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  • 1
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    Practical input optimization for aircraft parameter estimation experiments (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The object of this research was to develop an algorithm for the design of practical, optimal flight test inputs for aircraft parameter estimation experiments. A general, single pass technique was developed which allows global optimization of the flight test input design for parameter estimation using the principles of dynamic programming with the input forms limited to square waves only. Provision was made for practical constraints on the input, including amplitude constraints, control system dynamics, and selected input frequency range exclusions. In addition, the input design was accomplished while imposing output amplitude constraints required by model validity and considerations of safety during the flight test. The algorithm has multiple input design capability, with optional inclusion of a constraint that only one control move at a time, so that a human pilot can implement the inputs. It is shown that the technique can be used to design experiments for estimation of open loop model parameters from closed loop flight test data. The report includes a new formulation of the optimal input design problem, a description of a new approach to the solution, and a summary of the characteristics of the algorithm, followed by three example applications of the new technique which demonstrate the quality and expanded capabilities of the input designs produced by the new technique. In all cases, the new input design approach showed significant improvement over previous input design methods in terms of achievable parameter accuracies.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-191462 , NAS 1.26:191462
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Determining the accuracy of maximum likelihood parameter estimates with colored residuals (1994)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An important part of building high fidelity mathematical models based on measured data is calculating the accuracy associated with statistical estimates of the model parameters. Indeed, without some idea of the accuracy of parameter estimates, the estimates themselves have limited value. In this work, an expression based on theoretical analysis was developed to properly compute parameter accuracy measures for maximum likelihood estimates with colored residuals. This result is important because experience from the analysis of measured data reveals that the residuals from maximum likelihood estimation are almost always colored. The calculations involved can be appended to conventional maximum likelihood estimation algorithms. Simulated data runs were used to show that the parameter accuracy measures computed with this technique accurately reflect the quality of the parameter estimates from maximum likelihood estimation without the need for analysis of the output residuals in the frequency domain or heuristically determined multiplication factors. The result is general, although the application studied here is maximum likelihood estimation of aerodynamic model parameters from flight test data.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: NASA-CR-194893 , NAS 1.26:194893
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Optimal input design for aircraft instrumentation systematic error estimation (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new technique for designing optimal flight test inputs for accurate estimation of instrumentation systematic errors was developed and demonstrated. A simulation model of the F-18 High Angle of Attack Research Vehicle (HARV) aircraft was used to evaluate the effectiveness of the optimal input compared to input recorded during flight test. Instrumentation systematic error parameter estimates and their standard errors were compared. It was found that the optimal input design improved error parameter estimates and their accuracies for a fixed time input design. Pilot acceptability of the optimal input design was demonstrated using a six degree-of-freedom fixed base piloted simulation of the F-18 HARV. The technique described in this work provides a practical, optimal procedure for designing inputs for data compatibility experiments.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 91-2850 , AIAA Atmospheric Flight Mechanics Conference; Aug 12, 1991 - Aug 14, 1991; New Orleans, LA; United States
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Optimal input design for aircraft parameter estimation using dynamic programming principles (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A new technique was developed for designing optimal flight test inputs for aircraft parameter estimation experiments. The principles of dynamic programming were used for the design in the time domain. This approach made it possible to include realistic practical constraints on the input and output variables. A description of the new approach is presented, followed by an example for a multiple input linear model describing the lateral dynamics of a fighter aircraft. The optimal input designs produced by the new technique demonstrated improved quality and expanded capability relative to the conventional multiple input design method.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 90-2801 , AIAA Atmospheric Flight Mechanics Conference; Aug 20, 1990 - Aug 22, 1990; Portland, OR; United States
    Format: text
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  • 5
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    Recent extension driven by mantle upwelling beneath the Admiralty Mountains (East Antarctica) (2008)
    American Geophysical Union
    Details
    Publication Date: 2021-01-27
    Description: Northern Victoria Land is located at the boundary between an extended, presumably hot, region (West Antarctic Rift System) and the thick, possibly cold, East Antarctic craton. The style and timing of Tertiary deformation along with relationships with the magmatic activity are still unclear, and contrasting models have been proposed. We performed structural and morphotectonic analyses at the NE termination of northern Victoria Land in the Admiralty Mountains area, where the relationship between topography, tectonics, and magmatism is expected to be well pronounced. We found evidence of two subsequent episodes of faulting, occurring concurrently with the Neogene McMurdo volcanism. The first episode is associated with dextral transtension, and it is overprinted by extensional tectonics during the emplacement of large shield alkaline volcanoes. Upper mantle seismic tomography shows that the extensional regime is limited to regions overlying a low-velocity anomaly. We interpret this anomaly to be of thermal origin, and have tested the role of largescale upwelling on lithosphere deformation in the area. The results of this integrated analysis suggest that the morphotectonic setting of the region and the magmatism is likely the result of upwelling flow at the boundary between the cold cratonic and the hot stretched province (WARS), at work until recent time in this portion of the northern Victoria Land.
    Description: Published
    Description: TC4015
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: partially_open
    Keywords: Antarctica ; Admiralty Mountains ; Extensional Tectonics ; Mantle Upwelling ; Seismic Tomography ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Recent extension driven by mantle upwelling at craton edge beneath the Admiralty Mountains (Ross Sea, East Antarctica) (2007)
    Details
    Publication Date: 2017-04-04
    Description: Northern Victoria Land is located at the boundary between an extended, presumably hot, region (West Antarctic Rift System, WARS) and the thick, possibly cold East Antarctic craton. The style and timing of Tertiary deformation along with relationships with the magmatic activity are still unclear, and contrasting models have been proposed. We performed structural and morphotectonic analyses at the NE termination of northern Victoria Land in the Admiralty Mountains area, where the relationship between topography, tectonics and magmatism is expected to be well pronounced. We found evidence of two subsequent episodes of faulting, occurring concurrently with the Neogene Mc Murdo volcanism. The first episode is associated with dextral transtension and it is overprinted by extensional tectonics during the emplacement of large shield alkaline volcanoes. Upper mantle seismic tomography shows that the extensional regime is limited to regions overlying a low velocity anomaly. We interpret this anomaly to be of thermal origin, and have tested the role of large-scale upwelling on lithosphere deformation in the area. The results of this integrated analysis suggest that the morphotectonic setting of the region and the magmatism are likely the result of upwelling flow at the boundary between the cold cratonic and the hot stretched province (WARS), at work until recent time in this portion of the northern Victoria Land.
    Description: Programma Nazionale di Ricerca in Antartide (PNRA)
    Description: Submitted
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: open
    Keywords: Antarctica ; Extensional tectonic ; Mantle upwelling ; Seismic Tomography ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: manuscript
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  • 7
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    P-wave propagation heterogeneity and earthquake location in the Mediterranean region (2008)
    Blackwell Publishing Ltd
    Details
    Publication Date: 2012-02-03
    Description: We analyse P-wave traveltimes for the Mediterranean area, using both teleseismic and regional arrivals for shallow earthquakes reported in the Bulletins of the International Seismological Centre. We model delays between pairs of 0.5° × 0.5° cells, obtaining a detailed representation of the P traveltime heterogeneities. Examination of these anomalies shows the clear presence of geographically coherent patterns—consistent with known geological features—due to significant structure in the upper mantle. We present a scheme, based on an empirical heterogeneity correction (EHC) to P-wave traveltimes, to improve earthquake location. This method provides similar benefits to those of a location procedure based on ray tracing in a 3-D model, but it is simpler and computationally more efficient. The definition of the traveltime heterogeneity model, being based on a statistical procedure, bypasses most of the critical points and possible instabilities involved in model inversion. EHC relocation, applied to Mediterranean earthquakes, allows one to predict about 70 per cent of the estimated signal due to heterogeneity and produces epicentral and origin time-shifts of, respectively, 4.22 km and 0.35 s (rms). From a synthetic experiment, in which we use the proposed algorithm to retrieve known source locations, we estimate that the rms improvement achieved by the EHC relocation over a simpler, standard, 1-D location is more than 20 per cent for both epicentral mislocation and origin time-shifts.
    Description: Published
    Description: 232-254
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: earthquake location ; Mediterranean ; P waves ; traveltime ; upper mantle ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    P wave tomography of the mantle under the Alpine-Mediterranean area (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We study the upper mantle P wave velocity structure below the Euro-Mediterranean area, down to 1000 km depth, by seismic travel time tomography. We invert summary residuals constructed with both regional and teleseismic first arrival data reported by the International Seismological Centre (ISC) (1964–1995), introducing some alternative strategies in the travel time tomographic approach and a new scheme to correct teleseismic data for global mantle structure. Our high-resolution model PM0.5 is parameterized with three-dimensional (3-D) linear splines on a grid of nodes with 0.5 spacing in both horizontal directions and 50 km vertical spacing. We obtain about 26% root-mean-square (RMS) reduction of residuals by inversion in addition to roughly 31% reduction after summary rays formation and selection. Sensitivity analyses are performed through several test inversions to explore the resolution characteristics of the model at different spatial scales. The distribution of large-scale fast anomalies suggests that two different stages of a convection process presently coexist in very close regions. The mantle dynamics of western central Europe is dominated by blockage of subducted slabs at the 660 km discontinuity and ponding of seismically fast material in the transition zone. Contrarily, in the eastern Mediterranean, fast velocity material sinks into the lower mantle, suggesting that the flow of the cold downwelling here is not blocked by the 660 km discontinuity. On a smaller scale, the existence of tears in the subducted slab (lithospheric detachment) all along both margins of the Adriatic plate, as proposed by some authors, is not supported by our tomographic images.
    Description: Published
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: travel time ; body wave tomography ; upper mantle ; Europe-Mediterranean area ; Earth structure ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    Subduction and the depth of convection in the Mediterranean mantle (2008)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We tie together geological data, paleotectonic reconstruction, plate motion, and tomographic analysis to unravel the history of subduction and back arc extension of the eastern and central Mediterranean. In these two regions, extensional processes started contemporaneously, around 30 Myr ago, but with marked differences. In the eastern region, the Aegean basin opened slowly ( 1 cm/yr) behind a shallow dipping slab (40–45 ). The corresponding high-velocity anomaly extends inside the upper mantle and can be also followed in the midmantle down to a depth of at least 1500 km. Its descent into the midmantle initiated most probably during the Late Cretaceous, and the trench moved northeastward, following the path of the Eurasian plate and under the persistent push of the African plate. Conversely, in the central Mediterranean region, subduction initiated later, and the motion of the subducting slab is confined to the upper mantle, causing punctuated and rapid episodes of back arc extension (Provenc¸al and Tyrrhenian basins) behind a slab that dips steeply (75 ). We explore the causes that control how the slab subducted and interacted with the lower, more viscous part of the mantle.
    Description: Published
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: subduction ; Mediterranean ; mantle convection ; back-arc extension ; plate motion ; seismic tomography ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Improving Seismic Event Location: An Alternative to Three-dimensional Structural Models (2008)
    Birkhauser Basel
    Details
    Publication Date: 2017-04-04
    Description: We devise and apply a method to account for the effect of the aspherical structure of the Earth in locating earthquakes. This technique relies upon the ability to detect the average structural signal present in the residuals between source and receiver and correct for this signal during location, using a phenomenological description that we call Empirical Heterogeneity Corrections (EHC). EHC are employed in the relocation of a large set of well-constrained teleseismic earthquakes selected among the events reported by the Bulletins of the International Seismological Centre 1964–1995. The rms length of EHC relocation vectors for these events is about 10ukm. The method is also tested against a selected set of ground-truth events, both earthquakes and explosions, whose locations are independently known by nonseismic means. The rms length of the mislocation vectors for the test events, compared to their original mislocation in the reference 1-D model SP6, is reduced in the EHC relocation by 17% for explosions and 12% for earthquakes. Our technique provides a successful alternative to the use of 3-D structural models, approximately reaching the same value of effectiveness in improving event location.
    Description: Published
    Description: 319-347
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquake location ; P waves ; travel time ; teleseismic ; velocity anomaly ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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