4,227 research outputs found
Global Stabilization of Triangular Systems with Time-Delayed Dynamic Input Perturbations
A control design approach is developed for a general class of uncertain
strict-feedback-like nonlinear systems with dynamic uncertain input
nonlinearities with time delays. The system structure considered in this paper
includes a nominal uncertain strict-feedback-like subsystem, the input signal
to which is generated by an uncertain nonlinear input unmodeled dynamics that
is driven by the entire system state (including unmeasured state variables) and
is also allowed to depend on time delayed versions of the system state variable
and control input signals. The system also includes additive uncertain
nonlinear functions, coupled nonlinear appended dynamics, and uncertain dynamic
input nonlinearities with time-varying uncertain time delays. The proposed
control design approach provides a globally stabilizing delay-independent
robust adaptive output-feedback dynamic controller based on a dual dynamic
high-gain scaling based structure.Comment: 2017 IEEE International Carpathian Control Conference (ICCC
Flow Stability of Patchy Vector Fields and Robust Feedback Stabilization
The paper is concerned with patchy vector fields, a class of discontinuous,
piecewise smooth vector fields that were introduced in AB to study feedback
stabilization problems. We prove the stability of the corresponding solution
set w.r.t. a wide class of impulsive perturbations. These results yield the
robusteness of patchy feedback controls in the presence of measurement errors
and external disturbances.Comment: 22 page
Contact Line Instability and Pattern Selection in Thermally Driven Liquid Films
Liquids spreading over a solid substrate under the action of various forces
are known to exhibit a long wavelength contact line instability. We use an
example of thermally driven spreading on a horizontal surface to study how the
stability of the flow can be altered, or patterns selected, using feedback
control. We show that thermal perturbations of certain spatial structure
imposed behind the contact line and proportional to the deviation of the
contact line from its mean position can completely suppress the instability.
Due to the presence of mean flow and a spatially nonuniform nature of spreading
liquid films the dynamics of disturbances is governed by a nonnormal evolution
operator, opening up a possibility of transient amplification and nonlinear
instabilities. We show that in the case of thermal driving the nonnormality can
be significant, especially for small wavenumber disturbances, and trace the
origin of transient amplification to a close alignment of a large group of
eigenfunctions of the evolution operator. However, for values of noise likely
to occur in experiments we find that the transient amplification is not
sufficiently strong to either change the predictions of the linear stability
analysis or invalidate the proposed control approach.Comment: 13 pages, 14 figure
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