A Ladder-Lattice identification algorithm with shift-invariant directional (SID) parameter tracking technique is derived for the fast recursive least-squares (FRLS) identification applications. The method employs forg...
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A Ladder-Lattice identification algorithm with shift-invariant directional (SID) parameter tracking technique is derived for the fast recursive least-squares (FRLS) identification applications. The method employs forgetting with different weights on the (by latest data) modified and the unmodified part of the minimized quadratic form. The technique is implemented on a Ladder-Lattice computing structure with only small increase of complexity in comparison to the standard Ladder-Lattice structures. The parameter tracking rate and the numerical robustness with respect to insufficiently exciting data are considerably improved.
This paper provides empirical evidence on the cross-sectional and timeseries variation for the pricing of contracts that swap fixed-for floating-rate interest payments in eight international markets. Swap spreads defi...
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This paper provides empirical evidence on the cross-sectional and timeseries variation for the pricing of contracts that swap fixed-for floating-rate interest payments in eight international markets. Swap spreads defined as the difference between the fixed swap rate and the yield of a risk-free security of equal maturity are analyzed across markets. A framework, which allows to assess the ability of asymmetric default risk to generate observed spreads, is introduced and used to simulate default risk-adjusted swap rates. For typical yield curve and default conditions asymmetric default risk cannot generate positive swap spreads of the magnitude found in the data. These results are unchanged when incorporating expected or realized LIBOR spreads in the analysis.
The pH control problem in a continuous stirred tank reactor is studied from both atheoretical and application point of view. A reaction invariant model for an acid-base system, which is one of the most complete descri...
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The pH control problem in a continuous stirred tank reactor is studied from both atheoretical and application point of view. A reaction invariant model for an acid-base system, which is one of the most complete descriptions for the pH control problem, is utilized. The new controller obtained for the pH control problem is based on a linearization technique and requires that some steady-state experilnents be carried out on the process, before a controller implementation can be achieved. The proposed controller has been applied toa 6th order nonlinear simulation model of a pH process for the case of:(i) time-varying input feed pH concentrations and buffer concentrations,(ii) set-point reference input changes for the desired pH output. Based on the results of these simulations, the controller appears to be quite effective;in particular it gives significant improvements in the response compared to existing controllers proposed in the literature
We propose a recursive generalized total least-squares (RGTLS) estimator that is used in parallel with a noise covariance estimator (NCE) to solve the errors-in-variables problem for multi-input-single-output linear s...
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We propose a recursive generalized total least-squares (RGTLS) estimator that is used in parallel with a noise covariance estimator (NCE) to solve the errors-in-variables problem for multi-input-single-output linear systems with unknown noise covariance matrix. Simulation experiments show that the suggested RGTLS with NCE procedure outperforms the common recursive least squares (RLS) and recursive total instrumental variables (RTIV) estimators when all measured inputs and the measured output are noisy. Moreover, when all measured inputs are noise-free, RGTLS with NCE performs similarly to RLS, which in this special case is the optimal estimator, and again RTIV was inferior compared with the RGTLS and NCE procedure.
This paper presents a scaled system identification method for medical application in the fields of noninvasive nerve stimulation and neurological disease treatment. The recursive Least Squares (RLS) method with an imp...
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This paper presents a scaled system identification method for medical application in the fields of noninvasive nerve stimulation and neurological disease treatment. The recursive Least Squares (RLS) method with an implemented forgetting factor was used to estimate parameters, including inductance, within the nano range of a linear model, using input-output scaling factors. To estimate the parameters in the nano range, the input signal must have a very high frequency, which subsequently requires a very high sampling rate, and therefore expensive hardware and precise programming. In contrast, this technique allows for a lower sampling rate and an input signal with low frequency to identify the parameters characterizing the linear model, without requiring additional hardware for the estimation process. This method was used to provide a scaled identification bandwidth together with a reduced sampling rate to use a Transcutaneous Electrical Nerve Stimulation signal (TENS) by themself for the identification process. In addition, the proposed method identified the inductance of the conductive textile system, the most critical parameter to be estimated. The measured results indicated that the proposed RLS method along with a forgetting factor was an effective and robust method for estimating the parameters.
Indirect recursive identification algorithms have been suggested for robust control design in the literature. The purpose of this contribution is to clarify that such algorithms need proper calculation of the update d...
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Indirect recursive identification algorithms have been suggested for robust control design in the literature. The purpose of this contribution is to clarify that such algorithms need proper calculation of the update direction in undermodeled situations. An indirect pseudolinear regression is compared to a (more suitable) indirect recursive prediction-error method. Their asymptotic properties are examined through simulations, using a specific control structure.
This paper presents a new change detection method with the aid of subspace identification. The proposed method is based on monitoring a change in variance of a statistic generated by a recursive subspace identificatio...
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This paper presents a new change detection method with the aid of subspace identification. The proposed method is based on monitoring a change in variance of a statistic generated by a recursive subspace identification algorithm. An asymptotic property of the statistic is presented. Without changes during sampling, it is shown that, under relevant assumptions. the statistic converges in probability to a stack of noise vectors multiplied from the left side by a Toeplitz matrix. A numerical example illustrates that the proposed method can detect changes in the dynamics of a system, without being disturbed by changes in the dynamics of an input signal which are not our concern.
This paper proposes a fast moving window algorithm for QR and Cholesky decompositions by simultaneously applying data updating and downdating. The developed procedure is based on inner products and entails a similar d...
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This paper proposes a fast moving window algorithm for QR and Cholesky decompositions by simultaneously applying data updating and downdating. The developed procedure is based on inner products and entails a similar downdating to that of the Chambers’ approach. For adding and deleting one row of data from the original matrix, a detailed analysis shows that the proposed algorithm outperforms existing ones in terms or computational efficiency, if the number of columns exceeds 7. For a large number of columns, the proposed algorithm is numerically superior compared to the traditional sequential technique.
The “Leave-out Sign-dominant Correlation Regions” (LSCR) algorithm is extended to deliver a guaranteed confidence set for the parameters of a time-varying system at any given time. The algorithm is derived by assumi...
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The “Leave-out Sign-dominant Correlation Regions” (LSCR) algorithm is extended to deliver a guaranteed confidence set for the parameters of a time-varying system at any given time. The algorithm is derived by assuming that an upper bound on the parameter variation is available, and the delivered confidence set is valid without any prior knowledge of the noise. Simulation examples are provided to illustrate the performance of the algorithm.
Linearization of nonlinear systems is a very important topic in many practical applications. The linearization scheme of Gao and Snelgrove (1990) for weakly nonlinear Volterra systems using adaptive linear and nonline...
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Linearization of nonlinear systems is a very important topic in many practical applications. The linearization scheme of Gao and Snelgrove (1990) for weakly nonlinear Volterra systems using adaptive linear and nonlinear FIR filters is considered in this paper. The coefficients of these filters can be indirectly estimated using the Least Mean Squares (LMS) and recursive Prediction Error Method (RPEM) algorithms as done in Gan and Abd-Elrady (2008b). In this paper, these coefficients are directly estimated using the Nonlinear Filtered-x Least Mean Squares (NFxLMS) algorithm and the Spectral Magnitude Matching (SMM) method. Simulation study shows that the suggested direct approaches can significantly suppress spectral regrowth and reduce nonlinear distortion as well as the indirect approach.
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