Comment on “Method for Real-Time Frequency Response and Uncertainty Estimation”

Tischler, Mark B.; Ivler, Christina M.; Berger, Tom

doi:10.2514/1.g000780

Cited by 14 publications

(12 citation statements)

References 4 publications

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“…To obtain the coherence from the measured outputs, it is required to estimate input and output auto-spectra ( G xx and G yy , respectively) and cross-spectrum G xy (Tischler et al , 2015): where X ( f ) and Y ( f ) are input and output Fourier transforms, respectively, and the symbol † denotes the conjugate complex value. When computing the discrete Fourier transforms for obtaining X ( f ) and Y ( f ), Chirp Z-transform was used, as it allows to select for which frequency points the evaluations are done.…”

Section: Frequency Response Identificationmentioning

confidence: 99%

Spinning gasodynamic projectile system identification experiment design

Lichota

Jacewicz

Szulczyk

2020

AEAT

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Purpose The purpose of this paper is to present the methodology that was used to design a system identification experiment of a generic spinning gasodynamic projectile. For this object, because the high-speed spinning motion, it was not possible to excite the aircraft motion along body axes independently. Moreover, it was not possible to apply simultaneous multi-axes excitations because of the short time in which system identification experiments can be performed (multi-step inputs) or because it is not possible to excite the aircraft with a complex input (multi-sine signals) because of the impulse gasodynamic engines (lateral thrusters) usage. Design/methodology/approach A linear projectile model was used to obtain information about identifiability regions of stability and control derivatives. On this basis various sets of lateral thrusters’ launching sequences, imitating continuous multi-step inputs were used to excite the nonlinear projectile model. Subsequently, the nonlinear model for each excitation set was identified from frequency responses, and the results were assessed. For comparison, the same approach was used for the same projectile exited with aerodynamic controls. Findings It was found possible to design launching sequences of lateral thrusters that imitate continuous multi-step input and allow to obtain accurate system identification results in specified frequency range. Practical implications The designed experiment can be used during polygonal shooting to obtain a true projectile aerodynamic model. Originality/value The paper proposes a novel approach to gasodynamic projectiles system identification and can be easily applied for similar cases.

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Section: Frequency Response Identificationmentioning

confidence: 99%

Spinning gasodynamic projectile system identification experiment design

Lichota

Jacewicz

Szulczyk

2020

AEAT

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“…The recursive discrete Fourier transform has been applied successfully in flight tests and in wind-tunnel tests for real-time dynamic modeling in the frequency domain 5,20,22,[26][27][28][29][30][31][32][33] .…”

Section: F Recursive Discrete Fourier Transformmentioning

confidence: 99%

“…The combination of orthogonal optimized multisines and Eq. (36) has been applied successfully in wind tunnel tests with many inputs and outputs 29 , and in flight tests 27,28,[30][31][32][33] to efficiently compute frequency responses from time series data. This general approach is also the basis of effective methods for real-time frequency response estimation, both in the time domain 27 , and in the frequency domain [28][29][30][31][32][33] .…”

Section: Figure 18 Longitudinal Optimized Multisine Datamentioning

confidence: 99%

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Practical Aspects of the Frequency Domain Approach for Aircraft System Identification

Morelli

Grauer

2018

2018 Atmospheric Flight Mechanics Conference

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Practical aspects of the frequency-domain approach for aircraft system identification are explained and demonstrated. Topics related to experiment design, flight data analysis, and dynamic modeling are included. For demonstration purposes, simulated time series data and simulated flight data from an F-16 nonlinear simulation with realistic noise are used. This approach enables detailed evaluations of the techniques and results, because the true characteristics of the data and aircraft dynamics are known for the simulated data. Analytical techniques and practical considerations are examined for the finite Fourier transform, nonparametric frequency response estimation, parametric modeling in the frequency domain, experiment design for frequency-domain modeling, data analysis and modeling in the frequency domain, and real-time calculations. Flight data from a subscale jet transport aircraft are used to demonstrate some of the techniques and technical issues.

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“…This reply is written in response to a comment [2] on the subject paper, henceforth called the comment, authored by Tischler et al…”

Section: Introductionmentioning

confidence: 99%