首页期刊导航|Bulletin of the Polish Academy of Sciences
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Bulletin of the Polish Academy of Sciences
Bulletin of the Polish Academy of Sciences
Bulletin of the Polish Academy of Sciences

Bulletin of the Polish Academy of Sciences

0239-7528

Bulletin of the Polish Academy of Sciences/Journal Bulletin of the Polish Academy of Sciences
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    The pointwise completeness and the pointwise degeneracy of fractional descriptor discrete-time linear systems

    5页
    查看更多>>摘要：The Drazin inverse of matrices is applied to analysis of the pointwise completeness and of the pointwise degeneracy of the fractional descriptor linear discrete-time systems.Necessary and sufficient conditions for the pointwise completeness and the pointwise degeneracy of the fractional descriptor linear discrete-time systems are established.It is shown that every fractional descriptor linear discrete-time systems is not pointwise complete and it is pointwise degenerated in one step(for i =1).
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Discrete Fourier transform and permutations

    11页
    查看更多>>摘要：It is well known that the magnitudes of the coefficients of the discrete Fourier transform(DFT) are invariant under certain operations on the input data.In this paper,the effects of rearranging the elements of an input data on its DFT are studied.In the one-dimensional case,the effects of permuting the elements of a finite sequence of length N on its Discrete Fourier transform(DFT) coefficients are investigated.The permutations that leave the unordered collection of Fourier coefficients and their magnitudes invariant are completely characterized.Conditions under which two different permutations give the same DFT coefficient magnitudes are given.The characterizations are based on the automorphism group of the additive group ZN of integers modulo N and the group of translations of ZN.As an application of the results presented,a generalization of the theorem characterizing all permutations that commute with the discrete Fourier transform is given.Numerical examples illustrate the obtained results.Possible generalizations and open problems are discussed.In higher dimensions,results on the effects of certain geometric transformations of an input data array on its DFT are given and illustrated with an example.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Assignability of numerical characteristics of time-varying systems

    16页
    查看更多>>摘要：The main aim of this article is to survey and discuss the existing state of art concerning the assignability by a feedback of numerical characteristics of linear continuous and discrete time-varying systems.Most of the results present necessary or sufficient conditions for different formulation of the Lyapunov spectrum assignability problem.These conditions are expressed in terms of various controllability types and optimalizability of the controlled systems and certain properties of the free system such as:regularity,diagonalizability,boundness away,integral separation and reducibility.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Fractional order model of measured quantity errors

    8页
    查看更多>>摘要：The paper presents an interpretation of fractional calculus for positive and negative orders of functions based on sampled measured quantities and their errors connected with digital signal processing.The derivative as a function limit and the Griinwald-Letnikov differintegral are shown in chapter 1 due to the similarity of the presented definkion.Notation of fractional calculus based on the gradient vector of measured quantities and its geometrical and physical interpretation of positive and negative orders are shown in chapters 2 and 3.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Input-output decoupling for a 3D free-floating satellite with a 3R manipulator with state and input disturbances

    9页
    查看更多>>摘要：This work presents the results acquired during simulation studies done for a 3D free-floating satellite behaviour with input-output decoupling approach.The research object is a free-floating satellite with a 3 DoF rigid 3D manipulator where a noise disturbance was introduced.Different approaches are used to compensate the noise influence.Systems using a visual aid to determine the position of manipulator joints are not ideal and introduce some uncertainties.What is more,determining the position from joints encoders is not error-free while computing angular velocity from numerical differentiation introduces even greater disturbance to the system.A couple of scenarios were investigated where state of the manipulator,including its position and velocity,was disturbed with homogeneous noise.Also the control inputs of the manipulator were disturbed.Simulation results show that the biggest impact on the control quality has a scenario where the satellite's state has been disturbed with additive noise.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Fast optimal feedback controller for electric linear actuator used in spreading systems of road spreaders

    7页
    查看更多>>摘要：Modern and innovative road spreaders are now equipped with a special swiveling mechanism of the spreading disc.It allows for adjusting a symmetrical or asymmetrical spreading pattern and provides for the possibility to maintain the size of the spreading surface and achieve an accurately defined spreading pattern with spreading widths.Thus the paper presents a modelling and control design methodology,and the concept is proposed to design high-performance and optimal drive systems for spreading devices.The paper deals with a nonlinear model of an electric linear actuator and solution of the new intelligent/optimal control problem for the actuator.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    LQG/LTR control of input-delayed discrete-time systems

    10页
    查看更多>>摘要：A simple robust cheap LQG control is considered for discrete-time systems with constant input delay.It is well known that the full loop transfer recovery(LTR) effect measured by error function Δ(z) can only be obtained for minimum-phase(MPH) systems without time-delay.Explicit analytical expressions for Δ(z) versus delay d are derived for both MPH and NMPH(nonminimum-phase) systems.Obviously,introducing delay deteriorates the LTR effect.In this context the ARMAX system as a simple example of noise-correlated system is examined.The robustness of LQG/LTR control is analyzed and compared with state prediction control whose robust stability is formulated via LMI.Also,the robustness with respect to uncertain time-delay is considered including the control systems which are unstable in open-loop.An analysis of LQG/LTR problem for noise-correlated systems,particularly for ARMAX system,is included and the case of proper systems is analyzed.Computer simulations of second-order systems with constant time-delay are given to illustrate the performance and recovery error for considered systems and controllers.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    The comparison of fault distinguishability approaches-case study

    10页
    查看更多>>摘要：A comprehensive characterization of four selected fault distinguishability methods is presented herein.All considered methods are derived from structural residual approaches referring to model-based diagnostics.In particular,these methods are based on a binary diagnostic matrix,fault isolation system,sequences of symptoms,and their combinations.Fault distinguishability issues are discussed based on an example of four pressure vessel system.Substantial benefits are shown in fault distinguishability figures obtained by utilising extended knowledge regarding fault-symptom relation.Finally,the values of three fault distinguishability metrics are calculated for each method.For the case study,the highest score is achieved using the multivalued fault isolation method combined with a diagnosis utilising information regarding the antecedence of symptoms.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    A survey of the synchronization process of synchronous generators and power electronic converters

    15页
    查看更多>>摘要：The process of synchronization of synchronous generators and power electronic converters with the power grid may take on quite different forms.This is due to their specific principles of operation and essential differences in energy conversion process.However,since synchronous generators and power converter often operate in the same utility network,coherent rules should be defined for them.Therefore,this paper aims at a formulation of the uniform and consistent interpretation of synchronization with the power grid for both types of aforementioned units.The author starts from the classic interpretation of synchronization for synchronous generators and power electronic converters,considered as micro-generators,specifies their mathematical and numerical models and then performs simulation tests.Selected synchronization algorithms are described in detail.Simulation tests are used for analysis of the elaboration of outcomes.The results of simulation tests are handled to formulate a uniform interpretation of synchronization for the micro-generation systems considered.Based on the results obtained,appropriate parallels are built between the two systems being compared.It is shown that the synchronization processes are identical regardless of the micro-generation unit considered.Nonetheless,they differ significantly due to their properties in transient states.Inverter systems have higher dynamics but their disadvantage lies in the relatively high sensitivity to disturbances and the complex selection process of the synchronization algorithm.
      原文链接:
    • NSTL
    • Polska Akad Nauk

    Current-fed quasi-Z-source H7 inverter with reduced stress on SiC power devices

    10页
    查看更多>>摘要：This paper discusses selected problems regarding a high-frequency improved current-fed quasi-Z-source inverter(iCFqZSI) designed and built with SiC power devices.At first,new,modified topology of the impedance network is presented.As the structure is derived from the series connection of two networks,the voltage stress across the SiC diodes and the inductors is reduced by a factor of two.Therefore,the SiC MOSFETs may be switched with frequencies above 100 kHz and volume and weight of the passive components is decreased.Furthermore,additional leg with two SiC MOSFETs working as a bidirectional switch is added to limit the current stress during the short-through states.In order to verify the performance of the proposed solution a 6 kVA laboratory model was designed to connect a 400 V DC source(battery) and a 3x400 V grid.According to presented simulations and experimental results high-frequency iCFqZSI is bidirectional-k may act as an inverter,but also as a rectifier.Performed measurements show correct operation at switching frequency of 100 kHz,high quality of the input and output waveforms is observed.The additional leg increases efficiency by up to 0.6%-peak value is 97.8%.
      原文链接:
    • NSTL
    • Polska Akad Nauk