Control-canonical-form method applied to generating systems to improve dynamic stability characteristics

Contents The control-canonical-form (CCF) method is introduced for the purpose of applying it to high-order state-space single-input single or multiple-output (SISO or SIMO) and multiple-input multiple-output (MIMO) linear time-invariant system models to determine closed-loop systems (i.e. design robust controllers) from which enchanced dynamic stability characteristics and overall performance of these systems is achieved. The method has been applied successfully to a SISO 6th-order linearized state-space open-loop model (representing a simplified hydro power system), and to a MIMO 8th-order linearized state-space open-loop model (representing an 87.5 kVA synchronous machine with conventional exciter supplying power to an electric utility system through an interconnection network)

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Anwendung der kanonischen Form der Zustandsrückführung auf Erzeugersysteme zur Verbesserung der dynamischen Stabilitätseigenschaften

Übersicht Die Methode der kanonischen Form wird auf lineare zeitinvariante Systeme höherer Ordnung im Zustandsraum angewendet, die eine oder mehrere Eingangsgrößen bei einer oder mehreren Ausgangsgrößen aufweisen. Damit werden robuste Regler entworfen, welche die dynamische Stabilität und das gesamte Betriebsverhalten verbessern. Die Methode wurde erfolgreich auf ein linearisiertes Modell sechster Ordnung mit einem Eingang und einem Ausgang angewendet, das vereinfachend eine Wasserkraftanlage darstellt; außerdem auf ein linearisiertes Zustandsmodell achter Ordnung einer Synchronmaschine 87,5kVA mit konventioneller Erregung, die über ein Verbindungsnetzwerk in das öffentliche Netz einspeist.

     

Practical aspects of self‐tuning controllers

The contribution presents a class of Single Input Single Output (SISO) discrete self‐tuning controllers suitable for industrial applications. The proposed adaptive controllers can be divided into three groups. The first group covers PID adaptive algorithms with using of traditional methods. The second group is based on polynomial solutions of control problems and the third group is derived from the use of the minimization of linear quadratic criterion. All types of algorithms were unified and incorporated into a Matlab ‐ like Toolbox for self‐tuning control. Copyright © 1999 John Wiley & Sons, Ltd.     

Output‐feedback co‐ordinated decentralized adaptive tracking: The case of MIMO subsystems with delayed interconnections

Exact decentralized output‐feedback Lyapunov‐based designs of direct model reference adaptive control (MRAC) for linear interconnected delay systems with MIMO subsystems are introduced. The design process uses a co‐ordinated decentralized structure of adaptive control with reference model co‐ordination which requires an exchange of signals between the different reference models. It is shown that in the framework of the reference model co‐ordination zero residual tracking error is possible, exactly as in the case with SISO subsystems. We develop decentralized MRAC on the base of a priori information about only the local subsystems gain frequency matrices without additional a priori knowledge about the full system gain frequency matrix. To achieve a better adaptation performance we propose proportional, integral time‐delayed adaptation laws. The appropriate Lyapunov–Krasovskii type functional is suggested to design the update mechanism for the controller parameters, and in order to prove stability. Two different adaptive DMRAC schemes are proposed, being the first asymptotic exact zero tracking results for linear interconnected delay systems with MIMO subsystems. Copyright © 2005 John Wiley & Sons, Ltd.     

Joint optimization in MIMO multiple relay channels

The joint optimization of cooperative relays in a multiple-input multiple-output (MIMO) multiple relay aided communication system is discussed in this article. A simple linear optimization solution is designed and a multi-user scheduling algorithm is proposed. The new algorithm chooses users with larger cooperation diversity gains from the waiting list to serve; it can reduce inter-user interference and maintain space diversity caused by parallel transmission of multiple relays, and achieve higher system throughput. __________ Translated from Journal on Communications, 2008, 29(3): 40–46 [译自: 通信学报]     

Anisotropic piezoelectric properties of 1–3 ceramic / polymer composites comprising rods with elliptic cross section

This paper is concerned with the study of effective piezoelectric properties of 1–3 ferroelectric ceramic / polymer composites. The aim of this paper is to show the role of a combination of the electromechanical properties of components and microgeometry of the 1–3 composite in determining its anisotropic piezoelectric response. The system of ceramic rods in the form of elliptic cylinders is an important microgeometric factor that influences the piezoelectric coefficients and their anisotropy. Examples of the piezoelectric response and anisotropy are analysed for the 1–3 composites based on either “soft” or “hard” ceramic and having either piezo-active or piezo-passive matrix. Combinations of the ceramic and polymer components are found that provide different volume-fraction dependences of the piezoelectric coefficients d_3j^* d_{3j}^{*} and g_3j^* g_{3j}^{*} : both monotonic, both non-monotonic, monotonic d_3j^* d_{3j}^{*} and non-monotonic g_3j^* g_{3j}^{*} , and vice versa. Examples of volume-fraction dependences of electromechanical coupling factors k_3j^* k_{3j}^{*} are also considered. A comparison of the effective piezoelectric coefficients calculated by the effective field method and the finite element method is carried out for different compositions in wide ranges of the ratio of semiaxes of the ellipse and of volume fractions of the components. Good agreement between data calculated by means of the aforementioned methods is obtained for the 1–3 structure comprising the elliptic cylinders.     

Parameter estimation for MIMO system based on MUSIC and ML methods

The frequency offset and channel gain estimation problem for multiple-input multiple-output (MIMO) systems in the case of flat-fading channels is addressed. Based on the multiple signal classification (MUSIC) and the maximum likelihood (ML) methods, a new joint estimation algorithm of frequency offsets and channel gains is proposed. The new algorithm has three steps. A subset of frequency offsets is first estimated with the MUSIC algorithm. All frequency offsets in the subset are then identified with the ML method. Finally, channel gains are calculated with the ML estimator. The algorithm is a one-dimensional search scheme and therefore greatly decreases the complexity of joint ML estimation, which is essentially a multi-dimensional search scheme. __________ Translated from Journal of Electronics and Information Technology, 2008, 30(7): 1552–1556 [译自: 电子与信息学报]     

Diversity analysis of space-time-frequency coded broadband MIMO-OFDM system with correlation across space time and frequency

For the frequency selective and time variant multiple-input multiple-output (MIMO) channel model taking into account transmitting and receiving antenna correlation, the diversity of space-time-frequency coded broadband orthogonal frequency division multiplexing (MIMO-OFDM) system is analyzed. Based on the average pairwise error probability (PEP), the design criterion of space-time-frequency code (STFC) is expanded. For a given STFC, it is found that the achievable diversity order is related to the transmitter and the receiver correlation matrix as well as the time correlation and frequency correlation matrix. The maximum available diversity of STFC over the correlation channel is Lrank(P)rank(Q)rank(R _T). The space-time code and space-frequency code are special cases in our approach. Simulation results validate the findings. __________ Translated from Journal of Southeast University (Natural Science Edition), 2007, 37(4): 549–553 [译自: 东南大学学报(自然科学版)]     

The state-space realization of an n-dimensional transfer function

In this paper the non-minimal real state-space realization for n-dimensional transfer functions with polylinear numerators and denominators is stated and proved. It is also shown that the every existing realization of an n-dimensional transfer function can be achieved from the companion matrix of some (n + 1)-variable polynomial linear with respect to one of its variables.     

MULTIVARIABLE CONSTRAINED ADAPTIVE GPC: THEORY AND EXPERIMENTAL EVALUATION

This paper deals with on-line identification and constrained long-range predictive control of multivariable systems. It extends a recently proposed augmented upper diagonal factorization identification (AUDI) algorithm to identify input–output models of multivariable systems with distinct time delays. The multi-input, multi-output (MIMO AUDI) algorithm can simultaneously identify the process model order and process parameters. The MIMO AUDI algorithm is implemented by decomposing a MIMO system into as many multi-input, single-output (MISO) subsystems as the number of outputs and then identifying each MISO subsystem separately. The performance of the new MIMO AUDI algorithm is demonstrated by application to input–output data from a real process. The extension of this algorithm by incorporating a variable forgetting factor with a lower bound in its value is implemented on real plant data to demonstrate ‘alertness’ of the estimator. This paper evaluates the performance of the MIMO adaptive generalized predictive control algorithm with and without constraints by experimental application on a computer-interfaced, pilot-scale process. The MIMO adaptive GPC is shown to have good regulatory plus servo-tracking properties. © 1997 John Wiley & Sons, Ltd.     

Adaptive inverse control of unmodeled stable SISO and MIMO linear systems

Adaptive‐signal‐processing techniques have been employed with great success in such applications as: system identification, channel equalization, statistical prediction and noise/echo cancellation. From a mathematical point of view, there is little difference between these applications and the types of operations required by control systems to control a dynamical system. This paper presents an approach to control systems called adaptive inverse control in which adaptive‐signal‐processing techniques are used throughout. Adaptive inverse control comprises three simultaneous processes. The plant is automatically modeled using adaptive system identification techniques. The dynamic response of the system is adaptively controlled using the resulting model and methods related to channel equalization. Adaptive disturbance canceling is performed using methods similar to noise canceling. The method applies directly to stable single‐input single‐output (SISO) and multi‐input multi‐output (MIMO) plants, and does not require an a priori model of the system. If the plant is unstable, it must first be stabilized using conventional feedback. This implies that at least a rudimentary model need be made if the plant is unstable. Once the plant is stabilized, adaptive inverse control may be applied to the stabilized system. Copyright © 2002 John Wiley & Sons, Ltd.     

Some topologico-dynamical properties of linear passive reciprocal networks

The paper considers the complete solvability and the order of complexity of passive RLCT (T = multiwinding ideal transformer) networks. A topological approach based on the determinant polynomial of the matrix of hybrid equations, formed as a set of 1st-order differential and algebraic equations, reveals the structure of the formulation tree and the subnetworks accountable for degeneracies. Topological and algebraic degeneracies are defined. Necessary and sufficient conditions for complete solvability are derived, and two algorithms are given to determine the order of complexity topologically, i.e. without having an explicit state-space representation.     

Error-space estimate method for generalized synergic target tracking

To improve the tracking accuracy and stability of an optic-electronic target tracking system, the concept of generalized synergic target and an algorithm named error-space estimate method is presented. In this algorithm, the motion of target is described by guide data and guide errors, and then the maneuver of the target is separated into guide data and guide errors to reduce the maneuver level. Then state estimate is implemented in target state-space and error-space respectively, and the prediction data of target position are acquired by synthesizing the filtering data from target state-space according to kinematic model and the prediction data from errorspace according to guide error model. Differing from typical multi-model method, the kinematic and guide error models work concurrently rather than switch between models. Experiment results show that the performance of the algorithm is better than Kalman filter and strong tracking filter at the same maneuver level. __________ Translated from Journal of University of Electronic Science and Technology of China, 2007, 36(2): 217–219 [译自: 电子科技大学学报]     

应用神经网络的电动机控制系统

异步电动机控制系统是一个较难的工程问题。由于交流电动机机械系统具有非线性动态特性,以及交流电动机的某些状态变量无法测量,这些问题都使系统控制问题变得复杂。另外温度发生变化时,转子电阻发生很大变化,这又是一个控制系统难以克服的问题。使用神经网络的自适应控制技术来实现感应电动机的控制问题,第一种是单输入—单输出(SISO)系统,控制器使用静态多层感知器神经网络(MLP神经网络);第二种是多输入—多输出(MIMO)系统,控制器使用递归神经网络为动态控制系统方案。本文重点讨论MIMO系统。     

An AM-RLC scheme with adaptive acknowledgement interval

The acknowledged mode radio link control (AM-RLC) protocol is one of the most important radio protocols in wideband code division multiple access (WCDMA) and time division-synchronization code division multiple access (TD-SCDMA) mobile communication systems. A modified AM-RLC scheme with adaptive acknowledgement interval is proposed. At the receiver, the acknowledgement interval is dynamically changed according to the channel status. The simulation results show that the proposed AM-RLC scheme outperforms the fixed acknowledgement interval AM-RLC scheme in terms of frame delivery delay and protocol overhead. __________ Translated from Journal on Communications, 2008, 29(3): 119–122 [译自: 通信学报]     

Central suboptimal H∞ filter design for nonlinear polynomial systems

This paper presents the central finite‐dimensional H_∞ filter for nonlinear polynomial systems, which is suboptimal for a given threshold γ with respect to a modified Bolza–Meyer quadratic criterion including the attenuation control term with the opposite sign. In contrast to the previously obtained results, the paper reduces the original H_∞ filtering problem to the corresponding optimal H₂ filtering problem, using the technique proposed in (IEEE Trans. Automat. Control 1989; 34 :831–847). The paper presents the central suboptimal H_∞ filter for the general case of nonlinear polynomial systems based on the optimal H₂ filter given in (Int. J. Robust Nonlinear Control 2006; 16 :287–298). The central suboptimal H_∞ filter is also derived in a closed finite‐dimensional form for third (and less) degree polynomial system states. Numerical simulations are conducted to verify performance of the designed central suboptimal filter for nonlinear polynomial systems against the central suboptimal H_∞ filter available for the corresponding linearized system. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis of band gap of non-bravais lattice photonic crystal fiber

This article designs a novel type of non-bravais lattice photonic crystal fiber. To form the nesting complexperiod with positive and negative refractive index materials respectively, a cylinder with the same radius and negative refractive index is introduced into the center of each lattice unit cell in the traditional square lattice air-holes photonic crystal fiber. The photonic band-gap of the photonic crystal fiber is calculated numerically by the plane wave expansion method. The result shows that compared with the traditional square photonic band-gap fiber (PBGF), when R/Λ is 0.35, the refractive index of the substrate, airhole, and medium-column are 1.30, 1.0, and −1:0, respectively. This new PBGF can transmit signal by the photonic band-gap effect. When the lattice constant Λ varies from 1:5 μm to 3:0 μm, the range of the wavelength ranges from 880 nm to 2300 nm. __________ Translated from Optoelectronic Technology, 2007, 27(4): 257–260 [译自: 光电子技术]     

On Improved Representation Theorems For Multidimensional Lossless Bounded Matrices

An improved form of representation of multidimensional (k-D) discrete lossless two-ports in a form similar to the well-known Belevitch canonical form of classical one-dimensional network theory is presented. Representations of the transfer function matrix, chain matrix and hybrid matrix associated with discrete lossless multidimensional twoports are derived on the basis of our earlier result. An improved form of representation of multidimensional (k-D) discrete lossless two-ports in a form similar to the well-known Belevitch canonical polynomial associated with the system. This fact is true for both discrete and continuous systems and apparently has remained unnoticed even in ID.     

A novel hybrid fix‐LLL lattice reduction algorithm for MIMO detection system

Lenstra–Lenstra–Lovász (LLL) is an effective lattice reduction algorithm for multiple‐input multiple‐output (MIMO) systems, which was considered to achieve full diversity in the MIMO fading channel. In the LLL algorithm, size reduction is performed for pairs of consecutive basis vectors, and the concern of numerical stability is raised. However, the whole complexity of the LLL algorithm is of polynomial order, and its characteristics of the convergence perform poor in MIMO system. In this paper, a variant version, named the novel hybrid algorithm, which combines both fix measurement and round measurement, is proposed. By modifying the iteration criterion and choosing proper values of the parameters, the algorithm has a large probability to skip the size reduction and cause a faster convergence, It means in one algorithm iteration the LLL potential can be reduced as much as possible. Also, the performance bound derived by the proximity factor shows that the hybrid LLL has a minor performance loss compared to the LLL algorithm. As a direct consequence, in simulation results, the hybrid LLL algorithm can make a better compromise between the rate of convergence, complexity of the algorithm, and algorithmic performance. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Optimal approximation of head-related transfer function''s pole-zero model based on genetic algorithm

In the research on spatial hearing and virtual auditory space, it is important to effectively model the head-related transfer functions (HRTFs). Based on the analysis of the HRTFs’ spectrum and some perspectives of psychoacoustics, this paper applied multiple demes’ parallel and real-valued coding genetic algorithm (GA) to approximate the HRTFs’ zero-pole model. Using the logarithmic magnitude’s error criterion for the human auditory sense, the results show that the performance of the GA is on the average 39 % better than that of the traditional Prony method, and 46 % better than that of the Yule-Walker algorithm. __________ Translated from Journal of Southeast University (Science and Technology), 2006, 36(1): 19–24 (in Chinese)