Authors:
Dong-Eui Chang,
Wei Kang,
Arthur J. Krener,
Volume: 1, Page 1602 Paper number 1701
Abstract:
We present the quadratic and cubic normal forms of a nonlinear control
system around an equilibrium point. These are the normal forms under
change of state coordinates and invertible state feedback. The system
need not be linearly controllable. A control bifurcation of a nonlinear
system occurs when its linear approximation loses stabilizability.
We study some important control bifurcations, the analogues of the
classical fold, transcritical and Hopf bifurcations.
Authors:
Priya Ranjan,
Eyad H. Abed,
Volume: 1, Page 1608 Paper number 1702
Abstract:
Noise-driven systems tend to display special features in their power
spectra when approaching bifurcation or instability. These features,
called noisy precursors, can be of significant use since they can serve
as a warning signal for the impending loss of stability. Another phenomenon
that has received significant attention in the mathematical physics
and biology literature is that of stochastic resonance. In stochastic
resonance, the signal-to-noise ratio (SNR) is nonmonotonic with respect
to noise level. This cannot occur in linear systems. Most past studies
of stochastic resonance involve bistable systems with a weak external
periodic forcing. However, recently the same basic phenomenon has been
observed in autonomous systems operating along a limit cycle. In any
case, the combination of precursors and stochastic resonance provides
a tool for instability monitoring. In this paper, these observations
are applied to a discrete-time DC-DC converter model. Precursors of
period doubling instability are shown to occur. Also, stochastic resonance
and its impact on precursor strength is demonstrated. The calculations
show how the noise level should be selected to enhance detectability
of the impending bifurcation.
Authors:
Yong Wang,
Richard M. Murray,
Volume: 1, Page 1613 Paper number 1704
Abstract:
In this paper, we analyze the problem of bifurcation control from a
geometric perspective. Our goal is to provide coordinate free,
geometric conditions under which control can be used to alter the
bifurcation properties of a nonlinear control system. These insights
are expected to be useful in understanding the role that magnitude
and rate limits play in bifurcation control, as well as giving deeper
understanding of the types of control inputs that are required to
alter the nonlinear dynamics of bifurcating systems. We also use
a model from active control of rotating stall in axial compression
systems to illustrate the geometric sufficient conditions of stabilizability.
Authors:
Hua O. Wang,
Dong S. Chen,
Linda G. Bushnell,
Volume: 1, Page 1619 Paper number 1705
Abstract:
Bifurcation control deals with the modification of the bifurcation
characteristics of a parameterized nonlinear system by a judiciously
designed control input. In this paper, we consider the problem of dynamic
feedback control of bifurcations. In particular, previous results on
the control of bifurcations using washout filters are extended to some
general forms of dynamic feedback controllers. It is shown that high-pass
filters such as washout filters can be represented by a special form
of dynamic feedback controller. The control effect on bifurcations
can be readily assessed by analytical formulae. These dynamic feedback
controllers offer more flexibility over the original controller in
bifurcation control. The results are viable for the design and analysis
of nonlinear control systems involving bifurcations.
Authors:
Issa Amadou Tall,
Witold Respondek,
Volume: 1, Page 1625 Paper number 1707
Abstract:
We study the feedback group action on single-input nonlinear control
systems. We follow an approach of Kang and Krener based on analysing,
step by step, the action of homogeneous transformations on the homogeneous
part of the system. We construct a dual normal form and dual invariants
with respect to those obtained by Kang. We also propose a canonical
form and show that two systems are equivalent via a formal feedback
if and only if their canonical forms coincide. We give an explicit
construction of transformations bringing the system to its normal,
dual normal, and canonical form.
Authors:
Boumediene Hamzi,
Wei Kang,
Jean-Pierre Barbot,
Volume: 1, Page 1631 Paper number 1706
Abstract:
In this paper we deal with the problem of the analysis and the control
of Hopf bifurcations. The methodology we adopt is based on the normal
forms approach. We determine invariants which are numbers which does
not change with coordinate change and feedback. The characterization
of the Hopf bifurcation and the computation of the control law is based
on these invariants.
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