exponential stability of impulsive systems with application to uncertain sampled data systems we establish exponential stability of nonlinear time varying impulsive systems by employing lyapunov functions with discontinuity at the impulse times our stability conditions have the property that when specialized to linear impulsive systems the stability tests can be formulated as linear matrix inequalities lmis then we consider lti uncertain sampled data systems in which there are two sources of uncertainty the values of the process parameters can be unknown while satisfying a polytopic condition and the sampling intervals can be uncertain and variable we model such systems as linear impulsive systems and we apply our theorem to the analysis and state feedback stabilization we find a positive constant which determines an upper bound on the sampling intervals for which the stability of the closed loop is guaranteed the control design lmis also provide controller gains that can be used to stabilize the process we also consider sampled data systems with constant sampling intervals and provide results that are less conservative than the ones obtained for variable sampling intervals

an iqc approach to robust stability of aperiodic sampled data systems conditions for robust stability of sampled data systems with non uniform sampling patterns and structural uncertainties are derived the problem is tackled under the integral quadratic constraint iqc framework where the aperiodic sampling operation is modelled by an delay integration operator characterization based on integral quadratic constrains iqc is identified for this operator and the iqc theory is applied to derive convex stability criteria compared to the dominating lyapunov approach where the candidate lyapunov krasovskii functionals or looped functionals need to be tailored for the systems under consideration and therefore the stability conditions need to be re derived whenever additional uncertainties are considered the proposed approach has the advantage of avoiding such endeavor numerical examples are given to illustrate this main point and effectiveness of the proposed approach

new results on stability analysis for systems with discrete distributed delay the integral inequality technique is widely used to derive delay dependent conditions and various integral inequalities have been developed to reduce the conservatism of the conditions derived in this study a new integral inequality was devised that is tighter than existing ones it was used to investigate the stability of linear systems with a discrete distributed delay and a new stability condition was established the results can be applied to systems with a delay belonging to an interval which may be unstable when the delay is small or nonexistent three numerical examples demonstrate the effectiveness and the smaller conservatism of the method

multiple emitter location and signal parameter estimation processing the signals received on an array of sensors for the location of the emitter is of great enough interest to have been treated under many special case assumptions the general problem considers sensors with arbitrary locations and arbitrary directional characteristics gain phase polarization in a noise interference environment of arbitrary covariance matrix this report is concerned first with the multiple emitter aspect of this problem and second with the generality of solution a description is given of the multiple signal classification music algorithm which provides asymptotically unbiased estimates of 1 number of incident wavefronts present 2 directions of arrival doa or emitter locations 3 strengths and cross correlations among the incident waveforms 4 noise interference strength examples and comparisons with methods based on maximum likelihood ml and maximum entropy me as well as conventional beamforming are included an example of its use as a multiple frequency estimator operating on time series is included

technical communique stability and stabilization of nonuniform sampling systems this paper is concerned with nonuniform sampling systems where the sampling interval is time varying within a certain known bound the system is transformed into a time varying discrete time system where time varying parts due to the sampling interval variation are treated as norm bounded uncertainties using robust control techniques to reduce conservatism arising from modeling time varying parts as a single uncertainty the time varying parts are modeled as n uncertainties with larger n a less conservative stability condition is derived at sacrifice of more computation it is shown through a numerical example that the proposed stability condition is better than existing stability conditions

a new looped functional for stability analysis of sampled data systems abstract in this paper a new two sided looped functional is introduced for stability analysis of sampled data systems the functional fully utilizes the information on both the intervals x t to x t k and x t to x t k 1 based on the two sided functional an improved stability condition is derived in the form of linear matrix inequality lmi numerical examples show that the result computed by the presented condition approximates nearly the theoretical bound bound obtained by eigenvalue analysis and outperforms substantially others in the existing literature

conformal laplace superintegrable systems in 2d polynomial invariant subspaces 2nd order conformal superintegrable systems in n dimensions are laplace equations on a manifold with an added scalar potential and independent 2nd order conformal symmetry operators they encode all the information about helmholtz eigenvalue superintegrable systems in an efficient manner there is a 1 1 correspondence between laplace superintegrable systems and stackel equivalence classes of helmholtz superintegrable systems in this paper we focus on superintegrable systems in two dimensions n 2 where there are 44 helmholtz systems corresponding to 12 laplace systems for each laplace equation we determine the possible two variate polynomial subspaces that are invariant under the action of the laplace operator thus leading to families of polynomial eigenfunctions we also study the behavior of the polynomial invariant subspaces under a stackel transform the principal new results are the details of the polynomial variables and the conditions on parameters of the potential corresponding to polynomial solutions the hidden gl 3 algebraic structure is exhibited for the exact and quasi exact systems for physically meaningful solutions the orthogonality properties and normalizability of the polynomials are presented as well finally for all helmholtz superintegrable solvable systems we give a unified construction of one dimensional 1d and two dimensional 2d quasi exactly solvable potentials possessing polynomial solutions and a construction of new 2d pt symmetric potentials is established

improved results on h stability analysis of sampled data systems via looped functionals and zero equalities abstract this paper revisits the h stability analysis for sampled data system by employing lyapunov functional and loop functionals through existing methods such as the looped functional approach and zero equality in sampled data systems an improved result is derived in terms of linear matrix inequalities based on the proposed result by utilizing the relation of state vectors belonging to augmented vectors less conservative criteria are introduced the main objective of this study is to increase a maximum sampling value in both periodic and aperiodic sampling cases according to minimum sampling value using the proposed results h stability for sampled data systems with disturbance is studied lastly some numerical examples are utilized to confirm the superiority and effectiveness of the results by comparing them with the existing ones

new insights on stability of sampled data systems with time delay abstract this paper analyses the stability of sampled data systems with time delay by employing a two sided looped functional approach some improved conditions are derived to guarantee the stability of the system under consideration then based the conditions some intrinsic relationships between sampled data period and time delay are obtained from the illustrative example being solved by the proposed approach it is observed that the results obtained are significantly better than those obtained by existing methods more importantly from the simulation being carried out it is discovered that contrary to the findings in previous studies time delays in a system may enlarge the interval of sampled data periods and accelerate the rate of convergence of the system states rather than deteriorate the system performance

estimation of domain of attraction for aperiodic sampled data switched delayed neural networks subject to actuator saturation in this paper for the case of the asynchronous switching caused by that subsystem s switching occuring during a sampling interval the domain of attraction estimation problem is investigated for aperiodic sampled data switched delayed neural networks asdsdnns subject to actuator saturation a parameters dependent time scheduled lyapunov functional consisting of a novel looped functional is constructed using segmentation technology and linear interpolation by employing this novel functional and using an average dwell time adt approach exponential stability criteria are proposed for polytopic uncertain asdsdnns subject to actuator saturation and a relationship between adt and sampling period is revealed for asdsdnns as a corollary exponential stability criteria are proposed for nominal asdsdnns subject to actuator saturation furthermore by describing the domain of attraction as a time varying ellipsoid determined by the time scheduled lyapunov matrix the proposed theoretical conditions are transformed into a linear matrix inequality lmi based multi objective optimization problem the dynamic estimates of the domain of attraction for asdsdnns are solved numerical simulation examples are provided to illustrate the effectiveness of the proposed method

h sampled data fuzzy observer design for nonlinear parabolic pde systems this paper considers the h infty sampled data fuzzy observer sdfo design problem for nonlinear parabolic pde systems under spatially local averaged measurements slams initially the nonlinear pde system is accurately represented by the takagi sugeno t s fuzzy pde model then based on the t s fuzzy pde model a sdfo under slams is constructed for the state estimation to attenuate the effect of the exogenous disturbance and the design disturbance an h infty sdfo design under slams is developed in terms of linear matrix inequalities lmis by utilizing lyapunov functional and inequality techniques which can guarantees the exponential stability and satisfies an h infty performance for the estimation error fuzzy pde system lastly simulation results on the state estimation of the fitzhugh nagumo fhn equation are given to support the presented h infty sdfo design method

sampled data h exponential synchronization for delayed semi markov jump cdns a looped functional approach abstract this paper investigates the h exponential synchronization problem of delayed semi markov jump complex dynamical networks by utilizing the sampled data control scheme through introducing a semi markov jump model where the transition rate is related to the sojourn time the addressed issue is therefore more general by constructing a suitable lyapunov krasovskii functional with a looped functional and adopting an advanced inequality method sufficient conditions for the h exponential synchronization of delayed semi markov jump complex dynamical networks are presented a numerical example is finally employed to confirm the validity of the proposed method

stability analysis of uncertain sampled data systems with incremental delay using looped functionals the robust stability analysis of asynchronous and uncertain sampled data systems with constant incremental input delay is addressed in the looped functional framework these functionals have been shown to be suitable for the analysis of impulsive systems as they allow one to express discrete time stability conditions in an affine way enabling then the consideration of uncertain and time varying systems the stability conditions are obtained by first reformulating the sampled data system as an impulsive system and by then considering a tailored looped functional along with wirtinger s inequality a recently introduced inequality that has been shown to be less conservative than jensen s inequality several examples are given for illustration

on stability of systems with aperiodic sampling devices this technical note is concerned with stability analysis of aperiodic sampled data systems the stability problem is tackled from a pure discrete time point of view where the at sampling behavior of the system is modelled as the response of a nominal discrete time lti system in feedback interconnection with a structured uncertainty conditions under which the uncertainty is positive real pr are identified based on the pr property a number of integral quadratic constraints iqc are derived and the iqc theory is applied to derive stability conditions numerical examples are given to illustrate the effectiveness of the proposed approach

wirtinger based integral inequality application to time delay systems in the last decade the jensen inequality has been intensively used in the context of time delay or sampled data systems since it is an appropriate tool to derive tractable stability conditions expressed in terms of linear matrix inequalities lmis however it is also well known that this inequality introduces an undesirable conservatism in the stability conditions and looking at the literature reducing this gap is a relevant issue and always an open problem in this paper we propose an alternative inequality based on the fourier theory more precisely on the wirtinger inequalities it is shown that this resulting inequality encompasses the jensen one and also leads to tractable lmi conditions in order to illustrate the potential gain of employing this new inequality with respect to the jensen one two applications on time delay and sampled data stability analysis are provided

a generalized free matrix based integral inequality for stability analysis of time varying delay systems abstract this paper focuses on the delay dependent stability problem of time varying delay systems a generalized free matrix based integral inequality gfmbii is presented this inequality is able to deal with time varying delay systems without using the reciprocal convexity lemma it overcomes the drawback that the bessel legendre inequality is inconvenient to cope with a time varying delay system as the resultant bound contains a reciprocal convexity through the use of the derived inequality and by constructing a suitable lyapunov krasovskii function lkf improved stability criteria are presented in the form of linear matrix inequalities lmis two numerical examples are carried out to demonstrate that the results outperform the state of the art in the literature

extended dissipativity based non fragile sampled data control of fuzzy markovian jump systems with incomplete transition rates abstract this article addresses the topic of extended dissipative analysis and non fragile sampled data control for fuzzy markovian jump systems with incomplete transition rates where the extended dissipative analysis unifies the l 2 l h passivity q s r dissipativity performance in a framework first by making the best of the information in the sampling interval an appropriate closed loop function dependent sampling interval is constructed then with the addition of free weighting matrices approach and improved integral inequality technique sufficient conditions are obtained to ensure the considered systems are stochastically stable and extended dissipative respectively furthermore the corresponding two form of non fragile mode dependent sampled data controllers are also designed finally a simulation example is offered to verify the feasibility of the results

non fragile memory filtering of t s fuzzy delayed neural networks based on switched fuzzy sampled data control abstract this paper deals with the non fragile memory filtering issue of t s fuzzy delayed neural networks with randomly occurring time varying parameters uncertainties and variable sampling rates compared with existing sampled data control schemes an improved switched fuzzy memory sampled data control protocol is designed for the first time which involves not only a signal transmission delay but also switched topologies by developing some new terms and taking full advantage of the variable characteristics related to the actual sampling pattern a modified loose looped fuzzy membership functions fmfs dependent lyapunov krasovskii functional lkf is constructed based on the information of the time derivative of fmfs meanwhile some relaxed matrices chosen in lkf are not consequentially positive definite moreover with the lkf methodology and employing the developed estimation technique several optimized control algorithms with both a larger sampling period and upper bound of time varying delays for achieving the stabilization of the resultant t s fuzzy delayed neural networks are derived finally a numerical example is presented to demonstrate the superiority and applicability of the theoretical results

stabilization of t s fuzzy system with time delay under sampled data control using a new looped functional this paper investigates the sampled data stabilization problem for a takagi sugeno t s fuzzy system with time delay by taking the information of states within the intervals from t k to t and t to t k 1 into account a new two side delay dependent looped functional is introduced which can not only relax the monotonic constraint of lyapunov krasovskii functional lkf but also make better use of the actual sampling pattern furthermore the sampled data fuzzy controller is designed to contain both the present and delayed state information thereby enhancing the control performance and design flexibility based on the novel augmented lkf and improved bounding technique less conservative stability criteria are derived in the form of linear matrix inequalities the superiority of proposed results is shown by two simulation examples

unitary esprit how to obtain increased estimation accuracy with a reduced computational burden esprit is a high resolution signal parameter estimation technique based on the translational invariance structure of a sensor array previous esprit algorithms do not use the fact that the operator representing the phase delays between the two subarrays is unitary the authors present a simple and efficient method to constrain the estimated phase factors to the unit circle if centro symmetric array configurations are used unitary esprit the resulting closed form algorithm has an esprit like structure except for the fact that it is formulated in terms of real valued computations throughout since the dimension of the matrices is not increased this completely real valued algorithm achieves a substantial reduction of the computational complexity furthermore unitary esprit incorporates forward backward averaging leading to an improved performance compared to the standard esprit algorithm especially for correlated source signals like standard esprit unitary esprit offers an inexpensive possibility to reconstruct the impinging wavefronts signal copy these signal estimates are more accurate since unitary esprit improves the underlying signal subspace estimates simulations confirm that even for uncorrelated signals the standard esprit algorithm needs twice the number of snapshots to achieve a precision comparable to that of unitary esprit thus unitary esprit provides increased estimation accuracy with a reduced computational burden

dissipativity based sampled data control for fuzzy markovian jump systems abstract in this paper the problems of dissipativity analysis and sampled data control are considered for fuzzy markovian jump systems firstly by constructing a mode dependent lyapunov function consisting of the two sided closed loop function where the information of both intervals x tk to x t and x t to x t k 1 are fully utilized the stochastically stable criteria and strictly q s r dissipative criteria are proposed in the form of linear matrix inequalities lmis then on the basis of the strictly dissipativity criteria a controller with state feedback is designed for the studied systems at last a truck trailer model is shown to demonstrate the efficiency of the presented method

brief paper wirtinger s inequality and lyapunov based sampled data stabilization discontinuous lyapunov functionals appeared to be very efficient for sampled data systems fridman 2010 naghshtabrizi hespanha teel 2008 in the present paper new discontinuous lyapunov functionals are introduced for sampled data control in the presence of a constant input delay the construction of these functionals is based on the vector extension of wirtinger s inequality these functionals lead to simplified and efficient stability conditions in terms of linear matrix inequalities lmis the new stability analysis is applied to sampled data state feedback stabilization and to a novel sampled data static output feedback problem where the delayed measurements are used for stabilization

further refinements in stability conditions for time varying delay systems abstract this paper addresses the problem of assessing the stability of linear time invariant lti systems with time varying delay the first contribution is a new stability criterion specified as a negativity condition for a quadratic function parameterized by the delay this result mainly follows from an augmented affine parameter dependent lyapunov krasovskii functional which in turn takes advantages of convexity properties then as a second contribution we invoke a result from robust control literature to show how the proposed stability condition can be checked exactly in terms of linear matrix inequality lmi conditions the improvements obtained by the proposed refinements are illustrated via numerical examples drawn from the literature

direction of arrival estimation in time modulated linear arrays with unidirectional phase center motion a novel approach for estimating the direction of arrivals doas in time modulated linear arrays tmlas with unidirectional phase center motion upcm scheme is proposed in this paper based on the fact that the main beams of the patterns at different sidebands can be directed at different directions the corresponding received signals can be used to compose a received data space thus the spatial locations of the far field sources can be estimated by using multiple signal classification music algorithm simulation results of the doa estimation in an 8 element tmla with the upcm scheme validate the proposed approach where the performance such as the accuracy and resolution of the doa estimation is obtained through monte carlo simulations as compared to the doa estimation based on conventional uniform linear arrays ulas a much better resolution performance is obtained

regional stability analysis of discrete time dynamic output feedback under aperiodic sampling and input saturation this technical note addresses the problem of regional stability analysis of a continuous time plant controlled by a discrete time dynamic output feedback control law with saturation constraints under aperiodic sampling to cope with the aperiodic sampling problem the proposed approach is based on an impulsive system modeling and the use of looped functionals a generalized sector based relation is applied to tackle the control saturation effects from these ingredients conditions to ensure regional asymptotic stability of the closed loop system under aperiodic sampling are derived based on these conditions lmi based optimization problems are proposed to compute estimates of the region of attraction of the closed loop system or to maximize the bound on the maximal admissible interval between two successive sampling instants for which the regional stability can be ensured with respect to a given set of admissible states a numerical example illustrates the application of the results

brief paper a novel stability analysis of linear systems under asynchronous samplings this article proposes a novel approach to assess the stability of continuous linear systems with sampled data inputs the method which is based on the discrete time lyapunov theorem provides easy tractable stability conditions for the continuous time model sufficient conditions for asymptotic and exponential stability are provided dealing with synchronous and asynchronous samplings and uncertain systems an additional stability analysis is provided for the cases of multiple sampling periods and packet losses several examples show the efficiency of the method