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  • Other Sources  (12)
  • CYBERNETICS  (6)
  • OCEANOGRAPHY  (4)
  • ASTROPHYSICS  (1)
  • PHYSICS (GENERAL)  (1)
  • 1985-1989  (12)
  • 1989  (4)
  • 1987  (8)
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  • Other Sources  (12)
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  • 1985-1989  (12)
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  • 1
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    Wide swath ocean topography mapping with interferometric altimeters (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An interferometric radar altimeter is proposed to provide wide-swath high-resolution ocean topography. Several system design issues of such an interferometric altimeter are presented. Tradeoffs between processing of the interferometric signal using the so-called amplitude approach and the so-called phase approach are shown. The systematic errors associated with uncertainties in the interferometer baseline and the attitude of interferometer orientation are also discussed. Described is an approach using the measurements at orbit cross-over regions, together with the topography measurements from a traditional nadir-looking altimeter that are not contaminated by the baseline and attitude noises. Preliminary simulation results show that such an approach can generate an acceptable error level if the ocean surface does not change appreciably between the observations.
    Keywords: OCEANOGRAPHY
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  • 2
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    Deconvolution of sea state parameters from altimeter waveforms (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The paper reports on an on-going effort at the JPL to estimate the accuracy of ocean state parameters which have been obtained from the specular point probability density function (pdf) of the ocean surface. This pdf is obtained by the deconvolution of the return waveform of oceanographic altimeters such as Seasat, Geosat, or Topex.
    Keywords: OCEANOGRAPHY
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  • 3
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    Three dimensional numerical scattering from ocean-like surfaces (1987)
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    Publication Date: 2011-08-19
    Description: A new method of calculating the electric field scattered from two-dimensional conducting rough surfaces is presented. This method uses the operator conjugate gradients technique and the extended boundary condition equation. This avoids the build-up of round-off errors encountered in the inversion of large matrices. It also avoids the singularities of the integral kernels usually encountered in the method of moments. Techniques for improving the rate of convergence by applying physical constraints are discussed. This method is presently being used to calculate the polarization signatures from simulated ocean-like surfaces.
    Keywords: OCEANOGRAPHY
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  • 4
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    Kalman filtering, smoothing, and recursive robot arm forward and inverse dynamics (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The recursive difference equations of Kalman filtering and Bryson-Frazier fixed time-interval smoothing, arising in the state estimation theory for linear state space systems, are used here to solve problems of serial manipulator inverse and forward dynamics. The configuration analyzed is that of a joint connected N-link serial manipulator attached to an immobile base. The equivalence between the filtering and smoothing techniques from state estimation theory and recursive robot dynamics methods is demonstrated. Several areas for future research are suggested.
    Keywords: CYBERNETICS
    Type: IEEE Journal of Robotics and Automation (ISSN 0882-4967); RA-3; 624-639
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  • 5
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    Recursive forward dynamics for multiple robot arms moving a common task object (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recursive forward dynamics algorithms are developed and presented for an arbitrary number of robot arms moving a commonly held object. The multiarm forward dynamics problem is to find the angular accelerations at the joints and the contact forces that the arms impart to the task object. The problem also involves finding the acceleration of this object. The multiarm forward dynamics solutions provide a thorough physical and mathematical understanding of the way several arms behave in response to a set of applied joint moments. Such an understanding simplifies and guides the subsequent control design and experimentation process. The forward dynamics algorithms also provide the necessary analytical foundation for conducting analysis and simulation studies. The multiarm algorithms are based on the filtering and smoothing approach recently advanced for single-arm dynamics, and they can be built up modularly from the single-arm algorithms. The algorithms compute recursively the joint angle accelerations, the contact forces, and the task-object accelerations. Algorithms are also developed to evaluate in closed form the linear transformations from the active joint moments to the joint angle accelerations, to the task object accelerations, and to the task-object contact forces. A possible computing architecture is presented as a precursor to a more complete investigation of the computational performance of the dynamics algorithms.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Robotics and Automation (ISSN 1042-296X); 5; 510-521
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  • 6
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    Beyond the Kirchhoff approximation (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The three most successful models for describing scattering from random rough surfaces are the Kirchhoff approximation (KA), the small-perturbation method (SPM), and the two-scale-roughness (or composite roughness) surface-scattering (TSR) models. In this paper it is shown how these three models can be derived rigorously from one perturbation expansion based on the extinction theorem for scalar waves scattering from perfectly rigid surface. It is also shown how corrections to the KA proportional to the surface curvature and higher-order derivatives may be obtained. Using these results, the scattering cross section is derived for various surface models.
    Keywords: PHYSICS (GENERAL)
    Type: Radio Science (ISSN 0048-6604); 24; 681-693
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  • 7
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    Star formation in Seyfert galaxies (1987)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: An analysis of the IRAS data for a sample of classical (optically selected) Seyfert galaxies is presented. The IRAS fluxes at 25 micron, 60 micron, and 100 micron are found to be uncorrelated or only very weakly correlated with the UV/Optical continuum flux and the near and mid IR flux at 3.5 and 10 microns. To investigate the possibility that star formation accounts for the far IR flux, the IRAS measurements for the Seyfert galaxies are compared to IRAS observations of a sample of normal spiral galaxies, and a sample of Starburst galaxies. It is shown that the far IR luminosities and far IR colors of Seyfert galaxies are indistinguishable from those of the Starburst galaxies. Besides, normal galaxies are an order of magnitude less luminous than both the Seyfert and the Starburst galaxies. This indicates that star formation produces the bulk of the far infrared emission in Seyfert galaxies.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington Star Formation in Galaxies; p 669-674
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  • 8
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    Extracting ocean surface information from altimeter returns - The deconvolution method (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An evaluation of the deconvolution method for estimating ocean surface parameters from ocean altimeter waveforms is presented. It is shown that this method presents a fast, accurate way of determining the ocean surface parameters from noisy altimeter data. Three parameters may be estimated by using this method, including the altimeter-height error, the ocean-surface standard deviation, and the ocean-surface skewness. By means of a Monte Carlo experiment, an 'optimum' deconvolution algorithm and the accuracies with which the above parameters may be estimated using this algorithm are determined. Then the influence of instrument effects, such as errors in calibration and pointing-angle estimation, on the estimated parameters is examined. Finally, the deconvolution algorithm is used to estimate height and ocean-surface parameters from Seasat data.
    Keywords: OCEANOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 9761-977
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  • 9
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    Recursive inverse kinematics for robot arms via Kalman filtering and Bryson-Frazier smoothing (1987)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This paper applies linear filtering and smoothing theory to solve recursively the inverse kinematics problem for serial multilink manipulators. This problem is to find a set of joint angles that achieve a prescribed tip position and/or orientation. A widely applicable numerical search solution is presented. The approach finds the minimum of a generalized distance between the desired and the actual manipulator tip position and/or orientation. Both a first-order steepest-descent gradient search and a second-order Newton-Raphson search are developed. The optimal relaxation factor required for the steepest descent method is computed recursively using an outward/inward procedure similar to those used typically for recursive inverse dynamics calculations. The second-order search requires evaluation of a gradient and an approximate Hessian. A Gauss-Markov approach is used to approximate the Hessian matrix in terms of products of first-order derivatives. This matrix is inverted recursively using a two-stage process of inward Kalman filtering followed by outward smoothing. This two-stage process is analogous to that recently developed by the author to solve by means of spatial filtering and smoothing the forward dynamics problem for serial manipulators.
    Keywords: CYBERNETICS
    Type: AIAA PAPER 87-2261
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  • 10
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    Proceedings of the Workshop on Space Telerobotics, volume 3 (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Planning and scheduling for robot applications, trajectory planning for manipulators, and manipulator control are discussed.
    Keywords: CYBERNETICS
    Type: NASA-CR-184687 , JPL-PUBL-87-13-VOL-3 , NAS 1.26:184687 , Jan 20, 1987 - Jan 22, 1987; Pasadena, CA; United States
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