Xiaofu Ji

University of Newcastle, Newcastle, New South Wales, Australia

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Publications (30)23.02 Total impact

  • Xiaofu Ji, Hongye Su
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    ABSTRACT: Jensen’s inequality and extended Jensen’s inequality are two important integral inequalities when problems of stability analysis and controller synthesis for time-delay systems are considered. The extended Jensen’s inequality introduces two additional free matrices and is generally regarded to be less conservative than Jensen’s inequality. The equivalence between Jensen’s inequality and extended Jensen’s inequality in bounding the quadratic term in Lyapunov functional of time-delay systems is presented and theoretically proved. It is shown that the extended Jensen’s inequality does not decrease the lower bound of this quadratic term obtained using Jensen’s inequality, and then it does not reduce the conservativeness though two additional free matrices and are involved.
    Automatica 03/2015; 53. DOI:10.1016/j.automatica.2014.12.030 · 3.13 Impact Factor
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    Xiaofu Ji, Mingwei Ren, Hongye Su
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    ABSTRACT: This paper is concerned with the problem of designing a time-delay output feedback controller for master-slave synchronization of Lur'e systems. The time delay is divided into two intervals and different energy functions are defined in each interval, which together provide a new Lyapunov–Krasovskii functional and derive a new delay-dependent synchronization criterion. A sufficient condition for the existence of such a feedback controller is given, and an explicit expression of such a controller is also achieved. These algorithms are formulated in terms of linear matrix inequalities that can be solved easily. Chua's circuit is used to illustrate the effectiveness of the design method.
    Asian Journal of Control 01/2014; 16(1). DOI:10.1002/asjc.671 · 1.41 Impact Factor
  • Information Technology Journal 12/2013; 12(23):7534-7540. DOI:10.3923/itj.2013.7534.7540
  • Xiaofu Ji, Ceng Zu, Hongye Su
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    ABSTRACT: This paper is concerned with the problem of designing a time delay output feedback controller for the master-slave synchronisation of singular Lur'e systems. Based on the generalised Lyapunov-Krasovskii functional theory, a new delay-dependent synchronisation criterion is derived by dividing the time delay into two intervals and designing different energy functions in each interval. The controller design algorithm is also given in terms of non-linear matrix inequality. Two computational trackable algorithms, that is, linear matrix inequality algorithm and non-linear optimisation algorithm, are given respectively to solve this non-linear matrix inequality. A numerical example is used to illustrate the effectiveness of the design method.
    International Journal of Modelling Identification and Control 01/2013; 19(2):125 - 133. DOI:10.1504/IJMIC.2013.054316
  • Xianglin Zhu, Xiaofu Ji
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    ABSTRACT: This paper studies the H ∞ synthesis for discrete linear systems with state saturation nonlinearity. By introducing a free matrix whose infinity norm is less than or equal to 1, the state under saturation constraint is confined in a convex hull. Based on this, a bounded real lemma for discrete linear systems with state saturation is obtained in terms of matrix inequalities which can be solved by using the presented iterative linear matrix inequality algorithm. The synthesis problem is also solved and an explicit expression for the desired state feedback control law is given. A numerical example shows the effectiveness and correctness of the presented method.
    Kongzhi yu Juece/Control and Decision 01/2013; 28(2).
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    ABSTRACT: This paper concerns the stability analysis problem of discrete linear systems with state saturation using a saturation-dependent Lyapunov functional. We introduce a free matrix characterized by the sum of the absolute value of each elements for each row less than 1, which makes the state with saturation constraint reside in a convex polyhedron. A saturation-dependent Lyapunov functional is then designed to obtain a sufficient condition for such systems to be globally asymptotically stable. Based on this stability criterion, the state feedback control law synthesis problem is also studied. The obtained results are formulated in terms of bilinear matrix inequalities that can be solved by the presented iterative linear matrix inequality algorithm. Two numerical examples are used to demonstrate the effectiveness of the proposed method.
    Journal of Control Theory and Applications 11/2012; 10(4). DOI:10.1007/s11768-012-0176-x
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    ABSTRACT: In order to conquer the problems of traditional bearingless switched reluctance generators (BSRGs) such as nonlinear coupling between suspension subsystem and generation subsystem as well as radial force reduction at the aligned rotor position, a novel BSRG with hybrid stator is formulated in this paper. Its hybrid stator consists of suspension poles and generation poles, and can be independently controlled. To begin with, the basic structure and running principle are introduced. Then the main magnetic characteristics are analyzed. In the end, finite element method (FEM) is included to validate the performance of suspension subsystem and generating subsystem.
    Journal of Computational and Theoretical Nanoscience 05/2012; 11(1):570-573. DOI:10.1166/asl.2012.2983 · 1.34 Impact Factor
  • Xiaofu Ji, Mingwei Ren, Zebin Yang
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    ABSTRACT: This paper is concerned with stability analysis for discrete linear time delay systems with state saturation nonlinearity. By introducing a free matrix whose infinity norm is less than or equal to 1, the discrete state under state saturation constraint is confined in a convex hull. In this way, a sufficient criterion for discrete linear time-delay systems with state saturation to be asymptotically stable is obtained in terms of bilinear matrix inequalities that can be solved using the presented iterative linear matrix inequality algorithm. The state feedback control law synthesis problem is also solved and the corresponding iterative linear matrix synthesis algorithm is given. Two numerical examples are used to show that the presented method is applicable and effective.
    Control Conference (CCC), 2012 31st Chinese; 01/2012
  • Zebin Yang, Xinhua Zhang, Xiaofu Ji
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    ABSTRACT: This paper is concerned with the problem of designing a time-delay output feedback control law for masterslave synchronization of singular Lur’e systems. Using generalized Lyapunov stability theory, a sufficient condition for the existence of such feedback control law is given and an explicit expression of such control law is also achieved. These algorithms are formulated in terms of linear matrix inequalities, which can be easily performed numerically. A numerical example is used to illustrate the effectiveness of the design method.
    Journal of Control Theory and Applications 11/2011; 9(4). DOI:10.1007/s11768-011-0065-8
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    ABSTRACT: The problem of global asymptotic stability analysis and controller synthesis for a class of discrete linear time-delay systems with state saturation nonlinearities is investigated. With the introduction of a free matrix whose infinity norm is less than or equal to 1, the state of discrete linear time-delay systems with state saturation is bounded by a convex hull, which makes it feasible to apply a suitable Lyapunov functional to obtain a sufficient condition for global asymptotic stability. It is also shown that this condition can be extended to controller synthesis and discrete time-delay systems with partial state saturation. The obtained results are expressed in terms of matrix inequalities that can be solved by the presented iterative linear matrix inequality approach. The effectiveness of these results is demonstrated by some numerical examples.
    International Journal of Systems Science 03/2011; 42(3):397-406. DOI:10.1080/00207720903572406 · 1.58 Impact Factor
  • Xiaofu Ji, Yukun Sun, Hongye Su
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    ABSTRACT: A method to estimate the domain of attraction for a singular discrete linear system under a saturated linear feedback is established. Simple conditions are derived in terms of an auxiliary feedback matrix for determining if a given ellipsoid is contractively invariant. These conditions are expressed in terms of linear matrix inequalities. The largest contractively invariant ellipsoid can also be determined by solving an optimization problem with linear matrix inequality constraints. This result is extended to the design of feedback gain that results in the largest contractively invariant ellipsoid, which is also a linear matrix inequality optimization problem. A numerical example demonstrates the applicability and effectiveness of the presented method.Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
    Asian Journal of Control 03/2011; 13(2). DOI:10.1002/asjc.307 · 1.41 Impact Factor
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    ABSTRACT: The problem of robust H∞ control problem for a class of uncertain linear time-delay singularly perturbed systems is considered. Based on the Lyapunov-Kravoskii and linear matrix inequality approach, a bounded real lemma is obtained for the considered linear time-delay singularly perturbed system to be stable with disturbance attenuation level less than a given bound for perturbed parameter ε ∈ (0, ε*]. The robust H∞ performance analysis and robust H∞ controller synthesis problems are also solved. Two numerical examples are given to illustrate the applicability of the proposed approach.
    01/2011;
  • Qianwen Xiang, Yukun Sun, Xiaofu Ji
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    ABSTRACT: The least square support vector machine (LS-SVM) inductance model optimized by the particle swarm optimization (PSO) algorithm is presented for bearingless switched reluctance motor (BSRM). The training sample is first obtained using the 3D finite element model (FEM) of the prototype, and then LS-SVM model is built, whose hyper-parameters are optimized using PSO algorithm. The absolute error and relative error are computed, which demonstrate the high accuracy of the proposed model.
  • Xiaofu Ji, Zebin Yang, Hongye Su
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    ABSTRACT: The problem of robust stabilization for uncertain discrete singular time-delay systems is investigated. The considered systems are subject to norm-bounded parameter uncertainties and constant time delay. A linear matrix inequality (LMI) condition is proposed for a discrete singular time-delay system to be regular, causal and stable. With this condition, the problems of robust stability and stabilization are solved. The obtained results are formulated in terms of strict LMIs. An explicit expression of the desired state-feedback control law is also given, which involves no matrix decomposition. The proposed synthesis method is illustrated by a numerical example. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
    Asian Journal of Control 03/2010; 12(2):216 - 222. DOI:10.1002/asjc.167 · 1.41 Impact Factor
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    ABSTRACT: The robust D stabilization problem is considered for singular systems with polytopic uncertainties in this paper. Both the derivative matrix E and the state matrix A are with uncertainties, which were not considered before. First, with the introduction of some free matrices, a necessary and sufficient condition for the singular system to be D stable is proposed, based on which, the robust D stable problem is solved, and a sufficient condition for the closed system to be robust D stabilizable is obtained. The desired state feedback controller is given in an explicit expression. Numerical examples show the efficiency of the proposed approach. KeywordsSingular system-Robust D stabilization-Free matrices-LMI region
    Journal of Control Theory and Applications 01/2010; 8(2). DOI:10.1007/s11768-010-8077-3
  • Xiaofu Ji, Yukun Sun, Hongye Su
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    ABSTRACT: The problem of H∞ control for a class of linear systems with state saturation nonlinearities is considered in this paper. By introducing a row diagonally dominant matrix with negative diagonal elements and a diagonal matrix with positive elements, the H∞ control problem is reduced to a matrix inequality feasibility problem that can be solved by the proposed iterative linear matrix inequality algorithm. The effectiveness of the presented method is demonstrated by a numerical example. Copyright © 2009 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
    Asian Journal of Control 11/2009; 11(6):694 - 699. DOI:10.1002/asjc.151 · 1.41 Impact Factor
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    ABSTRACT: The mixed L 1/H-infinity control problem for a class of uncertain linear singular systems is considered using a matrix inequality approach. The purpose is to design a state feedback control law such that the resultant closed-loop system is regular, impulse-free, stable and satisfies some given mixed L 1/H-infinity performance. A sufficient condition for the existence of such control law is given in terms of a set of matrix inequalities by the introduction of inescapable set and *-norm. When these matrix inequalities are feasible, an explicit expression of the desired state feedback control law is given. A numerical example is used to demonstrate the applicability of the proposed approach.
    Journal of Control Theory and Applications 02/2009; 7(2):134-138. DOI:10.1007/s11768-009-7169-4
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    ABSTRACT: This paper deals with the problem of absolute stability and robust stability of a class of neutral systems with sector-bounded nonlinearity and mixed time-varying delays. Some new delay-dependent stability criteria are presented based on Lyapunov stability theory and formulated in terms of strict linear matrix inequalities (LMIs). Neither model transformation nor bounding technique for cross terms is required in obtaining the stability conditions. Since both the neutral- and discrete-delays are taken into account, the obtained criterion is less conservative than the previous ones, which is illustrated by numerical examples.
    Nonlinear Analysis Real World Applications 12/2008; DOI:10.1016/j.nonrwa.2007.07.003 · 2.34 Impact Factor
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    ABSTRACT: A multivariable nonlinear decoupling control strategy based on least squares support vector machine (LS-SVM) inverse system is presented for a L-lysine fermentation process. The invertibility of dynamic model for L-lysine fermentation process is verified and is obtained offline using a LS-SVM with Gaussian kernel, which connects in series with the original system and makes the complicated nonlinear multivariable system decoupled into several independent single-input-single-output (SISO) pseudo- linear subsystems. The simulation results demonstrate the applicability and superiority of the presented method.
    Natural Computation, 2008. ICNC '08. Fourth International Conference on; 11/2008
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    ABSTRACT: This note concerns the robust absolute stability analysis for a class of general neutral type Lurie indirect control systems with nonlinearity located in an infinite sector or finite one. By using Lyapunov functional of quadratic form with integral term and introducing some free-weighting matrices, some delay-dependent robust absolute stability criteria are presented in terms of strict linear matrix inequalities. Neither model transformation nor bounding technique is required here. The obtained criteria are less conservative than previous ones, which are illustrated by numerical examples. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
    Asian Journal of Control 11/2008; 10(6):698 - 707. DOI:10.1002/asjc.70 · 1.41 Impact Factor

Publication Stats

199 Citations
23.02 Total Impact Points

Institutions

  • 2015
    • University of Newcastle
      • School of Electrical Engineering and Computer Science
      Newcastle, New South Wales, Australia
  • 2008–2012
    • Jiangsu University
      Chenkiang, Jiangsu Sheng, China
  • 2005–2006
    • Zhejiang University
      • Institute of Cyber-Systems and Control
      Hang-hsien, Zhejiang Sheng, China