Showing papers on "Transfer function published in 1974"
01 Aug 1974
TL;DR: Analytical modeling of communication receivers to account for their nonlinear response to multiple input signals is discussed, based on the application of the Wiener-Volterra analysis of nonlinear functionals.
Abstract: Analytical modeling of communication receivers to account for their nonlinear response to multiple input signals is discussed. The method is based on the application of the Wiener-Volterra analysis of nonlinear functionals. The derived analytical relations were embodied in a computer program which provides nonlinear transfer functions of large circuits specified by their parameters. This method was applied to the prediction of behavior of communication receivers in the presence of interference. Examples illustrate the method and demonstrate its validity in the small-signal region.
425 citations
TL;DR: In this article, the authors investigated the use of the nonlinear device known as the Clegg integrator in the design of a nonlinear feedback system, which minimizes the effect of white sensor noise on the input to the plant.
Abstract: The problem considered is the design of a feedback system containing a linear, time invariant, minimum phase plant, whose parameters are known only within given bounds, such that the time response of the system remains within specified limits. A quasi-optimal design, for given design constraints, is one which minimizes the effect of white sensor noise on the input to the plant. An investigation was conducted on the use of the non linear device known as the Clegg integrator in the design of such a system. The describing function of the Clegg integrator has the same magnitude characteristic, apart from a scale factor, as the linear integrator, but has 52 deg less phase-lag, at all frequencies, than the linear integrator; thus, when used in a feedback system, it provides a larger stability margin than the linear integrator. This property allows the nonlinear feedback system to be designed so that the sensor noise is attenuated more than in the linear design.
182 citations
TL;DR: In this article, a method for modal damping determination, based on the principle of transfer function matching at the natural frequencies of the interaction system, is presented. But this method is physically realistic and consistent, and is shown to be adequate for engineering purposes.
Abstract: Normal mode analysis for soil-structure interaction is an approximation. Its adequacy depends largely on the technique used to determine the overall modal damping values. A method is presented herein for the modal damping determination, based on the principle of transfer function matching at the natural frequencies of the interaction system. This method is physically realistic and consistent, and is shown to be adequate for engineering purposes.
63 citations
TL;DR: In this paper, the problem of making the transfer function between disturbances and controlled outputs identically zero by using state feedback, feedforward control and dynamic compensation in linear timo invariant system is treated and a constructive solve ability condition is presented.
Abstract: The problem of making the transfer function between disturbances and controlled outputs identically zero by using state feedback, feedforward control and dynamic compensation in u linear timo invariant system is treated and a constructive solve ability condition is presented.
61 citations
TL;DR: In this article, principal component analysis in the frequency domain is used to replace the input/output variables by some function of smaller dimensions without much "loss of information" and the analogy between the "factor analysis" of time series in frequency domain and the minimal realization of state space models is pointed out.
Abstract: The identification of a multivariable stochastic system, usually, involves the estimation of a transfer function matrix, which is a general function of frequency. This estimation involves inversion of a large Hermitian matrix, which sometimes may become unwieldly. In this paper we describe how "principal component analysis" in the frequency domain may be used to replace the input/output variables by some function of smaller dimensions without much "loss of information." The analogy between the "factor analysis" of time series in frequency domain and the minimal realization of state space models is pointed out. The principal component approach described in this paper is applied in the case of a simulated system.
59 citations
TL;DR: An estimate of the number of active motor unitsN contributing to the myoelectric signal is obtained under the assumption that the individual motor-unit trains are statistically independent.
Abstract: A myoelectric signal, under isometric contraction of the muscle, is modelled as the output of a linear time-invariant system whose input is a stationary Poisson pulse train. The mean frequency γ of the Poisson pulse train and the transfer function of the linear system are evaluated using the spectral properties of the signal. An estimate of the number of active motor unitsN contributing to the myoelectric signal is obtained under the assumption that the individual motor-unit trains are statistically independent. The variation of γ andN with respect to load levels and electrode positions is examined experimentally.
47 citations
01 Jan 1974
TL;DR: In this article, a technique for identifying the modal properties of an elastic structure in a testing laboratory is presented, which is based upon the use of digital processing and the fast Fourier transform (FFT) to obtain transfer function data, and then use of a least squared error estimator t o identify modality properties from the transfer function.
Abstract: A technique for identifying the modal properties of an elastic structure in a testing laboratory is presented. The technique is based upon the use of digital processing and the fast Fourier transform (FFT) to obtain transfer function data, and then the use of a least squared error estimator t o identify modal properties from the transfer function data. Both analytical and experimental results are presented.
47 citations
Patent•
29 Jul 1974
TL;DR: In this paper, a system for determining the transfer function of a specimen from an input or driving signal and an output or response signal is proposed, where the driving and response signals are each divided into segments or frames of data, each frame of equal duration and a sum is formed for each frame.
Abstract: A system for determining the transfer function of a specimen from an input or driving signal and an output or response signal The driving signal and response signal are each divided into segments or frames of data, each frame of equal duration and a sum is formed for each frame of data A time-domain to frequency-domain transform is taken of the two sums; the transfer function is then determined from the transformed data
46 citations
TL;DR: This paper presents a new method for approximating a higher-order linear system transfer function by a lower-order model based on the requirement that the frequency response of the simplified model is to be matched with the frequencyresponse of the original system.
Abstract: This paper presents ft method for approximating a higher-order linear system transfer function by a lower-order model. The method is based on the requirement that the frequency response of the simplified model is to be matched with the frequency response of the original system. The frequency response matching is required in using simplified models for the analysis of nonlinear control systems. The reported new method is illustrated by means of a numerical example. A critical comparison of this method with other existing methods of model simplification is also presented.
42 citations
TL;DR: In this article, a classification of non-rational transfer functions based on the character of their singularities is proposed, which has important implications for the problem of finite dimensional approximations of infinite dimensional systems.
Abstract: Distributed effects are present in almost all physical systems. In some cases these can be safely ignored but there are many interesting problems where these effects must be taken into account. Most infinite dimensional systems which are important in control theory are specifiable in terms of a finite number of parameters and hence are, in principle, amenable to identification. The state-space theory of infinite dimensional systems has advanced greatly in the last few years and is now at a point where real applications can be contemplated. The realizability criteria provided by this work can be employed effectively in the first step of the identification procedure, i.e., in the selection of an appropriate infinite dimensional model. We show that there exists a natural classification of nonrational transfer functions, which is based on the character of their singularities. This classification has important implications for the problem of finite dimensional approximations of infinite dimensional systems. In addition, it reveals the class of transfer functions for which there exist models with spectral properties closely reflecting the properties of the singularities of the transfer functions. The study of models with infinitesimal generators having a connected resolvent sheds light on some open problems in classical frequency response methods. Finally, the methods used here allow one to see the finite dimensional theory itself more clearly as the result of placing it in the context of a larger theory.
41 citations
TL;DR: In this article, the power spectral effects of spline interpolators of all orders were investigated, and a general technique was given for finding the steady-state spectral effect of splines, when applied following uniform sampling of the input function.
Abstract: This paper discusses the power spectral effects of spline interpolators. A general technique is given for finding the steady-state spectral effects of splines of all orders, when applied following uniform sampling of the input function. The following observations are made: 1) the even order splines that were examined (second and fourth order) possessed divergent steady-state frequency transfer functions, 2) the degree of preservation of the power spectral density of the input process increased with the order of the (odd order) spline used for interpolation, and 3) the reconstruction of a stationary random process over a finite record length will, on the average, have less power than indicated by the steady-state transfer function.
01 Jan 1974
TL;DR: In this paper, the theory of complex mode shapes for damped oscillatory mechanical systems is explained, using the matrix of transfer functions in the Laplace domain, defined to be the solutions to the homogeneous system equation.
Abstract: The theory of complex mode shapes for damped oscillatory mechanical systems is explained, using the matrix of transfer functions in the Laplace domain. These mode shapes are defined to be the solutions to the homogeneous system equation. It is shown that a complete transfer matrix can be constructed once one row or column of it has been measured, and hence that mass, stiffness, and damping matrices corresponding to a lumped equivalent model of the tested structure can also be obtained from the measured data.
TL;DR: The numerical Laplace transform converts an experimental chromatogram into sets of discrete quantities, which enables statistical moments of the chromatograms to be calculated more accurately than with previous methods.
TL;DR: In this paper, a dynamic linearized model and the associated equivalent circuit for a controlled current induction motor are presented and the controlled variables of interest are identified and open-loop transfer functions are tabulated.
TL;DR: In this paper, a quantitative synthesis theory is presented for the self-Oscillating-Adaptive-System (SOAS), whose nonlinear element has a static, odd character with hard saturation.
TL;DR: In this paper, the numerator polynomials found in the Smith McMillan Form of the transfer function of a system are characterized, and the Smith-McMillan form is characterized.
Abstract: : The numerator polynomials found in the Smith McMillan Form of the transfer function of a system are characterized.
TL;DR: In this article, the authors presented a method of obtaining an analytical expression for the transfer function of a system in the form of a ratio of two polynomials of the complex variable, 8, from the frequency response-data.
Abstract: This article presents a method of obtaining an analytical expression for the transfer function of a system in the form of a ratio of two polynomials of the complex variable, 8, from the frequency response- data. The method alleviates the deficiencies of some of the other methods previously reported in the literature. First, it guarantees that the denominator polynomial, when factorized, would not have right-half plane poles and, second, there is no need to know the degrees of the numerator and denominator polynomials, a priori. By systematically examining the time response of the synthesized transfer function, say to a unit step function, the method guarantees that the form and the coefficient values of the transfer function which is finally arrived at do give the best fit to the frequency response data. The minimum mean square error criterion is used to judge the goodness of fit.
01 Nov 1974
TL;DR: In this article, the steady state response to a sinusoidal input has been used for the identification of linear systems, and the authors consider this approach to identify nonlinear systems shown in Figure I.
Abstract: Measurement of the steady state response to a sinusoidal input has long been an important technique for the identification of linear systems. In this paper we consider this approach to identification for the class of nonlinear systems shown in Figure I.
TL;DR: In this article, a frequency-variation method is established for identifying a linear system transfer function from a single set of frequency response data, which generally applies three different Cauer continued fraction forms.
Abstract: A frequency-variation method is established for identifying a linear system transfer function from a single set of frequency response data. The method generally applies three different Cauer continued fraction forms. Based on the real and imaginary parts of the frequency response data, a corresponding transfer function can be identified. The identification processes can be carried out with a digital computer.
TL;DR: Using integrated squared error as a fidelity criterion with the magnitude of the filter transfer function subject to a constraint, the optimum spatial filter is developed.
Abstract: Fourier-transform division filters are discussed. Using integrated squared error as a fidelity criterion with the magnitude of the filter transfer function subject to a constraint, the optimum spatial filter is developed. By consideration of the problem of image transformation, various methods for improving image reconstruction by altering image phase are discussed. The input-image phase and the desired output-image phase may be chosen to improve the performance of the filtering system. The problem is to shape the spectra of the input and the desired output. An algorithm, previously used for computing kinoforms, effectively determines an image phase that significantly improves the image reconstructed from the spatial filters.
TL;DR: In this paper, a rigorous mathematical dynamic model is developed to describe both the small and the large signal response of the system, and a discrete model that takes into account the commutation angle is presented.
Abstract: Controlled rectifiers are often incorporated in closed-loop systems. To determine the small signal performance of such systems the rectifier must be appropriately modelled. The paper reviews the existing models and compares their step response performance, Nyquist plots and stability boundaries. It is shown that a recently developed discrete model that takes into account the commutation angle is in good agreement with experimental results. The rectifier transfer function is obtained and the large signal non-linear behaviour discussed. A rigorous mathematical dynamic model developed is capable of describing both the small and the large signal response of the system.
TL;DR: In this article, three new canonic realizations of a digital filter transfer function using the continued-fractionexpansion techniques were derived, and three new realizations were used to derive new transfer functions.
Abstract: Three new canonic realizations of a digital-filter transfer function using the continued-fraction-expansion techniques are derived.
01 Feb 1974
TL;DR: In this paper, the frequency transfer function (ARTF) of an autoregressive scheme of suitable order m is estimated by means of an ARTFACT estimator, which is an Autogressive Transfer Function Approximator Converging to the Truth.
Abstract: : Given a sample Y(t), t = 1,2,...,T of a (zero mean stationary) time series, can one speak of the modeling problem. Using prediction k-steps ahead (for k = 1,...,h, a specified horizon), as the aim, the time series' modeling problem will be defined as determining the (infinite autoregressive) filter transforming the data to white noise. A finite parameter scheme is then an approximate model rather than a true model. A procedure will be described for optimally estimating the frequency transfer function (ARTF) of this filter by means of the frequency transfer function (ARTFACT) of an autogressive scheme of suitable order m. The author calls the estimator an ARTFACT since it is an Autogressive Transfer Function Approximator Converging to the Truth. In effect, a solution is offered to the problem of determining the order of finite parameter ARMA models to be fitted to stationary time series data. (Author)
TL;DR: In this paper, the theoretical background for extending the dynamic stability limit is presented, where the transfer function of a synchronous machine, connected to an infinite bus through reactance, reveals important characteristics of the machine when operating at large torque angles.
Abstract: The theoretical background for a new method of extending the dynamic stability limit is presented in this paper. Analysis of the transfer function of a synchronous machine, connected to an infinite bus through a reactance, reveals important characteristics of the machine when it is operating at large torque angles.
TL;DR: In this paper, an efficient numerical procedure is presented for calculation of the transfer function corresponding to a state-space description, which can be used to calculate transfer functions in any state space description.
Abstract: An efficient numerical procedure is presented for calculation of the transfer function corresponding to a state-space description.
TL;DR: The transfer function of the human ear in a free sound field is measured by an impulse response technique that eliminates disturbing responses in time and frequency domain caused by loudspeaker, probe microphone, and surrounding objects.
Abstract: The transfer function of the human ear in a free sound field is measured by an impulse response technique. The impulse response of the system is determined and the frequency response is computed with aid of a digital computer. Disturbing responses in time and frequency domain caused by loudspeaker, probe microphone, and surrounding objects are eliminated.
TL;DR: In this paper, the authors show how the sampled output of a dyadic-invariant linear system with a given sequency-domain transfer function, in response to a sampled input, can be determined by a term-wise multiplication of the sampled transfer function and the discrete Walsh transform of the input function, followed by an inverse Walsh transform, or a discrete dyadic convolution of the impulse response and the sampled input directly in the time domain.
Abstract: This short paper shows how the sampled output of a dyadic-invariant linear system with a given sequency-domain transfer function, in response to a sampled input, can be determined by 1) a term-wise multiplication of the sampled transfer function and the discrete Walsh transform of the sampled input function, followed by an inverse Walsh transform, or 2) a discrete dyadic convolution of the sampled impulse response and the sampled input directly in the time domain. Functions in both time and sequency domains are represented by column matrices, and discrete Walsh transformation is effected simply by the multiplication with a Walsh matrix. An example is included to illustrate both procedures. The validity of the solutions is further verified by showing that the governing dyadic differential equation of the system is satisfied.
TL;DR: In this paper, a unified treatment of many problems in digital pulse recording is presented, characterized by a reciprocal-space transfer function, which may be abstracted from published studies of sine wave recording.
Abstract: In this paper we present a unified treatment of many problems in digital pulse recording. The physics appropriate to each problem is characterized by a reciprocal-space transfer function, which may be abstracted from published studies of sine wave recording. Over twenty-five transfer functions are given in appendices. Given the transfer functions, an inverse Fourier transformation completes each problem. The fields, fluxes, and output voltage due to an arctangent magnetization profile in a tape of unit permeability are derived. A closely related case, that of a linear ramp magnetization, is treated briefly. A step function magnetization is considered for a tape of nonunit permeability in which, dependent upon the boundary conditions, demagnetization and remagnetization occur. Extensions of the theory of multitransition waveforms are undertaken, yielding the spectra of both regular and random sequences.