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Taylor, L. W., Jr.

Publications and source records attributed to Taylor, L. W., Jr..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Timoshenko beam modeling for parameter estimation of NASA Mini-Mast truss

In this paper a distributed parameter model for the estimation of modal characteristics of NASA Mini-Mast truss is proposed. A closed-form solution of the Timoshenko beam equation, for a uniform cantilevered beam with two concentrated masses, is derived so that the procedure and the computational effort for the estimation of modal characteristics are improved. A maximum likelihood estimator for the Timoshenko beam model is also developed. The resulting estimates from test data by using Timoshenko beam model are found to be comparable to those derived from other approaches.

Shen, Ji Y.↗
NASA NTRS1992

Likelihood estimation for distributed parameter models of large beam-like structures

A maximum likelihood estimation for distributed parameter models of large flexible structures was formulated. Distributed parameter models involve far fewer unknown parameters than independent modal characteristics or finite element models. The closed form solutions for the partial differential equations with corresponding boundary conditions were derived. The closed-form expressions of sensitivity functions led to highly efficient algorithms for analyzing ground or on-orbit test results. For an illustration of this approach, experimental data of the NASA Mini-Mast truss was used. The estimations of modal properties involve lateral bending modes and torsional modes. The results show that distributed parameter models are promising in the parameter estimation of large flexible structures.

Shen, J.-Y.↗
NASA NTRS1992

The Spacecraft Control Laboratory Experiment (SCOLE) - A reprise

The research experience of SCOLE developed by the NASA Langley Research Center is reviewed. Particular attention is given to the advances made in control and modeling techniques, the experimental facilities that are now available, and the continuing needs to advance and to validate the technologies in controlling flexible structures.

Taylor, L. W., Jr.↗
NASA NTRS1989

Maximum likelihood estimation for distributed parameter models of flexible spacecraft

A distributed-parameter model of the NASA Solar Array Flight Experiment spacecraft structure is constructed on the basis of measurement data and analyzed to generate a priori estimates of modal frequencies and mode shapes. A Newton-Raphson maximum-likelihood algorithm is applied to determine the unknown parameters, using a truncated model for the estimation and the full model for the computation of the higher modes. Numerical results are presented in a series of graphs and briefly discussed, and the significant improvement in computation speed obtained by parallel implementation of the method on a supercomputer is noted.

Taylor, L. W., Jr.↗
NASA NTRS1987

Distributed parameter modeling of the structural dynamics of the Solar Array Flight Experiment

A distributed-parameter model of the structural dynamics of the space-shuttle-deployed Solar Array Flight Experiment is developed and used to produce estimates of the modal frequencies and mode shapes. A lumped parameter version of the distributed model is used to estimate model characteristics by analyzing the measured responses of 32 targets. To make the modeling more tenable, a distributed parameter system is used to reduce the number of unknown parameters, a modified Newton-Raphson technique is used for rapid convergence, and a parallel processing supercomputer is used for more efficient computation. The performances of computers with a high-speed serial processor and with a high-speed parallel processor are compared. The best results are obtained with the modeling approach in which maximum likelihood estimation is applied to distributed parameter models.

Taylor, L. W., Jr.↗
NASA NTRS1986

Proceedings of the 2nd Annual SCOLE Workshop

Proceedings of the Second Annual Spacecraft Control Laboratory Experiment (SCOLE) Workshop held at the NASA Langley Research Center, Hampton, Va., December 9 to 10, 1985 are presented.

Taylor, L. W., Jr.↗
NASA NTRS1985

Time-optimal bang-bang slew of rigidized SCOLE configuration

This paper addresses: (1) an application of the well-known time-optimal bang-bang control theory to the design of minimal-time limited-torque single-axis slew maneuvers for the rigidized configuration of NASA Langley Research Center's Spacecraft Control Laboratory Experiment (SCOLE) and (2) the associated generic side effects due to spillover of slew motions and applied torques. Numerical experiments that helped pinpoint the specific causes of performance degradation are discussed. Analytical as well as scientifically interesting numerical research results are given.

Lin, J. G.↗
NASA NTRS1985

On-orbit systems identification of flexible spacecraft

The process of on-orbit systems identification of flexible spacecraft is examined in terms of the difficulties that are expected because of the potentially unmanageable number of unknown model parameters due to the very high order system models involved. A Jordon block canonical form and global model parameters are used to reduce the number of unknown parameters to manageable numbers. A Bayesian approach is discussed which enables the merging of theoretical models with ground or on-orbit test results by using Unconditional Maximum Likelihood Parameter Estimation. A Modified Newton-Raphson technique is proposed for determining the model parameter estimates and an expected fit error criterion is recommended for the determination of the model structure and order reduction.

Taylor, L. W., Jr.↗
NASA NTRS1984

Estimation of aerodynamic forces and moments on a steadily spinning airplane

A semiempirical method is presented for the estimation of aerodynamic forces and moments on a steadily rotating airplane model in a spin tunnel. The approach is based on the application of strip theory to determine a part of the aerodynamic coefficient (including rotational velocity) and then estimation of increments to these coefficients because of rotational flow over the stalled airplane. The theory is applied to a light, single-engine, general aviation airplane and the results are compared with the corresponding spin tunnel rotary balance test data.

Pamadi, B. N.↗
NASA NTRS1984

Spacecraft control research at NASA

Future missions is space will require controlling spacecraft which are both large and flexible. The limited inherent damping and the uncertain and changing dynamic characteristics of many of these vehicles, such as manned space stations and large antennas, will revolutionize spacecraft control requirements. In preparation for the time that such control systems are required, considerable research and technology development is necessary. A program is in place at NASA for the development of active control technology to support major initiatives for space station and advanced spacecraft. A number of key control technology program needs are cited in the paper as required for these and other future NASA missions together with an integrated controls/structures technology flight experiment to demonstrate and validate technology for large flexible structures.

Dahlgren, J. B.↗
NASA NTRS1984

On the prediction of auto-rotational characteristics of light airplane fuselages

A semi-empirical theory is presented for the estimation of aerodynamic forces and moments acting on a steadily rotating (spinning) airplane fuselage, with a particular emphasis on the prediction of its auto-rotational behavior. This approach is based on an extension of the available analytical methods for high angle of attack and side-slip and then coupling this procedure with strip theory for application to a rotating airplane fuselage. The analysis is applied to the fuselage of a light general aviation airplane and the results are shown to be in fair agreement with experimental data.

Pamadi, B. N.↗
NASA NTRS1983

Digital Instrumentation Analysis and Navigation System (DIANS) for system identification

Hardware, software, and performance features of the Digital Instrumentation and Navigation System (DIANS) designed for NASA research to collect flight data as a strap-down system are detailed. The support software for the system has a cross compiler, a linkage editor, and cross assembler, extended communication capabilities, postflight processing applications, and compilers for PASCAL, FORTRAN, CBASIC and MT. The DIANS microcomputer has a 1 Mbyte RAM module, a fast floating point processor board, a 68000 monoboard computer with 64 RAM, a 128 Kbyte bubble memory card, and a navigation radio. The system also carries a battery for full system operation for over an hour. The support software is also stored on a host mainframe computer, which has a CP/M operating system. Pitch, roll, and heading data are gathered from the on-board system, and communication is possible between the airborne and ground-based computer.

Smyth, R. K.↗
NASA NTRS1983

Estimation of parameters involved in high angle-of-attack aerodynamic theory using spin flight test data

The difficulty in applying parameter estimation techniques to spinning airplanes is due in part to the unwieldy number of possible combinations of terms in the equations of motion, when the model structure is unknown. The combination of high angle of attack and high rotation rate results in aerodynamic functions which are quite complex. For wing dominated configurations it is advantageous to use aerodynamic theory to generate the model structure. In this way, the number of unknown parameters is reduced and the model accuracy may be increased. Under conditions for which the theory is inadequate, however, model accuracy may be reduced. Strip theory, for example, is incapable of predicting autorotative rolling moments indicated by wind tunnel tests at angles of attack exceeding 40 degrees. An improved aerodynamic theory would be necessary to successfully apply the technique advanced for such regions.

Taylor, L. W., Jr.↗
NASA NTRS1983

An evaluation of aerodynamics modeling of spinning light airplanes

This paper extends the application of the modified strip theory for wing body combination of a spinning light airplane reported earlier. In addition, to account for the contribution of the tail plane, the shielding effect on vertical tail under steady state spin condition is modeled from basic aerodynamic considerations. The results of this combined analysis, presented for some light airplane configurations, are shown to be in good agreement with spin tunnel rotary balance test data.

Pamadi, B. N.↗
NASA NTRS1982

An estimation of aerodynamic forces and moments on an airplane model under steady state spin conditions

The problem of estimating the aerodynamic characteristics of a wing body configuration of a spinning airplane at extreme angles of attack and spin rates is approached by the application of strip theory. Semiempirical methods are used to estimate the aerodynamic force distributions over each component using static, nonrotational wind-tunnel test data. To these predictions, corrections are applied to account for the primary rotational flow effects which are significant at large spin rates. The results of this modified strip theory are shown to be in good agreement with spin tunnel rotary balance test data.

Pamadi, B. N.↗
NASA NTRS1982

Configurational and system requirements for control of large space systems

Control of large space systems, modeling, and control difficulties are discussed. Ground based analysis of spaceflight data are presented to determine structural dynamics characteristics for the purpose of revising control laws, and to trim the surface contour. Systems identification for adaptive control and automatic surface control are also considered.

Taylor, L. W., Jr.↗
NASA NTRS1982

An analytical technique for the analysis of airplane spin entry and recovery

The dynamic equations of motion for a spinning airplane are simplified to facilitate the analysis of spin entry and recovery maneuvers. Solutions of a nonlinear, first order equation for spin rate enable calculation of spin entry and recovery times and control required for recovery. The analysis is applied to a light airplane for which both aerodynamic data, rotory balance wind tunnel tests, and spin flight test data have been obtained. A comparison of predicted and actual transient spin responses is made which supports the validity of the analytical approach taken but which also illustrates the difficulty in obtaining accurate aerodynamic data for spinning airplanes. Certain normalized parameters of the reduced state spin equation suggest criteria for assessing the transient spin characteristics of light airplanes.

Taylor, L. W., Jr.↗