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Status report #4 on nonlinear and adaptive control

Fonte: Massachusetts Institute of Technology, Laboratory for Information and Decision Systems Publicador: Massachusetts Institute of Technology, Laboratory for Information and Decision Systems
Formato: 19 p.; 1863473 bytes; application/pdf
ENG
Relevância na Pesquisa
35.57%
prepared by Michael Athans, Gunter Stein, Lena Valavani ; submitted to NASA, Langley Research Center, Ames Research Center.; Includes bibliographical references.; Supported by NASA. NAG 2-297 MIT OSP no.95178

Status report #5 on nonlinear and adaptive control

Fonte: Massachusetts Institute of Technology, Laboratory for Information and Decision Systems Publicador: Massachusetts Institute of Technology, Laboratory for Information and Decision Systems
Formato: 17 leaves; 1621968 bytes; application/pdf
ENG
Relevância na Pesquisa
35.57%
prepared by Michael Athans, Gunter Stein, Lena Valavani ; submitted to NASA, Langley Research Center, Ames Research Center.; Includes bibliographical references.; Supported by a grant from NASA. NAG 2-297 MIT OSP no.95178

Visual Estimation and Control of Robot Manipulating Systems

ROBUFFO GIORDANO, PAOLO
Fonte: La Sapienza Universidade de Roma Publicador: La Sapienza Universidade de Roma
Tipo: Tese de Doutorado
EN
Relevância na Pesquisa
35.71%
With this sentence from his Metaphysica, Aristotle perfectly introduces us to the importance of eyesight for humans, as well as for any advanced living being. Since, to a large extent, robotics is concerned with the emulation of human skills in an artificial context, a natural requirement is to cope with vision for a full interaction with the world. In this respect, this Thesis explores the problem of exploiting visual information to control the motion of robotic systems equipped with onboard cameras. We build our proposals upon the Visual Servoing paradigm, which bridges Computer Vision (image processing, scene interpretation, feature extraction, etc.) with topics proper to the Control Theory field. Indeed, within Visual Servoing, a camera is modeled as a nonlinear function of the scene, i.e., of 3D states subject to rigid body kinematics. Therefore, visual pose control reduces to a problem of output regulation, or task realization if we conform to the robotic nomenclature. Once this view is adopted, any task realization algorithm can be used to fulfill a visual task, and, more in general, the problem can be tackled with the tools of Control Theory. In order to fully exploit this formulation, however, a suitable task-oriented modeling of robot manipulators is required. Therefore...

Eventum Mechanics of Quantum Trajectories: Continual Measurements, Quantum Predictions and Feedback Control

Belavkin, V. P.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/02/2007
Relevância na Pesquisa
35.57%
Quantum mechanical systems exhibit an inherently probabilistic nature upon measurement which excludes in principle the singular direct observability continual case. Quantum theory of time continuous measurements and quantum prediction theory, developed by the author on the basis of an independent-increment model for quantum noise and nondemolition causality principle in the 80's, solves this problem allowing continual quantum predictions and reducing many quantum information problems like problems of quantum feedback control to the classical stochastic ones. Using explicit indirect observation models for diffusive and counting measurements we derive quantum filtering (prediction) equations to describe the stochastic evolution of the open quantum system under the continuous partial observation. Working in parallel with classical indeterministic control theory, we show the Markov Bellman equations for optimal feedback control of the a posteriori stochastic quantum states conditioned upon these two kinds of measurements. The resulting filtering and Bellman equation for the diffusive observation is then applied to the explicitly solvable quantum linear-quadratic-Gaussian (LQG) problem which emphasizes many similarities and differences with the corresponding classical nonlinear filtering and control problems and demonstrates microduality between quantum filtering and classical control.; Comment: 39 pages. Review paper

Pull-Based Distributed Event-triggered Consensus for Multi-agent Systems with Directed Topologies

Yi, Xinlei; Lu, Wenlian; Chen, Tianping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.67%
This paper mainly investigates consensus problem with pull-based event-triggered feedback control. For each agent, the diffusion coupling feedbacks are based on the states of its in-neighbors at its latest triggering time and the next triggering time of this agent is determined by its in-neighbors' information as well. The general directed topologies, including irreducible and reducible cases, are investigated. The scenario of distributed continuous monitoring is considered firstly, namely each agent can observe its in-neighbors' continuous states. It is proved that if the network topology has a spanning tree, then the event-triggered coupling strategy can realize consensus for the multi-agent system. Then the results are extended to discontinuous monitoring, i.e., self-triggered control, where each agent computes its next triggering time in advance without having to observe the system's states continuously. The effectiveness of the theoretical results are illustrated by a numerical example finally.; Comment: arXiv admin note: text overlap with arXiv:1407.1377

Approximate Consensus Multi-Agent Control Under Stochastic Environment with Application to Load Balancing

Amelina, Natalia; Fradkov, Alexander; Jiang, Yuming; Vergados, Dimitrios J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/06/2013
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35.6%
The paper is devoted to the approximate consensus problem for networks of nonlinear agents with switching topology, noisy and delayed measurements. In contrast to the existing stochastic approximation-based control algorithms (protocols), a local voting protocol with nonvanishing step size is proposed. Nonvanishing (e.g., constant) step size protocols give the opportunity to achieve better convergence rate (by choosing proper step sizes) in coping with time-varying loads and agent states. The price to pay is replacement of the mean square convergence with an approximate one. To analyze dynamics of the closed loop system, the so-called method of averaged models is used. It allows to reduce analysis complexity of the closed loop system. In this paper the upper bounds for mean square distance between the initial system and its approximate averaged model are proposed. The proposed upper bounds are used to obtain conditions for approximate consensus achievement. The method is applied to the load balancing problem in stochastic dynamic networks with incomplete information about the current states of agents and with changing set of communication links. The load balancing problem is formulated as consensus problem in noisy model with switched topology. The conditions to achieve the optimal level of load balancing (in the sense that if no new task arrives...

Distributed Event-triggered Consensus for Multi-agent Systems with Directed Topologies

Yi, Xinlei; Lu, Wenlian; Chen, Tianping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.68%
In this paper, we study consensus problem in multi-agent system with directed topology by event-triggered feedback control. That is, at each agent, the diffusion coupling feedbacks are based on the information from its latest observations to its in-neighbours. We derive distributed criteria to determine the next observation time of each agent that are triggered by its in-neighbours' information and its own states respectively. We prove that if the network topology is irreducible, then under the event-triggered coupling principles, the multi-agent system reach consensus. Then, we extend these results to the case of reducible topology with spanning tree. In addition, these results are also extended to the case of self-triggered control, in terms that the next triggering time of each agent is computed based on the current states, i.e., without observing the system's states continuously. The effectiveness of the theoretical results are illustrated by numerical examples.

Pinning networks of coupled dynamical systems with Markovian switching couplings and event-triggered diffusions

Lu, Wenlian; Han, Yujuan; Chen, Tiaping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 02/02/2015
Relevância na Pesquisa
35.65%
In this paper, stability of linearly coupled dynamical systems with feedback pinning algorithm is studied. Here, both the coupling matrix and the set of pinned-nodes vary with time, induced by a continuous-time Markov chain with finite states. Event-triggered rules are employed on both diffusion coupling and feedback pinning terms, which can efficiently reduce the computation load, as well as communication load in some cases and be realized by the latest observations of the state information of its local neighborhood and the target trajectory. The next observation is triggered by certain criterion (event) based on these state information as well. Two scenarios are considered: the continuous monitoring, that each node observes the state information of its neighborhood and target (if pinned) in an instantaneous way, to determine the next triggering event time, and the discrete monitoring, that each node needs only to observe the state information at the last event time and predict the next triggering-event time. In both cases, we present several event-triggering rules and prove that if the conditions that the coupled system with persistent coupling and control can be stabilized are satisfied, then these event-trigger strategies can stabilize the system...

Morphogenesis by coupled regulatory networks: Reliable control of positional information and proportion regulation

Rohlf, Thimo; Bornholdt, Stefan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/08/2009
Relevância na Pesquisa
35.59%
Based on a non-equilibrium mechanism for spatial pattern formation we study how position information can be controlled by locally coupled discrete dynamical networks, similar to gene regulation networks of cells in a developing multicellular organism. As an example we study the developmental problems of domain formation and proportion regulation in the presence of noise, as well as in the presence of cell flow. We find that networks that solve this task exhibit a hierarchical structure of information processing and are of similar complexity as developmental circuits of living cells. Proportion regulation is scalable with system size and leads to sharp, precisely localized boundaries of gene expression domains, even for large numbers of cells. A detailed analysis of noise-induced dynamics, using a mean-field approximation, shows that noise in gene expression states stabilizes (rather than disrupts) the spatial pattern in the presence of cell movements, both for stationary as well as growing systems. Finally, we discuss how this mechanism could be realized in the highly dynamic environment of growing tissues in multi-cellular organisms.; Comment: Journal of Theoretical Biology, in press

Event-triggered Consensus for Multi-agent Systems with Asymmetric and Reducible Topologies

Yi, Xinlei; Lu, Wenlian; Chen, Tianping
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 05/07/2014
Relevância na Pesquisa
35.59%
This paper studies the consensus problem of multi-agent systems with asymmetric and reducible topologies. Centralized event-triggered rules are provided so as to reduce the frequency of system's updating. The diffusion coupling feedbacks of each agent are based on the latest observations from its in-neighbors and the system's next observation time is triggered by a criterion based on all agents' information. The scenario of continuous monitoring is first considered, namely all agents' instantaneous states can be observed. It is proved that if the network topology has a spanning tree, then the centralized event-triggered coupling strategy can realize consensus for the multi-agent system. Then the results are extended to discontinuous monitoring, where the system computes its next triggering time in advance without having to observe all agents' states continuously. Examples with numerical simulation are provided to show the effectiveness of the theoretical results.

Distributed Estimation with Information-Seeking Control in Agent Network

Meyer, Florian; Wymeersch, Henk; Fröhle, Markus; Hlawatsch, Franz
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.66%
We introduce a distributed, cooperative framework and method for Bayesian estimation and control in decentralized agent networks. Our framework combines joint estimation of time-varying global and local states with information-seeking control optimizing the behavior of the agents. It is suited to nonlinear and non-Gaussian problems and, in particular, to location-aware networks. For cooperative estimation, a combination of belief propagation message passing and consensus is used. For cooperative control, the negative posterior joint entropy of all states is maximized via a gradient ascent. The estimation layer provides the control layer with probabilistic information in the form of sample representations of probability distributions. Simulation results demonstrate intelligent behavior of the agents and excellent estimation performance for a simultaneous self-localization and target tracking problem. In a cooperative localization scenario with only one anchor, mobile agents can localize themselves after a short time with an accuracy that is higher than the accuracy of the performed distance measurements.; Comment: 17 pages, 10 figures

Controlling Chimeras

Bick, Christian; Martens, Erik A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.73%
Coupled phase oscillators model a variety of dynamical phenomena in nature and technological applications. Non-local coupling gives rise to chimera states which are characterized by a distinct part of phase-synchronized oscillators while the remaining ones move incoherently. Here, we apply the idea of control to chimera states: using gradient dynamics to exploit drift of a chimera, it will attain any desired target position. Through control, chimera states become functionally relevant; for example, the controlled position of localized synchrony may encode information and perform computations. Since functional aspects are crucial in (neuro-)biology and technology, the localized synchronization of a chimera state becomes accessible to develop novel applications. Based on gradient dynamics, our control strategy applies to any suitable observable and can be generalized to arbitrary dimensions. Thus, the applicability of chimera control goes beyond chimera states in non-locally coupled systems.

The impulse cutoff an entropy functional measure on trajectories of Markov diffusion process integrating in information path functional

Lerner, Vladimir S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.64%
Integrating discrete information extracted from random process solves the impulse cutoff entropy functional (EF) measure on trajectories Markov diffusion process, integrated in information path functional (IPF). Process additive functional defines EF reducing it to a regular integral functional. Compared to Shannon entropy measure of random state, cutting process on separated states decreases quantity information concealed in the states correlation holding hidden process information. Infinite dimensional process cutoffs integrate finite information in IPF whose information approaches EF restricting maximal information of the Markov process. Delta impulse and discrete impulse deliver equivalent information at each cutoff. Constructed finite restriction limits impulses discrete actions cutting the regular integral on EF increments between the cutoffs. Finite impulse step-up action transfers EF increment to following impulse whose step-down action cuts off information and step-up action starts imaginary-virtual impulse carrying entropy increment to next real cut. Step-down cut generates maximal information while step-up action delivers minimal information from impulse cut to next impulse step-down action. Virtual impulse transfers conjugated entropy increments during microprocess ending with adjoining increment within actual step-down action at cutoff. Extracting maximum of minimal impulse information and transferring minimal entropy between impulses implement maxmin-minimax principle of converting process entropy to information. Macroprocess extremal integrates imaginary entropy of microprocess and cutoff information of real impulses in IPF information physical process. EF cut measures Feller kernel information. Estimation extracting information confirms nonadditivity of EF measured process fractions.; Comment: 44 pages

Unstable Price Dynamics as a Result of Information Absorption in Speculative Markets

Patzelt, Felix; Pawelzik, Klaus R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.56%
In speculative markets, risk-free profit opportunities are eliminated by traders exploiting them. Markets are therefore often described as "informationally efficient", rapidly removing predictable price changes, and leaving only residual unpredictable fluctuations. This classical view of markets absorbing information and otherwise operating close to an equilibrium is challenged by extreme price fluctuations, in particular since they occur far more frequently than can be accounted for by external news. Here we show that speculative markets which absorb mainly self-generated information can exhibit both: evolution towards efficient equilibrium states as well as their subsequent destabilization. This peculiar dynamics, a generic instability arising from an adaptive control which annihilates predictable information, is realized in a minimal agent-based market model where the impacts of agents' strategies adapt according to their trading success. This adaptation implements a learning rule for the market as a whole minimizing predictable price changes. The model reproduces stylized statistical properties of price changes in quantitative detail, including heavy tailed log return distributions and volatility clusters. Our results demonstrate that the perpetual occurrence of market instabilities can be a direct consequence of the very mechanisms that lead to market efficiency.; Comment: Paper and supplement are combined in a single file. Changes in this Version: Added an introductory paragraph. Expanded discussion on the differences between the presented model and minority games. Added two supplementary figures

The information path functional approach for solution of a controllable stochastic problem

Lerner, Vladimir S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.76%
We study a stochastic control system, described by Ito controllable equation, and evaluate the solutions by an entropy functional (EF), defined by the equation functions of controllable drift and diffusion. Considering a control problem for this functional, we solve the EF control variation problem (VP), which leads to both a dynamic approximation of the process entropy functional by an information path functional (IPF) and information dynamic model (IDM) of the stochastic process. The IPF variation equations allow finding the optimal control functions, applied to both stochastic system and the IDM for joint solution of the identification and optimal control problems, combined with state consolidation. In this optimal dual strategy, the IPF optimum predicts each current control action not only in terms of total functional path goal, but also by setting for each following control action the renovated values of this functional controllable drift and diffusion, identified during the optimal movement, which concurrently correct this goal. The VP information invariants allow optimal encoding of the identified dynamic model operator and control. The introduced method of cutting off the process by applying an impulse control estimates the cutoff information...

Novel coupling scheme to control dynamics of coupled discrete systems

Shekatkar, Snehal M.; Ambika, G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
35.63%
We present a new coupling scheme to control spatio-temporal patterns and chimeras on 1-d and 2-d lattices and random networks of discrete dynamical systems. The scheme involves coupling with an external lattice or network of damped systems. When the system network and external network are set in a feedback loop, the system network can be controlled to a homogeneous steady state or synchronized periodic state with suppression of the chaotic dynamics of the individual units. The control scheme has the advantage that its design does not require any prior information about the system dynamics or its parameters and works effectively for a range of parameters of the control network. We analyze the stability of the controlled steady state or amplitude death state of lattices using the theory of circulant matrices and Routh-Hurwitz's criterion for discrete systems and this helps to isolate regions of effective control in the relevant parameter planes. The conditions thus obtained are found to agree well with those obtained from direct numerical simulations in the specific context of lattices with logistic map and Henon map as on-site system dynamics. We show how chimera states developed in an experimentally realizable 2-d lattice can be controlled using this scheme. We propose this mechanism can provide a phenomenological model for the control of spatio-temporal patterns in coupled neurons due to non-synaptic coupling with the extra cellular medium. We extend the control scheme to regulate dynamics on random networks and adapt the master stability function method to analyze the stability of the controlled state for various topologies and coupling strengths.; Comment: 22 pages...

Reduced-Complexity Nonlinear H ∞ Control of Discrete-Time Systems

Helton, J W; James, Matthew; McEneaney, W M
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.85%
In this note, we describe a reduced-complexity solution to the nonlinear H∞ control problem. This reduction applies to systems where some of the states are perfectly known, and is an intermediate problem between full state feedback and the standard meas

Gap metrics, representations, and nonlinear robust stability

James, Matthew; Smith, M C; Vinnicombe, G
Fonte: SIAM Publications Publicador: SIAM Publications
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
45.8%
Various alternative definitions for the nonlinear H2-, L 2-, and v-gap metrics are studied. The concept of β-conjugacy and multiplicative homogeneity are introduced to relate the metrics to each other and to compare the stability margins of nonlinear fee

Nonlinear H-∞ Control: Practicality of Implementing the Cheap Sensor Case

Helton, J W; James, Matthew; McEneaney, W M
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Conference paper
Relevância na Pesquisa
95.79%
In [5] we introduced a recipe for nonlinear H∞ controllers which takes advantage of extra perfect measurements and stated a theorem to the effect that this controller yielded the best possible "H∞" performance. Pure state feedback is an extreme situat

l ∞ -Bounded Robustness for Nonlinear Systems: Analysis and Synthesis

Huang, Shoudong; James, Matthew
Fonte: Institute of Electrical and Electronics Engineers (IEEE Inc) Publicador: Institute of Electrical and Electronics Engineers (IEEE Inc)
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
55.73%
The purpose of this paper is to describe systematic analysis and design tools for robust control problems with l∞ criteria. We first generalize the Hill-Moylan-Willems framework for dissipative systems to accommodate l∞ criteria, and then derive state