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Decision and Control and European Control Conference (CDC-ECC), 2011 50th IEEE Conference on

Date 12-15 Dec. 2011

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Displaying Results 1 - 25 of 1360
  • On the distinguishability of discrete linear time-invariant dynamic systems

    Publication Year: 2011 , Page(s): 3356 - 3361
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (422 KB) |  | HTML iconHTML  

    This paper introduces the notion of absolutely distinguishable discrete dynamic systems, with particular applicability to linear time-invariant (LTI) systems. The motivation for this novel type of distinguishability stems, in particular, from the stability and performance requirements of worst-case adaptive control methodologies. The main results presented herein show that, in most practical cases, a persistence of excitation type of condition and a minimum number of iterations are required to properly distinguish two dynamic systems. We also demonstrate that the former constraint can be written as a lower bound on the intensity of the exogenous disturbances. The applicability of the developed theory is illustrated with a set of examples. View full abstract»

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  • Funnel control in mechatronics: An overview

    Publication Year: 2011 , Page(s): 8000 - 8007
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB) |  | HTML iconHTML  

    This overview presents a simple high-gain adaptive controller - the funnel controller - and its possible applications in mechatronics. The funnel controller neither identifies nor estimates the system under control and is applicable for (nonlinear) systems being minimum-phase (or having stable zero-dynamics in the nonlinear case), having relative degree one or two and known sign of the high-frequency gain. So only “structural system properties” must be satisfied to allow for controller implementation. Moreover, control performance is robust to parameter uncertainties or variations not affecting the system structure. The proportional funnel controller assures tracking of time-varying reference signals with prescribed transient accuracy, i.e. the tracking error evolves within a “funnel” with prescribed boundary (i.e. a continuous function of time chosen by the control designer). To illustrate applicability of funnel control in “real world” measurement results are presented for speed and position control of an unknown rotatory system subject to (varying) friction and load disturbances. The results are compared with classical PI/PID control. View full abstract»

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  • Control of nonlinear bilateral teleoperation systems subject to disturbances

    Publication Year: 2011 , Page(s): 1765 - 1770
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (268 KB) |  | HTML iconHTML  

    Teleoperation systems, consisting of a pair of master and slave robots are subject to different types of disturbances such as joint frictions, varying contact points, unmodeled dynamics and unknown payloads. Such disturbances, when unaccounted for, cause poor teleoperation transparency and even instability. This paper presents a novel nonlinear bilateral control scheme, based on the concept of disturbance observer based control, to counter these disturbances and their negative effects on the teleoperation systems. The proposed disturbance observer based bilateral control law is able to achieve global asymptotic force tracking, and global exponential position and disturbance tracking in the presence of various disturbances. The minimum exponential convergence rate of the position and the disturbance tracking errors can be tuned by the controller parameters. Simulations are presented to show the effectiveness of the proposed control scheme. View full abstract»

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  • Direct optimization determination of auxiliary test signals for linear problems with model uncertainty

    Publication Year: 2011 , Page(s): 909 - 914
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB) |  | HTML iconHTML  

    Recently there has been increased interest in active approaches for fault detection which use auxiliary test signals. Theory and algorithms have been presented in the literature for the design of fault detection signals for linear systems with model uncertainty. These approaches cannot solve many problems with constraints. This paper gives the first direct optimization formulation of the more general constrained problem. The use of a direct optimization formulation allows the solution of problems not possible by the original algorithms such as problems with input and state constraints. Computational examples are given both to illustrate the theory and to discuss computational issues. View full abstract»

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  • Energy-aware opportunistic channel access with decentralized channel state information

    Publication Year: 2011 , Page(s): 3104 - 3109
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    Decentralized channel state information is utilized to design a multichannel access algorithm for uplink transmission with power adaptation. The base station does not coordinate the transmissions of mobile users and hence users employ random access transmission. The situation is modeled as a non-cooperative game, where mobile users attempt to maximize its individual throughput gain with the least transmission power consumption. It is shown that each user should access a channel with probability 1 if the channel gain exceeds some threshold and the energy consumption with threshold policy does not exceed randomized policy. The game is reformulated as a channel gain threshold adaptation game, whose Nash equilibrium is proven to exist and be unique with mild conditions. At last a distributed iterative algorithm is proposed for each user to find the optimal threshold without knowing the channel state distribution and other users' strategies, and is proven to converge to the unique Nash equilibrium. View full abstract»

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  • An internal-model principle for the synchronisation of autonomous agents with individual dynamics

    Publication Year: 2011 , Page(s): 2106 - 2111
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    The task of synchronising autonomous agents is solved by a networked controller that steers the agents towards a common trajectory. This paper extends existing analysis and design methods for sets of linear agents with individual dynamics. To formulate the basic condition under which agents can be synchronised, the notion of system inclusion is introduced. It is shown that the agents can be synchronised in a leader-follower structure by an appropriate networked controller if and only if the dynamics of the extended agents include the dynamics of the synchronous trajectory. The results are illustrated by their application to vehicle platooning. View full abstract»

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  • Individualized PID control of depth of anesthesia based on patient model identification during the induction phase of anesthesia

    Publication Year: 2011 , Page(s): 855 - 860
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1241 KB) |  | HTML iconHTML  

    This paper proposes a closed-loop propofol admission strategy for depth of hypnosis control in anesthesia. A population-based, robustly tuned controller brings the patient to a desired level of hypnosis. The novelty lies in individualizing the controller once a stable level of hypnosis is reached. This is based on the identified patient parameters and enhances suppression of output disturbances, representing surgical stimuli. The system was evaluated in simulation on models of 44 patients obtained from clinical trials. A large amount of improvement (20 - 30%) in load suppression performance is obtained by the proposed individualized control. View full abstract»

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  • Bounded control based on saturation functions of nonlinear under-actuated mechanical systems: The cart-pendulum system case

    Publication Year: 2011 , Page(s): 1759 - 1764
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (509 KB) |  | HTML iconHTML  

    We are concerned in this paper by bounded control of nonlinear underactuated dynamical systems. We focus our exposition on a feedback-based stabilization bounded control action shaped by saturation functions. A simple stabilizing controller for the well-known cart-pendulum system is then designed in this paper. Our control strategy describes in lumped linear time-invariant terms the concerned underactuated nonlinear system as a cascade nonlinear dynamical system consisted of a simple chain of four integrators with a high-order smooth nonlinear perturbation, and assumes initialization of the resulting underactuated system in the upperhalf plane. Our proposed feedback-based regulation design procedure involves the simultaneous combination of two control actions: one bounded linear and one bounded quasilinear. Control boundedness is provided in both involved control actions by specific saturation functions. The first bounded control action brings the non-actuated coordinate near to the upright position and keep it inside of a well-characterized small vicinity, whereas the second bounded control action asymptotically brings the whole state of the dynamical system to the origin. The necessary closed-loop stability analysis uses standard linear stability arguments as well as the traditional well-known Lyapunov method and the LaSalle's theorem. Our proposed control law ensures global stability of the closed-loop system in the upper half plane, while avoiding the necessity of solving either partial differential equations, nonlinear differential equations or fixed-point controllers. We illustrate the effectiveness of the proposed control strategy via numerical simulations. View full abstract»

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  • Stabilization of nonlinear systems with delay in the input through backstepping

    Publication Year: 2011 , Page(s): 7605 - 7610
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB) |  | HTML iconHTML  

    We propose a new solution to the problem of globally asymptotically stabilizing a nonlinear system in feedback form with a known pointwise delay in the input. The result covers a family of systems wider than those studied in the literature and endows with control laws with a single delay, in contrast to the existing one, which include two distinct pointwise delays or distributed delays. The design strategy is based on the construction of an appropriate Lyapunov-Krasovskii functional. View full abstract»

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  • A harmonic potential field approach for planning motion of a UAV in a cluttered environment with a drift field

    Publication Year: 2011 , Page(s): 7665 - 7671
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (845 KB) |  | HTML iconHTML  

    This paper tackles motion planning in a cluttered environment with a workspace containing a vector drift field that provides an external influence on the ability of an agent to alter its state. The aim is to develop a planner that can guide the agent to a target zone, avoid clutter and marginalize the influence of drift on motion or exploit its presence in carrying out a task. Here, a variant of the harmonic potential field approach to planning is suggested to jointly process the environment geometry and the drift field and produce a dense, vector field that can safely guide motion from anywhere in the workspace to the target while managing the presence of drift in the desired manner. The approach is developed and its capabilities are demonstrated using simulation. A provably-correct method is also presented for converting the planning action into an equivalent navigation control that suits a wide class of UAVs. View full abstract»

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  • Anti-windup synthesis for optimizing internal model control

    Publication Year: 2011 , Page(s): 5503 - 5508
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (283 KB) |  | HTML iconHTML  

    We develop new design procedures for optimizing anti-windup control applicable to open-loop stable multivariable plants subject to input saturations. The optimizing anti-windup control falls into a class of compensator commonly termed directionality compensation. The computation of the control involves the on-line solution of a low-order quadratic program in place of simple saturation. We exploit the equivalence of the quadratic program to a feedthrough term in parallel with a deadzone-like nonlinearity that satisfies a sector bound condition. This allows for LMI-based anti-windup synthesis using a decoupled structure similar to that proposed in the literature for anti-windup schemes with simple saturation. We demonstrate the effectiveness of the design compared to several schemes using a highly ill-conditioned benchmark example. View full abstract»

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  • Robust stability analysis of uncertain linear positive systems via integral linear constraints: L1- and L-gain characterizations

    Publication Year: 2011 , Page(s): 6337 - 6342
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (325 KB) |  | HTML iconHTML  

    Copositive Lyapunov functions are used along with dissipativity theory for stability analysis of uncertain linear positive systems. At the difference of standard results, linear supply-rates are employed for robustness and performance analysis and lead to L1- and L-gain characterizations. This naturally guides to the definition of Integral Linear Constraints (ILCs) for the characterization of input-output nonnegative uncertainties. It turns out that these integral linear constraints can be linked to the Laplace domain, in order to be tuned adequately, by exploiting the L1-norm and input/output signals properties. This dual viewpoint allows to prove that the static-gain of the uncertainties, only, is critical for stability. This fact provides a new explanation for the surprising stability properties of linear positive time-delay systems. The obtained stability and performance analysis conditions are expressed in terms of (robust) linear programming problems that are transformed into finite dimensional ones using the Handelman's Theorem. Several examples are provided for illustration. View full abstract»

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  • Optimal static output feedback design through direct search

    Publication Year: 2011 , Page(s): 296 - 301
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    This paper investigates the performance of using a direct search method to design optimal Static Output Feedback (SOF) controllers for Linear Time Invariant (LTI) systems. Considering the old age of both SOF problems and direct search methods, surprisingly good performances will be obtained compared to a state-of-the-art method. The motivation is to emphasize the fact that direct search methods are too much neglected by the control community. These methods are very rich for practical purposes on a lot of complex problems unyielding to classical optimization techniques, like linear matrix inequalities, thanks to their ability to explore even non-smooth functions on non-convex feasible sets. View full abstract»

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  • Adaptive consensus estimation of multi-agent systems

    Publication Year: 2011 , Page(s): 354 - 359
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (214 KB) |  | HTML iconHTML  

    This paper considers the effects of a penalty term in both the state and parameter estimates for multi-agent systems. It is assumed that the plant parameters are desired to be identified on-line and N agents are available to implement adaptive observers. Using an additive term which takes the form of a penalty on the mismatch between the state and parameter estimates, the proposed adaptive consensus estimation scheme ensures that both state and parameter estimates reach consensus. While the proposed adaptive consensus identifiers assume an all-to-all connectivity, the abstract framework that the adaptive identifiers are examined under, allows for any form of agent connectivity to be examined. As a measure of agreement of the estimates that is independent of the network topology, the deviation from the mean estimate for both the state and parameter estimates is defined and shown to converge to zero. Simulation studies of a second order system provide a verification of the proposed theoretical predictions. View full abstract»

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  • An efficient approach to the design of observers for continuous-time systems with discrete-time measurements

    Publication Year: 2011 , Page(s): 7549 - 7554
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (180 KB) |  | HTML iconHTML  

    This paper describes an efficient discretization approach for nonlinear continuous-time systems. A Carleman linearization approach is used to evaluate the exact coefficients of the Taylor-Lie expansion of the dynamics of the system. The resulting discretization scheme is used to build a discrete-time observer that displays good performance. The paper shows the advantages of using an integrated discretization - observation approach for large discretization intervals. View full abstract»

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  • Optimal relay UAV guidance-a new differential game

    Publication Year: 2011 , Page(s): 1024 - 1029
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (509 KB) |  | HTML iconHTML  

    A new differential game which admits a “closed form” solution is analyzed. In this paper guidance laws are developed to optimally position a relay Micro-UAV (MAV) to provide an operator at the base with real-time Intelligence, Surveillance, and Reconnaissance (ISR) by relaying communication and video signals when the rover MAV performing the ISR mission is out of radio contact range with the base. The ISR system is comprised of two MAVs, the Relay and the Rover, and a Base. The Relay strives to minimize the radio frequency (RF) power required for maintaining communications, while the Rover performs the ISR mission, which may maximize the required RF power. The optimal control of the Relay MAV entails the solution of a differential game. View full abstract»

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  • Minimum entropy approach for robot manipulator

    Publication Year: 2011 , Page(s): 2475 - 2480
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (607 KB) |  | HTML iconHTML  

    In this paper, a new algorithm for an adaptive PI controller for nonlinear systems subject to stochastic non-Gaussian disturbance is studied. The minimum entropy control is applied to decrease the closed-loop tracking error on an ILC basis. The key issue here is to divide the control horizon into a number of equal time intervals called batches. Within each interval, there are a fixed number of sample points. The design procedure is divided into two main algorithms, within each batch and between any two adjacent batches. A D-type ILC law is employed to tune the PI controller coefficients between two adjacent batches. However, within each batch, the PI coefficients are fixed. A sufficient condition is established to guarantee the stability of the closed-loop system. An analysis of the ILC convergence is carried out. Two-link robot manipulator example is included to demonstrate the use of the control algorithm, and satisfactory results are obtained. View full abstract»

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  • Control of two-steering-wheels vehicles with the Transverse Function approach

    Publication Year: 2011 , Page(s): 7349 - 7355
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB) |  | HTML iconHTML  

    The control of a wheeled vehicle with front and rear steering wheels is addressed. With respect to more classical car-like vehicles, an advantage of this type of mechanism is its enhanced maneuverability. The Transverse Function approach is used to derive feedback laws which ensure practical stabilization of arbitrary reference trajectories in the cartesian space, and asymptotic stabilization when the trajectory is feasible by the nonholonomic vehicle. Concerning this latter issue, previous results are extended to the case of transverse functions defined on the Special Orthogonal Group SO(3). View full abstract»

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  • Throwing motion control of the Pendubot and instability analysis of the zero dynamics

    Publication Year: 2011 , Page(s): 2849 - 2855
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB) |  | HTML iconHTML  

    This paper presents systematic methods for throwing motion control of the Pendubot based on the concept of explosively unstable zero dynamics. The Pendubot, an underactuated two-link planar robot, is investigated as a dynamic model of the superior limbs for imitation of human throwing motion whose models are fundamentally underactuated in nature. The controller is designed based on input-output linearization and output zeroing control since the Pendubot is not input-state linearizable. The originality of this paper is to intentionally destabilize the zero dynamics, a nonlinear dynamics which remains unobservable from the output when the partially linearized dynamics converges exponentially to zero, to generate dynamic acceleration of the ball. Mathematical analysis of ordinary differential equations guarantees the explosive instability of the zero dynamics. Numerical simulations verify the effectiveness of the proposed control strategy. View full abstract»

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  • Fault detection and diagnosis for general discrete-time stochastic systems using output probability density estimation

    Publication Year: 2011 , Page(s): 2094 - 2099
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (309 KB) |  | HTML iconHTML  

    A new approach of fault detection and diagnosis (FDD) for general stochastic systems in discrete-time is studied. Our work on this problem is motivated by the fact that most of the nonlinear control laws are implemented as digital controllers in reality. Different from the formulation of classical FDD problem, it is supposed that the measured information for the FDD is the probability density functions (PDFs) of the system output rather than its measured value. A radial basis function (RBF) neural network technique is proposed so that the output PDFs can be formulated in terms of the dynamic weighting of the RBFs neural network. Feasible criteria to detect and diagnose the system fault are provided by using linear matrix inequality (LMI) techniques. An illustrated example is included to demonstrate the efficiency of the proposed algorithm, and satisfactory results are obtained. View full abstract»

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  • Iterative fault tolerant control based on Stochastic Distribution

    Publication Year: 2011 , Page(s): 2100 - 2105
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB) |  | HTML iconHTML  

    A new design of a fault tolerant control (FTC)-based an adaptive, fixed-structure PI controller, with constraints on the state vector for nonlinear discrete-time system subject to stochastic non-Gaussian disturbance is studied. The objective of the reliable control algorithm scheme is to design a control signal such that the actual probability density function (PDF) of the system is made as close as possible to a desired PDF, and make the tracking performance converge to zero, not only when all components are functional but also in case of admissible faults. A Linear Matrix Inequality (LMI)-based FTC method is presented to ensure that the fault can be estimated and compensated for. A radial basis function (RBF) neural network is used to approximate the output PDF of the system. Thus, the aim of the output PDF control will be a RBF weight control with an adaptive tuning of the basis function parameters. The key issue here is to divide the control horizon into a number of equal time intervals called batches. Within each interval, there are a fixed number of sample points. The design procedure is divided into two main algorithms, within each batch, and between any two adjacent batches. A P-type ILC law is employed to tune the parameters of the RBF neural network so that the PDF tracking error decreases along with the batches. Sufficient conditions for the proposed fault tolerance are expressed as LMIs. An analysis of the ILC convergence is carried out. Finally, the effectiveness of the proposed method is demonstrated with an illustrated example. View full abstract»

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  • User friendly Box-Jenkins identification using nonparametric noise models

    Publication Year: 2011 , Page(s): 2148 - 2153
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (171 KB) |  | HTML iconHTML  

    The identification of SISO linear dynamic systems in the presence of output noise disturbances is considered. A `nonparametric' Box-Jenkins approach is studied: the parametric noise model is replaced by a nonparametric model that is obtained in a preprocessing step, and this without any user interaction. The major advantage for the user is that i) one method can be used to replace the classical ARX, ARMAX, OE, and Box-Jenkins models; ii) no noise model order should be selected. This makes the identification much easier to use for a wider public; iii) a bias on the plant model does not create a bias on the noise model. The disadvantage of the proposed nonparametric approach is a small loss in efficiency with respect to the optimal parametric choice. These results are illustrated on a series of well selected problems. View full abstract»

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  • Interactive tool for analysis of reset control systems

    Publication Year: 2011 , Page(s): 4765 - 4770
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    The paper describes an interactive tool focused on the analysis of reset control systems. Reset control systems are essentially linear control systems that reset certain controller states to zero according to a reset rule. The tool has been developed using Sysquake, a Matlab-like language with fast execution and excellent facilities for interactive graphics, and is delivered as a stand-alone executable that is readily accessible to students and users. The highly visual and strongly coupled nature of reset control system is very amenable to interactive tools, and the tool presented in this paper enables to discover a myriad of important properties of these systems. View full abstract»

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  • Reset observers for linear time-delay systems. A delay-independent approach

    Publication Year: 2011 , Page(s): 4152 - 4157
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB) |  | HTML iconHTML  

    A Reset observer (ReO) is a novel sort of observer consisting of an integrator, and a reset law that resets the output of the integrator depending on a predefined condition over its input and/or output. The introduction of the reset element in the adaptive laws can decrease the overshooting and settling time of the estimation process without sacrificing the rising time. Motivated by the interest in the design of state observers for systems with time-delay, which is an issue that often appears in process control, this paper contributes with the extension of the ReO to the time-delay system framework. The time-independent stability analysis of our proposal is addressed by means of linear matrix inequalities (LMIs). Simulation results show the potential benefit of the proposed reset observer compared with traditional linear observers. View full abstract»

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  • Admissible controls, modeling, and optimization for a new class of nonlinear stochastic delay systems

    Publication Year: 2011 , Page(s): 5613 - 5620
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB) |  | HTML iconHTML  

    The paper deals with several fundamental issues that have not been previously addressed in the modeling and optimization of nonlinear stochastic delay systems. For an example, consider the special case of a system with a delayed control term of the form f(u1(t + θ1), u2(t + θ2)), where the delays θi <; 0 are different and f(·) is not the sum of functions of each of the controls separately. The class of adapted relaxed controls is no longer adequate as the class of admissible controls, at least in the sense that the infimum of the costs over this class is not the infimum over the class of ordinary controls, and the limit of convergent sequences might be meaningless. We deal with such issues of admissibility and optimization for a large class of systems that includes the above example. The appropriate extensions and the proofs are not obvious. The issues are crucial for the convergence of numerical approximations to optimal control problems, as well as for the optimization problem to be well-defined. View full abstract»

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