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2008 American control Conference (ACC), vol.7

作者： Abhyudai Singh Joao Pedro Hespanha Center for Control Engineering and Computation University of California Santa Barbara CA USA

Stochastic fluctuations in protein levels are inevitable due to the probabilistic nature of gene expression. These fluctuations are attributed to two factors: intrinsic noise (noise associated with random transcription and translation events) and extrinsic noise (noise associated with fluctuations in the reaction rates due to correspondent fluctuations in cellular enzyme levels). We present results on how stochastic noise in proteins scales in a cascade of genes both in the presence and absence of extrinsic noise. In particular, we derive analytical formulas relating the noise in the proteins to the length, per stage magnification of the cascade and the amount of extrinsic noise present in the cell. We show that when there is no extrinsic noise the gene cascade acts like a noise attenuator where downstream proteins exhibit reduced noise. Moreover, for two different cascades with the same average final protein level, the cascade with the larger number of stages will have lower stochastic noise in the final protein. We also show that adding extrinsic noise can change the qualitative behavior of the cascade from a noise attenuator to a noise magnifier where downstream protein have increased noise. Furthermore, there exists a critical level of extrinsic noise above which the cascade with lower number of stages will have lesser noise in the final protein.

关键词： Proteins Noise level Stochastic resonance Fluctuations Gene expression Noise reduction Biochemistry Attenuators Stochastic processes Steady-state

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Robust hybrid source-seeking algorithms based on directional derivatives and their approximations

Robust hybrid source-seeking algorithms based on directional...

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IEEE Conference on Decision and control

作者： Christopher G. Mayhew Ricardo G. Sanfelice Andrew R. Teel Center for Control Engineering and Computation Electrical and Computer Engineering Department University of California Santa Barbara CA USA Laboratory for Information and Decision Systems Massachusetts Institute of Technology MA USA

ISBN: (纸本)9781424431236

A family of hybrid control algorithms is developed that steer a nonholonomic autonomous vehicle to the source of a scalar signal present in the environment. In an idealized setting, we develop a general hybrid control scheme that globally asymptotically stabilizes the vehicle position about the source. Pursuing a practical implementation, a series of perturbations to the family of controllers is introduced, resulting in a semi-global practical stability of the vehicle position about the source. An example of a recently developed conjugate direction-based controller fitting into this family is developed and demonstrated by simulation and experiment.

关键词： Robustness Remotely operated vehicles Mobile robots Robust control Stability Position measurement Noise measurement Working environment noise Chemical sensors Current measurement

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Robust source-seeking hybrid controllers for nonholonomic vehicles

Robust source-seeking hybrid controllers for nonholonomic ve...

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2008 American control Conference (ACC), vol.7

We develop a hybrid controller that drives a nonholonomic vehicle to the source of a radiation-like signal. The control signal depends only on measurements of the signal, which may be corrupted by noise, and internal states of the controller. The control strategy is inspired by a line minimization-based algorithm for unconstrained optimization of nonlinear functions without gradient information. We state the main properties of the algorithm and then discuss its implementation in a hybrid controller that coordinates the optimization algorithm with vehicle steering. We present semi-global practical convergence and stability results for the closed-loop system. These results are illustrated by simulation and experiment.

关键词： Robust control Remotely operated vehicles Mobile robots Noise measurement Convergence Vehicle driving Working environment noise Position measurement Tin Noise robustness

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The Broad Institute-Six Years Later

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CHEMISTRY & BIOLOGY 2010年第4期17卷 311-312页

作者： McCarthy, Alice Main Text “In June 2003 the scientific and medical communities at MIT Harvard University and its affiliated hospitals and the Whitehead Institute banded together as collaborating partners to form the Eli and Edythe L. Broad Institute based in Cambridge MA. The Broad Institute established with initial funding from a $100 million philanthropic donation from the Los Angeles-based Broad family was primarily viewed as a marriage between the Whitehead Institute's Center for Genome Research (WICGR) and the Harvard Institute of Chemistry and Cell Biology (ICCB). Eli Broad founder and chairman of AIG SunAmerica Inc. explained “the purpose of the Broad Institute is to create a new type of research institute to build on the accomplishments of the human genome project and to move to clinical applications to both prevent and cure diseases.” Every Thursday morning we meet with perhaps 20 faculty members and 100 other researchers to discuss what we're all doing and should be doing next. -David Altschuler This paragraph was written five years ago when the Broad Institute was in its very earliest days as a life science research community (McCarthy 2005). Since that time “the Broad” as it's known has kept true to Eli Broad's vision having attracted a talented group of researchers faculty trainees and professional staff. This 1600 person research community known internally as “Broadies” includes faculty staff and students from throughout the MIT and Harvard biomedical research communities and beyond with collaborations spanning over a hundred private and public institutions in more than 40 countries worldwide. “What is special about the Broad is that we have people from Harvard MIT and the Harvard hospitals come together and work on problems of shared interest that could not be solved in their own individuals labs” explains David Altshuler M.D. Ph.D. Deputy Director and one of the Broad's six core faculty members. “These problems require expertise beyond any one principal investigator and in

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Distributed policies for equitable partitioning: Theory and applications

Distributed policies for equitable partitioning: Theory and ...

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IEEE Conference on Decision and control

作者： Marco Pavone Emilio Frazzoli Francesco Bullo Laboratory for Information and Decision Systems Department of Aeronautics and Astronautics Massachusetts Institute of Technology Cambridge UK Center for Control Engineering and Computation University of California슠Santa Barbara USA

ISBN: (纸本)9781424431236

The most widely applied resource allocation strategy is to balance, or equalize, the total workload assigned to each resource. In mobile multi-agent systems, this principle directly leads to equitable partitioning policies in which (i) the workspace is divided into subregions of equal measure, (ii) each agent is assigned to a unique subregion, and (iii) each agent is responsible for service requests originating within its own subregion. In this paper, we design distributed and adaptive policies to allow a team of agents to achieve a convex and equitable partition of a convex workspace. Our approach is related to the classic Lloyd algorithm, and exploits the unique features of Power Diagrams. We discuss possible applications to routing of vehicles in stochastic and dynamic environments, and to wireless networks. Simulation results are presented and discussed.

关键词： Multiagent systems Partitioning algorithms Resource management Extraterrestrial measurements Logistics Surveillance Pervasive computing Computer architecture Decision feedback equalizers Routing

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Uniting a high performance, local controller with a global controller: the output feedback case for linear systems with input saturation

Uniting a high performance, local controller with a global c...

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2008 American control Conference (ACC), vol.7

作者： Christophe Prieur Andrew R. Teel LAAS-CNRS Université de Toulouse Toulouse France Center for Control Dynamical Systems & Computation (CCDC) Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

We consider linear control systems with saturation in the input for which we know two stabilizing output feedback controllers. One is a nonlinear globally asymptotically stabilizing controller, while the other one is a linear only locally asymptotically stabilizing controller. We look for a composite output feedback control law that is equal to the linear controller for initial conditions in a neighborhood of the origin and that is globally asymptotically stabilizing. We suggest a constructive approach to solve this uniting problem and to modify the linear local controller into a nonlinear global controller. Moreover since we want some robustness with respect to measurement noise, actuator errors and external disturbances, we consider hybrid output feedback controllers, following recent developments in the literature on robustness in hybrid systems. We illustrate our main result by means of numerical examples.

关键词： Linear feedback control systems control systems Output feedback Linear systems Nonlinear control systems Noise robustness Robust control Noise measurement Optimal control State feedback

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On visibility maintenance via controlled invariance for leader-follower Dubins-like vehicles

On visibility maintenance via controlled invariance for lead...

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IEEE Conference on Decision and control

作者： Fabio Morbidi Francesco Bullo Domenico Prattichizzo Dipartimento di Ingegneria dellInformazione Università di Siena Siena Italy Department of Mechanical Engineering and Center for Control Dynamical Systems and Computation University of California Santa Barbara CA USA

ISBN: (纸本)9781424431236

The paper studies the visibility maintenance problem (VMP) for a leader-follower pair of robots modelled as first-order dynamic systems and proposes an original solution based on the notion of controlled invariance. The nonlinear model describing the relative dynamics of the vehicles is interpreted as linear uncertain system, with the leader robot acting as an external disturbance. The VMP can then be reformulated as a linear constrained regulation problem with additive disturbances (DLCRP). New positive D-invariance conditions for linear uncertain systems with parametric disturbance matrix are introduced and used to solve the VMP when box bounds on the state, control input and disturbance are considered. The proposed design procedure can be easily adapted to provide the control with UBB disturbances rejection capabilities. As an extension, the paper addresses the VMP on a circle. Simulation experiments show the effectiveness of the proposed designs.

关键词： Robot sensing systems Robot kinematics Uncertain systems Vehicle dynamics Nonlinear dynamical systems control systems Linear systems Linear matrix inequalities Laser radar State feedback

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Increasingly correct message passing averaging algorithms

Increasingly correct message passing averaging algorithms

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IEEE Conference on Decision and control

作者： Kurt Plarre Francesco Bullo Department of Mechanical Engineering and Center for Control Dynamical Systems and Computation University of California슠Santa Barbara Santa Barbara CA USA Department of Mechanical Engineering University of California슠Santa Barbara CA USA

ISBN: (纸本)9781424431236

We study averaging algorithms, when implemented in large networks of wirelessly connected elements. We extend the notion of ¿increasing correctness¿ (IC) which was defined for cycle-free graphs, to general graphs. An averaging algorithm that is IC has meaningful outputs at each iteration. This makes it possible to stop the algorithm at any time, and use the output values computed up to that time. We prove that the class of IC averaging algorithms is nontrivial. We then present a simple IC averaging algorithm that is based on ideas from graphical models, and study its properties. Finally, we give example applications and simulations of IC averaging algorithms.

关键词： Message passing Robot sensing systems Integrated circuit modeling Graphical models Orbital robotics Computer networks Aggregates Convergence Mechanical engineering computational modeling

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Quantized average consensus via dynamic coding/decoding schemes

Quantized average consensus via dynamic coding/decoding sche...

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IEEE Conference on Decision and control

作者： Ruggero Carli Francesco Bullo Sandro Zampieri Center for Control Dynamical Systems and Computation University of California슠Santa Barbara Santa Barbara CA USA Department of Information Engineering sede di Vicenza Università di Padova Padova Italy

ISBN: (纸本)9781424431236

In the average consensus a set of linear systems has to be driven to the same final state which corresponds to the average of their initial states. This contribution presents a consensus strategy in which the systems can exchange information among themselves according to a fixed connected digital communication network. Beside the decentralized computational aspects induced by the choice of the communication network, we here have also to face the quantization effects due to the digital links. We here present and discuss two different encoding/decoding strategies with theoretical and simulation results on their performance.

关键词： Decoding Quantization Convergence Stochastic processes control systems Digital communication Additive noise Analytical models Linear systems Computer networks

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An EEG-based subject- and session-independent drowsiness detection

An EEG-based subject- and session-independent drowsiness det...

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International Joint Conference on Neural Networks (IJCNN)

作者： Chin-Teng Lin Nikhil R. Pal Chien-Yao Chuang Tzyy-Ping Jung Li-Wei Ko Sheng-Fu Liang Department of Electrical & Control Engineering and Brain Research Center National Chiao Tung University Hsinchu Taiwan Department of Brain Research Center National Chiao Tung University Calcutta India Department of Brain Research Center National Chiao Tung University Taiwan Department of Electrical & Control Engineering and Brain Research Center National Chiao-Tung University and Institute for Neural Computation University of California San Diego La Jolla CA USA Department of Electrical & Control Engineering and Brain Research Center National Chiao Tung University Taiwan Department of Brain Research Center National Chiao-Tung University and the Department of Computer Science and Information Engineering National Cheng Kung University Tainan Taiwan

Monitoring and predicting human cognitive state and performance using physiological signals such as Electroencephalogram (EEG) have recently gained increasing attention in the fields of brain-computer interface and cognitive neuroscience. Most previous psychophysiological studies of cognitive changes have attempted to use the same model for all subjects. However, the relatively large individual variability in EEG dynamics relating to loss of alertness suggests that for many operators, group statistics cannot be used to accurately predict changes in cognitive states. Attempts have also been made to build a subject-dependent model for each individual based on his/her pilot data to account for individual variability. However, such methods assume the cross-session variability in EEG dynamics to be negligible, which could be problematic due to electrode displacements, environmental noises, and skin-electrode impedance. Here first we show that the EEG power in the alpha and theta bands are strongly correlated with changes in the subjectpsilas cognitive state reflected through his driving performance and hence his departure from alertness. Then under very mild and realistic assumptions we derive a model for the alert state of the person using EEG power in the alpha and theta bands. We demonstrate that deviations (computed by Mahalanobis distance) of the EEG power in the alpha and theta bands from the corresponding alert models are correlated to the changes in the driving performance. Finally, for detection of drowsiness we use a linear combination of deviations of the EEG power in the alpha band and theta band from the respective alert models that best correlates with subjectpsilas changing level of alertness, indexed by subjectpsilas behavioral response in the driving task. This approach could lead to a practical system for noninvasive monitoring of the cognitive state of human operators in attention-critical settings.

关键词： Electroencephalography Brain modeling Brain models Distance measurement Correlation Spectral analysis Data models

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