Qing-Guo Wang

National University of Singapore, Tumasik, Singapore

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Publications (213)385.74 Total impact

  • Chao Yu · Qing-Guo Wang · Dan Zhang · Lei Wang · Jiangshuai Huang
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    ABSTRACT: The outlier detection problem for dynamic systems is formulated as a matrix decomposition problem with low rank and sparse matrices, and further recast as a semidefinite programming problem. A fast algorithm is presented to solve the resulting problem while keeping the solution matrix structure and it can greatly reduce the computational cost over the standard interior-point method. The computational burden is further reduced by proper construction of subsets of the raw data without violating low-rank property of the involved matrix. The proposed method can make exact detection of outliers in case of no or little noise in output observations. In case of significant noise, a novel approach based on under-sampling with averaging is developed to denoise while retaining the saliency of outliers, and so-filtered data enables successful outlier detection with the proposed method while the existing filtering methods fail. Use of recovered "clean" data from the proposed method can give much better parameter estimation compared with that based on the raw data.
    05/2015; DOI:10.1109/TCYB.2015.2430356
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    Lei Wang · Sheng-yong Chen · Qing-guo Wang
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    ABSTRACT: This paper investigates global synchronization of asymmetrically coupled dynamical networks with nonidentical nodes in the sense of boundedness. A novel bounded synchronization criterion is presented by checking the validity of inequality involving the second smallest eigenvalue of a redefined symmetric matrix associated with the asymmetric Laplacian matrix. In particular, this criterion can be used to determine the global exponential synchronization of asymmetrically coupled networks with identical nodes by the proposed symmetrization operation, without assuming the symmetry or irreducibility of the coupling matrix. Comparing with the existing contributions, our synchronization result is less conservative and can overcome the complexity of calculating eigenvalues of an asymmetric Laplacian matrix. Numerical experiments are carried out to demonstrate the effectiveness of the method.
    Communications in Nonlinear Science and Numerical Simulation 04/2015; 22(1-3). DOI:10.1016/j.cnsns.2014.08.022 · 2.57 Impact Factor
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    Lei Wang · Micheal Z.Q. Chen · Qing-guo Wang
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    ABSTRACT: This paper investigates synchronization issues of a heterogeneous complex network with a general switching topology in the sense of boundedness, when no complete synchronization manifold exists. Several sufficient conditions are established with the Lyapunov method and the differential analysis of convergence to determine the existence and estimate the convergence domain for the local and global bounded synchronization of a heterogeneous complex network. By using the consensus convergence of a switched linear system associated with the switching topology, explicit bounds of the maximum deviation between nodes are obtained in the form of a scalar inequality involving the property of the consensus convergence, the homogeneous and heterogeneous dynamics of individual nodes for the local and global cases. These analytical results are simple yet generic, which can be used to explore synchronization issues of various complex networks. Finally, a numerical simulation illustrates their effectiveness.
    Automatica 04/2015; 56:19-24. DOI:10.1016/j.automatica.2015.03.020 · 3.13 Impact Factor
  • Dan Zhang · Rongyao Ling · Qing-Guo Wang · Li Yu · Yu Feng
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    ABSTRACT: This paper is concerned with the sensor-network-based distributed stabilization of nonlinear large-scale systems with energy constraints and random sensor faults. Due to the limited power in sensors, techniques such as reduction of times and size of the transmission packet are utilized to save the energy. As for the sensor failure phenomenon, a set of binary variables is introduced to model it. Based on the switched system theory, the Lyapunov stability technique and some stochastic system analysis, a sufficient condition is established under which the closed-loop system is exponentially stable in the mean-square sense and achieves a prescribed disturbance attenuation level. The controller gain design algorithm is presented by using the cone complementarity linearization (CCL) method. A numerical example is finally given to show the effectiveness of the proposed design.
    Journal of the Franklin Institute 02/2015; DOI:10.1016/j.jfranklin.2015.01.028 · 2.26 Impact Factor
  • Binh Nguyen Le · Qing-Guo Wang · Tong Heng Lee
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    ABSTRACT: This paper deals with the problem of determining the stabilizing controller gain and plant delay ranges for a general delay system in feedback configuration. Such a problem admits no analytical solutions in general. Instead, the condition of the loop Nyquist plot's intersection with the critical point is employed to graphically determine stability boundaries in the gain-delay space and stability of regions divided by these boundaries is decided with the help of a new perturbation analysis of delay on change of closed-loop unstable poles. As a result, all the stable regions are obtained and each stable region captures the full information on the stabilizing gain intervals versus any delay of the process. The proposed method is applicable to both stable and unstable processes of any order with or without the right-half plane zeros. Several examples are provided for illustration and comparison with the existing methods.
    Journal of Process Control 01/2015; 25. DOI:10.1016/j.jprocont.2013.12.019 · 2.18 Impact Factor
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    Lei Wang · Wei-jie Feng · Michael Z. Q. Chen · Qing-Guo Wang
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    ABSTRACT: This study investigates the consensus problem for cooperative heterogeneous agents with non-linear dynamics in a directed communication network. Global bounded consensus is studied by employing a quadratic Lyapunov function, and a distributed consensus protocol is designed by solving a few lower-dimension linear matrix inequalities associated with the dynamics of the heterogeneous agents. A sufficient condition corresponding to the semi-positive definiteness of the Laplacian matrix and the non-linear dynamics of each agent is obtained to guarantee the boundedness of consensus. In particular, to avoid the calculation of matrix eigenvalues, a sufficient condition is also obtained in the form of several scalar inequalities involving the coupling strengths and the property of all paths between agent pairs under a proper path strategy. The presented framework for designing protocols is quite simple with limited conservatism, which can be effectively used to design consensus protocols of various weighted and directed networks.
    IET Control Theory and Applications 01/2015; 9(1):147-152. DOI:10.1049/iet-cta.2014.0530 · 1.84 Impact Factor
  • Qing-guo Wang · Wei-jie Feng · Michael Z.Q. Chen · Lei Wang
    IET Control Theory and Applications 12/2014; 8(18):2245-2252. DOI:10.1049/iet-cta.2013.1081 · 1.84 Impact Factor
  • Dan Zhang · Wen-an Zhang · Li Yu · Qing-Guo Wang
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    ABSTRACT: This paper is concerned with the problem of distributed fault detection for a class of large-scale systems with multiple uncertainties in measurements and communications. As a divide et impera approach is used to overcome the scalability issues of a centralized implementation, the large-scale system being monitored is modelled as the interconnection of several subsystems. A local fault detector is formed for each subsystem based on the measured local state of the subsystem as well as the transmitted variables of neighboring measurements. Phenomena such as the sensor saturation, the signal quantization, and the packet dropouts are addressed, where a unified model is proposed to capture these issues. The goal is to design a set of consensus based fault detectors such that, for all unknown disturbance and uncertain information, the estimation errors between the global residuals and the faults are minimized. By using the Lyapunov stability theory and some stochastic system analysis, a sufficient condition for the existence of desired fault detectors is established and the fault detector gains are computed by solving an optimization problem. A case study on the interconnected continuous stirred-tank reactor (CSTR) systems is finally given to show the effectiveness of the proposed design.
    Journal of the Franklin Institute 12/2014; DOI:10.1016/j.jfranklin.2014.11.006 · 2.26 Impact Factor
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    Wei-Jie Feng · Lei Wang · Qing-Guo Wang
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    ABSTRACT: The goal of traffic management is to efficiently allocate network resources via adjustment of source transmission rates and routes selection. Mathematically, it aims to solve a traditional utility maximization problem in a fair and distributed manner. In this paper, we first develop a generalized multi-path utility maximization problem which features a weighted average of the classical Kelly’s formulation and the Voice’s model. Next, we design from this broader framework a family of multi-path dual congestion control algorithms whose equilibrium point can both achieve a desired bandwidth utilization and preserve a notion of fairness among competing users. Global stability can be guaranteed for the proposed schemes in the absence of delays by use of a totally novel Lyapunov function. Moreover, when heterogeneous propagation delays are taken into account, we establish decentralized and scalable sufficient conditions for robust global stability by constructing a reasonable Lyapunov–Krasovskii functional candidate. These conditions give estimates for the maximum admissible delays that the controller can tolerate without losing stability. Finally, we verify the results through simulation.
    Automatica 11/2014; 50(12). DOI:10.1016/j.automatica.2014.10.061 · 3.13 Impact Factor
  • Binh Nguyen Le · Qing-Guo Wang · Tong Heng Lee · Zhuoyun Nie
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    ABSTRACT: A graphical method is extended to determine the stabilizing gain and delay ranges for a bi-proper delay system.•A bi-proper process is rare but causes great complications for the method because of possibility of infinite intersections of boundary functions within a finite delay range.•The properties of boundary functions from such processes are investigated in great details to show that finite boundary functions are sufficient to determine all stable regions for finite parameter intervals.•The formula is given for calculating this number.•Algorithms are established to find exact stabilizing gain and delay ranges.
    ISA Transactions 10/2014; 53(6). DOI:10.1016/j.isatra.2014.09.014 · 2.26 Impact Factor
  • Dan Zhang · Wenjian Cai · Qing-Guo Wang
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    ABSTRACT: This paper is concerned with the mixed H∞H∞ and passivity based state estimation for a class of discrete-time fuzzy neural networks with the estimator gain change, where a discrete-time homogeneous Markov chain taking value in a finite set Γ={0,1}Γ={0,1} is introduced to model this phenomenon. Based on the Markovian system approach and linear matrix inequality technique, a new sufficient condition has been derived such that the estimation error system is exponentially stable in the mean square sense and achieves a prescribed mixed H∞H∞ and passivity performance level. The estimator parameter is then determined by solving a set of linear matrix inequalities (LMIs). A numerical example is presented to show the effectiveness of the proposed design method.
    Neurocomputing 09/2014; 139:321–327. DOI:10.1016/j.neucom.2014.02.025 · 2.01 Impact Factor
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    ABSTRACT: This paper addresses the design of robust track-following dynamic output feedback controller for hard disk drives (HDDs) in face of parameter uncertainties which can enter into problem description in a possibly non-linear way. The design is performed in a probabilistic framework where the uncertain parameters are treated as random variables and the design specification is met with a given probability level. In particular, a sequential algorithm based on gradient iteration is employed to find a probabilistic robust feasible solution to the formulated problem. The design procedure is computationally tractable and its computational complexity does not depend on the number of uncertain parameters. Our case study allows natural frequency and damping ratio to vary within 8% and 10% from their nominal values for rigid body and all resonance modes. The designed controller achieves robustness in the presence of these uncertainties. Furthermore, the designed controller is implemented in real time on a commercial HDD.
    Mechatronics 09/2014; 24(6). DOI:10.1016/j.mechatronics.2014.02.007 · 1.82 Impact Factor
  • Dan Zhang · Wenjian Cai · Qing-Guo Wang
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    ABSTRACT: This paper is concerned with the energy-efficient filtering for a class of wireless sensor networks (WSNs). Due to the power limitation of WSNs, the measurement signal is transmitted to the remote filter infrequently and stochastically. A stochastic framework is proposed to formulate the filtering problem for such systems. A sufficient condition is established such that the filtering error system is mean-square stable and achieves a prescribed disturbance attenuation level in the H∞H∞ sense. The optimal filter design is presented to determine the filter gains. Relations between the transmission parameters, e.g., transmission probability, transmission intervals and the filtering performance are obtained. Finally, a continuous stirred tank reactor (CSTR) system is employed to evaluate the effectiveness of the proposed design.
    Signal Processing 08/2014; 101:134–141. DOI:10.1016/j.sigpro.2014.01.032 · 2.24 Impact Factor
  • Dan Zhang · Wenjian Cai · Qing-Guo Wang
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    ABSTRACT: This paper is concerned with the robust non-fragile filtering for a class of networked systems with distributed variable delays. We model such a complex delay system with an augmented switched system. For the filtering implementation uncertainty, a stochastic variable is employed to indicate random occurrence of the filter gain change, and a norm bound to measure the change size. The suitably weighted measurements are proposed for filter performance improvement, instead of direct use of the measurements themselves which may have significant delays and degrade the performance. With some improved stability and l 2 gain analysis for the switched systems, a new sufficient condition is obtained such that the filtering error system is exponentially stable in the mean square sense and achieves a prescribed H∞H∞ performance level. A numerical example is given to show the effectiveness of the proposed design.
    Journal of the Franklin Institute 07/2014; 351(7). DOI:10.1016/j.jfranklin.2014.03.009 · 2.26 Impact Factor
  • Dan Zhang · Rongyao Ling · Wenjian Cai · Qing-Guo Wang · Yu Feng
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    ABSTRACT: This paper is concerned with the non-fragile H∞ filtering for a class of discrete-time networked systems with multiple communication delays. We model such a complex delay system as a switched system. For the filtering implementation uncertainty, a stochastic variable is employed to describe the phenomenon of the randomly occurring filter gain change, and a norm bound is used to measure the change size. With the switched system theory and the stochastic system analysis, a new sufficient condition is obtained such that the filtering error system is exponentially stable in the mean square sense and achieves a prescribed H∞ performance level. A numerical example is given to show the effectiveness of the proposed design.
    2014 11th IEEE International Conference on Control & Automation (ICCA); 06/2014
  • Qing-Guo Wang · Binh-Nguyen Le · Tong-Heng Lee
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    ABSTRACT: An effective method is presented to find PID stabilizing region in controller parameters plane. The concept of stability boundaries in D-decomposition technique is extended to the parameterized stability boundary, which transforms boundary curves into boundary bands when one of the controller gains varies in a range. This eliminates the difficulty of using 3D graph to solve the problem with 3 parameters while maintaining the advantage of 2D method.
    2014 11th IEEE International Conference on Control & Automation (ICCA); 06/2014
  • Qing-Guo Wang · Chao Yu · Yong Zhang
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    ABSTRACT: This paper proposes an improved system identification method with Renormalization Group. Renormalization Group is applied to a fine data set to obtain a coarse data set. The least squares algorithm is performed on the coarse data set. The theoretical analysis under certain conditions shows that the parameter estimation error could be reduced. The proposed method is illustrated with examples.
    ISA Transactions 01/2014; 53(5). DOI:10.1016/j.isatra.2013.10.003 · 2.26 Impact Factor
  • Lei Wang · Wei Qian · Qing-Guo Wang
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    ABSTRACT: This paper investigates the global bounded synchronisation problem of complex dynamical networks of coupled nonidentical nodes with general time-varying topology through the Lyapunov function and graph theory. Several sufficient conditions in form of scalar inequalities are established so that the global bounded synchronisation of the general dynamical network can be evaluated by the stability of a linear time-varying system and the boundedness of a nonlinear function, both associated with the dynamics of nonidentical nodes. These analytical results are simple yet generic, without assuming the symmetry coupling configuration matrix or calculating their eigenvalues. They can be used to explore synchronisation issues of various complex networks. Numerical simulations show their effectiveness.
    International Journal of Systems Science 12/2013; 46(7):1-12. DOI:10.1080/00207721.2013.815825 · 1.58 Impact Factor
  • Dan Zhang · Qing-Guo Wang · Li Yu · Haiyu Song
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    ABSTRACT: This paper is concerned with the fuzzy-model-based fault detection for a class of nonlinear systems with networked measurements where there are significant uncertainties on information. A unified model is proposed to capture four sources of these uncertainties, namely, the sensor saturation, the signal quantization, the general medium access constraint, and the multiple packet dropouts. A simultaneous consideration of these issues reflects the practical networked systems much more closely than the existing works. The goal of this paper is to design a fault detector such that, for all unknown input, control input, and uncertain information, the estimation error between the residual and the fault is minimized. Using the switched system approach and some stochastic analyses, a sufficient condition for the existence of desired fault detector is established and the fault detector gains are computed by solving an optimization problem. Two numerical examples are given to show the effectiveness of the proposed design.
    IEEE Transactions on Instrumentation and Measurement 12/2013; 62(12):3148-3159. DOI:10.1109/TIM.2013.2272865 · 1.71 Impact Factor
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    ABSTRACT: In this paper, we consider uncertain linear and bilinear matrix inequalities which depend in a possibly nonlinear way on a vector of uncertain parameters. Motivated by recent results in statistical learning, we show that probabilistic guaranteed solutions can be obtained by means of randomized algorithms. In particular, we show that the Vapnik-Chevonenkis dimension (VC-dimension) of the two problems is finite, and we compute upper bounds on it. In turn, these bounds allow us to derive explicitly the sample complexity of the problems. Using these bounds, in the second part of the paper, we derive a sequential scheme, based on a sequence of optimization and validation steps. The algorithm is on the same lines of recent schemes proposed for similar problems, but improves both in terms of complexity and generality.
    2013 IEEE 52nd Annual Conference on Decision and Control (CDC); 12/2013