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An electronic throttle is a de servo drive which positions the throttle plate, thus providing drive-by-wire control of engine torque. In this paper, an approximate model-based robust nonlinear control (AMRNC) strategy is proposed for electronic throttle valve. The AMRNC includes two main parts: approximate model controller and uncertainty compensation. The approximate model controller, utilized as a feed forward controller, is developed from a linearization of the input-output model of the plant using Taylor expansion technique, and it is implemented using fuzzy system modeling. Moreover, a robustness filter in the feedback structure is employed as uncertainty compensation. The robust stability is established by Lyapunov stability theorem. A Simulation and an experiment are provided to verify the effectiveness of the AMRNC strategy. Index Terms--Approximate model, electronic throttle control (ETC), fuzzy logic, nonlinear control systems, robustness.

We address the problem of attaining proportionally fair rates using Aloha protocols at the medium access layer. We consider a wireless network where all nodes need not be in transmission ranges of each other. We show how the attempt probabilities in Aloha protocols should be set so that the achieved rates are globally proportionally fair. For both slotted and unslotted Aloha, we argue that each node can compute its optimal attempt probability just by knowing some minimal information about the network topology in its two-hop radius. Index Terms--Aloha networks, fairness, local information.

In this note, a class of nonlinear uncertain systems are considered, and uncertainties in the systems are assumed to be generated by exogenous dynamics. Robust control is designed by employing nonlinear observers to estimate the uncertainties. It is shown that, if a partial knowledge of the exogenous system is available and its known dynamics meet certain conditions or if input channel of the plant has certain properties, global stability and global estimation convergence can be achieved. In the latter case, the results on stability and convergence hold even if exogenous dynamics are completely unknown but bounded by some known function. Index Terms--Exosystem, Lyapunov direct method, robust control, uncertainty estimation.

We show how single-run-based measure-valued differentiation gradient estimators can be obtained. The key idea is to apply a change of measure a posterior to the mathematical analysis of the derivative. From the point of view of the likelihood ratio method, we show that likelihood ratio type gradient estimators can be applied in situations where the mathematical conditions needed for applying a likelihood ratio analysis are not met. Index Terms--Gradient estimation, likelihood ratios, measure-valued differentiation, Markov chains.

In this note, we deal with the robust "D-stability analysis for systems with both structured and unstructured uncertainties. First, an extension of the small gain theorem is presented for robust "D-stability analysis of systems with mixed-type uncertainties. Second, an edge verification result is obtained when the structured uncertainty is described by an interval plant. Finally, for some special root location regions, this problem has been converted to the computation problem of the maximal [H.sub.[infinity]] norm of a transfer function with parametric uncertainties and some explicit vertex results are obtained. It can be seen that the computation complexity is significantly reduced in these special cases. Index Terms--Interval plants, parametric [H.sub.[infinity]] problem, robust D-stability, vertex result.

In this note, we consider a fluid flow, single part-type, single unreliable machine production system with a bounded backlog/inventory space. We prove that, as in the unbounded case, the problem of minimizing an infinite horizon average demand loss/backlog/surplus cost is solved by a hedging point policy. An implicit equation is given, whose structure easily allows to numerically evaluate the optimal safety stock. The effect of system parameters on the optimal safety stock is analyzed and some numerical examples illustrate the presented results. Index Terms--Bounded inventory, hedging point, limited backlog, unreliable machine.

A new architecture for fault tolerant controllers is proposed for the generic class of descriptor systems. It is based on coprime factorization of nonproper systems and on the Youla parameterizatian of stabilizing controllers. Noticing that the Youla controllers include a so called residual signal, fault tolerant control is achieved. Nominal control and robust fault tolerance are addressed separately. Moreover, fault tolerant control can be improved with a scheme integrating fault diagnosis. The design of the diagnosis and fault tolerant control filters reduce to a standard [H.sub.[infinity]] -control problem of usual state-space system. Index Terms--Coprime factorization, descriptor systems, robust fault tolerant control, Youla parameterization.

The problem of computing controllers to enlarge the domain of attraction (DA) of equilibrium points of polynomial systems is considered. In order to deal with such a problem, a technique for computing static nonlinear output feedback controllers, which maximize the largest estimate of the DA (LEDA) induced by a given polynomial Lyapunov function, is proposed. The main contribution of the note is to show that a lower bound of the maximum achievable LEDA and a corresponding controller can be obtained through linear matrix inequality optimizations. Moreover, a necessary condition for tightness of this lower bound is presented, which is also a sufficient condition to establish the tightness of the lower bound of the LEDA for a given controller. Index Terms--Controller synthesis, domain of attraction, linear mattrix ineqaulity (LMI), Lyapunov function, polynomial systems.

This note is devoted to parameter estimation in linear regression and filtering, where the observation noise does not possess any "nice" probabllistic properties. In particular, the noise might have an "unknown-but-bounded" deterministic nature. The basic assumption is that the model regressors (inputs) are random. Optimal rates of convergence for the modified stochastic approximation and least-squares algorithms are established under some weak assumptions. Typical behavior of the algorithms in the presence of such deterministic noise is illustrated by numerical examples. Index Terms--Filtering, linear regression, parameter estimation, prediction, randomized algorithm.

In this paper, the design of controllers that incorporate structural and multiobjective performance requirements is considered. The control structures under study cover nested, chained, hierarchical, delayed interaction and communications, and symmetric systems. Such structures are strongly related to several modern-day and future applications including integrated flight propulsion systems, platoons of vehicles, micro-electro-mechanical systems, networked control, control of networks, production lines and chemical processes. It is shown that the system classes presented have the common feature that all stabilizing controllers can be characterized by convex constraints on the Youia-Kucera parameter. Using this feature, a solution to a general optimal performance problem that incorporates time domain and frequency domain constraints is obtained. A synthesis procedure is provided which at every step yields a feasible controller together with a measure of its performance with respect to the optimal. Convergence to the optimal performance is established. An example of a multinode network congestion control problem is provided that illustrates the effectiveness of the developed methodology. Index Terms--Input-output, multiobjective, structure.

This note focuses on disturbance propagation in vehicle strings. It is known that using only relative spacing information to follow a constant distance behind the preceding vehicle leads to string instability. Specifically, small disturbances acting on one vehicle can propagate and have a large effect on another vehicle. We show that this limitation is due to a complementary sensitivity integral constraint. We also examine how the disturbance to error gain for an entire platoon scales with the number of vehicles. This analysis is done for the predecessor following strategy as well as a control structure where each vehicle looks at both neighbors. Index Terms--Complementary sensitivity integral, interconnected systems, string stability.

We present an efficient algorithm for exact calculation and minimization of expected walling times of all passengers using a bank of elevators. The dynamics of the system are represented by a discrete-state Markov chain embedded in the continuous phase-space diagram of a moving elevator car. The chain is evaluated efficiently using dynamic programming to compute measures of future system performance such as expected waiting time, properly averaged over all possible future scenarios. A linear-time elevator group controller based on this method significantly outperforms benchmark algorithms and is completely within the computational capabilities of contemporary elevator bank controllers. Index Terms--Dynamic programming, group elevator scheduling, Markov chains, optimal control.

This note is devoted to the study of manufacturing systems with parallel production lines. By using overlapping decomposition method, a convergent recursive procedure is presented to estimate system production rate with high accuracy. The results obtained are illustrated by a case study at an automotive assembly plant. Index Terms--Aggregation, overlapping decomposition, parallel lines, production rate.

This note will address a linear minimum variance estimation of discrete-time systems with instantaneous and delayed measurements. Although the problem may be approached via system augmentation and standard Kalman filtering, the computation of filter may be expensive when the dimension of the system is high and the measurement lag is significant. In this note, a new tool, termed as reorganized innovation sequence, is presented for deriving the optimal filter. The optimal filter is given by two Riccati difference equations (RDEs) with the same dimension as that of the original system. The approach is shown to induce saving of computational cost us compared to the system augmentation approach, especially when the delay is large. Further, it can be extended to solving the more complicated [H.sub.[infinity]] fixed-lag smoothing in Krein space. Index Terms--Delayed measurement, discrete-time systems, innovation analysis, optimal filtering, Riccati equations.

The characteristic of the nonlinear part of the Wiener system is estimated. The system is driven by a Gaussian random process which may not be white. Three algorithms are presented, two semirecursive and one of the offline type. Their pointwise convergence in probability is shown and results of numerical simulation are given. Index Terms--Nonparametric identification, nonparametric regression, system identification, Wiener system.

A generalization of the notions of minimality, reachability, and observability for parameter dependent and multidimensional systems modeled by linear fractional transformations over noncommuting operators is presented. The multidimensional system results developed herein are formally similar to and directly specialize to the standard results when one-dimensional systems are considered. Index Terms--Multidimensional systems, minimality, reachability, observability, linear fractional transformations.

In this note, we consider a single-machine, single-part-type production system, operating in a defect-prone environment. It is assumed that there is a random yield proportion of nondefective parts, with known probability distribution. Over each production cycle, it is assumed that there is a single realization of the yield random variable. Furthermore, it is assumed that the system is operated under a periodic-review policy. Thus, the particular realization of the yield proportion cannot be determined prior to the end of the production horizon. The optimal production control, that minimizes a linear combination of expected surplus and shortage costs over the planning horizon is shown to he piecewise constant, and the appropriate production levels and control break-points are determined as functions of the yield rate distribution. Index Terms--Cost minimization, defect-prone, finite-horizon, production control, random yield.

Iterative feedback tuning (IFT) is a data-based method for the tuning of restricted complexity controllers. At each iteration, an update for the controller parameters is estimated from data obtained partly from the normal operation of the closed loop system and partly from a special experiment, in which the output signal obtained under normal operation is fed back at the reference input. The choice of a prefilter for the input data to the special experiment is a degree of freedom of the method. In this note, the prefilter is designed in order to enhance the accuracy of the IFT update. The optimal prefilter produces a covariance of the new controller parameter vector that is strictly smaller than the covariance obtained with the standard constant prefilter. Index Terms--Iterative feedback tuning (IFT), stochastic optimization.

Consider the problem of value iteration for solving Markov stochastic games. One simply iterates backward, via a Jacobi-like procedure. The convergence of the Gauss-Seidel form of this procedure is shown for both the discounted and ergodic cost problems, under appropriate conditions, with extensions to problems where one stops when a boundary is hit or if any one of the players chooses to stop, with associated costs. Generally, the Gauss-Seidel procedure accelerates convergence. Index Terms--Gauss-Seidel procedure, Markov games, numerical algorithms, stochastic games.

This note considers eigenstructure assignment in second-order descriptor linear systems via proportional plus derivative feedback. It is shown that the problem is closely related with a type of so-called second-order Sylvester matrix equations. Through establishing two general parametric solutions to this type of matrix equations, two complete parametric methods for the proposed eigenstructure assignment problem are presented. Both methods give simple complete parametric expressions for the feedback gains and the closed-loop eigenvector matrices. The first one mainly depends on a series of singular value decompositions, and is thus numerically simple and reliable. The second one utilizes the right factorization of the system, and allows the closed-loop eigenvalues to be set undetermined and sought via certain optimization procedures. An example shows the effect of the proposed approaches. Index Terms--Eigenstructure assignment, parametric solutions, proportional-plus-derivative feedback, right factorization, second-order descriptor linear systems, singular value decomposition.

This note investigates equivalent relations of detectability and persistency excitation (PE) for general nonlinear time-varying systems. Three new definitions relating to the detectability are proposed and discussed. As a preliminary result, we show that these detectability conditions are all equivalent under a mild assumption. Furthermore, two PE conditions that are a nonlinear-version extension of the PE proposed in present literature are defined. Very interestingly, it can be shown that these nonlinear-version PE conditions are both equivalent to the proposed detectability conditions under the same assumption. To the best of our knowledge, this is a first result about the connection between detectability and PE in the area of nonlinear time-varying systems. Moreover, by combining a newly developed stability criterion with the proposed results, an interesting example is given to illustrate how the classic PE conditions for linear systems can be extended and used in nonlinear systems. From this example, it can also be seen that the uniformly asymptotic stability can be guaranteed either using the detectability conditions or by the PE conditions based on our approach. Index Terms--Adaptive systems, detectability, equivalent relations, persistency excitation (PE), uniformly asymptotic stability.

Results on input-output [L.sub.p] stability of networked control systems (NCS) are presented for a large class of network scheduling protocols. It is shown that static protocols and a recently considered dynamical protocol called try-once-discard belong to this class. Our results provide a unifying framework for generating new scheduling protocols that preserve [L.sub.p] stability properties of the system if a design parameter is chosen sufficiently small. The most general version of our results can be used to treat NCS with data packet dropouts. The model of NCS and, in particular, of the scheduling protocol that we use appears to be novel and we believe that it will be useful in further study of these systems. The proof technique we use is based on the small gain theorem and it lends itself to an easy interpretation. We prove that our results are guaranteed to be better than existing results in the literature and we illustrate this via an example of a batch reactor. Index Terms--Disturbances, [L.sub.p] stability, networked control, nonlinear, stability.

In this note, a generalized Bezoutian matrix with respect to a polynomial sequence of interpolatory type is introduced. The operator representation relative to a pair of dual bases and the generalized Barnett-type factorization formula are derived. An intertwining relation and a Bezoutian reduction to a block diagonal form by congruence via a generalized Vandermonde matrix are presented, Fujiwara-Hermite and Routh-Hurwitz criteria in terms of this generalized Bezout matrix are obtained. Index Terms--Barnett-type formula, Bezoutian, Fujiwara-Hermite and Routh-Hurwitz criteria, polynomial sequence of interpolatory type.

The problem of modeling periodic signals is considered. The approach taken here is motivated by the well known theoretical results on the existence of periodic orbits for Lienard systems and previous results on modeling periodic signals by means of second-order nonlinear ordinary differential equations. The approach makes use of the appropriate conditions imposed on the polynomials of the Lienard's system to guarantee the existence of a unique and stable limit cycle. These conditions reduce the number of parameters required to generate accurate models. Index Terms--Identification, Lienard's equation, limit cycle, nonlinear systems, periodic orbit.

In this note, we consider the same class of systems as in a previous paper, i.e., a class of uncertain dynamic nonlinear systems preceded by unknown backlash-like hysteresis nonlinearities, where the hysteresis is modeled by a differential equation, in the presence of bounded external disturbances. By using backstepping technique, robust adaptive back, stepping control algorithms are developed. Unlike some existing control schemes for systems with hysteresis, the developed backstepping controllers do not require the uncertain parameters within known intervals. Also, no knowledge is assumed on the bound of the "disturbance-like" term, a combination of the external disturbances and a term separated from the hysteresis model. It is shown that the proposed controllers not only can guarantee global stability, but also transient performance. Index Terms--Adaptive control, backstepping, hysteresis, nonlinear system, robust control.

In several practical applications actuators are interconnected to a controlled plant through long cables. If the actuator operates at a fast sampling rate (with respect to the propagation delay of the cable) and its impedance cannot be neglected, wave reflections will occur and the transmitted pulse will be deformed--degrading the control quality. In this note, exploiting the scattering variables representation of the transmission line, we provide a framework for the design of active compensators to reduce the wave reflection problem. The compensators, implementable with regulated current and voltage sources, can be placed either on the actuator side or the plant side, and the only required prior knowledge is the transmission line characteristic impedance and the propagation delay. An adaptive implementation that obviates the need of the lines characteristic impedance, but still requires the knowledge of the propagation delay, is also presented. We prove the existence of an ideal scheme that transforms the line into a pure delay transfer which, unfortunately, yields an ill-posed interconnection and therefore has to be approximated for its practical application. The proposed design method is illustrated with a benchmark ac drives example consisting of a pulse width modulation inverter and an induction motor. Index Terms--Impedance, infinite dimensional systems, motor control, overvoltage, pulsewidth modulation (PWM) inverter, reflection coefficient, transmission lines, wave equation.

Feedback error learning (FEL) method has been proposed by Kawato et al. as a scheme of brain motor control in neurophysiology. Recently, Miyamura and Kimura have established a control theoretical validity of the FEL method in the framework of adaptive control and proved its stability based on the strictly positive realness. In this note, we propose another scheme for the feedback error learning method which does not require any positive real conditions. Index Terms--Adaptive control, feedback error learning, two-degree-of-freedom control.

In this note, we address the problem of transforming a nonlinear system into nonlinear observer canonical form in the extended state-space with the aid of dynamic system extension and introduction of virtual outputs. As an intermediate step for the general problem, we consider a restricted structure of dynamic extension, which is obtained, roughly speaking, by adding the chains of integrators to the outputs of original system. We propose sufficient conditions which can be verified using the system dynamics expressed in their original coordinates. An illustrative example is included that demonstrates the advantage of the proposed method over the conventional method. Index Terms--Dynamic observer error linearizatian, nonlinear observer, nonlinear system.

In this note, the second-order sliding-mode control problem is tackled by explicitly taking into account the presence of measurement error with unknown upper bound [delta]. Under sensible assumptions regarding the uncertain dynamics of a broad class of nonlinear plants, a new switching controller is proposed guaranteeing a sliding accuracy of order [OMICRON] ([delta]). Simulations highlight the robustness and good performance of the proposed approach, and confirm the expected precision order. Index Terms--Measurement noise, nonlinear systems, second-order sliding modes, uncertain systems.

Robust open-loop steering of a finite-dimensional quantum system is a central problem in a growing number of applications of information engineering. In this note, we reformulate the problem in the classical control-theoretic setting, and provide a precise definition of robustness of the control strategy. We then discuss and compare some significant problems from nuclear magnetic resonance in the light of the given definition. We obtain quantitative results that are consistent with the qualitative ones available in the physics literature. Index Terms--Adiabatic transition, quantum control, quantum systems, robustness.

The problem of the generalized output regulation is considered here. In contrast to the classical output regulation problem, where the references to be tracked and disturbances to be rejected are generated by an autonomous exogeneous system, for the generalized output regulation an exogenous system is driven by an unknown external reference signal. In such a way, the class of reference or disturbance signals is expanded. Presented result solves the full measurement feedback case and is based on the well-known notion of the regulator equation combined with the classical concept of the invariant distribution. Illustrative example, including MATLAB-SIMULINK simulations, is presented to demonstrate the suggested approach. Index Terms--Differential geometric, nonlinear continuous time systems, output regulation.

We show that Bezier carves can in fact be thought of as the solutions to linear optimal control problems, using results from Hermite interpolation in combination with traditional linear optimal control. This provides us with a computational view of Bezier curves that differs from the standard DeCasteljau Algorithm, and it furthermore points out the close relationship between Bezier curves and interpolating dynamic splines. Index Terms--Bezier curves, hermite interpolation, optimal control.

This paper considers mobile to base station power control for lognormal fading channels in wireless communication systems within a centralized information stochastic optimal control framework. Under a bounded power rate of change constraint, the stochastic control problem and its associated Hamilton-Jacobi-Bellman (HJB) equation are analyzed by the viscosity solution method; then the degenerate HJ equation is perturbed to admit a classical solution and a suboptimal control law is designed based on the perturbed HJB equation. When a quadratic type cast is used without a bound constraint on the control, the value function is a classical solution to the degenerate HJB equation and the feedback control is affine in the system power. In addition, in this case we develop approximate, but highly scalable, solutions to the HJB equation in terms of a local polynomial expansion of the exact solution. When the channel parameters are not known a priori, one can obtain on-line estimates of the parameters and get adaptive versions of the control laws. In numerical experiments with both of the above cost functions, the following phenomenon is observed: whenever the users have different initial conditions, there is an initial convergence of the power levels to a common level and then subsequent approximately equal behavior which converges toward a stochastically varying optimum. Index Terms--Dynamic programming, Hamilton-Jacobi-Bellman (HJB) equations, lognormal fading channels, power control, quality of service.

As a refined notion, impulsive-mode controllability is suggested for the general class of linear continuous descriptor systems. This notion reveals rich properties of the general descriptor systems in terms of admissibility of initial conditions, admissibility of feedback control, and impulsive-mode elimination. The condition for impulsive-mode controllability is derived and proved to be necessary and sufficient for the existence of admissible feedback controls eliminating impulsive modes. Under impulsive-mode controllability, admissible feedback controls are constructed for eliminating impulsive modes, on the basis of numerically reliable decompositions of the system's coefficient matrices. Index Terms--Descriptor systems, feedback control, impulsive-mode controllability.

We propose a parametric class of myopic scheduling and routing policies for open and closed multiclass queueing networks. In open networks, they steer the state of the system toward a predetermined and fixed target, while, in closed networks they steer instantaneous throughputs toward a fixed target. In both cases, the proposed policies measure distance from the target using a weighted norm. In open networks, we establish that for an L2 norm the corresponding policies are stable. In closed networks, we establish that with proper target selection the corresponding policy is efficient, that is, attains bottleneck throughput in the infinite population limit. In both open and closed networks, the proposed policies are amenable to distributed implementation using local state information. We exploit the work in a previous paper to select appropriate parameter values and outline how optimal parameter values can be computed. We report numerical results indicating that we obtain near-optimal policies (when the optimal can be computed) and significantly outperform heuristic alternatives. This work has applications in a number of areas including optimizing the processing of information in sensor networks. Index Terms--Fluid models, multiclass queueing networks, routing, scheduling, sensor networks.

This paper deals with the problem of model (in)validation of discrete time, causal, linear time-invariant (LTI) stable models subject to slowly linear time-varying structured uncertainty, using frequency domain data corrupted by additive noise. It is well known that in the case of structured LTI uncertainty the problem is NP hard in the number of uncertainty blocks. The main contribution of this paper shows that, on the other hand, if one considers arbitrarily slowly time varying uncertainty and noise in [L.sub.2], then tractable, convex necessary and sufficient conditions for (in)validation can be obtained. Additional results include a discussion of the case where the noise is characterized in terms of the [L.sub.[infinity]] norm. Index Terms--Frequency domain model (in)validation, linear matrix inequalities, structured slowly linear time-varying (SLTV) uncertainty.

We identify a class of feedforward nonlinear systems that are linearizable by a coordinate change. Then we develop explicit expressions for the Lyapunov-based integrator forwarding recursive procedure of Sepulchre, Jankovic, and Kokotovic, which has its roots in a coordinate transformation proposed by Mazenc and Praly. The explicit expressions that we develop allow us to also find closed-form control laws for several classes of systems that are not feedback linearizable, including some that are in the feedforward form and others that are in what we refer to as the "block-feedforward" form. Performance advantages of Lyapunov-based forwarding controllers over nested saturation controllers have been well illustrated in the literature on examples. The analytical expressions for the Lyapunov functions and the control laws allow us to give quantitative performance bounds. Index Terms--Backstepping, feedback linearization, forwarding, Lyapunov function, stabilization.