275 research outputs found
Model Reduction for Aperiodically Sampled Data Systems
Two approaches to moment matching based model reduction of aperiodically
sampled data systems are given. The term "aperiodic sampling" is used in the
paper to indicate that the time between two consecutive sampling instants can
take its value from a pre-specified finite set of allowed sampling intervals.
Such systems can be represented by discrete-time linear switched (LS) state
space (SS) models. One of the approaches investigated in the paper is to apply
model reduction by moment matching on the linear time-invariant (LTI) plant
model, then compare the responses of the LS SS models acquired from the
original and reduced order LTI plants. The second approach is to apply a moment
matching based model reduction method on the LS SS model acquired from the
original LTI plant, and then compare the responses of the original and reduced
LS SS models. It is proven that for both methods, as long as the original LTI
plant is stable, the resulting reduced order LS SS model of the sampled data
system is quadratically stable. The results from two approaches are compared
with numerical examples
Event-triggered boundary control of constant-parameter reaction-diffusion PDEs: a small-gain approach
This paper deals with an event-triggered boundary control of
constant-parameters reaction-diffusion PDE systems. The approach relies on the
emulation of backstepping control along with a suitable triggering condition
which establishes the time instants at which the control value needs to be
sampled/updated. In this paper, it is shown that under the proposed
event-triggered boundary control, there exists a minimal dwell-time
(independent of the initial condition) between two triggering times and
furthermore the well-posedness and global exponential stability are guaranteed.
The analysis follows small-gain arguments and builds on recent papers on
sampled-data control for this kind of PDE. A simulation example is presented to
validate the theoretical results.Comment: 10 pages, to be submitted to Automatic
Delay-Based Controller Design for Continuous-Time and Hybrid Applications
Motivated by the availability of different types of delays in embedded systems and biological circuits, the objective of this work is to study the benefits that delay can provide in simplifying the implementation of controllers for continuous-time systems. Given a continuous-time linear time-invariant (LTI) controller, we propose three methods to approximate this controller arbitrarily precisely by a simple controller composed of delay blocks, a few integrators and possibly a unity feedback. Different problems associated with the approximation procedures, such as finding the optimal number of delay blocks or studying the robustness of the designed controller with respect to delay values, are then investigated. We also study the design of an LTI continuous-time controller satisfying given control objectives whose delay-based implementation needs the least number of delay blocks. A direct application of this work is in the sampled-data control of a real-time embedded system, where the sampling frequency is relatively high and/or the output of the system is sampled irregularly. Based on our results on delay-based controller design, we propose a digital-control scheme that can implement every continuous-time stabilizing (LTI)
controller. Unlike a typical sampled-data controller, the hybrid controller introduced here -— consisting of an ideal sampler, a digital controller, a number of modified second-order holds and possibly a unity feedback -— is robust to sampling jitter and can operate at arbitrarily high sampling frequencies without requiring expensive, high-precision computation
Dissipativity-based Framework for Stability Analysis of Aperiodically Sampled Nonlinear Systems with Time-varying Delay
International audienceIn this paper, we provide novel conditions for stability analysis of aperiodically sampled nonlinear control systems subjected to time-varying delay. The proposed approach can also deal with cases in which delay is larger than the sampling interval. It is applicable to a general class of nonlinear systems and provides sufficient criteria for stability that aid in making trade-offs between control performance and the bounds on sampling interval and delay. As a stepping stone, a preliminary and generic result based on dissipativity, is introduced to analyse the exponential stability of a class of feedback-interconnected systems. The nonlinear sampled-data system is remodelled to consider the effects of sampling and delay in the dissipativity framework, as perturbations to the nominal closed-loop system. This leads to constructive stability conditions for a continuous time closed-loop system given by the feedback interconnection of the nominal closed-loop system and an operator(s) that captures the effects of sampling and delay. For Linear Time-Invariant (LTI) systems, we recover simple Linear Matrix Inequality (LMI) and frequency domain conditions previously proposed in the robust control framework
Sequence-based Anytime Control
We present two related anytime algorithms for control of nonlinear systems
when the processing resources available are time-varying. The basic idea is to
calculate tentative control input sequences for as many time steps into the
future as allowed by the available processing resources at every time step.
This serves to compensate for the time steps when the processor is not
available to perform any control calculations. Using a stochastic Lyapunov
function based approach, we analyze the stability of the resulting closed loop
system for the cases when the processor availability can be modeled as an
independent and identically distributed sequence and via an underlying Markov
chain. Numerical simulations indicate that the increase in performance due to
the proposed algorithms can be significant.Comment: 14 page
An open-loop method for reduction of torque ripple and an associated thermal-management technique
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (leaves 202-204).by Arthur Joseph Kalb.M.S
Seismic Data Strong Noise Attenuation Based on Diffusion Model and Principal Component Analysis
Seismic data noise processing is an important part of seismic exploration
data processing, and the effect of noise elimination is directly related to the
follow-up processing of data. In response to this problem, many authors have
proposed methods based on rank reduction, sparse transformation, domain
transformation, and deep learning. However, such methods are often not ideal
when faced with strong noise. Therefore, we propose to use diffusion model
theory for noise removal. The Bayesian equation is used to reverse the noise
addition process, and the noise reduction work is divided into multiple steps
to effectively deal with high-noise situations. Furthermore, we propose to
evaluate the noise level of blind Gaussian seismic data using principal
component analysis to determine the number of steps for noise reduction
processing of seismic data. We train the model on synthetic data and validate
it on field data through transfer learning. Experiments show that our proposed
method can identify most of the noise with less signal leakage. This has
positive significance for high-precision seismic exploration and future seismic
data signal processing research.Comment: 10 pages, 13 figures. This work has been submitted to the IEEE for
possible publication. Copyright may be transferred without notice, after
which this version may no longer be accessibl
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