a new nonlinear robust disturbance observer abstract this paper presents a new nonlinear robust disturbance observer by using only the input output information for minimum phase dynamical systems with arbitrarily relative degrees the model uncertainties the nonlinear parts of the system are merged into the disturbance term and are regarded as a part of the disturbance the disturbance is assumed bounded however the upper and lower bounds are assumed unknown the new disturbance observer is inspired by the vss control theory whereas the upper and lower bounds of the disturbance are adaptively updated the estimation error of the disturbance can be made as small as necessary by choosing the design parameters the attraction of the proposed method lies in its robustness to disturbance and easiness to be implemented example and simulation results show the effectiveness of the proposed algorithm

observer design using a generalized time scaled block triangular observer form this paper presents an observer design for uncontrolled nonlinear multi output continuous time systems based on a time scaled block triangular observer form tbtof the tbtof generalizes an established block triangular observer form btof by including generalized time scaling functions tsfs which have both state and output dependence introducing these stability preserving tsfs broadens the class of systems which admits a btof based observer design necessary conditions for the tsfs are provided when a tbtof exists an observer can be constructed subsystem at a time sufficient conditions are given to prove estimate error stability a physical example illustrates the tbtof construction and observer design

the commutation theorem for tensor products over von neumann algebras abstract a general commutation theorem is proved for tensor products of von neumann algebras over common von neumann subalgebras roughly speaking if the non common parts of two von neumann algebras m 1 and m 2 on the same hilbert space are appropriately separated by commuting type i von neumann algebras n 1 and n 2 then the commutant of the von neumann algebra generated by m 1 and m 2 is generated by the relative commutants m 1 n 1 and m 2 n 2 as well as by the intersection of the commutants of all concerned von neumann algebras this theorem extends both tomita s classical commutation theorem and a splitting result in tensor products proved recently in the factor case by l ge and r v kadison applications are given to a decomposition criterion in ordinary tensor products and to a partial solution of a conjecture of s popa concerning the maximal injectivity of tensor products of maximal injective von neumann subalgebras

lyapunov based range identification for paracatadioptric systems many applications require the interpretation of the euclidean coordinates of features of a 3 d object through 2 d images in this paper the relative range and the euclidean coordinates of an object or camera undergoing general affine motion are determined for paracatadioptric imaging systems via a nonlinear observer the nonlinear observer asymptotically determines the range information provided that the motion parameters are known the observer is developed through a lyapunov based design and stability analysis and simulation results are provided that illustrate the performance of the state estimator the contributions of this paper are that the developed observer 1 can be applied to both affine and nonaffine systems 2 can be used for both the fixed and moving camera configurations 3 is continuous and 4 yields an asymptotic result

independence properties in subalgebras of ultraproduct ii1 factors let mn be a sequence of finite factors with dim mn and denote by m mn their ultraproduct over a free ultrafilter we prove that if q m is either an ultraproduct q qn of subalgebras qn mn with qn mnqn mn n or the centralizer q b m of a separable amenable subalgebra b m then for any separable subspace x m q m there exists a diffuse abelian von neumann subalgebra in q which is free independent to x relative to q m some related independence properties for subalgebras in ultraproduct ii1 factors are also discussed

full factors and co amenable inclusions we show that if m is a full factor and n subset m is a co amenable subfactor with expectation then n is also full this answers a question of popa from 1986 we also generalize a theorem of tomatsu by showing that if m is a full factor and sigma g curvearrowright m is an outer action of a compact group g then sigma is automatically minimal and m g is a full factor which has w spectral gap in m finally in the appendix we give a proof of the fact that several natural notions of co amenability for an inclusion n subset m of von neumann algebras are equivalent thus closing the cycle of implications given in anantharaman delaroche s paper in 1995

the dual parameterization approach to optimal least square fir filter design subject to maximum error constraints this paper is concerned with the design of linear phase finite impulse response fir digital filters for which the weighted least square error is minimized subject to maximum error constraints the design problem is formulated as a semi infinite quadratic optimization problem using a newly developed dual parameterization method in conjunction with the caratheodory s dimensional theorem an equivalent dual finite dimensional optimization problem is obtained the connection between the primal and the dual problems is established a computational procedure is devised for solving the dual finite dimensional optimization problem the optimal solution to the primal problem can then be readily obtained from the dual optimal solution for illustration examples are solved using the proposed computational procedure

visually guided ranging from observations of points lines and curves via an identifier based nonlinear observer abstract in this paper we consider the problem of estimating the range information of features on an affine plane in r 3 by observing its image with the aid of a ccd camera wherein we assume that the camera is undergoing a known motion the features considered are points lines and planar curves located on planar surfaces of static objects the dynamics of the moving projections of the features on the image plane have been described as a suitable differential equation on an appropriate feature space this dynamics is used to estimate feature parameters from which the range information is readily available in this paper the proposed identification has been carried out via a newly introduced identifier based observer performance of the observer has been studied via simulation

convergence analysis of the extended kalman filter used as an observer for nonlinear deterministic discrete time systems in this paper convergence analysis of the extended kalman filter ekf when used as an observer for nonlinear deterministic discrete time systems is presented based on a new formulation of the first order linearization technique sufficient conditions to ensure local asymptotic convergence are established furthermore it is shown that the design of the arbitrary matrix plays an important role in enlarging the domain of attraction and then improving the convergence of the modified ekf significantly the efficiency of this approach compared to the classical version of the ekf is shown through a nonlinear identification problem as well as a state and parameter estimation of nonlinear discrete time systems

entropy of some automorphisms of the ii 1 factor of the free group in infinite number of generators letl f be theii 1 factor defined by the free groupf in infinite number of generators it is shown that for a class of automorphisms ofl f arising from bijections of the set of generators off on itself and including the free shift the entropy is zero

approximately diagonalizing matrices over c y abstract let x be a compact metric space which is locally absolutely retract and let c x c y mn be a unital homomorphism where y is a compact metric space with dim y 2 it is proved that there exists a sequence of n continuous maps i m y x i 1 2 n and a sequence of sets of mutually orthogonal rank one projections p1 m p2 m pn m c y mn such that this is closely related to the kadison diagonal matrix question it is also shown that this approximate diagonalization could not hold in general when dim y 3

on actions of amenable groups on ii1 factors abstract given a ii 1 factor m with separable predual and a free action of a countable amenable discrete group g on m we show that the crossed product m g has property resp is mcduff when m itself has property resp is mcduff

brief paper observer forms for perspective systems the estimation of three dimensional position information from two dimensional images in computer vision systems can be formulated as a state estimation problem for a nonlinear perspective dynamic system the multi output state estimation problem has been treated by several authors using methods for nonlinear observer design this paper shows that a perspective system can be transformed to two observer forms and provides constructive methods for arriving at the transformations these observer forms lead to straightforward observer designs first it is shown that using an output transformation the system admits an observer form which leads to an observer with linear error dynamics a second observer design is based on a time scaled block triangular form both designs assume a commonly used observability condition the designs are demonstrated in simulation

sub stonean spaces and corona sets mathematics institute university of copenhagen universitetsparken 5 dk 2100 denmark communicated by a cannes received july 1983 a self contained account of the theory of sub stonean spaces and their relations to stonean spaces and rickart spaces is given of particular interest are the corona sets of the form p x x for locally compact u compact spaces because these highly nontrivial sub stonean spaces lend themselves to tech cohomological considerations the theory of sub stonean spaces is essential for our solution of the diagonalization problem for c x m found in k grove and g k pedersen diagonalizing matrices over c x submitted for publication

fullness connes χ groups and ultra products of amalgamated free products over cartan subalgebras ultra product algebras associated with amalgamated free products over cartan subalgebras are investigated as applications their connes x groups are computed in terms of ergodic theory and also we clarify what condition makes them full factors i e their inner automorphism groups become closed

maximal injective subalgebras of tensor products of free group factors in this article we prove the following results let l f ni be the free group factor on ni generators ni 2 and gi be one of standard generators of l f ni for 1 i n let ai be the abelian von neumann subalgebra of l f ni generated by gi then the abelian von neumann subalgebra i 1nai is a maximal injective von neumann subalgebra of i 1nl f ni when n is equal to infinity we obtain strongly stable ii1 factors or called mcduff factors that contain maximal injective abelian von neumann subalgebras

efficient algorithm for solving semi infinite programming problems and their applications to nonuniform filter bank designs an efficient algorithm for solving semi infinite programming problems is proposed in this paper the index set is constructed by adding only one of the most violated points in a refined set of grid points by applying this algorithm for solving the optimum nonuniform symmetric antisymmetric linear phase finite impulse response fir filter bank design problems the time required to obtain a globally optimal solution is much reduced compared with that of the previous proposed algorithm

abelian strict approximation in aw algebras and weyl von neumann type theorems in this paper for a c algebra a with m m a an aw algebra or equivalently for an essential norm closed two sided ideal a of an aw algebra m we investigate the strict approximability of the elements of m from commutative c subalgebras of a in the relevant case of the norm closed linear span a of all finite projections in a semi finite aw algebra m we shall give a complete description of the strict closure in m of any maximal abelian self adjoint subalgebra masa of a we shall see that the situation is completely different for discrete respectively continuous m in the discrete case for any masa c of a the strict closure of c is equal to the relative commutant c m while in the continuous case under certain conditions concerning the center valued quasitrace of the finite reduced algebras of m satisfied by all von neumann algebras c is already strictly closed thus in the continu ous case no elements of m which are not already belonging to a can be strictly approximated from commutative c subalgebras of a in spite of this pathology of the strict topology in the case of the norm closed linear span of all finite projections of a continuous semi finite aw algebra we shall prove that in general situations including also this case any normal y 2 m is equal modulo a to some x 2 m which belongs to an order theoretical closure of an appropriate commutative c subalgebra of a in other words if we replace the strict topology with order theoretical approximation weyl von neumann berg sikonia type theo rems will hold in substantially greater generality

brief paper an ekf based nonlinear observer with a prescribed degree of stability the topic of this article is a nonlinear observer based on a slight modification of the extended kalman filter the purpose of this modification is twofold first the degree of stability can be assigned in advance and secondly this modification allows an effective treatment of the nonlinearities using the second method of lyapunov it is proved that the proposed observer is an exponential observer to examine the practical usefulness the proposed observer is applied to the highly nonlinear flux and angular velocity estimation problem for induction machines

generator masas in q deformed araki woods von neumann algebras and factoriality to any strongly continuous orthogonal representation of r on a real hilbert space hr hiai constructed q deformed araki woods von neumann algebras for 1 q 1 which are w algebras arising from non tracial representations of the q commutation relations the latter yielding an interpolation between the bosonic and fermionic statistics we prove that if the orthogonal representation is not ergodic then these von neumann algebras are factors whenever dim hr 2 and q 1 1 in such case the centralizer of the q quasi free state has trivial relative commutant in the process we study generator masas in these factors and establish that they are strongly mixing

higher order complementary filters a higher order generalization of magnitude and power complementary filters is proposed the proposed scheme is shown to have superior frequency characteristics compared to the ordinary complementary filters applications of these generalized complementary filters include subband coding for audio and video and sharpening of magnitude characteristics of digital filters this new design procedure can be used to generate ordinary multichannel magnitude and power complementary filters with sharper passband responses a new method is outlined to obtain the class of filters that satisfies the higher order complementary condition for an arbitrary number of channels

state observer for a class of nonlinear systems and its application to machine vision in this note we consider the state observer problem for a class of nonlinear systems which are usually encountered in the machine vision study the formulation of the state observer is motivated by the sliding mode methods and adaptive control techniques the proposed observer is applied to the identification problems of the motion parameters and space position of a moving object by using the perspective observation of a single point it is clarified that the rotation parameters can be observed by using the observation of one camera and the position and translation parameters cannot be observed by using one camera and must appeal to stereo vision simulation results show that the proposed algorithm is effective

hnn extensions of von neumann algebras abstract reduced hnn extensions of von neumann algebras as well as c algebras will be introduced and their modular theory factoriality and ultraproducts will be discussed in several concrete settings detailed analysis on them will be also carried out

minimal ambient nuclear c algebras abstract we provide examples of ambient nuclear c algebras of non nuclear c algebras with no proper intermediate c algebras in particular this gives the first examples of minimal ambient nuclear c algebras of non nuclear c algebras for this purpose we study generic cantor systems of infinite free product groups

design of nonuniform near allpass complementary fir filters via a semi infinite programming technique in this correspondence we consider the problem of designing a set of nonuniform near allpass complementary finite impulse response fir filters this problem can be formulated as a quadratic semi infinite programming problem where the objective is to minimize the sum of the ripple energy for the individual filters subject to the passband and stopband specifications as well as to the allpass complementary specification the dual parameterization method is used for solving the linear quadratic semi infinite programming problem

the radial masa in free orthogonal quantum groups abstract we prove that the radial subalgebra in free orthogonal quantum group factors is maximal abelian and mixing and we compute the associated bimodule the proof relies on new properties of the jones wenzl projections and on an estimate of certain scalar products of coefficients of irreducible representations

on maximal injective subalgebras of tensor products of von neumann algebras abstract let m i be a von neumann algebra and b i be a maximal injective von neumann subalgebra of m i i 1 2 if m 1 has separable predual and the center of b 1 is atomic e g b 1 is a factor then b 1 b 2 is a maximal injective von neumann subalgebra of m 1 m 2 this partly answers a question of popa

maximal amenability and disjointness for the radial masa abstract we prove that the radial masa c in the free group factor is disjoint from other maximal amenable subalgebras in the following sense any distinct maximal amenable subalgebra cannot have diffuse intersection with c

range identification for perspective vision systems in this note a new observer is developed to determine range information and hence the three dimensional 3 d coordinates of an object feature moving with affine motion dynamics or the more general ricatti motion dynamics with known motion parameters the unmeasurable range information is determined from a single camera provided an observability condition is satisfied that has physical significance to develop the observer the perspective system is expressed in terms of the nonlinear feature dynamics the structure of the proposed observer is inspired by recent disturbance observer results the proposed technique facilitates a lyapunov based analysis that is less complex than the sliding mode based analysis derived for recent observer designs the analysis demonstrates that the 3 d task space coordinates of the feature point can be asymptotically identified simulation results are provided that illustrate the performance of the observer in the presence of noise

a class of magnitude complementary loudspeaker crossovers necessary and sufficient conditions are developed for a pair of transfer functions to have magnitude responses which sum to a constant if in addition the transfer function pair is constrained to be all pass complementary the transfer function pair so obtained is well suited for loudspeaker crossover applications such crossover systems are characterized by a pair of transfer functions which exhibit the same phase angle at all frequencies this property has twofold implications i in active crossover biamplified audio systems whereby the low frequencies and high frequencies are reproduced using separate power amplifiers in phase crossover transfer functions require less power in subsequent amplifier stages than other designs to achieve a given acoustic sound pressure level and ii the summed acoustic magnitude response is least sensitive to noncoincidental mounting of the low and high frequency transducers when the crossover transfer functions exhibit the same phase angle at all frequencies the class of transfer functions realizable is quite wide and includes squared versions of butterworth chebyshev and elliptic transfer functions of all orders

maximal amenable subalgebras of von neumann algebras associated with hyperbolic groups we prove that for any infinite maximal amenable subgroup h in a hyperbolic group g the von neumann subalgebra lh is maximal amenable inside lg it provides many new explicit examples of maximal amenable subalgebras in ii 1 factors we also prove similar maximal amenability results for direct products of relatively hyperbolic groups and orbit equivalence relations arising from measure preserving actions of such groups

motion recovery by using stereo perspective observation the motion recovery for a class of movements in the space is considered in this note by using the stereo perspective observation of at least three points the motion equation that is considered can cover a wide class of practical movements in the space the asymptotic estimation of the motion parameters which are all time dependent variables is developed based on the second method of lyapunov furthermore the proposed algorithm can be modified to deal with occlusion phenomenon to illustrate the performance of the proposed algorithm it is compared with the extended kalman filter ekf by computer simulations

stochastic stability of the discrete time extended kalman filter the authors analyze the error behavior for the discrete time extended kalman filter for general nonlinear systems in a stochastic framework in particular it is shown that the estimation error remains bounded if the system satisfies the nonlinear observability rank condition and the initial estimation error as well as the disturbing noise terms are small enough this result is verified by numerical simulations for an example system

design of interpolative sigma delta modulators via semi infinite programming this correspondence considers the optimized design of interpolative sigma delta modulators sdms the first optimization problem is to determine the denominator coefficients the objective of the optimization problem is to minimize the passband energy of the denominator of the loop filter transfer function excluding the dc poles subject to the continuous constraint of this function defined in the frequency domain the second optimization problem is to determine the numerator coefficients in which the cost function is to minimize the stopband ripple energy of the loop filter subject to the stability condition of the noise transfer function ntf and signal transfer function stf these two optimization problems are actually quadratic semi infinite programming sip problems by employing the dual parameterization method global optimal solutions that satisfy the corresponding continuous constraints are guaranteed if the filter length is long enough the advantages of this formulation are the guarantee of the stability of the transfer functions applicability to design of rational infinite impulse response iir filters without imposing specific filter structures and the avoidance of iterative design of numerator and denominator coefficients our simulation results show that this design yields a significant improvement in the signal to noise ratio snr and have a larger stability range compared with the existing designs

a new observer for perspective vision systems under noisy measurements a simple design of observers for the range identification problem in perspective vision systems is given based on nonlinear contraction theory and synchronization exponential convergence to the object coordinates is achieved in the presence of significant measurement noise the performance is improved by synchronization among a group of observers

asymptotic structure of free araki woods factors the purpose of this paper is to investigate the structure of shlyakhtenko s free araki woods factors using the framework of ultraproduct von neumann algebras we first prove that all the free araki woods factors gamma h mathbb r u t prime prime are omega solid in the following sense for every von neumann subalgebra q subset gamma h mathbb r u t prime prime that is the range of a faithful normal conditional expectation and such that the relative commutant q cap m omega is diffuse we have that q is amenable next we prove that the continuous cores of the free araki woods factors gamma h mathbb r u t prime prime associated with mixing orthogonal representations u mathbb r rightarrow mathcal o h mathbb r are omega solid type mathrm ii infty factors finally when the orthogonal representation u mathbb r rightarrow mathcal o h mathbb r is weakly mixing we prove a dichotomy result for all the von neumann subalgebras q subset gamma h mathbb r u t prime prime that are globally invariant under the modular automorphism group sigma t varphi u of the free quasi free state varphi u

entropy determinants and l 2 torsion we show that for any amenable group and any z module m of type fl with vanishing euler characteristic the entropy of the natural action on the pontryagin dual of m is equal to the l 2 torsion of m as a particular case the entropy of the principal algebraic action associated with the module z z f is equal to the logarithm of the fuglede kadison determinant of f whenever f is a non zero divisor in z this conrms a conjecture of deninger as a key step in the proof we provide a general szeg o type approximation theorem for the fuglede kadison determinant on the group von neumann algebra of an amenable group as a consequence of the equality between l 2 torsion and entropy we show that the l 2 torsion of a non trivial amenable group with nite classifying space vanishes this was conjectured by luck finally we establish a milnor turaev formula for the l 2 torsion of a nite acyclic chain complex

factoriality type classification and fullness for free product von neumann algebras abstract we give a complete answer to the questions of factoriality type classification and fullness for arbitrary free product von neumann algebras

the design of uniformly and nonuniformly spaced pseudoquadrature mirror filters in the past quadrature mirror filters qmf s have been used to derive both uniformly and nonuniformly spaced filterbanks a pair of qmf s divides a signal into two equal bands which can be decimated at 2 1 and subsequently combined to reconstruct the original signal in order to derive filterbanks with more than two bands qmf s are combined in a binary tree structure pseudoquadrature mirror filters are similar to qmf s but can be designed to split a signal directly into any number of equally spaced bands thus generalizing the qmf concept in this paper the theory of pseudoquadrature mirror filters is reviewed these filters retain the desirable property that the channel signals from a uniformly spaced bank of m filters can be decimated by m 1 then interpolated and reassembled to reproduce the original signal an extension is made to the theory to allow a set of nonuniformly spaced filters to be derived from a uniformly spaced set and still retain all the desirable characteristics another extension to the theory is the derivation of a family of different sized filterbanks all derived from the same original prototype potential applications for the new filterbanks include improvements in subband coding of speech and music and analog scrambling of speech

identification of riccati dynamics under perspective and orthographic observations the problem of identifying motion and shape parameters of a planar object undergoing a riccati motion from the associated optical flow generated on the image plane of a single ccd camera is studied the optical flow is generated by projecting feature points on the object onto the image plane via perspective and orthographic projections an important result we show is that under perspective projection the parameters of a specific riccati dynamics that extend the well known rigid motion can be identified up to choice of a sign the paper also discusses other riccati equations obtained from quadratic extension of a rigid motion and affine motion for each of the various motion models considered and for each of the two projection models we show that the extent to which motion and shape parameters can be recovered from optical flow can in fact be recovered from the linear approximation of the optical flow we also extend our analysis to a pair of cameras

diagonalizing matrices over c x a complete characterization of those compact hausdorff spaces is given such that for every n each normal element in the algebra c x mn of continuous functions from x to mn can be continuously diagonalized the conditions are that x be a sub stonean space with dim x 2 and carries no nontrivial g bundles over any closed subset for g a symmetric group or the circle group in particular diagonalization is assured on every totally disconnected sub stonean space but also on connected spaces of the form y y where y is a simply connected noncompact graph

a new state observer for perspective systems in this note we consider the problem of estimating the state of a class of perspective systems the problem can be converted into the observation of a dynamical system with nonlinearities a new discontinuous state observer which is motivated by the sliding mode control method and adaptive techniques is proposed for the obtained dynamical system the assumptions are reasonable and the convergence conditions are intuitive and have apparently physical interpretations the attraction of the new method is that the algorithm is very simple and easy to be implemented and it is robust to measurement noises further minor a priori knowledge of the system is required in the new formulation simulation results show the superiority of the new method to the traditional ones

a noncommutative extended de finetti theorem abstract the extended de finetti theorem characterizes exchangeable infinite sequences of random variables as conditionally i i d and shows that the apparently weaker distributional symmetry of spreadability is equivalent to exchangeability our main result is a noncommutative version of this theorem in contrast to the classical result of ryll nardzewski exchangeability turns out to be stronger than spreadability for infinite sequences of noncommutative random variables out of our investigations emerges noncommutative conditional independence in terms of a von neumann algebraic structure closely related to popa s notion of commuting squares and kummerer s generalized bernoulli shifts our main result is applicable to classical probability quantum probability in particular free probability braid group representations and jones subfactors

range identification of features on an object using a single camera in this paper an adaptive nonlinear estimator is developed to identify the range and the 3d euclidean coordinates of feature points on a moving object using a single fixed camera no explicit model is used to describe the movement of the object homography based techniques are used in the development of the object kinematics while an adaptive nonlinear estimator is designed by employing signal filters lyapunov design methods are utilized to facilitate the design of the estimator and filters as well as the convergence and stability analysis the performance of the estimator is demonstrated by simulation results