Authors:
Gregory J. Toussaint,
Tamer Bas;ar,
Francesco Bullo,
Volume: 1, Page 2078 Paper number 801
Abstract:
This paper presents new techniques for controlling the motion of an
underactuated vehicle when disturbances are present and only imperfect
state measurements are available for feedback. A state feedback controller
is developed and then it is converted to an imperfect state measurement
feedback controller. The state feedback tracking control law uses
an H-infinity-optimal design and produces a locally exponentially stable
closed-loop system. The imperfect state measurement feedback controller
combines the state feedback control law with an H-infinity-filter to
estimate the states and achieves a modified form of disturbance attenuation.
The state estimator exploits a unique structure in the nonlinear equations
of motion to develop a direct solution. The Matlab simulations illustrate
both control algorithms for an underactuated ship model.
Authors:
Zhong-Ping Jiang,
Iven M.Y. Mareels,
Volume: 1, Page 2084 Paper number 802
Abstract:
It is well-known from linear systems theory that an integral control
law is needed for asymptotic set-point regulation under parameter perturbations.
This paper presents a similar result for a class of nonlinear systems
in the presence of an unknown equilibrium due to uncertain nonlinearities
and dynamic uncertainties. Both partial-state and output feedback cases
are considered. A procedure for robust nonlinear integral controller
design is presented and illustrated via a practical example of fan
speed control.
Authors:
Chunjiang Qian,
Wei Lin,
Volume: 1, Page 2090 Paper number 803
Abstract:
This paper shows that for a significant class of nonlinear systems
with uncontrollable unstable linearization, global practical output
tracking is achievable by smooth feedback, although asymptotic output
tracking is usually not possible, even locally. Smooth tracking controllers
are explicitly constructed via a modified adding a power integrator
approach. This new design method also leads to solutions to various
open control problems, including practical output tracking of an underactuated
unstable two degrees of freedom mechanical system.
Authors:
Manjula S. Sugathadasa,
Clyde F. Martin,
Wijesuriya P. Dayawansa,
Volume: 1, Page 2096 Paper number 804
Abstract:
In wildlife telemetry and several other applications, some or all
of the measurements consist of angles made with very poor accuracy.
In these cases classical extended Kalman filtering, where the angles
are treated as linear variables, tend to introduce errors in estimation
on a sporadic basis due to incorrect handling of the angles. Here we
propose a correction term in Kalman filtering equation which will ensure
that the angular terms are treated in an invariant fashion.
Authors:
Frédéric Mazenc,
Silviu-Iulian Niculescu,
Volume: 1, Page 2100 Paper number 805
Abstract:
Sufficient conditions ensuring that a nonlinear system with disturbances
having a delay is delay independent globally asymptotically stable
are given. The proof carried out relies extensively on a characterization
of the stability property in term of Lyapunov function. The result
is applied to some biological systems and neural networks. It is also
used to construct a stabilizing memoryless controller for a second
order system with state-delay.
Authors:
Daniel Liberzon,
A. Stephen Morse,
Eduardo D. Sontag,
Volume: 1, Page 2106 Paper number 806
Abstract:
We introduce a new definition of the minimum-phase property for general
smooth nonlinear control systems. The definition does not rely on
a particular choice of coordinates in which the system takes a normal
form or on the computation of zero dynamics. It requires the state
and the input of the system to be bounded by a suitable function of
the output and derivatives of the output, modulo a decaying term depending
on initial conditions. The class of minimum-phase systems thus defined
includes all affine systems in global normal form whose internal dynamics
are input-to-state stable and also all left-invertible linear systems
whose transmission zeros have negative real parts. We explain how the
new concept enables one to develop a natural extension to nonlinear
systems of a basic result from linear adaptive control.
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