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Showing papers by "Petar V. Kokotovic published in 2000"


Journal ArticleDOI
TL;DR: In this paper, the authors consider systems with unmodeled dynamics appearing at the input, and present a redesign that preserves global asymptotic stability with respect to relative degree zero and minimum phase.

50 citations


Proceedings ArticleDOI
12 Dec 2000
TL;DR: In this article, the authors address the problem of output feedback tracking control of a class of Euler-Lagrange systems subject to nonlinear dissipative loads by imposing a monotone damping condition on the nonlinearities of the unmeasured states.
Abstract: We address the problem of output feedback tracking control of a class of Euler-Lagrange systems subject to nonlinear dissipative loads. By imposing a monotone damping condition on the nonlinearities of the unmeasured states, the common restriction that the nonlinearities be globally Lipschitz is removed. The proposed observer-controller scheme renders the origin of the error dynamics uniformly globally asymptotically stable.

45 citations


Proceedings ArticleDOI
25 Sep 2000
TL;DR: In this paper, the zero dynamics of a particular input-output pair may be stabilizable by another input, making indirect single-input single-output (SISO) passivation feasible.
Abstract: Unstable (nonminimum) zero dynamics are an obstacle to direct feedback passivation. In multivariable (MIMO) systems, the zero dynamics of a particular input-output pair may be stabilizable by another input, making indirect single-input single-output (SISO) passivation feasible. This indirect passivation methodology is illustrated by a design for a simplified model of turbocharged diesel engine and tested by simulation on a higher-order model.

37 citations


Journal ArticleDOI
TL;DR: Two redesigns to robustify backstepping control laws against dynamic uncertainties in the input of the plant are presented, and a passivating control law is constructed from a control Lyapunov function obtained by backstepped.
Abstract: We present two redesigns to robustify backstepping control laws against dynamic uncertainties in the input of the plant. In the first redesign we construct a passivating control law from a control Lyapunov function obtained by backstepping. The second redesign is a simplification of the first, useful for high-order systems. We also compare the stability margins of the two main versions of backstepping: cancellation and L/sub G/V-backstepping.

34 citations


Journal ArticleDOI
TL;DR: In this article, a certainty equivalence adaptive control scheme is proposed for dynamic systems where the position of the operating point is unkown, which extends and clarifies the wash-out filter practice.
Abstract: For dynamic systems where the position of the operating point is unkown a certainty equivalence adaptive control scheme is proposed which extends and clarifies the wash-out filter practice. Stability properties of the adaptive controller are derived. For slow adaptation, a singular perturbation analysis is carried out to derive additional stability properties and design criteria. Conditions are given under which the proposed scheme achieves exponential stability of the unkown operating point.

27 citations


Proceedings ArticleDOI
28 Jun 2000
TL;DR: In this paper, the authors consider nonlinear systems in feed forward form and redesign nested saturation control laws to guarantee global asymptotic stability in the presence of unmodeled dynamics appearing at the system input.
Abstract: We consider nonlinear systems in feedforward form and redesign nested saturation control laws to guarantee global asymptotic stability in the presence of unmodeled dynamics appearing at the system input. Unlike most previous results, this redesign is applicable to a large class of unmodeled dynamics, including actuators that change the relative degree of the system.

14 citations


Proceedings ArticleDOI
12 Dec 2000
TL;DR: In this article, the robustness of nonlinear observer design was analyzed for uncertainties in the nonlinearities, and bounds were given within which the observer error gradually increases with an increase in the uncertainty.
Abstract: Analyzes the robustness of a nonlinear observer design introduced previously by the authors. For uncertainties in the nonlinearities, bounds are given within which the observer error gradually increases with an increase in the uncertainty. For dynamic modeling errors, a robust output-feedback design is developed using ISS small-gain tools. A jet engine compressor example is used to illustrate the design.

9 citations


Book ChapterDOI
01 Jan 2000
TL;DR: The ongoing ‘activation process’ in nonlinear control is described, through which some of the earlier descriptive concepts are being converted into constructive design tools applicable to common classes of nonlinear systems.
Abstract: We describe the ongoing ‘activation process’ in nonlinear control, through which some of the earlier descriptive concepts are being converted into constructive design tools applicable to common classes of nonlinear systems. This process is a confluence of several research streams with activated stability, passivity and geometric concepts.

6 citations



Proceedings ArticleDOI
12 Dec 2000
TL;DR: In this article, a nonlinear control law for axial flow compressors with a ring of bleed valves is proposed. But the control law does not guarantee the region of attraction.
Abstract: A nonlinear control law is designed for a low order model of an axial flow compressor with a ring of bleed valves after the last compressor stage. The controller is implemented on a low speed, three stage experimental compressor. The region of attraction guaranteed by the control law is experimentally determined and is larger than that of the uncontrolled compressor.

2 citations