Andrea Ferrise

Non Adaptive Second-Order Generalized Integrator for Identification of a Biased Sinusoidal Signal

This note presents a new algorithm that is designed to identify the frequency, magnitude, phase and offset of a biased sinusoidal signal. The structure of the algorithm includes an orthogonal system generator based on a second-order generalized integrator. The proposed strategy has the advantages of a fast and accurate signal reconstruction capability and a good rejection to noise.

A Frequency-Locked-Loop Filter for Biased Multi-Sinusoidal Estimation

In this paper, an adaptive filter, based on a third-order generalized integrator, is proposed to estimate all the parameters of a biased sinusoid. The averaging theory is used to prove that the filter identifies the unknown frequency of the signal, in the case of a pure biased sinusoid in input. Moreover, in the case of a generic periodic signal, the method provides an estimate of the fundamental frequency by converging to a limit cycle in its vicinity. The robustness of the proposed approach with respect to noise in the input signal is analyzed. A filter bank is also presented to deal with the reconstruction problem of a generic multi-sinusoidal signal. Simulation results are also provided to compare the performances of the method with existing ones.

Biased Sinusoidal Disturbance Compensation With Unknown Frequency

This note combines an adaptive frequency estimation scheme with a fractional-order controller for unknown biased sinusoidal disturbance rejection. The disturbance is estimated via an adaptive orthogonal signals generator based on a third-order generalized integrator. A fractional-order controller is designed which guarantees the closed-loop stability of the system if the location of the plant frequency response, at the estimated frequencies, lies in an half-plane passing through the origin of the complex plane.

Multi-Sinusoidal Signal Estimation by an Adaptive SOGI-Filters Bank

Abstract In this paper, a new method for frequency, amplitude and phase estimation of a multi-harmonic signal is proposed. The approach described herein uses an orthogonal signals generator based on a Second-Order Generalized Integrator (SOGI). The method is implemented as a dynamic third-order system, for each sinusoidal component, and has significant advantages over prior methods since it allows an on-line estimation of all unknown signal parameters. An adaptive tuning algorithm of the SOGI resonant frequency is shown in both cases of single-sinusoidal or multi-sinusoidal signal. The effectiveness of the proposed algorithm is demonstrated through simulated experiments and comparisons with existing methods.

LCDiXRay: a user-friendly program for powder diffraction indexing of columnar liquid crystals

The formulation of a standard computerized procedure for the indexing of powder X-ray diffraction (PXRD) patterns of columnar liquid crystals, with the determination of all structural information extracted from a properly indexed PXRD spectrum and the attribution of the columnar mesophase symmetry, is presented. In particular, the proposed program notably accelerates the identification of columnar mesophases together with the in situ determination of their structural parameters such as mesophase type, space group, cell parameters, cross-section area, intermolecular stacking distance between consecutive discoids and, in the case of ordered mesophases, the estimation of the number of molecules constituting each discoid.

An adaptive quasi-notch filter for a biased sinusoidal signal estimation

This note presents an alternative approach to classical adaptive notch filters designed to identify the frequency, magnitude, phase and offset of a biased sinusoidal signal. The algorithm takes advantages of an adaptive law for the resonant frequency of a third-order generalized integrator as a part of an orthogonal-signals generator system. The resulting estimator presents a dynamic order equal to 4. The strength of the discussed strategy results in a fast and accurate signal tracking capability and a good rejection to noise. The properties of the algorithm are verified in simulations in a range of signal conditions, such as step and sweep changes in frequency and voltage sag confirming the effectiveness of the strategy for estimation and tracking of time-varying parameters.

Periodic disturbance rejection with unknown frequency and unknown plant structure

Abstract This paper deals with asymptotic rejection of a multi-sinusoidal signal for linear single-input single-output stable systems with unknown structure. An adaptive orthogonal signals generator is used to both reconstruct the disturbance and cancel its effect on the system output. An interesting feature is that the disturbance is removed by the generated internal signals with no additional dynamics in the cancellation algorithm. A fractional-order controller is designed which guarantees the closed-loop stability of the system if the location of the plant frequency response at the estimated frequencies lies in a half-plane passing through the origin of the complex plane, i.e. no information about the order of the system to be controlled, the relative degree, the nature of its poles and zeros, is required. The case of multi-sinusoidal disturbance is also analyzed. Simulations and comparisons with existing approaches are presented that highlight the performances of the proposed method.

Periodic disturbance rejection for fractional-order dynamical systems

Abstract This paper proposes a simple fractional-order derivative controller, based on an adaptive orthogonal signals generator, which permits both to reconstruct an unknown multi-sinusoidal disturbance and cancel its effect on the system output. An interesting feature is that the disturbance is removed by the generated internal signals with no additional dynamics in the cancellation algorithm. An opportune choice of the fractional-order controller guarantees the closed-loop stability of the system if the location of the plant frequency response at the estimated frequencies belongs to a halfplane passing through the origin of the complex plane, i.e. no information about the order of the system to be controlled, the relative degree, the nature of its poles and zeros, is required. The case of multi-sinusoidal disturbance is also analyzed. Simulations are presented that highlight the performances of the proposed method.

Biased sinusoidal disturbance rejection with plant uncertainty via an adaptive third-order generalized integrator

In this paper a method to reject periodic biased disturbances of unknown frequency is presented. The entire set of unknown disturbance parameters is estimated via a third-order generalized integrator (TOGI). An interesting property of the method is that internal signals of TOGI are combined linearly to produce the control signal, resulting in a very simple algorithm. Only a single adaptive parameter permits to govern the system. It is shown that, within the assumptions of an averaging analysis, the adaptive system is stable and completely rejects the disturbance, even if a rough estimation of the plant is available. Bounds on the uncertainty of the plant are given in terms of the bounds on the input disturbance. Simulations demonstrate the properties of the algorithm in a variety of conditions.

Structural properties of the SOGI system for parameters estimation of a biased sinusoid

In this paper, a real-time method, based on the Second Order Generalized Integrator (SOGI), is presented to estimate amplitude, frequency, phase and offset of a biased sinusoidal signal. The estimation is performed by simple straightforward explicit formulas involving the unknown signal and output signals measurements of the SOGI system. Numerical experiments are shown that confirm the strength of the method in a wide range of signal conditions, such as step and sweep changes in frequency.