40,786 research outputs found
Observability and observer design for switched linear systems
Hybrid vehicles, HVAC systems in new/old buildings, power networks, and the like require safe, robust control that includes switching the mode of operation to meet environmental and performance objectives. Such switched systems consist of a set of continuous-time dynamical behaviors whose sequence of operational modes is driven by an underlying decision process. This thesis investigates feasibility conditions and a methodology for state and mode reconstruction given input-output measurements (not including mode sequence). An application herein considers insulation failures in permanent magnet synchronous machines (PMSMs) used in heavy hybrid vehicles.
Leveraging the feasibility literature for switched linear time-invariant systems, this thesis introduces two additional feasibility results: 1) detecting switches from safe modes into failure modes and 2) state and mode estimation for switched linear time-varying systems. This thesis also addresses the robust observability problem of computing the smallest structured perturbations to system matrices that causes observer infeasibility (with respect to the Frobenius norm). This robustness framework is sufficiently general to solve related robustness problems including controllability, stabilizability, and detectability.
Having established feasibility, real-time observer reconstruction of the state and mode sequence becomes possible. We propose the embedded moving horizon observer (EMHO), which re-poses the reconstruction as an optimization using an embedded state model which relaxes the range of the mode sequence estimates into a continuous space. Optimal state and mode estimates minimize an L2-norm between the measured output and estimated output of the associated embedded state model. Necessary conditions for observer convergence are developed. The EMHO is adapted to solve the surface PMSM fault detection problem
On an integral variant of incremental input/output-to-state stability and its use as a notion of nonlinear detectability
We propose a time-discounted integral variant of incremental
input/output-to-state stability (i-iIOSS) together with an equivalent Lyapunov
function characterization. Continuity of the i-iIOSS Lyapunov function is
ensured if the system satisfies a certain continuity assumption involving the
Osgood condition. We show that the proposed i-iIOSS notion is a necessary
condition for the existence of a robustly globally asymptotically stable
observer mapping in a time-discounted ``-to-'' sense. In
combination, our results provide a general framework for a Lyapunov-based
robust stability analysis of observers for continuous-time systems, which in
particular is crucial for the use of optimization-based state estimators (such
as moving horizon estimation).Comment: replaced with accepted versio
On output feedback nonlinear model predictive control using high gain observers for a class of systems
In recent years, nonlinear model predictive control schemes have been derived that guarantee stability of the closed loop under the assumption of full state information. However, only limited advances have been made with respect to output feedback in connection to nonlinear predictive control. Most of the existing approaches for output feedback nonlinear model predictive control do only guarantee local stability. Here we consider the combination of stabilizing instantaneous NMPC schemes with high gain observers. For a special MIMO system class we show that the closed loop is asymptotically stable, and that the output feedback NMPC scheme recovers the performance of the state feedback in the sense that the region of attraction and the trajectories of the state feedback scheme are recovered for a high gain observer with large enough gain and thus leading to semi-global/non-local results
Revisit emission spectrum and entropy quantum of the Reissner-Nordstr\"{o}m black hole
Banerjee and Majhi's recent work shows that black hole's emission spectrum
could be fully reproduced in the tunneling picture, where, as an intriguing
technique, the Kruskal extension was introduced to connect the left and right
modes inside and outside the horizon. Some attempt, as an extension, was
focused on producing the Hawking emission spectrum of the (charged)
Reissner-Nordstr\"{o}m black hole in the Banerjee-Majhi's treatment.
Unfortunately, the Kruskal extension in their observation was so badly defined
that the ingoing mode was classically forbidden traveling towards the center of
black hole, but could quantum tunnel across the horizon with the probability
. This tunneling picture is unphysical. With
this point as a central motivation, in this paper we first introduce such a
suitable Kruskal extension for the (charged) Reissner-Nordstr\"{o}m black hole
that a perfect tunneling picture can be provided during the charged particle's
emission. Then, under the new Kruskal extension, we revisit the Hawking
emission spectrum and entropy spectroscopy as tunneling from the charged black
hole. The result shows that the tunneling method is so universally robust that
the Hawking blackbody emission spectrum from a charged black hole can be well
reproduced in the tunneling mechanism, and its induced entropy quantum is a
much better approximation for the forthcoming quantum gravity theory.Comment: 7 page
On the Stringy Hartle-Hawking State
We argue that non-perturbative stringy effects render the
Hartle-Hawking state associated with the eternal black hole
singular at the horizon. We discuss implications of this observation on
firewalls in string theory
Through the Looking Glass: Why the "Cosmic Horizon" is not a horizon
The present standard model of cosmology, CDM, contains some
intriguing coincidences. Not only are the dominant contributions to the energy
density approximately of the same order at the present epoch, but we note that
contrary to the emergence of cosmic acceleration as a recent phenomenon, the
time averaged value of the deceleration parameter over the age of the universe
is nearly zero. Curious features like these in CDM give rise to a
number of alternate cosmologies being proposed to remove them, including models
with an equation of state w = -1/3. In this paper, we examine the validity of
some of these alternate models and we also address some persistent
misconceptions about the Hubble sphere and the event horizon that lead to
erroneous conclusions about cosmology.Comment: Accepted for publication by MNRAS, 6 pages, 3 figure
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