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At least 145 records · Page 8

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NASA NTRS1987

A Modal-Parameter Extraction Procedure

Procedure accommodates multiple input excitations. Improved modalparameter extraction procedure applicable to linear, time-invariant systems derived in 92-page report. Algorithm allows multiple noncoherent input excitations applied to structure and generates consistent set of modal parameters. Procedure extension of simultaneous frequency-domain (SFD) techniques achieved through investigation of two automatic methods for reducing effective problem size while minimizing amount of user interaction. In several sample runs, independentcoordinate reduction method shown more accurate method for small sample size. Principle-component method used to estimate number of modes active in given frequency range.

Kurdila, A. H.↗

NASA NTRS1986

Evaluation of automated decisionmaking methodologies and development of an integrated robotic system simulation. Appendix A: ROBSIM user's guide

The purpose of the Robotics Simulation Program is to provide a broad range of computer capabilities to assist in the design, verification, simulation, and study of robotics systems. ROBSIM is program in FORTRAN 77 for use on a VAX 11/750 computer under the VMS operating system. This user's guide describes the capabilities of the ROBSIM programs, including the system definition function, the analysis tools function and the postprocessor function. The options a user may encounter with each of these executables are explained in detail and the different program prompts appearing to the user are included. Some useful suggestions concerning the appropriate answers to be given by the user are provided. An example user interactive run in enclosed for each of the main program services, and some of the capabilities are illustrated.

Haley, D. C.↗

NASA NTRS1987

NESSUS/expert and NESSUS/FPI in the Probabilistic Structural Analysis Methods (PSAM) program

The Numerical Evaluation of Stochastic Structures under Stress (NESSUS) is the primary computer code being developed in the NASA Probabilistic Structural Analysis Methods (PSAM) project. It consists of four modules NESSUS/EXPERT, NESSUS/FPI, NESSUS/PRE and NESSUS/FEM. This presentation concentrates on EXPERT and FPI. To provide an effective interface between NESSUS and the user, an expert system module called NESSUS/EXPERT is being developed. That system uses the CLIPS artificial intelligence code developed to NASA-JSC. The code is compatible with FORTRAN, the standard language for codes in PSAM. The user interacts with the CLIPS inference engine, which is linked to the knowledge database. The perturbation database generated by NESSUS/FEM and managed in EXPERT is used to develop the so-called response or performance model in the random variables. Two independent probabilistic methods are available in PSAM for the computation of the probabilistic structural response. These are the Fast Probability Integration (FPI) method and Monte Carlo simulation. FPI is classified as an advanced reliability method and has been developed over the past ten years by researchers addressing the reliability of civil engineering structures. Monte Carlo is a well-established technique for computing probabilities by conducting a number of deterministic analyses with specified input distributional information.

Burnside, O. H.↗

NASA NTRS1987

Artificial intelligence and its impact on combat aircraft

As the threat becomes more sophisticated and weapon systems more complex to meet the threat, the need for machines to assist the pilot in the assessment of information becomes paramount. This is particularly true in real-time, high stress situations. The advent of artificial intelligence (AI) technology offers the opportunity to make quantum advances in the application of machine technology. However, if AI systems are to find their way into combat aircraft, they must meet certain criteria. The systems must be responsive, reliable, easy to use, flexible, and understandable. These criteria are compared with the current status used in a combat airborne application. Current AI systems deal with nonreal time applications and require significant user interaction. On the other hand, aircraft applications require real time, minimum human interaction systems. In order to fill the gap between where technology is now and where it must be for aircraft applications, considerable government research is ongoing in NASA, DARPA, and three services. The ongoing research is briefly summarized. Finally, recognizing that AI technology is in its embryonic stage, and the aircraft needs are very demanding, a number of issues arise. These issues are delineated and findings are provided where appropriate.

Ott, Lawrence M.↗

NASA NTRS1987

A generic applications subroutine library for the MPP

A new methodology to increase the utility of the Massively Parallel Processor (MPP) was developed, and is presented as an addition to the current methods of using the MPP. This methodology provides for the development of an MPP side abstraction layer that is callable from any host side high level language. Routines in the abstraction layer have the option of using a powerful software tool for accessing the stager as virtual memory. An additional abstraction layer that allows for remote access to the MPP via DECnet is discussed. This integrated approach to programming the MPP is a valuable tool for the implementation of interactive user driver systems that require the computational capabilities of the MPP as well as a controlled user view. It is expected that this methodology will be used to integrate the MPP into many such systems, and thus promote greater use of the MPP by scientific researchers who are accustomed to user friendly environments.

Gough, Michael L.↗

NASA NTRS1987

Knowledge based jet engine diagnostics

A fielded expert system automates equipment fault isolation and recommends corrective maintenance action for Air Force jet engines. The knowledge based diagnostics tool was developed as an expert system interface to the Comprehensive Engine Management System, Increment IV (CEMS IV), the standard Air Force base level maintenance decision support system. XMAM (trademark), the Expert Maintenance Tool, automates procedures for troubleshooting equipment faults, provides a facility for interactive user training, and fits within a diagnostics information feedback loop to improve the troubleshooting and equipment maintenance processes. The application of expert diagnostics to the Air Force A-10A aircraft TF-34 engine equipped with the Turbine Engine Monitoring System (TEMS) is presented.

Jellison, Timothy G.↗

NASA NTRS1988

Space station commonality analysis

This study was conducted on the basis of a modification to Contract NAS8-36413, Space Station Commonality Analysis, which was initiated in December, 1987 and completed in July, 1988. The objective was to investigate the commonality aspects of subsystems and mission support hardware while technology experiments are accommodated on board the Space Station in the mid-to-late 1990s. Two types of mission are considered: (1) Advanced solar arrays and their storage; and (2) Satellite servicing. The point of departure for definition of the technology development missions was a set of missions described in the Space Station Mission Requirements Data Base. (MRDB): TDMX 2151 Solar Array/Energy Storage Technology; TDMX 2561 Satellite Servicing and Refurbishment; TDMX 2562 Satellite Maintenance and Repair; TDMX 2563 Materials Resupply (to a free-flyer materials processing platform); TDMX 2564 Coatings Maintenance Technology; and TDMX 2565 Thermal Interface Technology. Issues to be addressed according to the Statement of Work included modularity of programs, data base analysis interactions, user interfaces, and commonality. The study was to consider State-of-the-art advances through the 1990s and to select an appropriate scale for the technology experiments, considering hardware commonality, user interfaces, and mission support requirements. The study was to develop evolutionary plans for the technology advancement missions.

Source record↗

NASA NTRS1989

Integrated tools for control-system analysis

The basic functions embedded within a user friendly software package (MATRIXx) are used to provide a high level systems approach to the analysis of linear control systems. Various control system analysis configurations are assembled automatically to minimize the amount of work by the user. Interactive decision making is incorporated via menu options and at selected points, such as in the plotting section, by inputting data. There are five evaluations such as the singular value robustness test, singular value loop transfer frequency response, Bode frequency response, steady-state covariance analysis, and closed-loop eigenvalues. Another section describes time response simulations. A time response for random white noise disturbance is available. The configurations and key equations used for each type of analysis, the restrictions that apply, the type of data required, and an example problem are described. One approach for integrating the design and analysis tools is also presented.

Ostroff, Aaron J.↗

NASA NTRS1990

UMI - An interactive supervisory and shared control system for telerobotics

An interactive user interface, User-Macro-Interface (UMI), and its complete task execution system are developed and implemented for utilization by an operator to describe, simulate and execute tasks on a multiarm telerobot. The sequences or primitives can be executed on a graphics simulator or on the JPL Telerobot which incorporates two task execution manipulators, one manipulation used for positioning cameras, and two 6-degree-of-freedom force-reflecting hand controllers employed for shared and teleoperation modes of execution. The UMI interface is to be used as the operator interface at a local command site to prepare and send commands to a remote space telerobot.

Backes, Paul G.↗

NASA NTRS1990

Diagnosing multiple faults in SSM/PMAD

Multiple fault diagnosis for SSM/PMAD (space station module/power management and distribution) using the knowledge management design system as applied to the SSM/PMAD domain (KNOMAD-SSM/PMAD) is discussed. KNOMAD-SSM/PMAD provides a powerful facility for knowledge representation and reasoning which has been used to build the second generation of FRAMES (fault recovery and management expert system). FRAMES now handles the diagnosis of multiple faults and provides support for a more powerful interface for user interaction during autonomous operation. There are two types of multiple fault diagnosis handled in FRAMES. The first diagnoses hard faults, soft faults, and incipient faults simultaneously. The second diagnoses multiple hard faults which occur in close proximity in time to one another. Multiple fault diagnosis in FRAMES is performed using a rule-based approach. This rule-based approach, enabled by the KNOMAD-SSM/PMAD system, has proven to be powerful. Levels of autonomy are discussed, focusing on the approach taken in FRAMES for providing at least three levels of autonomy: complete autonomy, partial autonomy, and complete manual mode.

Riedesel, Joel↗

NASA NTRS1992

Analyzing Satellite Images Of The Ocean

PC-SEAPAK is user-interactive software package specifically developed for analysis of data from satellites in oceanographic research. Program used to process and interpret data obtained from Nimbus-7/Coastal Zone Color Scanner (CZCS) and NOAA Advanced Very High Resolution Radiometer (AVHRR). PC-SEAPAK copyrighted product with all copyright vested in National Aeronautics and Space Administration.

Mcclain, Charles R.↗

NASA NTRS1991

User interface issues in supporting human-computer integrated scheduling

The topics are presented in view graph form and include the following: characteristics of Operations Mission Planner (OMP) schedule domain; OMP architecture; definition of a schedule; user interface dimensions; functional distribution; types of users; interpreting user interaction; dynamic overlays; reactive scheduling; and transitioning the interface.

Cooper, Lynne P.↗

NASA NTRS1991

A finite mixtures algorithm for finding classes in images

The authors describe an algorithm for estimating the proportions of classes in a SAR (synthetic aperture radar) image without any user interaction. The method assumes that the image is a mixture of a known number of different pixel types. A maximum likelihood estimate of the parameters of the resulting mixture distribution is then used to find the proportions for the various classes. The technique was successfully applied to aircraft SAR images of sea ice. Computer simulations were used to determine the relative errors of the technique. The technique performs well even with extremely noisy images.

Samadani, Ramin↗

NASA NTRS1993

Building a generalized distributed system model

The key elements in the 1992-93 period of the project are the following: (1) extensive use of the simulator to implement and test - concurrency control algorithms, interactive user interface, and replica control algorithms; and (2) investigations into the applicability of data and process replication in real-time systems. In the 1993-94 period of the project, we intend to accomplish the following: (1) concentrate on efforts to investigate the effects of data and process replication on hard and soft real-time systems - especially we will concentrate on the impact of semantic-based consistency control schemes on a distributed real-time system in terms of improved reliability, improved availability, better resource utilization, and reduced missed task deadlines; and (2) use the prototype to verify the theoretically predicted performance of locking protocols, etc.

Mukkamala, R.↗

NASA NTRS1992

Life insurance risk assessment using a fuzzy logic expert system

In this paper, we present a knowledge based system that combines fuzzy processing with rule-based processing to form an improved decision aid for evaluating risk for life insurance. This application illustrates the use of FuzzyCLIPS to build a knowledge based decision support system possessing fuzzy components to improve user interactions and KBS performance. The results employing FuzzyCLIPS are compared with the results obtained from the solution of the problem using traditional numerical equations. The design of the fuzzy solution consists of a CLIPS rule-based system for some factors combined with fuzzy logic rules for others. This paper describes the problem, proposes a solution, presents the results, and provides a sample output of the software product.

Carreno, Luis A.↗

NASA NTRS1993

An estimate of the second law thermodynamic efficiency of the various units comprising an Environmental Control and Life Support System (ECLSS)

The objective of this paper is to present an estimate of the second law thermodynamic efficiency of the various units comprising an Environmental Control and Life Support System (ECLSS). The technique adopted here is based on an evaluation of the 'lost work' within each functional unit of the subsystem. Pertinent information for our analysis is obtained from a user interactive integrated model of an ECLSS. The model was developed using ASPEN. A potential benefit of this analysis is the identification of subsystems with high entropy generation as the most likely candidates for engineering improvements. This work has been motivated by the fact that the design objective for a long term mission should be the evaluation of existing ECLSS technologies not only the basis of the quantity of work needed for or obtained from each subsystem but also on the quality of work. In a previous study Brandhorst showed that the power consumption for partially closed and completely closed regenerable life support systems was estimated as 3.5 kw/individual and 10-12 kw/individual respectively. With the increasing cost and scarcity of energy resources, our attention is drawn to evaluate the existing ECLSS technologies on the basis of their energy efficiency. In general the first law efficiency of a system is usually greater than 50 percent. From literature, the second law efficiency is usually about 10 percent. The estimation of second law efficiency of the system indicates the percentage of energy degraded as irreversibilities within the process. This estimate offers more room for improvement in the design of equipment. From another perspective, our objective is to keep the total entropy production of a life support system as low as possible and still ensure a positive entropy gradient between the system and the surroundings. The reason for doing so is as the entropy production of the system increases, the entropy gradient between the system and the surroundings decreases, and the system will gradually approach equilibrium with the surroundings until it reaches the point where the entropy gradient is zero. At this point no work can be extracted from the system. This is called the 'dead state' of the system.

Chatterjee, Sharmista↗

NASA NTRS1993

Magellan spacecraft and memory state tracking: Lessons learned, future thoughts

Numerous studies have been dedicated to improving the two main elements of Spacecraft Mission Operations: Command and Telemetry. As a result, not much attention has been given to other tasks that can become tedious, repetitive, and error prone. One such task is Spacecraft and Memory State Tracking, the process by which the status of critical spacecraft components, parameters, and the contents of on-board memory are managed on the ground to maintain knowledge of spacecraft and memory states for future testing, anomaly investigation, and on-board memory reconstruction. The task of Spacecraft and Memory State Tracking has traditionally been a manual task allocated to Mission Operations Procedures. During nominal Mission Operations this job is tedious and error prone. Because the task is not complex and can be accomplished manually, the worth of a sophisticated software tool is often questioned. However, in the event of an anomaly which alters spacecraft components autonomously or a memory anomaly such as a corrupt memory or flight software error, an accurate ground image that can be reconstructed quickly is a priceless commodity. This study explores the process of Spacecraft and Memory State Tracking used by the Magellan Spacecraft Team highlighting its strengths as well as identifying lessons learned during the primary and extended missions, two memory anomalies, and other hardships encountered due to incomplete knowledge of spacecraft states. Ideas for future state tracking tools that require minimal user interaction and are integrated into the Ground Data System will also be discussed.

Bucher, Allen W.↗

NASA NTRS1993

The development and application of the self-adaptive grid code, SAGE

The multidimensional self-adaptive grid code, SAGE, has proven to be a flexible and useful tool in the solution of complex flow problems. Both 2- and 3-D examples given in this report show the code to be reliable and to substantially improve flowfield solutions. Since the adaptive procedure is a marching scheme the code is extremely fast and uses insignificant CPU time compared to the corresponding flow solver. The SAGE program is also machine and flow solver independent. Significant effort was made to simplify user interaction, though some parameters still need to be chosen with care. It is also difficult to tell when the adaption process has provided its best possible solution. This is particularly true if no experimental data are available or if there is a lack of theoretical understanding of the flow. Another difficulty occurs if local features are important but missing in the original grid; the adaption to this solution will not result in any improvement, and only grid refinement can result in an improved solution. These are complex issues that need to be explored within the context of each specific problem.

Davies, Carol B.↗