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IEEE Conference on decision and control

作者： Daniel Coutinho Minyue Fu Carlos E. de Souza Group of Automation and Control Systems Faculty of Engineering Pontifícia Universidade Católica do Rio Grande do Sul Porto Alegre Brazil School of Electrical Engineering and Computer Science University of Newcastle Callaghan NSW Australia Department of Systems and Control Laboratory Nacional de Computação Científica Petropolis Rio de Janeiro Brazil

ISBN: (纸本)9781424431236

A considerable amount of research has been done on the use of logarithmic quantizers for networked feedback control systems. However, most results are developed for the case of a single quantizer (either measurement or control signal quantization). In this paper, we investigate the case of simultaneous input and output quantization for SISO linear output feedback systems. Firstly, we show that the problem of quadratic stabilization via quantized feedback can be addressed with no conservativeness by means of the sector bound approach. Secondly, we provide a bound on the maximal admissible sector bound via a scaled H ¿ optimization problem.

关键词： Output feedback Linear feedback control systems control systems Linear systems Quantization Communication system control Feedback control Communication channels Digital control Bandwidth

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Message passing and distributed statistical inference 45

Message passing and distributed statistical inference

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45th Annual Allerton Conference on Communication, control, and Computing 2007

作者： Chandrasekaran, Venkat Johnson, Jason Kreidl, O. Patrick Malioutov, Dmitry Sanghavi, Sujay Willsky, Alan S. Department of Electrical Engineering and Computer Science Laboratory for Information and Decision Systems MIT CambridgeMA United States

ISBN: (纸本)9781605600864

In this paper , we summarize several research directions involving message-passing algorithms and distributed fusion. The starting point is inference for graphical models , but the different constraints and objectives found in sensor networks suggest new questions. In addition to providing pointers to a variety of other parts of our research in this area , we spend most of our time on two research investigations. The irst involves team-theoretic approaches to distributed decision-making and the development of message-passing algorithms for sensor network organization in order to optimize distributed team objectives. The second deals with the exploitation of so-called walk-sum analysis for distributed linear estimation. In particular under an easily checked condition for walk-summability , we can show that essentially any messaging strategy converges to the optimal distributed solution;moreover with modest use of local memory , this remains true in the presence of random message losses. We also describe how this framework leads to a tractable max-spanning tree problem for optimal adaptive message routing-i.e. , for determining a spanning tree for the next wave of messages to reduce an upper bound on estimation error as quickly as possible.

关键词： Sensor networks

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Formal embedding of the Spring Loaded Inverted Pendulum in an Asymmetric hopper 9

Formal embedding of the Spring Loaded Inverted Pendulum in a...

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2007 9th European control Conference, ECC 2007

作者： Poulakakis, Ioannis Grizzle, J.W. Control Systems Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48105 United States

ISBN: (纸本)9783952417386

The control of running is discussed in terms of a model called the Asymmetric Spring Loaded Inverted Pendulum (ASLIP), shown in Fig. 1. The ASLIP consists of a Spring Loaded Inverted Pendulum (SLIP) with the addition of pitch dynamics, and can be used to study the sagittal plane motion of bipedal running. A hybrid controller for the ASLIP is developed that acts on two levels. In the first level, continuous in-stride control is used to stabilize the torso at a desired posture, and to create an invariant surface on which the stance dynamics of the closed-loop system is diffeomorphic to the center of mass dynamics of a SLIP. In the second level, event-based control is employed to stabilize the closed-loop hybrid system along a periodic orbit of the SLIP dynamics. These results provide a systematic framework for designing control laws with provable stability properties which take advantage of existing SLIP controllers that are known to induce elegant running motions in legged models. © 2007 EUCA.

关键词： Closed loop systems

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Stochastic control for nanoparticle manipulation using electric fields

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International Journal of Nanomanufacturing 2007年第6期1卷 751-761页

作者： Kyprianou, Andreas Loucaides, Neophytos Polydorides, Nick Georghiou, George Charalambous, Charalambos D. Doumanides, Charalambos Department of Mechanical and Manufacturing Engineering University of Cyprus Kallipoleos 75 Nicosia 1678 Cyprus Department of Electrical and Computer Engineering University of Cyprus Kallipoleos 75 Nicosia 1678 Cyprus Laboratory for Information and Decision Systems Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge MA United States

A simplified model is used to study the dynamics of a nanoparticle suspended in a fluid under Dielectrophoretic (DEP) force. The model considers the DEP force (considering only dipoles formed and not higher order polarisation) and the Brownian motion of the particle. Stochastic control and estimation methods are introduced to provide control action via DEP force that pushes the particle in a specific direction. The control action employed is based on alternating the polarity of the electric field that induces the force exerted on the particle. Despite the simplicity of the model, a sufficient insight into the nature of applying stochastic control techniques can be derived. Simulations are also presented to illustrate the proposed stochastic control techniques, by simulating the behaviour of the controlled nanoparticle system described by a stochastic differential equation driven by Brownian motion subject to optimal DEP force computed by solving an optimal stochastic control problem. © 2007, Inderscience Publishers.

关键词： Nanoparticles

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Design of state estimators for linear discrete-time systems with constrained error variance 9

Design of state estimators for linear discrete-time systems ...

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2007 9th European control Conference, ECC 2007

作者： Milias, Andreas Bitsoris, George Department of Electrical and Computer Engineering University of Patras Patras26500 Greece Automatic Control Laboratory ETH Zurich Switzerland Control Systems Laboratory University of Patras Patras26500 Greece

ISBN: (纸本)9783952417386

In this paper, the state estimation problem with constrained error variance for linear discrete-time systems is investigated. To this end, in a first stage, the vector variance equation describing the evolution of the state error variance is established. Then, by applying results from the theory of positively invariant polyhedral sets of discrete-time systems, necessary and sufficient conditions for the state error variance to respect linear constraints are developed. Thus, the determination of the state estimator parameters is reduced to a nonlinear programming problem which can be solved by using various optimization algorithms. © 2007 EUCA.

关键词： State estimation

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Level-triggered control of a scalar linear system

Level-triggered control of a scalar linear system

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2007 Mediterranean Conference on control and Automation, MED

作者： Rabi, Maben Baras, John S. Automatic Control Laboratory School of Electrical Engineering Royal Institute of Technology Stockholm 100 44 Sweden Institute for Systems Research Department of Electrical and Computer Engineering University of Maryland College Park MD 20742 United States

ISBN: (纸本)142441282X

In networked control systems, because of limits on communication rates, control waveforms are frequently piece-wise constant with limits on rates at which they can switch levels. It is, therefore, natural to expect event-triggered control switchings to perform more efficiently than time-triggered ones. This article verifies the validity of this supposition. A method for designing good level-triggered control schemes is obtained by reducing the continuous time problem to one in discrete time. Then, by numerical procedures, the performance of the level-triggered scheme is computed for comparison with that of the periodically switched control scheme. © 2007 IEEE.

关键词： Networked control systems

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Maximum Entropy Relaxation for Graphical Model Selection Given Inconsistent Statistics

Maximum Entropy Relaxation for Graphical Model Selection Giv...

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IEEE/SP Workshop on Statistical Signal Processing (SSP)

作者： Venkat Chandrasekaran Jason K. Johnson Alan S. Willsky Laboratory for Information and Decision Systems Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA USA

We develop a novel approach to approximate a specified collection of marginal distributions on subsets of variables by a globally consistent distribution on the entire collection of variables. In general, the specified marginal distributions may be inconsistent on overlapping subsets of variables. Our method is based on maximizing entropy over an exponential family of graphical models, subject to divergence constraints on small subsets of variables that enforce closeness to the specified marginals. The resulting optimization problem is convex, and can be solved efficiently using a primal-dual interior-point algorithm. Moreover, this framework leads naturally to a solution that is a sparse graphical model.

关键词： Entropy Graphical models Statistics Random variables Statistical distributions Signal processing algorithms Laboratories Biomedical signal processing Probability distribution Geophysics

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Resource Allocation in Multiple Access Channels

Resource Allocation in Multiple Access Channels

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Asilomar Conference on Signals, systems & computers

作者： Ali ParandehGheibi Atilla Eryilmaz Asuman Ozdaglar Muriel Medard Laboratory for Information and Decision Systems Electrical Engineering and Computer Science Department Massachusetts Institute of Technology Cambridge MA USA Electrical and Computer Engineering Ohio State Uinversity OH USA

We consider the problem of rate allocation in a Gaussian multiple-access channel, with the goal of maximizing a utility function over transmission rates. In contrast to the literature which focuses on linear utility functions, we study general concave utility functions. We present a gradient projection algorithm for this problem. Since the constraint set of the problem is described by exponentially many constraints, methods that use exact projections are computationally intractable. Therefore, we develop a new method that uses approximate projections. We use the polymatroid structure of the capacity region to show that the approximate projection can be implemented by a recursive algorithm in time polynomial in the number of users. We further propose another algorithm for implementing the approximate projections using rate-splitting and show improved bounds on its convergence time.

关键词： Resource management Polynomials Multiaccess communication Throughput Fading Laboratories Quality of service Projection algorithms Convergence Bandwidth

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Monopedal running control: SLIP embedding and virtual constraint controllers

Monopedal running control: SLIP embedding and virtual constr...

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2007 IEEE/RSJ International Conference on Intelligent Robots and systems

作者： Ioannis Poulakakis J. W. Grizzle Control Systems Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA

Two feedback controllers that induce stable running gaits on a three-degree-of-freedom asymmetric hopper, termed the asymmetric spring loaded inverted pendulum (ASLIP), see Fig. 1, are compared in terms of their steady-state and transient behaviors. In each case, feedback is used to create a lower-dimensional hybrid subsystem that determines the existence and stability properties of periodic motions of the full-dimensional closed-loop system. The first controller creates a one degree-of-freedom subsystem through imposing two suitably selected (virtual) holonomic constraints on the configuration variables of the ASLIP. The second controller asymptotically imposes a single (virtual) holonomic constraint to create a two-degree-of-freedom subsystem that is diffeomorphic to a standard spring loaded inverted pendulum (SLIP). The two controllers induce identical steady-state behaviors. Under transient conditions, however, the underlying compliant nature of the SLIP allows significantly larger disturbances to be accommodated, with less actuator effort, and without violation of the unilateral constraints between the leg end and the ground.

关键词： Legged locomotion Springs Leg control systems Steady-state Actuators Adaptive control Predictive models Torso Nonlinear dynamical systems

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Kinematic simulative analysis of virtual potential field method for AUV trajectory planning

Kinematic simulative analysis of virtual potential field met...

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Mediterranean Conference on control and Automation (MED)

作者： M Barisic Z. Vukic N. Miskovic Department of Computer and Control Engineering Laboratory for Underwater Systems and TechnologiesFaculty of Electrical Engineering and Computing University of Zagreb Zagreb Croatia

This paper deals with an analysis of applicability, capabilities, benefits and pitfalls of using a virtual potential field approach to autonomously planning trajectories in non-communicating autonomous underwater vehicles (AUV-s). Virtual potentials represent an approach to this problem with cross-layer design features. Examples of different layers of control that can be achieved with the same fundamental approach are: obstacle-avoidance, energy-optimal trajectories, forming up with other moving agents, controlled formation fragmentation into well-posed sub-formation etc. This paper shows, on the basis of extensive simulated experiments, that such a trajectory planner based on virtual potentials, guarantees good extendibility, scalability and performance in a hard-real-time hardware-in-the-loop system.

关键词： Kinematics Analytical models Trajectory Computational modeling computer simulation Electric variables measurement Feature extraction Stability Underwater vehicles Communication system control

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