Uniform asymptotic stability of linear non-autonomous systems

In this paper a new method is developed for obtaining necessary and sufficient conditions which, when satisfied, guarantee that a linear non-autonomous system will be uniformly asymptotically stable. The method is essentially an extension of two earlier theorems on the asymptotic stability of linear autonomous systems; these theorems, developed by the same author, are here extended to non-autonomous systems. Basically, the method consists of ascertaining whether a certain matrix is positive definite. In general, it is shown that this knowledge is necessary and sufficient to determine whether a linear non-autonomous system is exponentially stable and hence uniformly asymptotically stable.     

Example applications of the linear adaptive design technique

Adaptive controllers can be designed by a variety of different methodologies that have been developed over the past 35 years. However, all these methodologies have one thing in common; they lead to adaptive controllers that are intriniscatly non-linear in structure. Recently a new, unorthodox approach to the adaptive control problem has been developed. This new methodology leads to a new class of adaptive controllers that, in many cases, are entirely linear and have all-constant parameters (constant gains). In the present paper this new approach to adaptive control is used to design‘linear adaptive controllers’for two example applications, and the closed-loop adaptive performance obtained in each case is illustrated by digital simulation tests. These results demonstrate that the new linear adaptive controllers are able to produce a surprisingly high-degree of adaptation over significant ranges of plant parameter variations and disturbances.     

Position control for a linear slider with twin linear drives

In this paper, position control of a linear slider with twin linear drives is considered. Recently, for high‐speed response, several linear motors have been used for linear slider systems. In such a linear slider, if the linear drives are controlled individually, their position responses may undergo vibrational disturbance by interaction with the output of the motors. To control this vibration, this paper presents a dynamic model of a linear slider system which consists of two motion systems decoupled by coordinate transformation, and proposes a feedback controller which is designed for these two decoupled systems. The effectiveness of the proposed method is confirmed by experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(4): 68–76, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10291     

Online trained support vector machines‐based generalized predictive control of non‐linear systems

In this work, an online support vector machines (SVM) training method (Neural Comput. 2003; 15 : 2683–2703), referred to as the accurate online support vector regression (AOSVR) algorithm, is embedded in the previously proposed support vector machines‐based generalized predictive control (SVM‐Based GPC) architecture (Support vector machines based generalized predictive control, under review), thereby obtaining a powerful scheme for controlling non‐linear systems adaptively. Starting with an initially empty SVM model of the unknown plant, the proposed online SVM‐based GPC method performs the modelling and control tasks simultaneously. At each iteration, if the SVM model is not accurate enough to represent the plant dynamics at the current operating point, it is updated with the training data formed by persistently exciting random input signal applied to the plant, otherwise, if the model is accepted as accurate, a generalized predictive control signal based on the obtained SVM model is applied to the plant. After a short transient time, the model can satisfactorily reflect the behaviour of the plant in the whole phase space or operation region. The incremental algorithm of AOSVR enables the SVM model to learn the new training data pair, while the decremental algorithm allows the SVM model to forget the oldest training point. Thus, the SVM model can adapt the changes in the plant and also in the operating conditions. The simulation results on non‐linear systems have revealed that the proposed method provides an excellent control quality. Furthermore, it maintains its performance when a measurement noise is added to the output of the underlying system. Copyright © 2006 John Wiley & Sons, Ltd.     

Iterative solution of boundary element approximations for electric and magnetic fields

The calculation of potentials in homogeneous and isotropic media by the boundary element method has the advantage that a harmonic solution of Laplace's equation is obtained for given approximated boundary conditions. The technique leads to the solution of linear systems with full matrices of dimension 1000–10,000 for medium- and large-sized three-dimensional problems, An efficient solution procedure of the linear systems is required. While the iterative solution of the large and sparse linear systems arising from the finite difference or the finite element method is well documented, the systems resulting from the boundary element method are typically solved by direct methods. However, in many cases an iterative solver needs far fewer operations to achieve a sufficient accuracy. Importantly, there are many alternative methods, each of them well suited for different types of problem. Here, we provide an overview of state-of-the-art iterative solvers. We will discuss the particular methods that have been successfully applied to systems arising from field calculations in the high-voltage engineering by the boundary element method. The selection of appropriate methods is discussed. We demonstrate that iterative solutions can be much faster than direct solvers with regards to the number of operations. Furthermore, these solvers are optimally suited for today's supercomputers because they can be efficiently vectorized and parallelized.     

A numerical filtering method for linear state-space models with Markov switching

A class of discrete-time random processes arising in engineering and econometrics applications consists of a linear state-space model whose parameters are modulated by the state of a finite-state Markov chain. Typical filtering approaches are collapsing methods, which approximate filtered distributions by mixtures of Gaussians, each Gaussian corresponding to one possibility of the recent history of the Markov chain, and particle methods. This article presents an alternative approach to filtering these processes based on keeping track of the values of the underlying filtered density and its characteristic function on grids. We prove that it has favorable convergence properties under certain assumptions. On the other hand, as a grid method, it suffers from the curse of dimensionality, and so is only suitable for low-dimensional systems. We compare our method to collapsing filters and a particle filter with examples, and find that it can outperform them on 1- and 2-dimensional problems, but loses its speed advantage on 3-dimensional systems. Meanwhile, our method has a proven theoretical convergence rate that is probably not achieved by collapsing and particle methods.     

On the critical behavior of linear and nonlinear dielectricpermittivity on approaching the critical consolute point

Results are presented of the dielectric permittivity ε and nonlinear dielectric effects (NDE) in binary mixtures on approaching the critical consolute point (CCP), focusing first on Piekara's findings [Phys. Rev. Vol.42, pp. 445-447, 1932, and C. R. Acad. Sci. Paris Vol. 203, pp. 1058-1059, 1936]. The presented results cover changes in temperature and pressure. For NDE particular attention is given to complex liquid features of critical mixtures appearing in ε and NDE tests. The latter are presented for the stationary and dynamic (time-resolved NDE) behavior. New results for NDE in nitrobenzene, hexane mixture with the lowest measurement frequency ever applied and in benzonitrile-isooctane mixture for dielectric permittivity are also included. For the latter, the first test of the relation: dε/dT α (T - T_C) ^-α is shown     

A Proposed Architecture for Polarization-Switching D/A Converter (PDAC)

The integration of ferroelectric capacitors with very large-scale integrated (VLSI) circuits on semiconductor wafers has been commercially viable for about one and a half decades. The primary applications of ferroelectric integrated circuits have been oriented to non-volatile memories and Gigabit dynamic random access memories (DRAMs). One potential application for ferroelectric capacitors is polarization-switching digital-to-analog converters (PDACs). In principle, PDACs make use of ferroelectric switching; i.e., spontaneous polarization is used as a new medium for data conversion other than the conventional conversion media such as voltage, current and charge. PDACs are analogous to charge-redistribution data converters that make use of charge and are implemented with normal linear capacitors. In addition to using a novel data-conversion medium, polarization-switching data converters require a novel architecture for circuit implementation. Presented here is a proposed architecture for PDACs. SPICE simulations verify the functionality of an 8-bit bipolar PDAC.     

Efficient implementation of pseudochaotic piecewise linear maps with high digitization accuracies

In this paper we discuss the efficient implementation of pseudochaotic piecewise linear maps with high digitization accuracies, taking the R'enyi chaotic map as a reference. The proposed digital architectures are based on a novel algorithmic approach that uses carry save adders for the nonlinear arithmetic modular calculations arising when computing piecewise linear maps with a finite precision. As a result, the system can be implemented by digital circuits obtaining high throughputs, which are not dependent on the digital resolution while involving a hardware complexity linearly proportional to the number of bits used for representing the discretized state. The proposed solutions result to be particularly suitable for the implementation of pseudorandom number generators based on pseudochaos, or for the definition of efficient digital blocks that can be integrated in most of the pseudochaotic cyphers proposed in the literature. Copyright © 2010 John Wiley & Sons, Ltd.     

Disordered lattice networks: general theory and simulations

In this work we develop a theory for describing random networks of resistors of the most general topology. This approach generalizes and unifies several statistical theories available in literature. We consider an n‐dimensional anisotropic random lattice where each node of the network is connected to a reference node through a given random resistor. This topology includes many structures of great interest both for theoretical and practical applications. For example, the one‐dimensional systems correspond to random ladder networks, two‐dimensional structures model films deposited on substrates and three‐dimensional lattices describe random heterogeneous materials. Moreover, the theory is able to take into account the anisotropic percolation problem for two‐ and three‐dimensional structures. The analytical results allow us to obtain the average behaviour of such networks, i.e. the electrical characterization of the corresponding physical systems. This effective medium theory is developed starting from the properties of the lattice Green's function of the network and from an ad hoc mean field procedure. An accurate analytical study of the related lattice Green's functions has been conducted obtaining many closed form results expressed in terms of elliptic integrals. All the theoretical results have been verified by means of numerical Monte‐Carlo simulations obtaining a remarkably good agreement between numerical and theoretical values. Copyright © 2005 John Wiley & Sons, Ltd.     

混合工质沸腾换热气泡形成功的推导及分析

推导和分析了混合工质及纯工质发生均质沸腾、壁面沸腾时气泡形成功,得出相同条件下混合工质气泡形成功比纯工质气泡形成功大,解释了混合工质沸腾换热系数降低的原因。     

Optimal filtering for incompletely measured polynomial states over linear observations

In this paper, the optimal filtering problem for polynomial system states over linear observations with an arbitrary, not necessarily invertible, observation matrix is treated proceeding from the general expression for the stochastic Ito differential of the optimal estimate and the error variance. As a result, the Ito differentials for the optimal estimate and error variance corresponding to the stated filtering problem are first derived. A transformation of the observation equation is introduced to reduce the original problem to the previously solved one with an invertible observation matrix. The procedure for obtaining a closed system of the filtering equations for any polynomial state over linear observations is then established, which yields the explicit closed form of the filtering equations in the particular case of a third‐order state equation. In the example, performance of the designed optimal filter is verified against a conventional extended Kalman–Bucy filter. Copyright © 2007 John Wiley & Sons, Ltd.     

A general stability criterion for switched linear systems having stable and unstable subsystems

We report conditions on a switching signal that guarantee that solutions of a switched linear system converge asymptotically to zero. These conditions apply to continuous, discrete‐time and hybrid switched linear systems, those having both stable subsystems and mixtures of stable and unstable subsystems. Copyright © 2012 John Wiley & Sons, Ltd.     

A linear synchronous generator with a power of 30 kW for wave-power engineering

A floating buoy absorber that allows direct conversion of wave energy into electricity using a linear generator is a simple, but promising, device for conversion of wave energy. Results of studies of direct conversion of wave energy using a moored floating point absorber and linear synchronous generator are considered in this paper. The average power and performance of a linear synchronous generator have been determined for a significant wave. An algorithm for calculations of equivalent frequencies and emf amplitudes has been suggested for a modular design of the linear synchronous generator. The analytical expressions and dependences to determine the number of pole pairs and modules, as well as the main dimensions of the machine, have been obtained. It has been concluded that it is necessary to increase the number of poles of a linear generator to obtain an efficient design with reduced weight and overall dimensions. Application of the concentrated winding and permanent magnets with a tangential position has been justified. The parameters of electromagnetic fields and the synchronous generator for different operational conditions have been determined by the finite-element method. The design data and parameters of the six-module, 16-pole SLGPM-30-16 permanent magnet linear generator with a rating power of 30 kW are considered. The design has been optimized by calculations of the electromagnetic field; as a result, a weight of the generator has been reduced and much higher specific ratings than those in similar developments and in other devices for converting ocean-wave energy have been obtained.     

Toepler's spark law in a GIS with compressed SF/sub 6/-N/sub 2/ mixture

This paper deals with the experimental measurements and analysis of the formative time lags to breakdown and an estimation of the Toepler's constant for gas gaps, under the application of 50 Hz AC voltage. The experiments were carried out in a 145 kV gas insulated system (GIS) bus duct with pure N/sub 2/, pure SF/sub 6/ and SF/sub 6/-N/sub 2/ mixture as insulating media. The formative time lags to breakdown in the gas gaps were measured using a fast response capacitive sensor. Toepler's spark law has been used to explain the breakdown phenomenon in the GIS and the values of Toepler's constant (k/sub t/), which gives an estimation of the formative time lags, were determined. Results show that the formative time lags vary inversely with gas pressure and the gas mixture concentrations for two gaps studied (0.46 mm and 0.61 mm). In the case of another gap (0.20 mm), the variation in the formative time lags with pressure as well as SE, concentration in the mixture has been found to be negligibly small between gas mixtures, although significant variation can be seen between pure SF/sub 6/ and pure N/sub 2/. Toepler's constant, k/sub t/, increases with gas pressure as well as SF/sub 6/ concentration in the mixture for the gaps studied. Hence, k/sub t/ is a function of the gas pressure and the concentrations of SF/sub 6/ in the gas mixture for the above-mentioned gaps.     

Searchless tuning of linear controllers for the minimum of quadratic criterion

A searchless method of calculating the tunings of typical controllers is developed for linear plants with a time delay, the use of which makes it possible to minimize the quadratic criterion I ₂ with respect to an internal disturbance. The basic idea of the method consists in obtaining the complex frequency response of a suboptimal linear controller, followed by approaching the characteristic of a typical controller to this frequency response in the essential frequency band using the least squares method. Recommendations on selecting the smoothing filter time constant and the suboptimal system’s dynamic error are given for a system comprising a PID controller and a second-order plant with a time delay.     

Mover design and performance analysis of linear synchronous reluctance motor with multiflux barrier

A synchronous reluctance motor has many advantages because it has no permanent magnet, such as low back emf in high‐speed operation, maintaining performance in a high‐temperature environment, and so on. Therefore, many rotor constructions have been studied and developed. The rotor with multiflux barrier structure has the merit of easy construction and high performance. The linear synchronous reluctance motor has been developed. It is necessary to improve the performance of the mover design for industrial use, because of its low power factor. In this paper, we propose a novel configuration of mover for the linear synchronous reluctance motor, and examine the static characteristics of the motor with reluctance equalization design by means of the finite element method. From analytical results, it is demonstrated that the static characteristics of the linear synchronous reluctance motor are greatly improved by the reluctance equalization design at the iron layer in the mover. © 2002 Scripta Technica, Electr Eng Jpn, 138(4): 61–69, 2002; DOI 10.1002/eej.1139     

基于高斯混合模型及近似线性规划的风电系统校正控制方法

提出一种基于高斯混合模型及近似线性规划的风电系统校正控制方法。考虑到风电及负荷功率预测误差的非高斯特性及相关性,建立了描述风电及负荷功率联合概率分布的高斯混合模型。考虑切负荷、发电机功率调整以及统一潮流控制器等控制措施,以控制代价最小为目标函数,构建了计及电压、频率及线路潮流等静态安全约束的风电系统校正控制优化问题的数学模型。为求解含不确定变量的非线性优化问题,依据高斯混合模型的性质,在稳态运行点的邻域内将非线性约束近似转化为线性约束,用线性规划方法求解,并不断迭代直至收敛。最后,将该方法应用于修改后的IEEE 10机39节点算例系统验证其有效性,与场景法的对比结果表明该方法求解效率较高,且具有较好的经济性。     

Mathematical simulation and parameter determination of regulation of a linear electrical reciprocating machine

A linear switched-reluctance electrical machine (LEM) intended to be used as an electric-power generator together with a free-piston internal-combustion engine (ICE) has been analyzed. Taking into account the hard service conditions of an electrical machine (EM) in close proximity to a cylinder ICE, hottemperature zones and heavy mechanical loads of the EM of the vent-inductor type have been recommended to be used. Development of a control system for this type of machine is one of the most complicated problems when developing it. It has been suggested to determine the reasonable principles and regulating algorithms of the machine that is being considered, as well as its regulation system and energy-data evaluation, on the basis of a model of the electromagnetic process. Taking into account the characteristic properties of the linear switched-reluctance machine as a modeling object, a mathematical model has been developed to solve the problems mentioned above. As stator phases have separate coil-flux guides and are not connected magnetically, the electromagnetic processes in each phase are analyzed independently. For experimental corroboration of ideas for design calculation, an experimental model of the machine has been constructed. Parameters required for modeling the characteristics’ correspondences of flux linkage and phase current’s generating force at various positions of a moving element have been determined for this machine experimentally. Performance of the linear switched reluctance electrical reciprocating machine has been analyzed with the mathematical model with moving-element movement frequencies unfeasible for study on a proving stand. Reasonable parameters of the current pulses’ phases of the machine have been determined, and its energy data have been evaluated. The obtained results have confirmed the correctness of the design approaches, choice of regulation principles, and adjustment of a linear vent-inductor electrical machine of forward and backward action and the feasibility of using it as an electric-power generator together with a free-piston ICE.