Showing papers by "Petar V. Kokotovic published in 1998"
16 Dec 1998
TL;DR: It is shown for nonlinear systems that sampling sufficiently fast an input-to-state stabilizing (ISS) continuous time control law results in an ISS sampled-data control law that can be modeled by a functional differential equation (FDE).
Abstract: It is shown for nonlinear systems that sampling sufficiently fast an input-to-state stabilizing (ISS) continuous time control law results in an ISS sampled-data control law. Two main features of our approach are: we show how the nonlinear sampled-data system can be modeled by a functional differential equation (FDE); and we exploit a Razumikhin type theorem for ISS of FDE that was proved by Teel (1998) to analyze the sampled-data system.
128 citations
TL;DR: A feedback controller that globally stabilizes a broad range of possible equilibria in a nonlinear compressor model with a novel backstepping design that retains the system's useful nonlinearities which would be cancelled in a feedback linearizing design.
Abstract: Compressor stall and surge are complex nonlinear instabilities that reduce the performance and can cause failure of aircraft engines. We design a feedback controller that globally stabilizes a broad range of possible equilibria in a nonlinear compressor model. With a novel backstepping design we retain the system's useful nonlinearities which would be cancelled in a feedback linearizing design. The design control law is simple and, moreover, it is optimal with respect to a meaningful nonquadratic cost functional. As in a previous bifurcation-theoretic design, we change the character of the bifurcation at the stall inception point from subcritical to supercritical. However, since we approach the bifurcation control using Lyapunov tools, our controller achieves not only local but also global stability. The controller requires minimal modeling information and simpler sensing (rotating stall is stabilized without measuring its amplitude).
103 citations
TL;DR: In this article, a stabilizing controller for moored and free-floating ships is constructed by backstepping to meet two design objectives: one local and the other global, where the local objective is to design an H∞-optimal controller for the linearized plant and the global objective is inverse optimality for the nonlinear system.
34 citations
21 Jun 1998
TL;DR: This paper presents three controllers that globally stabilize a benchmark nonlinear system that is not in a class to which existing constructive methodologies are applicable.
Abstract: This paper presents three controllers that globally stabilize a benchmark nonlinear system. Neither affine in control nor of triangular structure, the system is not in a class to which existing constructive methodologies are applicable.
18 citations
TL;DR: For strict feedback nonlinear systems with relative degree ϒ, the authors showed that there exists a coordinate transformation under which input-output feedback linearization with Butterworth pole placement is an O(ǫ)-approximation of the cheap control that minimizes a quadratic cost functional with control weighting ǫ 2r.
14 citations
TL;DR: The skewness of the compressor characteristic, a single parameter shape signifier, is shown to determine the key qualitative properties of feedback control on the third-order Moore-Greitzer model.
Abstract: Rotating stall and surge, two instability mechanisms limiting the performance of aeroengines compressors, are studied on the third-order Moore-Greitzer model. The skewness of the compressor characteristic, a single parameter shape signifier, is shown to determine the key qualitative properties of feedback control.
8 citations
16 Dec 1998
TL;DR: In this paper, the authors show that stability margins provided by optimal control laws increase when the penalty on the control in the quadratic cost functional is allowed to approach zero, which implies increased robustness with respect to input strictly passive dynamic uncertainties.
Abstract: We show that stability margins provided by optimal control laws increase when the penalty on the control in the quadratic cost functional is allowed to approach zero. This implies increased robustness with respect to input strictly passive dynamic uncertainties. The result is also extended to a class of nonlinear systems.