SEARCH · Search NASA

Results for “System Identification”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21

All sources NASA NTRS DOE OSTI

NASA NTRS1976

Specification of inputs and instrumentation for flutter testing of multivariable systems

The application of system identification methods in flutter testing of aeroelastic structure is discussed. The accuracy with which flutter parameters are estimated depends upon the test plan and on the algorithms used to reduce the data. The techniques for selecting the kinds and optimal positions of inputs and instrumentation, under typical test constraints, are presented. Identification results for both the input/output transfer function and the value of physical parameters are given. Numerical results on the optimal input spectrum and the accelerometer location for estimating flutter parameters of a two dimensional wing are obtained using these algorithms. Current work on applying system identification methods to high order three dimensional aeroelastic structures is reported.

Gupta, N. K.↗

NASA NTRS1997

High Accuracy Evaluation of the Finite Fourier Transform Using Sampled Data

Many system identification and signal processing procedures can be done advantageously in the frequency domain. A required preliminary step for this approach is the transformation of sampled time domain data into the frequency domain. The analytical tool used for this transformation is the finite Fourier transform. Inaccuracy in the transformation can degrade system identification and signal processing results. This work presents a method for evaluating the finite Fourier transform using cubic interpolation of sampled time domain data for high accuracy, and the chirp Zeta-transform for arbitrary frequency resolution. The accuracy of the technique is demonstrated in example cases where the transformation can be evaluated analytically. Arbitrary frequency resolution is shown to be important for capturing details of the data in the frequency domain. The technique is demonstrated using flight test data from a longitudinal maneuver of the F-18 High Alpha Research Vehicle.

Morelli, Eugene A.↗

NASA NTRS2018

Tracking Components

This poster outlines the findings during a 10-week, full-time summer internship at NASA’s Stennis Space Center (SSC) in Mississippi. As an intern with RA10, the Project Management Division of Center Operations Directorate, I contributed to tasks related to the advancement of systems and operations across SSC. My main priority was to optimize the transportation process of work order kits delivered from the Michoud Assembly Facility (MAF) in New Orleans, Louisiana. An example work order kit would include instructions and materials to complete the replacement of a broken light switch. Unfortunately, kits that arrive at SSC often contain incorrect parts, which results in returning to MAF to get the necessary parts. Integrating a wireless tracking and identification system could improve this way of operating by providing a parts lists and kit location. This idea of using wireless technology will essentially cut costs, time and effort. The main objective for this summer is to develop options for affordable tracking and identification systems that can be used across the agency.

Meredith, Shelby↗

DOE OSTI2024

Advanced Sensor Deployment for Distribution System State Estimation and Fault Identification

Distribution systems are currently facing steep operational challenges as a result of the rapidly increasing integration of renewables and other distributed energy resources (DERs) at both the primary and secondary circuit levels. Distribution utilities and system operators have traditionally had some visibility of their primary circuits using low-frequency supervisory control and data acquisition systems, and they have had very poor if not zero visibility of the secondary circuits where the presence of DERs is constantly increasing. Therefore, this paper presents simulation studies to demonstrate the benefits of an advanced, high-fidelity sensor technology, called as the Meta-Alert System (MAS), developed by Electrical Grid Monitoring, Ltd. (EGM), on the distribution grid. First, a reliable model of the EGM sensors is developed, and then two use cases, distribution system state estimation (DSSE) and fault identification are simulated to evaluate the performance of the MAS technology. Simulation results on the Electric Power Research Institute J1 feeder demonstrate that the MAS can effectively participate in system-level DSSE programs and can detect and locate faults faster than traditional distribution protection schemes.

distribution system↗

NASA NTRS1988

Orbiter Flying Qualities (OFQ) Workstation user's guide

This project was devoted to the development of a software package, called the Orbiter Flying Qualities (OFQ) Workstation, for working with the OFQ Archives which are specially selected sets of space shuttle entry flight data relevant to flight control and flying qualities. The basic approach to creation of the workstation software was to federate and extend commercial software products to create a low cost package that operates on personal computers. Provision was made to link the workstation to large computers, but the OFQ Archive files were also converted to personal computer diskettes and can be stored on workstation hard disk drives. The primary element of the workstation developed in the project is the Interactive Data Handler (IDH) which allows the user to select data subsets from the archives and pass them to specialized analysis programs. The IDH was developed as an application in a relational database management system product. The specialized analysis programs linked to the workstation include a spreadsheet program, FREDA for spectral analysis, MFP for frequency domain system identification, and NIPIP for pilot-vehicle system parameter identification. The workstation also includes capability for ensemble analysis over groups of missions.

Myers, Thomas T.↗

NASA NTRS1972

Bounded state space

This investigation is divided functionally into three different areas: (1) study of bounded state space, (2) nonlinear smoothing theory, and (3) system identification. (1) Study of bounded state space: necessary and sufficient conditions for an optimal control are obtained for a bounded state space optimal control problem. The difficulty of determining the so-called jump conditions is eliminated; however, the problem of determining the points where the response either enters or leaves the boundary still remains unsolved. (2) Nonlinear smoothing theory: nonlinear fixed-interval, fixed-point and fixed-lag smoothing of a random signal generated by a stochastic differential equation are investigated. Results on the asymptotic stability of a linear constant-parameter fixed-interval smoothing filter are obtained. (3) System identification: a particular stochastic modelling problem is solved. An Ito stochastic integral equation is used to mathematically model a black box having multiple inputs and multiple outputs. A new method for identifying system parameters is presented.

Eyman, E. D.↗

NASA NTRS1988

Extension and validation of a method for locating damaged members in large space trusses

The damage location approach employs the control system capabilities for the structure to test the structure and measure the dynamic response. The measurements are then used in a system identification algorithm to produce a model of the damaged structure. The model is compared to one for the undamaged structure to find regions of reduced stiffness which indicate the location of damage. Kabe's 3,4 stiffness matrix adjustment method was the central identification algorithm. The strength of his method is that, with minimal data, it preserves the representation of the physical connectivity of the structure in the resulting model of the damaged truss. However, extensive storage and computational effort were required as a result. Extension of the damage location method to overcome these problems is the first part of the current work. The central system identification algorithm is replaced with the MSMT method of stiffness matrix adjustment which was previously derived by generalizing an optimal-update secant method form quasi-Newton approaches for nonlinear optimization. Validation of the extended damage location method is the second goal.

Smith, Suzanne Weaver↗

NASA NTRS1995

Dissipative rendering and neural network control system design

Model-based control system designs are limited by the accuracy of the models of the plant, plant uncertainty, and exogenous signals. Although better models can be obtained with system identification, the models and control designs still have limitations. One approach to reduce the dependency on particular models is to design a set of compensators that will guarantee robust stability to a set of plants. Optimization over the compensator parameters can then be used to get the desired performance. Conservativeness of this approach can be reduced by integrating fundamental properties of the plant models. This is the approach of dissipative control design. Dissipative control designs are based on several variations of the Passivity Theorem, which have been proven for nonlinear/linear and continuous-time/discrete-time systems. These theorems depend not on a specific model of a plant, but on its general dissipative properties. Dissipative control design has found wide applicability in flexible space structures and robotic systems that can be configured to be dissipative. Currently, there is ongoing research to improve the performance of dissipative control designs. For aircraft systems that are not dissipative active control may be used to make them dissipative and then a dissipative control design technique can be used. It is also possible that rendering a system dissipative and dissipative control design may be combined into one step. Furthermore, the transformation of a non-dissipative system to dissipative can be done robustly. One sequential design procedure for finite dimensional linear time-invariant systems has been developed. For nonlinear plants that cannot be controlled adequately with a single linear controller, model-based techniques have additional problems. Nonlinear system identification is still a research topic. Lacking analytical models for model-based design, artificial neural network algorithms have recently received considerable attention. Using their universal approximation property, neural networks have been introduced into nonlinear control designs in several ways. Unfortunately, little work has appeared that analyzes neural network control systems and establishes margins for stability and performance. One approach for this analysis is to set up neural network control systems in the framework presented above. For example, one neural network could be used to render a system to be dissipative, a second strictly dissipative neural network controller could be used to guarantee robust stability.

Gonzalez, Oscar R.↗

NASA NTRS1996

On-orbit application of H-infinity to the middeck active controls experiment: Overview of results

The Middeck Active Control Experiment (MACE) was successfully completed during the flight of STS-67 in March 1995. MACE provided an on-orbit validation of modem robust control theory and system identification techniques through the testing of a flexible, multi-instrument, science platform in the micro-gravity environment of the Space Shuttle's Middeck. As part of this experiment, H-infinity control design was validated in zero gravity (0-G) environment. The control objective was to isolate a payload sensor from a 5O Hz bandwidth disturbance occurring on the test article. Controllers were designed with the use of finite element models developed using 1 -G measurements and a measurement model obtained by applying system identification techniques to open loop data obtained on orbit. Over 50 single-input, single-output and multi-input, multi-output, single and multi-axis H-infinity control designs were evaluated on-orbit. Up to 19 dB reduction in vibration levels and 25 Hz bandwidth of control were achieved.

Woods-Vedeler, Jessica A.↗

NASA NTRS2011

Flight Test Results of a GPS-Based Pitot-Static Calibration Method Using Output-Error Optimization for a Light Twin-Engine Airplane

As part of the NASA Aviation Safety Program (AvSP), a novel pitot-static calibration method was developed to allow rapid in-flight calibration for subscale aircraft while flying within confined test areas. This approach uses Global Positioning System (GPS) technology coupled with modern system identification methods that rapidly computes optimal pressure error models over a range of airspeed with defined confidence bounds. This method has been demonstrated in subscale flight tests and has shown small 2- error bounds with significant reduction in test time compared to other methods. The current research was motivated by the desire to further evaluate and develop this method for full-scale aircraft. A goal of this research was to develop an accurate calibration method that enables reductions in test equipment and flight time, thus reducing costs. The approach involved analysis of data acquisition requirements, development of efficient flight patterns, and analysis of pressure error models based on system identification methods. Flight tests were conducted at The University of Tennessee Space Institute (UTSI) utilizing an instrumented Piper Navajo research aircraft. In addition, the UTSI engineering flight simulator was used to investigate test maneuver requirements and handling qualities issues associated with this technique. This paper provides a summary of piloted simulation and flight test results that illustrates the performance and capabilities of the NASA calibration method. Discussion of maneuver requirements and data analysis methods is included as well as recommendations for piloting technique.

Martos, Borja↗

NASA NTRS1998

Joint Institute for Advancement of Flight Sciences

The program objectives were defined in the original proposal entitled "Program of Research in Flight Dynamics in the JIAFS at NASA Langley Research Center" which was originated March 20, 1975, and in yearly renewals of the research program dated December 1, 1979 to December 1, 1998. The program included three major topics: 1) Improvement of existing methods and development of new methods for flight and wind tunnel data analysis based on system identification methodology. 2) Application of these methods to flight and wind tunnel data obtained from advanced aircraft. 3) Modeling and control of aircraft, space structures and spacecraft. The principal investigator of the program was Dr. Vladislav Klein, Professor at The George Washington University, Washington, D.C.. Thirty-seven Graduate Research Scholar Assistants, two of them doctoral students, also participated in the program. The results of the research conducted during nineteen years of the total co-operative period were published in 23 NASA technical reports, 2 D.Sc. Dissertations, 14 M.S. Theses and 33 papers. The list of these publications is included. The results were also reported in more than 30 seminar lectures presented at various research establishments world-wide. For contributions to the research supported by the co-operative agreement, three NASA Awards were received: 1) NASA LARC Group Achievement Award, May 30, 1990, to Dr. V. Klein as a member of the X-29 Drop Model Team. 2) NASA Medal for Exceptional Engineering Achievement, March 27, 1992, to Dr. V. Klein for innovative contributions in the development of advanced techniques and computer programs in the field of system identification. 3) NASA LaRC Team Excellence Award, May 7, 1994, to Dr. V. Klein as a member of the X-31 Drop Model Team.

Source record↗

NASA NTRS1967

Run numbering system for use with data recorders

Run numbering identification system provides a permanent identification on the recorder traces of data runs. It automatically enters, by pulse coding, the number of the current data run on the recorder trace. The system uses a keyboard, registers, converters, amplifiers, and a pulse generator.

Pease, L. L.↗

DOE OSTI2024

Use of Legacy Maritime Protocols Increases Exploitability of Virtual Aids to Navigation

With increased reliance on Virtual Aid(s) to Navigation (VAtoN) - also known as electronic Aid(s) to Navigation (eAtoN), or virtual buoys - a cyber event is likely to cause disruption to international maritime shipping. VAtoN has no physical hardware for visual reference and displays only on a vessel’s Electronic Chart Display Information System (ECDIS) and Automatic Radar Plotting Aid (ARPA); therefore, mariners must rely on the accuracy of the information provided. As VAtoN uses the National Maritime Electronics Association (NMEA) 0183 protocol for both Global Navigation Satellite System (GNSS) and Automatic Identification System (AIS), an insecure protocol that has been proven susceptible to spoofing, denial, and manipulation, the likelihood of a cyber-related event increases substantially.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

NASA NTRS1966

Chart system simplifies identification of complex design assemblies

Identification breakdown chart that lists the component parts required for any specific end item is used to identify rapidly and accurately, from numerous drawings, all the component parts of a complex design assembly. Cylindrical and complex configurations are depicted as continuous flat surfaces for ready identification.

Morin, H. P.↗

NASA NTRS1974

Specialists Meeting on Rotorcraft Dynamics, Moffett Field, Calif., February 13-15, 1974, Proceedings

Analysis of specific problems in rotorcraft dynamics. Topics include hingeless rotor theory, dynamic stall modelling, periodic systems identification, analysis of complex systems with phasing matrices, flapping stability, flap-lag dynamics at high advance ratios, finite element analysis and fuselage free-vibration characteristics, coupled rotor/frame vibration methods, gust response characteristics with unsteady stall effects, antiresonance theory, cyclic feathering motions and dynamic loads, control load envelope shaping, rotor aeroelasticity, use of Floquet theory, theory of proprotors and tilt-rotors, two-bladed teetering rotors, stability of air and ground resonance, vertical-plane pendulum absorbers, multicyclic jet-flap control, engine/frame interface dynamics, and others. The minutes of the question and answer periods following the presentations are presented in the supplement. Individual items are announced in this issue.

Source record↗

NASA NTRS1978

Preliminary design activities for solar heating and cooling systems

Information on the development of solar heating and cooling systems is presented. The major emphasis is placed on program organization, system size definition, site identification, system approaches, heat pump and equipment design, collector procurement, and other preliminary design activities.

Source record↗

NASA NTRS1979

Performance verification and system parameter identification of spacecraft tape recorder control servo

Design adequacy of the lead-lag compensator of the frequency loop, accuracy checking of the analytical expression for the electrical motor transfer function, and performance evaluation of the speed control servo of the digital tape recorder used on-board the 1976 Viking Mars Orbiters and Voyager 1977 Jupiter-Saturn flyby spacecraft are analyzed. The transfer functions of the most important parts of a simplified frequency loop used for test simulation are described and ten simulation cases are reported. The first four of these cases illustrate the method of selecting the most suitable transfer function for the hysteresis synchronous motor, while the rest verify and determine the servo performance parameters and alternative servo compensation schemes. It is concluded that the linear methods provide a starting point for the final verification/refinement of servo design by nonlinear time response simulation and that the variation of the parameters of the static/dynamic Coulomb friction is as expected in a long-life space mission environment.

Mukhopadhyay, A. K.↗

NASA NTRS1982

Direct system parameter identification of mechanical structures with application to modal analysis

In this paper a method is described to estimate mechanical structure characteristics in terms of mass, stiffness and damping matrices using measured force input and response data. The estimated matrices can be used to calculate a consistent set of damped natural frequencies and damping values, mode shapes and modal scale factors for the structure. The proposed technique is attractive as an experimental modal analysis method since the estimation of the matrices does not require previous estimation of frequency responses and since the method can be used, without any additional complications, for multiple force input structure testing.

Leuridan, J. M.↗