Application of multivariable search techniques to the shaping of minimum total heat re-entry bodies at hyberbolic velocity
Heat minimization and optimal shapes for bodies of revolution entering earth atmosphere at hyperbolic speeds
Hague, D. S.↗
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Results for “multivariate”
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.
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Decoupling in the design and synthesis of multivariable control systems.
Time invariant linear control system decoupling using state variable feedback, determining synthesis procedure to obtain desired closed loop configurations
Falb, P. L.↗
Design studies of a gamma-ray scatter atmospheric density gauge by a multivariable search method.
Gamma ray scattering gauge design optimum parameters to measure Mars atmospheric density
Gardner, R. P.↗
State variable feedback decoupling and design of multivariable systems.
State variable feedback design of m-input, m- output time invariant linear systems requiring noninteraction and exact transfer functions, considering coupled core nuclear reactor
Schultz, D. G.↗
Tests of composite hypotheses for the multivariate exponential family
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Matthes, T. K.↗
Adaptive control of multivariable systems
Stable adaptive control design for linear time- invariant system with same number of inputs as outputs, considering disturbance effect
Lindorff, D. P.↗
Use of multivariable asymptotic expansions in a satellite theory
Initial conditions and perturbative force of satellite are restricted to yield motion of equatorial satellite about oblate body. In this manner, exact analytic solution exists and can be used as standard of comparison in numerical accuracy comparisons. Detailed numerical accuracy studies of uniformly valid asymptotic expansions were made.
Dallas, S. S.↗
Computational Forms for the Transformed Covariance Matrix of Multivariate Normal Populations
The case is considered of a matrix B which is k x n of rank k. Matrix equations are given which define the generalized inverse of B and are used to develop the transformed covariance matrix.
Roberts, M. A.↗
An Expression for the Transformed Covariance Matrix of Multivariate Normal Populations
The problem is considered of classifying into one of m distinct n-variate classes an arbitrary n-channel multispectral measurement vector x. The classification procedure used is the maximum likelihood procedure. Information loss in compressing the n-channel data to k channels is taken to be the difference in the average interclass divergences (or probability of misclassification) in n-space and in k-space. Data compression is accomplished by kxn linear transformation i.e., multiplication of the spectral n-vector by a kxn matrix of rank k.
Decell, H. P., Jr.↗
Decoupling in linear time-varying multivariable systems
The necessary and sufficient conditions for the decoupling of an m-input, m-output, linear time varying dynamical system by state variable feedback is described. The class of feedback matrices which decouple the system are illustrated. Systems which do not satisfy these results are described and systems with disturbances are considered. Some examples are illustrated to clarify the results.
Sankaran, V.↗
Multivariant function model generation
The development of computer programs applicable to space vehicle guidance was conducted. The subjects discussed are as follows: (1) determination of optimum reentry trajectories, (2) development of equations for performance of trajectory computation, (3) vehicle control for fuel optimization, (4) development of equations for performance trajectory computations, (5) applications and solution of Hamilton-Jacobi equation, and (6) stresses in dome shaped shells with discontinuities at the apex.
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Craters on Earth, Moon, and Mars - Multivariate classification and mode of origin
Testing extraterrestrial craters and candidate terrestrial analogs for morphologic similitude is treated as a problem in numerical taxonomy. According to a principal-components solution and a cluster analysis, 402 representative craters on the Earth, the Moon, and Mars divide into two major classes of contrasting shapes and modes of origin. Craters of net accumulation of material (cratered lunar domes, Martian calderas, and all terrestrial volcanoes except maars and tuff rings) group apart from craters of excavation (terrestrial meteorite impact and experimental explosion craters, typical Martian craters, and all other lunar craters). Maars and tuff rings belong to neither group but are transitional. The classification criteria are four independent attributes of topographic geometry derived from seven descriptive variables by the principal-components transformation. Morphometric differences between crater bowl and raised rim constitute the strongest of the four components.
Pike, R. J.↗
Method of identifying clusters representing statistical dependencies in multivariate data
Approach is first to cluster and then to compute spatial boundaries for resulting clusters. Next step is to compute, from set of Monte Carlo samples obtained from scrambled data, estimates of probabilities of obtaining at least as many points within boundaries as were actually observed in original data.
Borucki, W. J.↗
Recursive identification and tracking of parameters for linear and nonlinear multivariable systems
The problem of identifying constant and variable parameters in multi-input, multi-output, linear and nonlinear systems is considered, using the maximum likelihood approach. An iterative algorithm, leading to recursive identification and tracking of the unknown parameters and the noise covariance matrix, is developed. Agile tracking, and accurate and unbiased identified parameters are obtained. Necessary conditions for a globally, asymptotically stable identification process are provided; the conditions proved to be useful and efficient. Among different cases studied, the stability derivatives of an aircraft were identified and some of the results are shown as examples.
Sidar, M.↗
Multivariate normal integration
Monte Carlo program evaluates integrals over rectangular regions for dimensions less than six and over elliptical regions in bivariate case. Program gives positive definite symmetric variance/covariance matrix factorization and calculates reciprocal of lower triangular matrix and product of diagonal elements of triangular matrix.
Falls, L. W.↗
Multivariate Analysis, Retrieval, and Storage System (MARS). Volume 6: MARS System - A Sample Problem (Gross Weight of Subsonic Transports)
The Mars system is a tool for rapid prediction of aircraft or engine characteristics based on correlation-regression analysis of past designs stored in the data bases. An example of output obtained from the MARS system, which involves derivation of an expression for gross weight of subsonic transport aircraft in terms of nine independent variables is given. The need is illustrated for careful selection of correlation variables and for continual review of the resulting estimation equations. For Vol. 1, see N76-10089.
Hague, D. S.↗
Stimulation of a turbofan engine for evaluation of multivariable optimal control concepts
The development of control systems for jet engines requires a real-time computer simulation. The simulation provides an effective tool for evaluating control concepts and problem areas prior to actual engine testing. The development and use of a real-time simulation of the Pratt and Whitney F100-PW100 turbofan engine is described. The simulation was used in a multi-variable optimal controls research program using linear quadratic regulator theory. The simulation is used to generate linear engine models at selected operating points and evaluate the control algorithm. To reduce the complexity of the design, it is desirable to reduce the order of the linear model. A technique to reduce the order of the model; is discussed. Selected results between high and low order models are compared. The LQR control algorithms can be programmed on digital computer. This computer will control the engine simulation over the desired flight envelope.
Seldner, K.↗
On the invertibility of linear multivariable systems
Some results concerning invertibility of a class of linear, time-invariant systems are presented. It is shown that by an appropriate factorization of the transfer matrix of such a system, the problem of checking its invertibility can be reduced to that of checking the invertibility of a lower-order system. A sufficient condition for invertibility is also obtained.
Patel, R. V.↗