SwePub - sökning: WFRF:(Kao Chung Yao)

Numrering	Referens	Omslagsbild	Hitta
1.	Kao, ChungYao, et al. (författare) Simple stability criteria for systems with time-varying delays 2004 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 40:8, s. 1429-1434 Tidskriftsartikel (refereegranskat)abstract This paper considers the problem of checking stability of linear feedback systems with time-varying but bounded delays. Simple but powerful criteria of stability are presented for both continuous-time and discrete-time systems. Using these criteria, stability can be checked in a closed loop Bode plot. This makes it easy to design the system for robustness.
2.	Almér, Stefan, et al. (författare) Global stability analysis of DC-DC converters using sampled-data modeling 2004 Ingår i: PROCEEDINGS OF THE 2004 AMERICAN CONTROL CONFERENCE, VOLS 1-6. - 0780383354 ; , s. 4549-4554 Konferensbidrag (refereegranskat)abstract The paper presents stability analysis of a class of pulse-width modulated (PWM) systems which incorporates many different DC-DC converters. Two types of pulse-width modulation (digital and analog control) are considered. A procedure is developed for systematic search for Lyapunov functions. The state space is partitioned in such a way that stability is verified if a set of coupled Linear Matrix Inequalities (LMIs) is feasible. Global stability is considered as well as the computation of local regions of attraction.
3.	Almér, Stefan, et al. (författare) Hybrid control techniques for switched-mode DC-DC converters part I : The step-down topology 2007 Ingår i: 2007 American Control Conference. - : IEEE. - 1424409888 - 9781424409884 ; , s. 5450-5457 Konferensbidrag (refereegranskat)abstract Several recent techniques from hybrid and optimal control are evaluated on a power electronics benchmark problem. The benchmark involves a number of practically interesting operating scenarios for a fixed-frequency synchronous step-down dc-dc converter. The specifications are defined such that good performance only can be obtained if the switched and nonlinear nature of the problem is respected during the design phase.
4.	Almér, Stefan, et al. (författare) Stability analysis of a class of PWM systems 2007 Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 52:6, s. 1072-1078 Tidskriftsartikel (refereegranskat)abstract This note considers stability analysis of a class of pulsewidth modulated (PWM) systems that incorporates several different switched mode dc-de- converters. The systems of the class typically have periodic solutions. A sampled data model is developed and used to prove stability of these solutions. Conditions for global and local exponential stability are derived using quadratic and piecewise quadratic Lyapunov functions. The state space is partitioned and the stability conditions are verified by checking a set of coupled linear matrix inequalities (LMIs).
5.	Beccuti, A. G., et al. (författare) Hybrid control techniques for switched-mode DC-DC converters part II : The step-up topology 2007 Ingår i: 2007 American Control Conference, Vols 1-13. - 1424409888 - 9781424409884 ; , s. 5464-5471 Konferensbidrag (refereegranskat)abstract Several recent techniques from hybrid and optimal control are evaluated on a power electronics benchmark problem. The benchmark involves a number of practically interesting operating scenarios for a fixed-frequency step-up dc-dc converter. The specifications are defined such that good performance can only be obtained if the switched and nonlinear nature of the problem is respected during the design phase.
6.	Cantoni, Michael, et al. (författare) Robustness Analysis for Feedback Interconnections of Distributed Systems via Integral Quadratic Constraints 2012 Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 57:2, s. 302-317 Tidskriftsartikel (refereegranskat)abstract A framework is established for directly accommodating feedback interconnections of unstable distributed-parameter transfer functions in robust stability analysis via integral quadratic constraints (IQCs). This involves transfer function homotopies that are continuous in a nu-gap metric sense. As such, the development includes the extension of nu-gap metric concepts to an irrational setting and the study of uncertainty-set connectedness in these terms. The main IQC based robust stability result is established for constantly-proper transfer functions in the Callier-Desoer algebra; i.e. finitely many unstable poles and a constant limit at infinity. Problems of structured robust stability analysis and robust performance analysis are considered to illustrate use of the main result. Several numerical examples are also presented. These include stability analysis of an autonomous system with uncertain time-delay and a closed-loop control system, accounting for both the gain and phase characteristics of the distributed-parameter uncertainty associated with the nominal rational plant model used for controller synthesis.
7.	Fujioka, Hisaya, et al. (författare) LQ optimal control for a class of pulse width modulated systems 2007 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 43:6, s. 1009-1020 Tidskriftsartikel (refereegranskat)abstract We consider linear quadratic optimal control for a class of pulse width modulated systems. The problem is motivated from a practical application-digital control of switching power converters. The control synthesis problem is posed based on a sampled data model of the original switching dynamics and a linear quadratic criterion that takes the intersampling behavior into account.
8.	Fujioka, Hisaya, et al. (författare) Robust tracking with H-infinity performance for PWM systems 2009 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 45:8, s. 1808-1818 Tidskriftsartikel (refereegranskat)abstract Control synthesis for robust tracking is considered for a class of pulse-width modulated systems that appear, for example, in power electronics applications. The control objective is to regulate a high frequency ripple signal to robustly track a constant reference signal in an average sense. To achieve this goal, a new H-infinity control problem with integral action and average sampling is proposed. The solution of this problem involves a hybrid lifting framework which requires a careful elaboration in order to develop an algorithm that allows one to solve the design problem by the standard state space formulas for H-infinity control. The design procedure is verified on a synchronous buck converter.
9.	Jönsson, Ulf T., et al. (författare) A Popov criterion for networked systems 2007 Ingår i: Systems & control letters (Print). - : Elsevier BV. - 0167-6911 .- 1872-7956. ; 56:9-10, s. 603-610 Tidskriftsartikel (refereegranskat)abstract We consider robustness analysis of heterogeneous and homogeneous networked systems based on integral quadratic constraints (IQCs). First, we show how the analysis decomposes into lower dimensional problems if the interconnection structure is exploited. This generally leads to a significant reduction of the computational complexity. Secondly, by considering a set of IQCs that characterizes the eigenvalues of the interconnection matrices of symmetrically networked systems, we derive a Popov-like criterion for such systems. In particular, when the nodes of the networked system are single-input-single-output linear time-invariant operators, the criterion can be illustrated using a generalized Popov plot. In such cases. the Popov criterion is also a necessary condition in the sense that if the criterion is violated then a destabilizing network with the specified eigenvalue distribution can be constructed.
10.	Jönsson, Ulf T., et al. (författare) A Scalable Robust Stability Criterion for Systems With Heterogeneous LTI Components 2010 Ingår i: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 55:10, s. 2219-2234 Tidskriftsartikel (refereegranskat)abstract A scalable robust stability criterion for interconnected systems with heterogeneous linear time-invariant components is presented in this paper. The criterion involves only the properties of individual components and the spectrum of the interconnection matrix, which can be verified with relatively low computational effort, and more importantly maintains scalability of the analysis. Our main result shows that if the components are single-input-single-output (SISO), then the criterion has an appealing graphical interpretation which resembles the classical Nyquist criterion.
11.	Jönsson, Ulf T., et al. (författare) A Scalable Robust Stability Criterion for Systems with Heterogeneous LTI Components 2009 Ingår i: 2009 AMERICAN CONTROL CONFERENCE. - 9781424445233 ; , s. 2898-2903 Konferensbidrag (refereegranskat)abstract A scalable robust stability criterion for networked interconnected systems with heterogeneous linear time-invariant components is presented in this paper. The criterion involves only the properties of individual components and the spectrum of the interconnection matrix, which can be verified with relatively low computational effort, and more importantly maintains scalability of the analysis. Moreover, if the components are single-input-single-output (SISO), the criterion has an appealing graphical interpretation which resembles the classical Nyquist criterion.
12.	Kao, Chung-Yao, et al. (författare) A MATLAB toolbox for robustness analysis 2004 Ingår i: Proceedings of the IEEE International Symposium on Computer-Aided Control System Design. ; , s. 297-302, s. 297-302 Konferensbidrag (refereegranskat)abstract Verification of control systems is often done using extensive simulation. This gives the engineer useful qualitative information about the system performance. However, simulation cannot be used to rigorously prove stability and robustness of the system. Such properties can only be verified using mathematical analysis which for many realistic systems becomes rather involved. This paper presents the MATLAB toolbox IQCβ. It provides a user friendly interface for advanced semi-automatic systems analysis.
13.	Kao, Chung-Yao, et al. (författare) Characterization of robust stability of a class of interconnected systems 2009 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 45:1, s. 217-224 Tidskriftsartikel (refereegranskat)abstract We consider robust stability analysis of a class of large scale interconnected systems. The individual subsystems may be different but they are assumed to share a property that characterizes a set of interconnection matrices which lead to stable overall systems. The main contribution of the paper is to show that, for the case where the network interconnection matrix is normal, (robust) stability verification can be simplified to a low complexity problem of checking whether the frequency response of the individual subsystems and the eigenvalues of the interconnection matrix can be mutually separated using a class of quadratic forms. Most interestingly, it is shown that this criterion is also necessary, in the sense that if the criterion is violated, an interconnection matrix of the same eigenvalue distribution can be found to make the overall system unstable.
14.	Kao, Chung-Yao, et al. (författare) Robust stability analysis of linear systems with time-varying delays 2005 Ingår i: Proceedings of the 16th IFAC World Congress. - 008045108X Konferensbidrag (refereegranskat)abstract Robust stability of linear systems in presence of bounded uncertain time-varying time delays is studied. The time delay robustness problem is treated in the Integral Quadratic Constraint framework. The stability criterion is formulated as a frequency dependent linear matrix inequality, or equivalently as a Semi-Definite Program (SPD). Therefore, the criterion can be checked efficiently by using various SDP solvers.
15.	Kao, Chung-Yao, et al. (författare) Specialized fast algorithms for IQC feasibility and optimization problems 2004 Ingår i: Automatica. - : Elsevier BV. - 0005-1098 .- 1873-2836. ; 40:2, s. 239-252 Tidskriftsartikel (refereegranskat)abstract The conventional way to treat integral quadratic constraint (IQC) problems is to transform them into semi-definite programs (SDPs). SDPs can then be solved using interior point methods which have been proven efficient. This approach, however, is not always the most efficient since it introduces additional decision variables to the SDP, and the additional decision variables sometimes largely increase the complexity of the problem. In this paper, we demonstrate how to solve IQC problems by other alternatives. More specifically, we consider two cutting plane algorithms. We will show that in certain cases these cutting plane algorithms can solve IQC problems much faster than the conventional approach. Numerical examples, as well as some explanations from the point of view of computational complexity, are provided to support our point.
16.	Kao, Chung-Yao, et al. (författare) Stability analysis of systems with uncertain time-varying delays 2007 Ingår i: Automatica. - : Elsevier BV. - 0005-1098. ; 43:6, s. 959-970 Tidskriftsartikel (refereegranskat)abstract Stability of systems in the presence of bounded uncertain time-varying delays in the feedback loop is studied. The delay parameter is assumed to be an unknown time-varying function for which the upper bounds on the magnitude and the variation are given. The stability problem is treated in the integral quadratic constraint (IQC) framework. Criteria for verifying robust stability are formulated as feasibility problems over a set of frequency-dependent linear matrix inequalities. The criteria can be equivalently formulated as semi-definite programs (SDP) using Kalman-Yakubovich-Popovlemma. As such, checking robust stability can be performed in a computationally efficient fashion. (C) 2007 Elsevier Ltd. All rights reserved.
17.	Kao, Chung-Yao, et al. (författare) Stability Criteria for Systems with Bounded Uncertain Time-varying Delay 2003 Ingår i: European Control Conference ECC 2003. ; , s. 1578-1583 Konferensbidrag (refereegranskat)abstract Stability in presence of bounded uncertain time-varying time delays in the feedback loop of a system is studied. The stability problem is treated in the Integral Quadratic Constraint (IQC) framework. The stability criterion is formulated as frequency dependent linear matrix inequalities. The criterion can be equivalently formulated as a Semi-Definite Program (SDP) using Kalman-Yakubovich-Popov lemma. Therefore, checking the criterion can be done efficiently by using various SDP solvers
18.	Khong, Sei Zhen, et al. (författare) Robust synchronisation of unstable linear time-invariant systems 2015 Konferensbidrag (refereegranskat)abstract A framework based on the gap metric and integral quadratic constraints (IQCs) is developed for analysing robust synchronisation of heterogenous linear time-invariant networks. Both the agents and the communication channels are allowed to be dynamic and unstable. Structural properties of the uncertainty are described by IQCs and exploited in synchronisation analysis as a means to reduce conservatism. The homotopy employed in IQC analysis is defined with respect to the graph topology as induced by the gap metric, whereby open-loop unstable dynamics are accommodated. The results in this paper extend recent developments, which have been shown to unify several existing synchronisation analysis methods in the literature.
19.	Khong, Sei Zhen, et al. (författare) Robust Synchronization in Multi-Agent Networks with Unstable Dynamics 2018 Ingår i: IEEE Transactions on Control of Network Systems. - : IEEE. - 2325-5870. ; 5:1, s. 205-214 Tidskriftsartikel (refereegranskat)abstract The problem of synchronization in heterogenous linear time-invariant networks is investigated. An approach blending the theory of integral quadratic constraints (IQCs) with the gap metric is proposed to study the problem within a unifying framework, where both the agents and communication channels can be dynamic, infinite-dimensional, unstable, and uncertain. Structural properties of the uncertainty are described by IQCs and exploited in the analysis to reduce conservatism. The homotopy employed in IQC analysis is defined with respect to the graph topology induced by the gap metric, whereby open-loop unstable dynamics are accommodated. Sufficient conditions for synchronism are provided, extending recent developments which have been shown to unify several existing synchronization analysis results in the literature.
20.	Lovisari, Enrico, et al. (författare) Synchronization of Networks of Heterogeneous Agents With Common Nominal Behavior 2015 Ingår i: IEEE Transactions on Automatic Control. - 0018-9286. ; 60:3, s. 671-683 Tidskriftsartikel (refereegranskat)abstract This paper deals with the problem of synchronization in networks of heterogeneous agents with common nominal behavior. The agents are modeled as (possibly nonlinear) perturbed versions of a common SISO nominal LTI operator, and they are interconnected via a sparse memoryless interconnection operator, coherent with the communication graph underlying the network. The network is said to synchronize if the outputs of the agents tend to align along given directions, the most important case being consensus, or agreement. The paper provides a general result, based on IQCs, that ensures synchronization of the network with robustness w.r.t. uncertainties in the interconnection and in each agent's dynamics. Scalability issues are discussed in the scenario where the interconnection operator is a constant normal matrix, yielding the generalization of the very popular linear consensus algorithm. The wide range of applicability of the proposed criterion is shown by providing synchronization conditions in some important examples. Whenever possible, graphical criteria are proposed for checking the required conditions.
21.	Mariethoz, Sebastien, et al. (författare) Comparison of Hybrid Control Techniques for Buck and Boost DC-DC Converters 2010 Ingår i: IEEE Transactions on Control Systems Technology. - 1063-6536 .- 1558-0865. ; 18:5, s. 1126-1145 Tidskriftsartikel (refereegranskat)abstract Five recent techniques from hybrid and optimal control are evaluated on two power electronics benchmark problems. The benchmarks involve a number of practically interesting operating scenarios for fixed-frequency synchronous dc-dc converters. The specifications are defined such that good performance can only be obtained if the switched and nonlinear nature of the problem is accounted for during the design phase. A nonlinear action is featured in all methods either intrinsically or as external logic. The designs are evaluated and compared on the same experimental platform. Experiments show that the proposed methods display high performances, while respecting circuit constraints, thus protecting the semiconductor devices. Moreover, the complexity of the controllers is compatible with the high-frequency requirements of the considered application.
22.	Megretski, Alexandre, et al. (författare) Integral Quadratic Constraints 2010 Ingår i: The Control Handbook, Second Edition. - 9781420073669 ; 1 Bokkapitel (refereegranskat)
23.	Wallin, Ragnar, 1962-, et al. (författare) A Cutting Plane Method for Solving KYP-SDPs 2006 Rapport (övrigt vetenskapligt/konstnärligt)abstract Semidefinite programs originating from the Kalman-Yakubovich-Popov lemma are convex optimization problems and there exist polynomial time algorithms that solve them. However, the number of variables is often very large making the computational time extremely long. Algorithms more efficient than general purpose solvers are thus needed. To this end structure exploiting algorithms have been proposed, based on the dual formulation. In this paper a cutting plane algorithm is proposed. In a comparison with a general purpose solver and a structure exploiting solver it is shown that the cutting plane based solver can handle optimization problems of much higher dimension.
24.	Wallin, Ragnar, 1962-, et al. (författare) A Cutting Plane Method for Solving KYP-SDPs 2008 Ingår i: Automatica. - : Elsevier. - 0005-1098 .- 1873-2836. ; 44:2, s. 418-429 Tidskriftsartikel (refereegranskat)abstract Semidefinite programs originating from the Kalman-Yakubovich-Popov lemma are convex optimization problems and there exist polynomial time algorithms that solve them. However, the number of variables is often very large making the computational time extremely long. Algorithms more efficient than general purpose solvers are thus needed. To this end structure exploiting algorithms have been proposed, based on the dual formulation. In this paper a cutting plane algorithm is proposed. In a comparison with a general purpose solver and a structure exploiting solver it is shown that the cutting plane based solver can handle optimization problems of much higher dimension.
25.	Wallin, Ragnar, 1962-, et al. (författare) A Decomposition Approach for Solving KYP-SDPs 2005 Ingår i: Proceedings of the 16th IFAC World Congress. - 9783902661753 ; , s. 1021-1021 Konferensbidrag (refereegranskat)abstract Semidefinite programs originating from the Kalman-Yakubovich-Popov lemma are convex optimization problems and there exist polynomial time algorithms that solve them. However, the number of variables is often very large making the computational time extremely long. Algorithms more efficient than general purpose solvers are thus needed. In this paper a generalized Benders decomposition algorithm is applied to the problem to improve efficiency.

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