45,303 research outputs found
Nonlinear internal models for output regulation
No full textIn this note, we show how nonlinear internal models can be effectively used in the design of output regulators for nonlinear systems. This result provides a significant enhancement of the nonequilibrium theory for output regulation, which we have presented in a recent paper
Limit sets, zero dynamics and internal models in the problem of nonlinear output regulation
No full textNon-Gaussianity beyond slow roll in multi-field inflation
No full textByrnes C, Tasinato G. Non-Gaussianity beyond slow roll in multi-field inflation. JCAP. 2009;2009(08):016.We study the non-Gaussianity generated during multiple-field inflation. Weprovide an exact expression for the bispectrum parameter f_NL which is validbeyond the slow-roll regime, valid for certain classes of inflationary models.We then study a new, exact multi-field inflationary model considering a casewhere the bispectrum grows to observable values at the end of inflation. Weshow that in this case the trispectrum is also large and may even provide thedominant signal of non-Gaussianity
Further results on output regulation by pure error feedback
No full textThis work addresses the design of internal model-based regulators for nonlinear systems by error feedback in the general "non-equilibrium" framework proposed in (Byrnes and Isidori, 2003). The material presented here is specifically meant to complement the work in (Byrnes and Isidori, 2004) where a procedure for designing nonlinear internal model-based regulators was presented for systems having relative degree 1. Copyright © 2005 IFAC
Analysis and simulation of a controlled rigid spacecraft: stability and instability near attractors
No full textThe authors give an analysis and simulation of the asymptotic properties of various closed-loop trajectories of the rigid-body model of a controlled spacecraft. Recent results are described which show that the rigid body for a spacecraft controlled by two independent pairs of gas jets is locally controllable but not locally asymptotically stabilizable about reference attitudes. The authors analyze, in the context of feedback stabilization about an attractor, the asymptotic properties of closed-loop trajectories when a feedback law driving the motion to a revolute cycle about a principle axis is implemented. Simulations support such convergence but indicate that convergence is quite slow, due to the fact that this cycle lies, as it must, on an invariant center manifold for this system. In particular, while the design is based on a nonlinear enhancement of root-locus theory, such attractors have no linear analogu
Review of local non-Gaussianity from multi-field inflation
No full textByrnes C, Choi K-Y. Review of local non-Gaussianity from multi-field inflation. Advances in astronomy. 2010;2010:1-18.We review models which generate a large non-Gaussianity of the local form. We first briefly consider three models which generate the non-Gaussianity either at or after the end of inflation/ the curvaton scenario, modulated (p)reheating and an inhomogeneous end of inflation. We then focus on ways of generating the non-Gaussianity during inflation. We derive general conditions which a product or sum separable potential must satisfy in order to generate a large local bispectrum during slow-roll inflation. As an application we consider two-field hybrid inflation. We then derive a formalism not based on slow roll which can be applied to models in which the slow-roll parameters become large before inflation ends. An exactly soluble two-field model is given in which this happens. Finally we also consider further non-Gaussian observables/ a scale dependence of f_NL and the trispectrum
Interior Point Control of a Heat Equation Using Zero Dynamics Design
No full textIn this work the authors show how the zero dynamics design methodology, developed in a series of papers for boundary control of distributed parameter systems, can be extended to include interior point control for tracking problems and disturbance rejection for a one dimensional heat equation. In particular we demonstrate how simple control laws can be obtained for solving MIMO set-point control problems using colocated interior point control and actuation. The results apply also to a much wider class on one dimensional problems and also to some interesting nonlinear problems. In this conference work we restrict to the case of the heat equation and present two examples. In the first example we consider a problem with two interior controls. The tracking problem consists of a setpoint control at one interior point while tracking a sinusoid at another interior point. In our second example we consider a multivariable set-point control problem. © 2006 IEEE
Dedicated to the memory of Christopher I. Byrnes
No full textThe Byrnes-Isidori form with respect to the relative degree is studied for time-varying linear multi-input, multi-output systems. It is clarified in which sense this form is a normal form. (A,B)-invarianttime-varying subspaces are defined and the maximal(A,B)-invariant time-varying subspace included in the kernel of C is characterized. This is exploited to characterize the zero dynamics of the system. Finally, a high-gain derivative output feedback controller is introduced for the class of systems with higher relative degree and stable zero dynamics. All results are also new for time-invariant linear systems.MSC 93C05, 93D1
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bifurcation analysis of the zero dynamics and the practical stabilization of nonlinear minimum-phase systems
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