego,Dept Mech Engn, La Jolla, CA 92093 USA .
    Menta, Sandeep
    Indian Institute of Technology System (IIT System), Dept Elect Engn, Madras 600036, Tamil Nadu, India.
    Formation Control and Trajectory Tracking of Nonholonomic Mobile Robots2018In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 26, no 6, p. 2250-2258Article in journal (Refereed)
    Abstract [en]

    In this brief, we design Lyapunov-based control laws to achieve two multi-objective tasks for a network of open-loop unstable, nonholonomic mobile inverted pendulum (MIP) robots, using a connected undirected graph for inter-agent communication. Using the first protocol, translationally invariant formations are achieved along with the synchronization of attitudes and heading velocities to desired values. Using the second protocol, the robots move into a formation and asymptotically track a trajectory. The control laws are based on the kinematic model of the mobile robot, and control torques for the MIPs are extracted using a two-loop control architecture. Both the protocols guarantee boundedness of the linear heading velocity, which is necessary for the stability of the two-loop control architecture. The proposed control laws are experimentally validated on indigenously built MIP robots.

  • 11.
    Zhang, Weidong
    et al.
    Department of Automation, Shanghai Jiaotong University.
    Lin, Chen
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Multivariable smith predictors design for nonsquare plants2006In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 14, no 6, p. 1145-1149Article in journal (Refereed)
    Abstract [en]

    The goal of this brief is to provide a solution to the optimal design problem of decoupled multivariable Smith Predictor for general linear stable plants with multiple time delays. The design procedure is divided into three steps. In the first step, a nonsquare plant is factored into the "delay free" part and delay part, and the "delay free" part is further factored into minimum phase part and nonminimum phase part. In the second step, the factorization is utilized to analytically derive the optimal multivariable Smith Predictor based on only output feedback. Finally, the controller is shaped by a filter for specified inputs and a simple procedure is developed to quantitatively tune the closed-loop response expressed in time domain or frequency domain

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