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Showing papers on "Transfer function published in 2001"


Book ChapterDOI
01 Jan 2001
TL;DR: In this paper, the problem of absolute stability of an indirect control system with a single nonlinearity was investigated by using a method which differs from the second method of Lyapunov.
Abstract: The problem of absolute stability of an ?indirect control? system with a single nonlineartiy ia investlgated by using a method which differs from the second method of Lyapunov. The main condition of the obtained criterion of absolute stability is expressed in terms of the transfer function of the system linear part. It is also shown that by fonning the standard Lyapunov function -?a quadratic form plus the integral of the nonlinearity? It is not possible In the case considered here to obtain a wider stability domain than the one obtained from the presented criterion. Graphical criteria of absolute continuinty are also given by means of the phase-amplitude characteristic or by what is known as ?the modified phase-amplitude characteristic? of the system linear part.

305 citations


Journal ArticleDOI
TL;DR: A new electromyogram generation and detection model, based on the separation of the temporal and spatial properties of the muscle fiber action potential and of the volume conductor, includes the capacitive tissue properties.
Abstract: The authors propose a new electromyogram generation and detection model. The volume conductor is described as a nonhomogeneous (layered) and anisotropic medium constituted by muscle, fat and skin tissues. The surface potential detected in space domain is obtained from the application of a two-dimensional spatial filter to the input current density source. The effects of electrode configuration, electrode size and inclination of the fibers with respect to the detection system are included in the transfer function of the filter. Computation of the signal in space domain is performed by applying the Radon transform; this permits to draw considerations about spectral dips and clear misunderstandings in previous theoretical derivations. The effects of generation and extinction of the action potentials at the fiber end plate and at the tendons are included by modeling the source current, without any approximation of its shape, as a function of space and time and by using again the Radon transform. The approach, based on the separation of the temporal and spatial properties of the muscle fiber action potential and of the volume conductor, includes the capacitive tissue properties.

272 citations


Journal ArticleDOI
TL;DR: Sufficient conditions for the existence of the desired controllers are given in terms of a linear matrix inequality (LMI) when this LMI is feasible, and the expected memoryless state feedback controllers can be easily constructed via convex optimization.
Abstract: This note is concerned with the H/sub /spl infin// and positive-real control problems for linear neutral delay systems. The purpose of H/sub /spl infin// control is the design of a memoryless state feedback controller which stabilizes the neutral delay system and reduces the H/sub /spl infin// norm of the closed-loop transfer function from the disturbance to the controlled output to a prescribed level, while the purpose of positive-real control is to design a memoryless state feedback controller such that the resulting closed-loop system is stable and the closed-loop transfer function is extended strictly positive real. Sufficient conditions for the existence of the desired controllers are given in terms of a linear matrix inequality (LMI). When this LMI is feasible, the expected memoryless state feedback controllers can be easily constructed via convex optimization.

169 citations


Journal ArticleDOI
TL;DR: The technological need and the complex character (nonlinearities, spatial variations, batch nature) of the RTCVD process motivate the need to control the wafer temperature profile using a nonlinear feedback controller based on a distributed process model.
Abstract: hile most deal with vv processes undergraduate process control courses still dynamics and control of lumped chemical using linear transfer function models, key technological needs in growth areas such as semiconductor manufacturing, nanotechnology, biotechnology, and unmanned aerial vehicles have motivated extensive research on analysis and control of complex nonlinear distributed systems across all engineering disciplines. From a control point of view, the distinguishing feature of complex distributed systems is that they give rise to nonlinear control problems that involve the regulation of highly distributed control variables by using spatially-distributed control actuators and measurement sensors. Thus, complex distributed systems cannot be effectively controlled with control methods which assume that the state, manipulated and tobe-controlled variables exhibit lumped behavior or with linear control algorithms derived on the basis of IinearAinearized distributed models. icant nonuniformity of the wafer temperature profile. This, in turn, may lead to film deposition uniformity that does not meet the tight requirements set by the industry (SIA, 1997). This technological need and the complex character (nonlinearities, spatial variations, batch nature) of the RTCVD process motivate the need to control the wafer temperature profile using a nonlinear feedback controller based on a distributed process model. A typical example of this class of problems is the control of titania aerosol reactors to achieve a nearly monodisperse particle-size distribution (Kalani and Christofides, 2000); this is required for titania pigments to obtain the maximum hiding powder per unit mass. Titania aerosol Control of Particle-Size Distributions.

134 citations


Journal ArticleDOI
01 Nov 2001
TL;DR: It is shown that the search-space expansion scheme can enhance the possibility of converging to a global optimum in the DE search and the chosen frequency-domain error criterion make the proposed approach quite efficacious for optimally approximating unstable and/or nonmimimum-phase linear systems.
Abstract: The problem of optimally approximating linear systems is solved by a differential evolution algorithm (DEA) incorporating a search-space expansion scheme. The optimal approximate rational model with/without a time delay for a system described by its rational or irrational transfer function is sought such that a frequency-domain L/sup 2/-error criterion is minimized. The distinct feature of the proposed model approximation approach is that the search-space expansion scheme can enhance the possibility of converging to a global optimum in the DE search. This feature and the chosen frequency-domain error criterion make the proposed approach quite efficacious for optimally approximating unstable and/or nonmimimum-phase linear systems. The simplicity and robustness of the modified DEA in terms of easy implementation and minimum assumptions on search space are demonstrated by two numerical examples.

117 citations


Journal ArticleDOI
TL;DR: The parameters of first and second order plant transfer functions, stable or unstable, with time delay can be found exactly, assuming no measurement errors, from measurements of the parameters of a single asymmetrical limit cycle in a relay controlled feedback loop.

116 citations


Book
01 Jan 2001
TL;DR: In this paper, the authors present a survey of the state-of-the-art S&R models and their application in the space and frequency domain, including the Fourier series and Fourier transform.
Abstract: Introduction - Modeling Applications. Conceptual S&R Model. Performance Prediction Approaches. Surveillance and Reconnaissance Systems - Introduction. Imaging with IR and EO Sensors. Image Formation. Imaging System parameters. Synthetic Aperture Radar. Choice of Imaging Sensors. Examples of Surveillance and Reconnaissance Sensors. Historical Review of S&R Modeling - Pre-1950. 1950-1970. 1970-Present. Linear Shift Invariant Imaging Systems - Linearity and Shift Invariance. The Impulse Function. The Fourier Series and Fourier Transform. LSI Imaging System. Imaging in the Space and Frequency Domain. Imaging With Components. Simplifying LSI Imager Analysis to One Dimension. Sampled Imaging Systems. SAR Impulse Response and Transfer Function. Information Extraction Measures - Direct Performance Measures. Theory of Signal Detection. Range/Time Measures. Performance Estimate Measures. Information and Difference Metrics. Information Extraction Performance Predictors - Scale, Resolution, and Sharpness. Contrast and Noise. Artifacts. Summary Measures. Target and Environmental Considerations - Target Effects. Deception and Denial. Atmospheric Effects. Image Processing Considerations - Bandwidth Compression. Enhancement Processing. Display and Observer Considerations - Displays. Observer Characteristics. Observer Models. Performance Prediction Models - Parameter-based Models. Image-Based Models. Sensor Performance Conversions - Johnson Criteria and NIIRS. Conversion with Models. Comparing Sensor Performance Conversions. Performance Conversion as a Function of Target Size. Conclusions and Future Directions - Spectral Domain. Temporal Effects. Search. SAR.

104 citations


Book
01 Jan 2001
TL;DR: In this article, the authors present linear systems with one degree of freedom and finite numbers of degrees of freedom for feedback linearization and sliding control with one-degree-of-freedom.
Abstract: Preface Contributors 1. Statics Vector Algebra Centroids and Surface Properties Moments and Couples Equilibrium Dry Friction 2. Dynamics Fundamentals Kinematics of a Point Dynamics of a Particle Planar Kinematics of a Rigid Body Dynamics of a Rigid Body 3. Mechanics of Materials Stress Deflection and Stiffness Fatigue 4. Theory of Mechanisms Fundamentals Position Analysis Velocity and Acceleration Analysis Kinetostatics 5. Machine Components Screws Gears Springs Rolling Bearings Lubrication and Sliding Bearings 6. Theory of Vibration Introduction Linear Systems with One Degree of Freedom Linear Systems with Finite Numbers of Degrees of Freedom Machine-Tool Vibrations 7. Principles of Heat Transfer Heat Transfer Thermodynamics Conduction Heat Transfer Convection Heat Transfer 8. Fluid Dynamics Fluids Fundamentals Hydraulics 9. Control Introduction Signals Transfer Functions Connection of Elements Poles and Zeros Steady-State Error Time-Domain Performance Frequency-Domain Performances Stability of Linear Feedback Systems Design of Closed-Loop Control Systems by Pole-Zero Methods Design of Closed-Loop Control Systems by Frequential Methods State Variable Models Nonlinear Systems Nonlinear Controllers by Feedback Linearization Sliding Control Appendix: Differential Equations and Systems of Differential Equations Index

101 citations


Patent
30 Mar 2001
TL;DR: In this article, the authors present a methodology for process modeling and control and the software system implementation of this methodology, which includes a rigorous, nonlinear process simulation model, the generation of appropriate linear models derived from the rigorous model, and an adaptive, linear model predictive controller (MPC) that utilizes the derived linear models.
Abstract: A methodology for process modeling and control and the software system implementation of this methodology, which includes a rigorous, nonlinear process simulation model, (10) the generation of appropriate linear models derived from the rigorous model, and an adaptive, linear model predictive controller (MPC) (30) that utilizes the derived linear models. A state space, multivariable, model predictive controller (MPC) is the preferred choice for the MPC since the nonlinear simulation model is analytically translated into a set of linear state equations and thus simplifies the translation of the linearized simulation equations to the modeling format required by the controller. Various other MPC modeling forms such as transfer functions, impulse response coefficients, and step response coefficients may also be used. The methodology is very general in that any model predictive controller using one of the above modeling forms can be used as the controller. The methodology also includes various modules that improve reliability and performance. For example, there is a data pretreatment module used to pre-process the plant measurements for gross error detection. A data reconciliation and parameter estimation module is then used to correct for instrumentation errors and to adjust model parameters based on current operating conditions. The full-order state space model can be reduced by the order reduction module to obtain fewer states for the controller model. Automatic MPC tuning is also provided to improve control performance.

96 citations


Journal ArticleDOI
TL;DR: In this article, the problem of designing the linear state observers such that, for all admissible parameter uncertainties, the observation process remains robustly stable and the transfer function from exogenous disturbances to error state outputs meets the prespecified H∞ norm upper bound constraint, independently of the time delay.

96 citations


Journal ArticleDOI
TL;DR: In this article, the validity of various dynamic models of induction machines is investigated in the perturbation frequency region below 35 Hz using three types of basic excitations: perturbations in the shaft torque, supply voltage and supply frequency.
Abstract: The paper deals with the validity of various dynamic models of induction machines. The fifth-order Park model and various reduced-order models are used to predict the low-frequency dynamic response of a 15 kW induction machine, and the theoretical results are compared with an extensive series of measurements. Several transfer functions are investigated in the perturbation frequency region below 35 Hz using three types of basic excitations: perturbations in the shaft torque, supply voltage and supply frequency. The maximum perturbation frequency for an error less than 10% is used to study the validity range of the models; this range is evaluated for each model and transfer function, using the data of 31 different machines. The influence of the machine parameters and various physical phenomena is studied. The results show that a large number of transfer functions is needed for judging the general validity of a dynamic model.

Journal Article
TL;DR: A survey of the literature on well-posed linear systems can be found in this article, where a simple way to generate conservative systems via a second-order differential equation in a Hilbert space is described.
Abstract: We survey the literature on well-posed linear systems, which has been an area of rapid development in recent years. We examine the particular subclass of conservative systems and its connections to scattering theory. We study some transformations of well-posed systems, namely duality and time-flow inversion, and their effect on the transfer function and the generating operators. We describe a simple way to generate conservative systems via a second-order differential equation in a Hilbert space. We give results about the stability, controllability and observability of such conservative systems and illustrate these with a system modeling a controlled beam.

Journal ArticleDOI
TL;DR: In this paper, the Ornstein-Uhlenbeck neuronal model is investigated under the assumption that the amplitude of the noise is signal dependent, and a linear approximation of the input-output transfer function is developed.

Patent
18 Jun 2001
TL;DR: In this paper, a single frequency relay station receives a signal from a master station, and retransmits it, using a digital filter to subtract from the signal components which arise from multipath interference and coupling interference.
Abstract: A single frequency relay station receives a signal from a master station, and retransmits it. Before retransmitting the signal, the relay station uses a digital filter to subtract from the signal components which arise from multipath interference and coupling interference. The coefficients used by the digital filter are derived from characteristics of the multipath interference and the overall transfer function of the relay station. These are derived by turning off the retransmission, so that the multipath interference can be estimated from the received signal, and commencing the retransmission again, to determine the transfer function. A simplified inverse fast Fourier transform is used to simplify the calculations.

Journal Article
TL;DR: A new method is defined for processing audio signals, with the aim to recreate an audible simulation of the modification imposed on the original signal by a complex system, based on the linear convolution of the "dry" original signal with the impulse response of the system.
Abstract: This work defines a new method for processing audio signals, with the aim to recreate an audible simulation (auralization) of the modification imposed on the original signal by a complex system. The new method is the extension of the classic auralization process based on the linear convolution of the "dry" original signal with the impulse response of the system. The extension allows for the emulation of non-linear systems, characterized in terms of harmonic distortion at several orders. The work first presents the mathematical framework of the proposed implementation, then it is shown how a not linear system can be experimentally characterized by a new measurement method of multiple impulse responses at various harmonic orders, and finally it is shown how these impulse responses can be employed in a multiple convolution process: an experimental demonstration is given of the similarity of the numerically processed sound with the live recording coming from a highly distorting device. INTRODUCTION The traditional auralization process is in common use since some years [1]. The method is usually employed for adding to dry music or speech recordings a set of information related to an acoustic space (and optionally to the sound system installed in it) such as reverberation and frequency response. Usually the system is modeled as a linear, time invariant process, and thus it is completely characterized by its impulse response. Several measurement techniques have been developed for measuring the impulse response of a system [2,3,4] or for predicting it in the case of large rooms [5,6,7], small rooms [8,9] and taking into account the directivity of sources and receivers [10]. Furthermore, efficient implementations are available for realizing the convolution process in frequency domain, for example with the traditional selectand-save algorithm [11], or with partitioned-block frequency filtering methods, pioneered by Soo and Pang [12] for the case of an impulse response subdivided in equally-sized blocks, and further refined by Gardner and McGrath [13,14] with the introduction of the partition of the impulse response in different-size blocks, which allows for very little Input/Output delay. In all those cases, anyway, the two constraints imposed on the system (linearity and time invariance) must be closely respected. In fact, even minor deviations from linearity or time invariance can disrupt completely the measurement of the impulse response [15,16], and even if these problems are circumvented with more advanced measurement techniques [15], the auralization obtained by the linear convolution process cannot represent faithfully the non-linear effects, which instead are often present in real-world systems, and which happen to be subjectively well noticeable. This situation is responsible for the fact that the sounds obtained with the traditional auralization method usually are perceived as slightly unrealistic, artificial, or unnaturally “clean”, due to the complete absence of the “natural” artifacts that are usually present in the real systems. FARINA ET AL. NOT LINEAR CONVOLUTION AES 110 CONVENTION, AMSTERDAM, NETHERLANDS, 2001 MAY 12–15 2 These effects are particularly important when the auralization method is employed for subjective comparison of different electro acoustic reproduction systems, as it is common in the car-audio field of application. The non-linear effects are an important part of the evaluation of the perceived sound quality, and their complete removal causes a harmful bias of the subjective responses. Recently the authors developed a novel measurement method [15], which allows for the complete characterization of the linear and not linear behavior of a complex system with a single measurement. The result of this measurement procedure is a set of impulse responses, the first being the traditional linear response, and the other the responses at several harmonic orders. From these measurement results, all the traditional metrics for describing the distortion of a reproduction system can be derived easily. Here it is proposed to employ this set of impulse responses in a multiple convolution process, capable of reconstructing the complete modification that happens to a signal passing through the complex system. The theory behind the new processing method is briefly recalled, then the results of actual measurement on distorting systems are shown, and finally it is demonstrated (also with audible examples) how the proposed method can accurately reproduce the distortion effects produced by non-linear reproduction systems THEORY The following picture describes the flow diagram of a system obtained by a distorting transducer (memory-less distortion) driving a subsequent linear system with memory: Not-linear system K[x(t)] Noise n(t) input x(t) + output y(t) linear system w(t)⊗h(t) distorted signal w(t) Figure 1. Flow diagram of the complex system Neglecting the noise, the transfer function of this system can be described, in general, by means of a Volterra series expansion: ( ) ( ) ( ) ( ) ( ) ∑ ∑ ∑ −

Journal ArticleDOI
TL;DR: A hybrid method based on the segmentation technique, the finite-element method, and a matrix Lanczos-Pade algorithm for the analysis of microwave circuits is introduced, and the problem of frequency dependence of the matrix of excitation vectors is analytically overcome.
Abstract: A hybrid method based on the segmentation technique, the finite-element method, and a matrix Lanczos-Pade algorithm (SFELP) for the analysis of microwave circuits is introduced in this paper. This method computes symmetric matrix-Pade approximations of a matrix transfer function for any number of inputs and outputs via a Lanczos-type process (SyMPVL) for obtaining the generalized admittance matrix of a microwave circuit on a wide band of frequencies. The formulation that provides the three-dimensional finite-element/segmentation method is suitable for applying the symmetric Pade via Lanczos algorithm, except for the frequency dependence of the matrix of excitation vectors. In this paper, this problem is analytically overcome for the case in which excitation vectors correspond to modes of homogeneous waveguides or transmission lines. The accuracy and efficiency of the proposed method are shown by means of different examples.

Journal ArticleDOI
TL;DR: Results obtained in the identification procedure show that good matching can be obtained with either negative or positive leakage inductance values, and cast some light on the possible physical meaning that circuit parameters may have.
Abstract: This paper presents a novel way to obtain parameters of synchronous-machine equivalent circuits from standstill frequency response data using a hybrid genetic algorithm. The genetic algorithm is capable of finding a global minimum within a search interval of the fitness function used to match the equivalent circuit and the measured machine transfer functions, notwithstanding the initial guess of the identification process. Therefore, methods such as the maximum likelihood estimation technique, could be substantially enhanced. Results obtained in the identification procedure show that good matching can be obtained with either negative or positive leakage inductance values. These results cast some light on the possible physical meaning that circuit parameters may have. Finite-element modeling is used here to determine the transfer functions of a turbine generator. This approach is consistent with the general aim of obviating the requirement of field testing.

Patent
Boris A. Kurchuk1
26 Jan 2001
TL;DR: In this paper, an optoelectronic receiver having a variable transfer function to compensate for operational condition change is described, where a control circuit provides a signal to the tunable filter.
Abstract: An optoelectronic receiver having a variable transfer function to compensate for operational condition change. The receiver comprises a linear circuit having a tunable filter. A control circuit provides a signal to the tunable filter. The control circuit is connected to one or more sensors which sense one or more operational conditions. The control circuit signal is a function of the one or more sensed operational conditions. The control signal is input to the tunable filter which adjusts the linear circuit's transfer function based on the control signal. Further disclosed are an integrated circuit and optical communication system having the inventive optoelectronic receiver. A method for adjusting an optoelectronic signal in a receiver is also disclosed.

Journal ArticleDOI
TL;DR: An efficient noise control algorithm based on the delayless subband adaptive filter that reduces the computational complexity of the delay less subband filter by decomposing the secondary path response into a set of subband functions.
Abstract: In this paper, we present an efficient noise control algorithm based on the delayless subband adaptive filter. The algorithm reduces the computational complexity of the delayless subband filter by decomposing the secondary path response into a set of subband functions. In this new algorithm, the filtered reference signal is generated for each subband by using a short impulse response filter that models the secondary path transfer function in a subband-decomposed form. Computational efficiency of the presented method originates from the fact that the filtering process occurs only in one subband for each reference input sample. Furthermore, computational efficiency is enhanced when the presented algorithm is combined with an online identification of the secondary path transfer function. We also propose a frequency-domain implementation of the presented algorithm. In this implementation, it is shown that the computational complexity is further reduced by employing the block-processing approach.

Journal ArticleDOI
TL;DR: In this article, the Mueller matrix is expressed in terms of fundamental system parameters that describe the voltage transfer functions (known as the Jones matrix) of the various system devices in physical terms and thus provide a means for comparing with engineering calculations and investigating the effects of design changes.
Abstract: Modern digital cross-correlators permit the simultaneous measurement of all four Stokes parameters. However, the results must be calibrated to correct for the polarization transfer function of the receiving system. The transfer function for any device can be expressed by its Mueller matrix. We express the matrix elements in terms of fundamental system parameters that describe the voltage transfer functions (known as the Jones matrix) of the various system devices in physical terms and thus provide a means for comparing with engineering calculations and investigating the effects of design changes. We describe how to determine these parameters with astronomical observations. We illustrate the method by applying it to some of the receivers at the Arecibo Observatory.

Journal ArticleDOI
TL;DR: In this article, a frequency-domain method for distortion analysis of general periodically switched nonlinear circuits is presented, which generalizes Zadeh's time-varying network functions and bifrequency transfer functions from linear time-invariant systems to nonlinear time-variant systems.
Abstract: This paper presents a new frequency-domain method for distortion analysis of general periodically switched nonlinear circuits. It generalizes Zadeh's time-varying network functions and bifrequency transfer functions from linear time-varying systems to nonlinear time-varying systems. The periodicity of time-varying network functions of linear and nonlinear periodically time-varying systems is investigated using time-varying Volterra series. We show that a periodically switched nonlinear circuit can be characterized by a set of coupled periodically switched linear circuits. Distortion of the periodically switched nonlinear circuit is obtained by solving these linear circuits. This result is a generalization of the multi-linear theory known for nonlinear time-invariant circuits. We also show that the aliasing effect encountered in noise analysis of switched analog circuits exists in distortion analysis of periodically switched nonlinear circuits. Computation associated with the folding effect can be minimized by using the adjoint network of periodically switched linear circuits, in particular, the frequency reversal theorem. The method presented in this paper has been implemented in a computer program. Distortion of practical switched circuits is analyzed and the results are compared with SPICE simulation.

Journal ArticleDOI
TL;DR: Based on polynomial s-transfer functions of transient heat conduction through a building construction, a novel and simple model is developed for building thermal load calculation in this article, where the coefficients of the model are independent from time step and the time step can be varied according to the requirement during simulation.

Journal ArticleDOI
TL;DR: In this paper, a new method to estimate magnetotelluric (MT) transfer functions using radio transmitters as the source has been developed using an extended version of Weidelt's C function expansion.
Abstract: A new method to estimate magnetotelluric (MT) transfer functions using radio transmitters as the source has been developed using an extended version of Weidelt’s C function expansion. The expansion coefficients are found from solving a mixed determined linear inverse problem by a truncated singular‐value decomposition technique with a truncation level determined automatically from the data. Synthetic tests with both noise‐free and noisy data show the new method is accurate and robust with respect to lack of transmitters in certain bands. A test profile with 42 stations from a dump‐site investigation in the Netherlands shows that the estimated transfer functions are remarkably stable and smooth as a function of frequency and distance along the profile. Compared with the standard band‐averaging technique, even the formal error bars are generally smaller and more realistic with the new method because the bias introduced by assuming that transfer functions are constant in a small subband is removed.

Book
29 Nov 2001
TL;DR: In this paper, the Popov method was used to prove the stability of two-dimensional control systems with the Watt governor and the theory of stability of motion linear electric circuits transfer functions and frequency responses of linear blocks.
Abstract: The Watt governor and the mathematical theory of stability of motion linear electric circuits transfer functions and frequency responses of linear blocks controllability, observability, stabilization two-dimensional control systems phase portraits discrete systems the Aizerman conjecture the Popov method.

Journal ArticleDOI
TL;DR: In this article, a separable nonlinear least-squares method is proposed for the estimation of the coefficients and poles of Kautz and Laguerre filters, which has similar computational loads but better convergence properties than their corresponding algorithms that solve the unseparated problem.
Abstract: Kautz and Laguerre filters are effective linear regression models that can describe accurately an unknown linear system with a fewer parameters than finite-impulse response (FIR) filters. This is achieved by expanding the transfer functions of the Kautz and Laguerre filters around some a priori knowledge, concerning the dominating time constants or resonant modes of the system to be identified. When the estimation of these filters is based on a minimization of the least-squares error criterion, the minimization problem becomes separable with respect to the linear coefficients. Therefore, the original unseparated problem can be reduced to a separated problem in only the nonlinear poles, which is numerically better conditioned than the original unseparated one. This paper proposed batch and recursive algorithms that are derived using this separable nonlinear least-squares method, for the estimation of the coefficients and poles of Kautz and Laguerre filters. They have similar computational loads, but better convergence properties than their corresponding algorithms that solve the unseparated problem. The performance of the suggested algorithms is compared to alternative batch and recursive algorithms in some system identification examples. Generally, it is shown that the proposed batch and recursive algorithms have better convergence properties than the alternatives.

Journal ArticleDOI
TL;DR: In this article, the torque control of a harmonic drive system for constrained-motion and free-motion applications is examined in detail, and a nominal model for the system is obtainedin each case from experimental frequency responses of the system, and the deviation ofthe system from the model is encapsulated by a multiplicative uncertainty.
Abstract: In this paper, the torque control of a harmonic drive system for constrained-motion andfree-motion applications is examined in detail. A nominal model for the system is obtainedin each case from experimental frequency responses of the system, and the deviation ofthe system from the model is encapsulated by a multiplicative uncertainty. Robust torquecontrollers are designed using this information in an

Journal ArticleDOI
TL;DR: In this article, poles and zeros are defined for continuous-time, linear, time-varying systems, where a zero is a function of time corresponding to an exponential input whose transmission to the output is blocked.
Abstract: Definition of poles and zeros are presented for continuous-time, linear, time-varying systems. For a linear, time-varying state equation, a set of time-varying poles defines a stability-preserving variable change relating the original state equation to an upper triangular state equation. A zero is a function of time corresponding to an exponential input whose transmission to the output is blocked. Both definitions are shown to be generalizations of existing definitions of poles and zeros for linear, time-varying systems and are consistent with the definitions for linear, time-invariant systems. A computation procedure is presented using a QR decomposition of the transition matrix for the state equation. A numerical example is given to illustrate this procedure.

Journal ArticleDOI
TL;DR: An algorithm for estimation of the optimal "system" parameters of time sequences (TSs) computed by the finite-difference time-domain (FDTD) method, with the goal of accurate representation of the time-signature using low-order models.
Abstract: We propose an algorithm for estimation of the optimal "system" parameters of time sequences (TSs) computed by the finite-difference time-domain (FDTD) method, with the goal of accurate representation of the time-signature using low-order models. The FDTD method requires computation of very long time sequences to accurately characterize the slowly decaying transient behavior of resonant structures. Therefore, it becomes critical to investigate methods of reducing the computational time for such objects. Several researchers have argued that the FDTD-TS can be modeled as the impulse response (IR) of an autoregressive moving average (ARMA) transfer function. However, it is known that determination of ARMA parameters by IR matching is a complex nonlinear optimization problem. Hence, many existing methods in EM literature tend to use Prony-based, linear predictor-type spectrum estimation algorithms, which minimize a linearized "equation error" criterion that approximates the true nonlinear model-fitting error criterion. As a result, significantly high model orders are needed by these methods to achieve good corroboration in the frequency domain, especially when a magnitude spectrum has deep nulls or notches. We propose to use a deterministic ARMA approach, which minimizes the true nonlinear criterion iteratively, and attains significantly improved IR fit over Prony's (1795) method using fewer ARMA model parameters. For a given time-sequence of an analyzed circuit, the issues of model order selection and choice of decimation factor are also addressed systematically. The improved performance of the proposed algorithm is demonstrated with transient simulation and signal analysis of microstrip structures which manifest deep nulls in the frequency domain.

Journal ArticleDOI
TL;DR: Numerical results indicate that a reduced-order model with a system matrix of dimension less than 20/spl times/20 can accurately reproduce the broad-band behavior of multiscreen FSSs originally modeled with several hundreds or thousands of unknowns.
Abstract: A method is presented for generating a broad-band rational interpolant approximation of the reflection coefficient of multiple-screen frequency-selective surfaces (FSSs). The technique is structured around a linearization of the system provided by a spectral domain moment method-based analysis of the FSS, followed by a model-order reduction of the linearized system using the dual rational Arnoldi method. This process creates a rational interpolant of the linearized system that matches its transfer function and its derivatives at several expansion points in the Laplace domain. Numerical results indicate that a reduced-order model with a system matrix of dimension less than 20/spl times/20 can accurately reproduce the broad-band behavior of multiscreen FSSs originally modeled with several hundreds or thousands of unknowns.

Journal ArticleDOI
TL;DR: In this article, the Mueller matrix is expressed in terms of fundamental system parameters that describe the voltage transfer functions (known as the Jones matrix) of various system devices in physical terms and thus provide a means for comparing with engineering calculations and investigating the effects of design changes.
Abstract: Modern digital crosscorrelators permit the simultaneous measurement of all four Stokes parameters. However, the results must be calibrated to correct for the polarization transfer function of the receiving system. The transfer function for any device can be expressed by its Mueller matrix. We express the matrix elements in terms of fundamental system parameters that describe the voltage transfer functions (known as the Jones matrix) of the various system devices in physical terms and thus provide a means for comparing with engineering calculations and investigating the effects of design changes. We describe how to determine these parameters with astronomical observations. We illustrate the method by applying it to some of the receivers at the Arecibo Observatory.