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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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At least 199 records · Page 11

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NASA NTRS1985

Identification and control of structures in space

Work during the period July 1 - December 31, 1985, has concentrated on the application of the equations derived in the preceding period to the maneuvering and vibration suppression of the Spacecraft Control Laboratory Experiment (SCOLE) model. Two different situations have been considered: (1) a space environment and (2) a laboratory environment. This report covers the first case and consists of a paper entitled Maneuvering and Vibration Control of Flexible Spacecraft, presented at the Workshop on Structural Dynamics and Control Interaction of Flexible Structures, Marshall Space flight Center, Huntsville, AL, April 22 to 24, 1986. The second case will be covered in the report for the next period.

Meirovitch, L.↗

NASA NTRS1987

Numerical simulation of three-dimensional supersonic inlet flow fields

Supersonic inlet flows with mixed external-internal compressions of an axisymmetric inlet model were computed using a combined implicit-explicit (Beam-Warming-Steger/MacCormack) method for solving the three-dimensional unsteady, compressible Navier-Stokes equations in conservation form. Numerical calculations were made of various flows typically found in supersonic inlets such as shock-wave intersections, flow spillage around the cowl lip, shock-wave/boundary-layer interactions, control of shock-induced flow separation by means of boundary layer bleed, internal normal (terminal) shocks, and the effects of flow incidence. Computed results were compared with available wind tunnel data.

Kawamura, T.↗

NASA NTRS1988

Active region evolution in the chromosphere and transtition region

Images in the C IV 1548 A and the Si II 1526 S lines taken with the ultraviolet spectrometer polarimeter (UVSP) instrument on board the Solar Maximum Mission (SMM) satellite were combined into movies showing the evolution of active regions and the neighboring supergranulation over several days. The data sets generally consist of 240 by 240 arc second rasters with 3 arc second pixels taken one per orbit (about every 90 minutes). The images are projected on a latitude/longitude grid to remove the forshortening as the region rotates across the solar disk and further processed to remove jitter and gain variations. Movies were made with and without differential rotation. Although there are occasional missing orbits, these series do not suffer from the long nighttime gaps that occur in observations taken at a single groundbased observatory and are excellent for studying changes on time scales of several hours. The longest sequence processed to date runs from 20 Oct. 1980 to 25 Oct. 1980. This was taken during an SMM flare buildup study on AR 2744. Several shorter sequences taken in 1980 and 1984 will also be shown. The results will be presented on a video disk which can be interactively controlled to view the movies.

Shine, R. A.↗

NASA NTRS1988

Space-borne computing for the year 2000 and beyond

The influence and utilization of computers in space science investigations greatly enhances the ability to address difficult and complicated questions about the Universe. Space Science is wholly dependent on computers because the data acquired from instruments on the spacecraft are not only complicated in form but also voluminous. Athough a great deal of attention has been paid to develop efficient and powerful computing systems on-ground, research in the area of spaceborne computing is far from satisfactory. On-board processing of data will be important in future planetary missions where telemetry rates constrain the total amount of data which can be returned and decisions may have to be made in real time. Little thought has been given to a dynamic man-machine interface with regard to scientific real-time interactive control of flight experiments. Careful thinking is therefore essential to define appropriate spaceborne computing requirements for the future. It is imperative that powerful multiprocessing systems for on-board processing be experimentally impleneted and evaluated in selected application missions. The presentation addresses key issues and attempts to define the requirements for such processing with some of NASA's future missions in perspective. The resulting architectural and performance issues and possible developments are also addressed.

Iyer, Ravi K.↗

NASA NTRS1989

Dynamic analysis of space structures including elastic, multibody, and control behavior

The problem is to develop analysis methods, modeling stategies, and simulation tools to predict with assurance the on-orbit performance and integrity of large complex space structures that cannot be verified on the ground. The problem must incorporate large reliable structural models, multi-body flexible dynamics, multi-tier controller interaction, environmental models including 1g and atmosphere, various on-board disturbances, and linkage to mission-level performance codes. All areas are in serious need of work, but the weakest link is multi-body flexible dynamics.

Pinson, Larry↗

NASA NTRS1989

New multivariable capabilities of the INCA program

The INteractive Controls Analysis (INCA) program was developed at NASA's Goddard Space Flight Center to provide a user friendly, efficient environment for the design and analysis of control systems, specifically spacecraft control systems. Since its inception, INCA has found extensive use in the design, development, and analysis of control systems for spacecraft, instruments, robotics, and pointing systems. The (INCA) program was initially developed as a comprehensive classical design analysis tool for small and large order control systems. The latest version of INCA, expected to be released in February of 1990, was expanded to include the capability to perform multivariable controls analysis and design.

Bauer, Frank H.↗

NASA NTRS1989

An alternative control structure for telerobotics

A new teletobotic control concept which couples human supervisory commands with computer reasoning is presented. The control system is responsive and accomplishes an operator's commands while providing obstacle avoidance and stable controlled interactions with the environment in the presence of communication time delays. This provides a system which not only assists the operator in accomplishing tasks but modifies inappropriate operator commands which can result in safety hazards and/or equipment damage.

Boissiere, Peter T.↗

NASA NTRS1990

Presentation on a Space Acceleration Measurement System (SAMS)

The primary objective of the Space Acceleration Measurement Systems (SAMS) project is to provide an acceleration measurement system capable of serving a wide variety of space experiments. The design of the system being developed under this project takes into consideration requirements for experiments located in the middeck, in the orbiter bay, and in Spacelab. In addition to measuring, conditioning, and recording accelerations, the system will be capable of performing complex calculations and interactive control. The main components consist of a remote triaxial optical storage device. In operation, the triaxial sensor head produces output signals in response to acceleration inputs. These signals are preamplified, filtered and converted into digital data which is then transferred to optical memory. The system design is modular, facilitating both software and hardware upgrading as technology advances. Two complete acceleration measurement flight systems will be build and tested under this project.

Chase, Theodore L.↗

NASA NTRS1992

Decoupling Control For Oblique-Wing Airplane

Technical memorandum proposes procedure for mathematical synthesis of control signals proportional to commanded deflections of rudder, elevators, and ailerons of oblique-wing airplane. Procedure designed to generate signals compensating for aerodynamical and inertial cross-coupling among yawing, pitching, and rolling motions. Control interactions decoupled by feedforward and feedback.

Kempel, Robert W.↗

NASA NTRS1991

A walk through the planned CS building

Using the architectural plan views of our future computer science building as test objects, we have completed the first stage of a Building walkthrough system. The inputs to our system are AutoCAD files. An AutoCAD converter translates the geometrical information in these files into a format suitable for 3D rendering. Major model errors, such as incorrect polygon intersections and random face orientations, are detected and fixed automatically. Interactive viewing and editing tools are provided to view the results, to modify and clean the model and to change surface attributes. Our display system provides a simple-to-use user interface for interactive exploration of buildings. Using only the mouse buttons, the user can move inside and outside the building and change floors. Several viewing and rendering options are provided, such as restricting the viewing frustum, avoiding wall collisions, and selecting different rendering algorithms. A plan view of the current floor, with the position of the eye point and viewing direction on it, is displayed at all times. The scene illumination can be manipulated, by interactively controlling intensity values for 5 light sources.

Khorramabadi, Delnaz↗

NASA NTRS1991

Introduction in IND and recursive partitioning

This manual describes the IND package for learning tree classifiers from data. The package is an integrated C and C shell re-implementation of tree learning routines such as CART, C4, and various MDL and Bayesian variations. The package includes routines for experiment control, interactive operation, and analysis of tree building. The manual introduces the system and its many options, gives a basic review of tree learning, contains a guide to the literature and a glossary, and lists the manual pages for the routines and instructions on installation.

Buntine, Wray↗

NASA NTRS1992

Geostationary Operational Environmental Satellite (GOES-N report). Volume 2: Technical appendix

The contents include: operation with inclinations up to 3.5 deg to extend life; earth sensor improvements to reduce noise; sensor configurations studied; momentum management system design; reaction wheel induced dynamic interaction; controller design; spacecraft motion compensation; analog filtering; GFRP servo design - modern control approach; feedforward compensation as applied to GOES-1 sounder; discussion of allocation of navigation, inframe registration and image-to-image error budget overview; and spatial response and cloud smearing study.

Source record↗

NASA NTRS1991

Introduction to IND and recursive partitioning, version 1.0

This manual describes the IND package for learning tree classifiers from data. The package is an integrated C and C shell re-implementation of tree learning routines such as CART, C4, and various MDL and Bayesian variations. The package includes routines for experiment control, interactive operation, and analysis of tree building. The manual introduces the system and its many options, gives a basic review of tree learning, contains a guide to the literature and a glossary, lists the manual pages for the routines, and instructions on installation.

Buntine, Wray↗

NASA NTRS1991

The application of controlled structures technology to adaptive optics

Viewgraphs on the application of controlled structures technology (CST) to adaptive optics are presented. Topics covered include: a typical large optical system (LDR); overview of current optical programs; typical adaptive optics system; actuation approaches for deforming a mirror; control approach comparison; control structure interaction (CSI) control bandwidth limitations; applications of CST concepts to optics; distributed control approaches; quasistatic error correction; low authority control (LAC); and high authority control (HAC) design methodology.

Anderson, Eric H.↗

NASA NTRS1992

A comparison of force control algorithms for robots in contact with flexible environments

In order to perform useful tasks, the robot end-effector must come into contact with its environment. For such tasks, force feedback is frequently used to control the interaction forces. Control of these forces is complicated by the fact that the flexibility of the environment affects the stability of the force control algorithm. Because of the wide variety of different materials present in everyday environments, it is necessary to gain an understanding of how environmental flexibility affects the stability of force control algorithms. This report presents the theory and experimental results of two force control algorithms: Position Accommodation Control and Direct Force Servoing. The implementation of each of these algorithms on a two-arm robotic test bed located in the Center for Intelligent Robotic Systems for Space Exploration (CIRSSE) is discussed in detail. The behavior of each algorithm when contacting materials of different flexibility is experimentally determined. In addition, several robustness improvements to the Direct Force Servoing algorithm are suggested and experimentally verified. Finally, a qualitative comparison of the force control algorithms is provided, along with a description of a general tuning process for each control method.

Wilfinger, Lee S.↗

NASA NTRS1991

Fusing human and machine skills for remote robotic operations

The question of how computer assists can improve teleoperator trajectory tracking during both free and force-constrained motions is addressed. Computer graphics techniques which enable the human operator to both visualize and predict detailed 3D trajectories in real-time are reported. Man-machine interactive control procedures for better management of manipulator contact forces and positioning are also described. It is found that collectively, these novel advanced teleoperations techniques both enhance system performance and significantly reduce control problems long associated with teleoperations under time delay. Ongoing robotic simulations of the 1984 space shuttle Solar Maximum EVA Repair Mission are briefly described.

Schenker, Paul S.↗

NASA NTRS2000

Automated, Parametric Geometry Modeling and Grid Generation for Turbomachinery Applications

The objective of this Phase I project is to develop a highly automated software system for rapid geometry modeling and grid generation for turbomachinery applications. The proposed system features a graphical user interface for interactive control, a direct interface to commercial CAD/PDM systems, support for IGES geometry output, and a scripting capability for obtaining a high level of automation and end-user customization of the tool. The developed system is fully parametric and highly automated, and, therefore, significantly reduces the turnaround time for 3D geometry modeling, grid generation and model setup. This facilitates design environments in which a large number of cases need to be generated, such as for parametric analysis and design optimization of turbomachinery equipment. In Phase I we have successfully demonstrated the feasibility of the approach. The system has been tested on a wide variety of turbomachinery geometries, including several impellers and a multi stage rotor-stator combination. In Phase II, we plan to integrate the developed system with turbomachinery design software and with commercial CAD/PDM software.

Harrand, Vincent J.↗

NASA NTRS2001

Asthenia--does it exist in space?

OBJECTIVE: First popularized as neurasthenia in the late 1800s by American George Beard, asthenia has been viewed by Russian psychologists and flight surgeons as a major problem that affects cosmonauts participating in long-duration space missions. However, there is some controversy about whether this syndrome exists in space; this controversy is attributable in part to the fact that it is not recognized in the current American psychiatric diagnostic system. METHODS: To address this issue empirically, we retrospectively examined the data from our 4 1/2-year, NASA-funded study of crew member and mission control interactions during the Shuttle/Mir space program. Three of the authors identified eight items of stage 1 asthenia from one of our measures, the Profile of Mood States (POMS). Scores on these items from 13 Russian and American crew members were compared with scores derived from the opinions of six Russian space experts. RESULTS: Crew members' scores in space were significantly lower than the experts' scores on seven of the eight items, and they generally were in the "not at all" to "a little" range of the item scales. There were no differences in mean scores before and after launch or across the four quarters of the missions. There were no differences in response between Russian and American crew members. CONCLUSIONS: We could not demonstrate the presence of asthenia in space as operationally defined using the POMS. However, the POMS addresses only emotional and not physiological aspects of the syndrome, and the subject responses in our study generally were skewed toward the positive end of the scales. Further research on this syndrome needs to be done and should include physiological measures and measures that are specific to asthenia.

Non-NASA Center↗