delay dependent robust h control for t s fuzzy system with interval time varying delay this paper is concerned with the problem of robust h control for uncertain t s fuzzy systems with interval time varying delay that is the delay is assumed to be a time varying function belonging to an interval by defining new lyapunov functions and making use of novel techniques to achieve delay dependence new conditions for the existence of robust h controller are obtained based on the parallel distributed compensation pdc method in this article all the conditions are shown in terms of linear matrix inequalities lmis which can be solved efficiently by using the lmi optimization techniques two numerical examples are given to illustrate the less conservatism of the proposed method

event triggered fuzzy h control for a class of nonlinear networked control systems using the deviation bounds of asynchronous normalized membership functions this paper is concerned with the event triggered h control for a nonlinear networked control system a new event triggered transmission scheme is first proposed to reduce the network bandwidth utilization under this scheme the nonlinear networked control system is formulated as a takagi sugeno fuzzy threshold error dependent system with asynchronous normalized membership functions then by using the deviation bounds of asynchronous normalized membership functions some sufficient conditions on the existence of the parameters of the event triggered transmission scheme and the fuzzy controller are derived such that the takagi sugeno fuzzy threshold error dependent system with asynchronous normalized membership functions is asymptotically stable with a prescribed h attenuation level it is shown that the proposed design method can reduce the conservativeness of some existing results finally two examples are given to demonstrate the effectiveness of the proposed design method and the event triggered transmission scheme

stabilization of networked stochastic time delay fuzzy systems with data dropout this paper deals with the problem of stabilization for networked stochastic systems with transmitted data dropout the plant in the networked control system ncs under consideration is a discrete stochastic time delay nonlinear system represented by a takagi sugeno fuzzy model exponential stability criteria of the ncs are developed by using a common quadratic lyapunov function and a fuzzy lyapunov function respectively a stabilization controller with convergence rate constraint can be designed by solving a set of linear matrix inequalities that is numerically feasible with commercially available software three numerical examples are presented to demonstrate the effectiveness of the proposed methods

network based output tracking control for t s fuzzy systems using an event triggered communication scheme this paper is concerned with network based output tracking control for a t s fuzzy system an event triggered communication scheme under which the threshold depends on the latest successfully transmitted sampled data is introduced to reduce network resource utilization taking the event triggered communication scheme and the asynchronous operation between the fuzzy system and the fuzzy controller the resulting system is modeled as an asynchronous threshold error dependent system with an interval time varying delay a new delay dependent criterion for l 2 gain tracking performance of the asynchronous system is derived by applying the deviation bounds of asynchronous normalized membership functions based on this performance criterion some criteria on the existence of the fuzzy tracking controller are established a co design algorithm is presented to obtain the control gains and the event triggering parameters simultaneously an example is given to illustrate the effectiveness of the proposed method

on delay dependent approach for robust stability and stabilization of t s fuzzy systems with constant delay and uncertainties this paper investigates robust stability analysis and stabilization of delay and uncertain systems approximated by a takagi sugeno t s fuzzy model an innovative approach is proposed to develop delay dependent stability criteria of the systems which makes use of less redundant information to construct lyapunov function employs an integral equation method to handle the cross product terms and alleviates the requirements of the bounding technique and model transformations that have been popularly adopted in many existing references this leads to significant improvement in the stability performance with far fewer unknown variables in the stability computation from the derived stability criteria a new memoryless state feedback control is further developed the controller gain and the maximum allowable delay bound of the closed loop control system can be obtained simultaneously by solving an optimization problem numerical examples are also given to demonstrate the theoretical results

new approach to delay dependent stability analysis and stabilization for continuous time fuzzy systems with time varying delay this paper is concerned with delay dependent stability analysis and stabilization problems for continuous time takagi and sugeno t s fuzzy systems with a time varying delay a new method for the delay dependent stability analysis and stabilization is suggested which is less conservative than other existing ones first based on a fuzzy lyapunov krasovskii functional lkf a delay dependent stability criterion is derived for the open loop fuzzy systems in the derivation process some free fuzzy weighting matrices are introduced to express the relationships among the terms of the system equation and among the terms in the leibniz newton formula then a delay dependent stabilization condition based on the so called parallel distributed compensation pdc scheme is worked out for the closed loop fuzzy systems the proposed stability criterion and stabilization condition are represented in terms of linear matrix inequalities lmis and compared with the existing ones via two examples finally application to control of a truck trailer is also given to illustrate the effectiveness of the proposed design method

a study of the effects of grid non orthogonality on the solution of shallow water equations in boundary fitted coordinate systems in the present study an existing two dimensional boundary fitted model j hydraul eng asce 122 9 1996 512 is used to study the effect of grid non orthogonality on the solution of shallow water equations using boundary fitted grids the linearized two dimensional shallow water equations are expressed in terms of the grid angle and aspect ratio the truncation errors of the finite difference approximations used in the solution of the governing equations are shown to be dependent on the grid angle and the aspect ratio the coefficient of the truncation error was shown to increase with the decrease in the grid angle the rms errors in model predicted surface elevations and velocities for the case of seiching in a rectangular basin are found to increase gradually as the grid resolution decreases from 174 to 80 grid points per wavelength or as the grid angle decreases from 90 to 50 and increases rather sharply for a grid angle of 30 at grid resolutions less than 80 gridpoints per wavelength the model predicted surface elevations for the case of tidal forcing in a rectangular basin are found to be insensitive to the grid angle at grid resolutions higher than 600 gridpoints per wavelength the rms error in the model predicted velocities is found to increase gradually as the grid angle decreases from 90 to 30 or as the grid resolution decreases from 1400 gridpoints per wavelength to 400 gridpoints per wavelength and increases sharply as the grid resolution decreases from 400 to 150 gridpoints per wavelength two dimensional depth averaged hydrodynamic modeling of tidal circulation in narragansett bay using three different boundary fitted grids showed that the model predicted surface elevations are insensitive to the grid angle at grid resolutions as low as 200 gridpoints per wavelength however the model predicted velocities were found to increase as the grid resolution decreases from 600 to 200 gridpoints per wavelength we conclude from this study that grid angle and grid resolution affects the accuracy of the model predicted currents and the numerical dispersion increases with the decrease in grid angle or grid resolution and these are in agreement with that reached by sankaranarayanan and spaulding dispersion and stability analyses of shallow water equations in boundary fitted coordinates department of ocean engineering university of rhode island 2001 p 33 through a fourier analysis of the discretized equations in boundary fitted coordinates

technical communique absolute stability of time delay systems with sector bounded nonlinearity this paper deals with the problem of absolute stability of time delay systems with sector bounded nonlinearity some new delay dependent stability criteria are obtained and formulated in the form of linear matrix inequalities lmis neither model transformation nor bounding technique for cross terms is involved through derivation of the stability criteria numerical examples show that the results obtained in this paper improve the estimate of the stability limit over some existing result

the sensitivity and accuracy of fourth order finite difference schemes on nonuniform grids in one dimension abstract we construct local fourth order finite difference approximations of first and second derivatives on nonuniform grids in one dimension the approximations are required to satisfy symmetry relationships that come from the analogous higher dimensional fundamental operators the divergence the gradient and the laplacian for example we require that the discrete divergence and gradient be negative adjoint of each other div grad and the discrete laplacian is defined as lap divgrad the adjointness requirement on the divergence and gradient guarantees that the laplacian is a symmetric negative operator the discrete approximations we derive are fourth order on smooth grids but the approach can be extended to create approximations of arbitrarily high order we analyze the loss of accuracy in the approximations when the grid is not smooth and include a numerical example demonstrating the effectiveness of the higher order methods on nonuniform grids

delay dependent stability analysis and control synthesis of fuzzy dynamic systems with time delay this paper focuses on the delay dependent stability analysis and stabilization for fuzzy control systems with time delay based on linear matrix inequality lmi approach a delay dependent stability criteria has been developed the design schemes of stabilization via state feedback is developed and then the result is extended to the case of observer based output feedback all the researching results are presented by means of lmis two illustrative examples are given to illustrate the validity of the proposed design procedures

analysis of stability and accuracy of finite difference schemes on a skewed mesh numerical stability and accuracy of finite difference schemes on a skewed non uniform mesh are investigated to provide guidelines for mesh design and for devising appropriate solution methods when mesh skewness is unavoidable in the current analysis a linear advection diffusion equation in a cartesian coordinate system is transformed into a curvilinear one corresponding to a skewed mesh a finite difference approximation of the transformed equation leads to the leading order error terms which are responsible for time step restrictions and numerical instability a truncation error analysis of central difference approximation reveals the effects of mesh non uniformity and skewness on the solution quality in addition a modified wavenumber analysis is performed for the central and upwind difference schemes coupled with time integration methods to examine the effects of mesh skewness angle and flow direction relative to the mesh angle on the numerical stability in general severe mesh skewness leads to restrictions on the allowable cell peclet number and time step size and also increases phase and amplitude errors

a formula for estimation of truncation errors of convection terms in a curvilinear coordinate system abstract a formula for truncation errors of convection terms arising from the navier stokes equation in a curvilinear coordinate system is derived these truncation error terms are interpreted in terms of grid size grid uniformity grid line angle flow angle and derivatives of flow properties to gain physical insights from the formula the role of these factors in determining truncation errors is discussed it is shown that an optimal grid arrangement cannot be obtained without considering the interactions between the grid and the flow field the effect of the grid orthogonality on truncation errors is also analyzed for simple cases the derived formula provides a useful indicator for truncation error distribution which yields guidelines for grid adaption

improved delay dependent robust stabilization conditions of uncertain t s fuzzy systems with time varying delay this paper aims to develop simplified yet improved delay dependent robust control for uncertain t s fuzzy systems with time varying delay this is achieved through constructing new lyapunov krasovskii functionals and improving jensen s inequality unlike existing work in this area the approach developed in this paper employs neither free weighing matrices nor model transformations as a result simplified yet improved stability conditions are obtained for t s fuzzy systems with norm bounded type uncertainties for controller synthesis of the fuzzy systems the stabilization problem with memoryless state feedback control is solved via utilizing a cone complementarity minimization algorithm numerical examples are given to demonstrate the effectiveness of the proposed approach

to transmit or not to transmit a discrete event triggered communication scheme for networked takagi sugeno fuzzy systems this paper first proposes a discrete event triggered communication scheme for a class of networked takagi sugeno t s fuzzy systems this scheme has two main features 1 whether or not the sampled state should be transmitted is determined by the current sampled state and the error between the current sampled state and the latest transmitted state compared with those in a periodic time triggered communication scheme the communication bandwidth utilization is considerably reduced while preserving the desired control performance and 2 it is a discrete event triggered communication scheme due to the fact that the triggered conditions are only measured and checked at a constant sampling period compared with a continuous event triggered communication scheme the special hardware for continuous measurement and computation is no longer needed second a networked t s fuzzy model is delicately constructed which not only considers nonuniform time scales in the networked t s fuzzy model and the parallel distributed compensation fuzzy control rules but includes the aforementioned state error as well third a stability criterion and a stabilization criterion about the networked t s fuzzy system are derived respectively the stability criterion and stabilization criterion can provide a tradeoff to balance the required communication resource and the desired performance lowering the desired performance allows the network to allocate more limited bandwidth to other nodes in need finally a numerical example is given to show the effectiveness of the proposed method

robust h control for nonlinear systems over network a piecewise analysis method a piecewise analysis method pam is proposed to investigate the h performance analysis and h control design for nonlinear networked control systems nncss which are presented in the form of t s fuzzy model with time varying input delay different from the existing method in dealing with the time varying delay the whole variation interval of the delay is divided into two subintervals with equal length respecting for the delay belonging each subinterval new criteria on h performance analysis of the nncss are obtained by checking the variation of the derivative of the lyapunov functional in the two subintervals then criteria for the h controller design are obtained by using the convexity properties of the matrix inequality and some other new analysis techniques which are shown in terms of nonlinear matrix inequalities and can be solved by using a cone complementarity liberalization method as application of the derived results h controller design is carried out for the nonlinear mass spring system discussion shows that the proposed method is less conservative than the existing references

robust fuzzy control for uncertain discrete time nonlinear markovian jump systems without mode observations this paper studies the robust fuzzy control problem of uncertain discrete time nonlinear markovian jump systems without mode observations the takagi and sugeno t s fuzzy model is employed to represent a discrete time nonlinear system with norm bounded parameter uncertainties and markovian jump parameters as a result an uncertain markovian jump fuzzy system mjfs is obtained a stochastic fuzzy lyapunov function flf is employed to analyze the robust stability of the uncertain mjfs which not only is dependent on the operation modes of the system but also directly includes the membership functions then based on this stochastic flf and a non parallel distributed compensation non pdc scheme a mode independent state feedback control design is developed to guarantee that the closed loop mjfs is stochastically stable for all admissible parameter uncertainties the proposed sufficient conditions for the robust stability and mode independent robust stabilization are formulated as a set of coupled linear matrix inequalities lmis which can be solved efficiently by using existing lmi optimization techniques finally it is also demonstrated via a simulation example that the proposed design method is effective

a novel dropout compensation scheme for control of networked t s fuzzy dynamic systems this paper considers the problem of h state feedback control for networked nonlinear systems under unreliable communication links with packet dropouts the nonlinear plant in this paper is described by a takagi sugeno t s fuzzy model the packet dropouts in both sensor to controller s c and controller to actuator c a channels are considered which are modeled by bernoulli processes a new compensation scheme for the estimation of missing packets is proposed and a piecewise state feedback controller is designed so that the resulting closed loop control system is stochastically stable with guaranteed h performance then the results are extended to the case when both network induced delays and packet dropouts exist in communication links finally some numerical examples are given to illustrate the procedure of the proposed approaches and the optimal h performance in comparison to the existing approaches

new approach on robust delay dependent h _ infty control for uncertain t s fuzzy systems with interval time varying delay this paper investigates the robust h infin control for takagi sugeno t s fuzzy systems with interval time varying delay by employing a new and tighter integral inequality and constructing an appropriate type of lyapunov functional delay dependent stability criteria are derived for the control problem because neither any model transformation nor free weighting matrices are employed in our theoretical derivation the developed stability criteria significantly improve and simplify the existing stability conditions also the maximum allowable upper delay bound and controller feedback gains can be obtained simultaneously from the developed approach by solving a constrained convex optimization problem numerical examples are given to demonstrate the effectiveness of the proposed methods

an improved result on the stability of uncertain t s fuzzy systems with interval time varying delay this paper is concerned with the stability of uncertain t s fuzzy systems with interval time varying delay by uniformly dividing the delay interval into multiple segments and constructing an appropriate augmented lyapunov krasovskii functional some less conservative stability criteria are obtained which include some existing results as special cases since a tighter bounding inequality is employed to deal with time varying delay dependent integral items then some sources of computational complexity such as the general convex combination and free weighting matrices are not necessary to be adopted in the derivation of our results as a result the developed criteria not only theoretically improve some existing results but also have higher computational efficiency numerical examples are given to demonstrate the effectiveness of the proposed method

a priori mesh quality estimation via direct relation between truncation error and mesh distortion the purpose of the present work is the derivation and evaluation of a priori mesh quality indicators for structured unstructured as well as hybrid grids emphasis is placed on deriving direct relations between the indicators and mesh distortion the work is based on use of the finite volume discretization for evaluation of first order spatial derivatives the analytic form of the truncation error is derived and applied to elementary types of mesh distortion including typical hybrid grid interfaces the corresponding analytic expressions provide direct relations between computational accuracy and the degree of stretching skewness shearing and non alignment of the mesh

delay dependent h control for uncertain fuzzy systems with time varying delays this paper addresses the robust stabilization and robust h control problems of uncertain fuzzy delayed systems via a parallel distributed compensation pdc scheme the uncertainties are norm bounded and the delay may be either constant or time varying and either differentiable or non differentiable presented in this paper are some robust stabilization and robust h control criteria which are delay dependent in general and delay derivative dependent when the delay is differentiable these results enjoy much less conservatism and more computational simplicity compared with those in the existing literature and permit if the delay is differentiable the derivative to be larger than one some examples are given to illustrate the results in this paper

fuzzy weighting dependent approach to h_ infty filter design for time delay fuzzy systems this correspondence is concerned with the hinfin filter design for takagi sugeno t s fuzzy systems with state delay a delay dependent design method is proposed in terms of linear matrix inequalities lmi the main contribution is the use of fuzzy weighting dependent lyapunov functionals which can reduce the conservatism arisen from the quadratic lyapunov functional approach an illustrative example is given to show the effectiveness of the present method

robust h_ infty control for uncertain takagi sugeno fuzzy systems with interval time varying delay this paper is concerned with the problem of robust hinfin control for a class of uncertain time delay fuzzy systems the time delay is assumed to be a time varying continuous function belonging to a given interval which means that the lower and upper bounds for the time varying delay are available no restriction on the derivative of the time varying delay is needed which allows the time delay to be a fast time varying function the takagi sugeno t s uncertain fuzzy model with interval time varying delay is adopted based on the lyapunov krasovskii functional approach some delay dependent conditions for the existence of robust hinfin controller are formulated in the form of linear matrix inequalities lmis when these lmis are feasible an hinfin controller is presented a numerical example is given to demonstrate the effectiveness of the proposed method

high order finite difference schemes on non uniform meshes with good conservation properties numerical simulation of turbulent flows dns or les requires numerical methods that are both stable and free of numerical dissipation one way to achieve this is to enforce additional constraints such as discrete conservation of mass momentum and kinetic energy the objective of this work is to generalize the high order schemes of morinishi et al to non uniform meshes while maintaining conservation properties of the schemes as much as possible this generalization is achieved by preserving symmetries of the uniform mesh case the proposed schemes do not simultaneously conserve mass momentum and kinetic energy however depending on the form of the convective term conservation of either momentum or energy in addition to mass can be achieved it is shown that the conservation properties of the generalized schemes are as good as those of the standard second order finite difference scheme on non uniform meshes while the accuracy of the new schemes is definitely superior the predicted conservation properties are demonstrated numerically in inviscid flow simulations

h sub spl infin control for networked systems with random communication delays this note is concerned with a new controller design problem for networked systems with random communication delays two kinds of random delays are simultaneously considered i from the controller to the plant and ii from the sensor to the controller via a limited bandwidth communication channel the random delays are modeled as a linear function of the stochastic variable satisfying bernoulli random binary distribution the observer based controller is designed to exponentially stabilize the networked system in the sense of mean square and also achieve the prescribed h sub spl infin disturbance attenuation level the addressed controller design problem is transformed to an auxiliary convex optimization problem which can be solved by a linear matrix inequality lmi approach an illustrative example is provided to show the applicability of the proposed method

relaxed stability and stabilization conditions of networked fuzzy control systems subject to asynchronous grades of membership this paper presents relaxed stability and stabilization conditions for takagi sugeno t s fuzzy systems under network environments subject to asynchronous grades of membership because of the introduction of a communication network the favorable property in the point to point connection that is sharing the identical premises in the fuzzy plant and the fuzzy controllers cannot be arbitrarily employed to widen the applicability of the fuzzy control method under network environments a novel method is provided to reconstruct the synchronous time scale grades of membership at the controller as those in the plant as a result the aforementioned favorable property can be conditionally used in the derivation of the stability and stabilization criteria for the system under consideration controlled over a communication network numerical examples have been given to illustrate the effectiveness of the proposed approach

a priori grid quality estimation for high order finite differencing structured grids using the finite differencing method contain two sources of grid induced truncation errors the first is dependent on the solution field the second is related only to the metrics of the grid transformation the accuracy of the grid transformation metrics is affected by the inverse metrics which are spatial derivatives of the grid in the generalised coordinates the truncation errors contained in the inverse metrics are generated by the spatial schemes fourier analysis shows that the dispersion errors by spatial schemes have similarities to the transfer function of spatial filters this similarity is exploited to define a grid quality metric that can be used to identify areas in the mesh that are likely to generate significant grid induced errors an inviscid vortex convection benchmark case is used to quantify the correlation between the grid quality metric and the solution accuracy for three common geometric features found in grids abrupt changes in the grid metrics skewness and grid stretching a strong correlation is obtained provided that the grid transformation errors are the most significant sources of error

mode independent fuzzy fault tolerant variable sampling stabilization of nonlinear networked systems with both time varying and random delays this paper develops a fault tolerant variable sampling control vsc scheme for a class of nonlinear networked control systems ncss with time varying state and random network delays an uncertain continuous takagi sugeno t s fuzzy system with both state and input varying delays in the presence of possible actuator faults is obtained equivalently on the basis of the input delay methodology a tighter bounding lemma is proposed so as to gain less conservative closed loop stability criteria delay dependent conditions in terms of linear matrix inequalities are derived for the mode independent fault tolerant stabilizing controller of the resulting markovian network based system by employing a novel stochastic lyapunov krasovskii l k functional an illustrative example is simulated to show the validity of the obtained results

technical communique robust stabilization of uncertain systems with unknown input delay this paper is concerned with the robust controller design for uncertain input delayed systems the time delay is assumed to be an unknown constant a controller with delay feedback for the robust stabilization of the system is proposed the stability criterion of the closed loop system is derived in terms of linear matrix inequalities lmis examples show that in many cases our method can give less conservative results than those by the existing methods moreover for the same cases our controllers have lower feedback gains than the existing ones