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Results for “fault-tolerant”

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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NASA NTRS1977

The aircraft energy efficiency active controls technology program

Broad outlines of the NASA Aircraft Energy Efficiency Program for expediting the application of active controls technology to civil transport aircraft are presented. Advances in propulsion and airframe technology to cut down on fuel consumption and fuel costs, a program for an energy-efficient transport, and integrated analysis and design technology in aerodynamics, structures, and active controls are envisaged. Fault-tolerant computer systems and fault-tolerant flight control system architectures are under study. Contracts with leading manufacturers for research and development work on wing-tip extensions and winglets for the B-747, a wing load alleviation system, elastic mode suppression, maneuver-load control, and gust alleviation are mentioned.

Hood, R. V., Jr.↗
NASA NTRS1971

Logic design for dynamic and interactive recovery.

Recovery in a fault-tolerant computer means the continuation of system operation with data integrity after an error occurs. This paper delineates two parallel concepts embodied in the hardware and software functions required for recovery; detection, diagnosis, and reconfiguration for hardware, data integrity, checkpointing, and restart for the software. The hardware relies on the recovery variable set, checking circuits, and diagnostics, and the software relies on the recovery information set, audit, and reconstruct routines, to characterize the system state and assist in recovery when required. Of particular utility is a handware unit, the recovery control unit, which serves as an interface between error detection and software recovery programs in the supervisor and provides dynamic interactive recovery.

Carter, W. C.↗
NASA NTRS1973

Braid read-only memory

Transformer-type memory is fault-tolerant array of independent read-only memory units. Information pattern in each unit is written by weaving wires through array of linear (nonswitching) transformers. Presence or absence of a bit is determined by whether a given wire threads or bypasses given transformer.

Mckenna, J. F.↗
NASA NTRS1972

A survey of an introduction to fault diagnosis algorithms

This report surveys the field of diagnosis and introduces some of the key algorithms and heuristics currently in use. Fault diagnosis is an important and a rapidly growing discipline. This is important in the design of self-repairable computers because the present diagnosis resolution of its fault-tolerant computer is limited to a functional unit or processor. Better resolution is necessary before failed units can become partially reuseable. The approach that holds the greatest promise is that of resident microdiagnostics; however, that presupposes a microprogrammable architecture for the computer being self-diagnosed. The presentation is tutorial and contains examples. An extensive bibliography of some 220 entries is included.

Mathur, F. P.↗
NASA NTRS1972

Program for computer aided reliability estimation

A computer program for estimating the reliability of self-repair and fault-tolerant systems with respect to selected system and mission parameters is presented. The computer program is capable of operation in an interactive conversational mode as well as in a batch mode and is characterized by maintenance of several general equations representative of basic redundancy schemes in an equation repository. Selected reliability functions applicable to any mathematical model formulated with the general equations, used singly or in combination with each other, are separately stored. One or more system and/or mission parameters may be designated as a variable. Data in the form of values for selected reliability functions is generated in a tabular or graphic format for each formulated model.

Mathur, F. P.↗
NASA NTRS1972

Automation of reliability evaluation procedures through CARE - The computer-aided reliability estimation program.

Description of an on-line interactive computer program called CARE (Computer-Aided Reliability Estimation) which can model self-repair and fault-tolerant organizations and perform certain other functions. Essentially CARE consists of a repository of mathematical equations defining the various basic redundancy schemes. These equations, under program control, are then interrelated to generate the desired mathematical model to fit the architecture of the system under evaluation. The mathematical model is then supplied with ground instances of its variables and is then evaluated to generate values for the reliability-theoretic functions applied to the model.

Mathur, F. P.↗
NASA NTRS1972

Autonomous power subsystem design for an Outer Planet Spacecraft.

This paper describes the overall design of the Thermoelectric Outer Planet Spacecraft (TOPS) power subsystem. It discusses the implementation of spacecraft requirements into a fault-tolerant design in which an on-board self-test and repair computer is utilized to provide autonomous operation. Development of a protected bus concept is discussed whereby electrical power supplied to essential spacecraft loads is maintained in the event of major on-board power blackouts. Particular attention is given to describing the interfaces and operation of the power subsystem with the spacecraft control computer subsystem. Autonomous power management operations are discussed where the on-board computer adjusts the spacecraft load demand to provide maximum utilization of source power for a given mission mode.

Andrews, R. E.↗
NASA NTRS1973

Highly reliable processor system for space application.

Description of a redundant processor organization which can be implemented with off-the-shelf processors for fault-tolerant operation. Reconfiguration can be performed automatically in a transientless manner. To support this system configuration and redundancy management concept, an operating system referred to as a synchronous executive has been designed. This system is directed at real-time closed-loop space applications where minimum response time, no degradation of software solution, and system simplicity are of importance. The system is based on a multicomputer organization with each machine solving the same problem based on a common set of inputs. Processor status is fed to a higher-level device which selects a controlling processor for controlling outputs and monitoring computers for fault detection.

Tsou, H. S. E.↗
NASA NTRS1973

A unified method for analyzing mission reliability for fault tolerant computer systems.

For fault-tolerant computer systems consisting of multiple classes of modules, a unified method for analyzing mission reliability is proposed and evaluated. The analysis proceeds by generalizing the notions of standby and N modular redundancy into a concept called hybrid-degraded redundancy. The probabilistic evaluation of the unified redundancy concept is then developed to yield, for a given modular class, the joint distribution of success and the number of nonfailed modules from that class, at special times. With this information, a Markov chain analysis gives the reliability of an entire sequence of phases (mission profile).

Bricker, J. L.↗
NASA NTRS1974

Error-correcting codes for high-speed digital computers

Published document discusses method for correcting errors. According to this method, computer operation becomes fault-tolerant, i.e., its operation is error-free in spite of single hardware element malfunction. Also, method provides for detection and correction of repetitive and spurious processing and transmission errors.

Campbell, R. D.↗
NASA NTRS1974

On-line diagnosis of sequential systems, 2

The theory and techniques applicable to the on-line diagnosis of sequential systems, were investigated. A complete model for the study of on-line diagnosis is developed. First an appropriate class of system models is formulated which can serve as a basis for a theoretical study of on-line diagnosis. Then notions of realization, fault, fault-tolerance and diagnosability are formalized which have meaningful interpretations in the the context of on-line diagnosis. The diagnosis of systems which are structurally decomposed and are represented as a network of smaller systems is studied. The fault set considered is the set of faults which only affect one component system is the network. A characterization of those networks which can be diagnosed using a purely combinational detector is achieved. A technique is given which can be used to realize any network by a network which is diagnosable in the above sense. Limits are found on the amount of redundancy involved in any such technique.

Sundstrom, R. J.↗
NASA NTRS1974

Management and design of long-life systems; Proceedings of the Symposium, Denver, Colo., April 24-26, 1973

The long life of Pioneer interplanetary spacecraft is considered along with a general accelerated methodology for long-life mechanical components, dependable long-lived household appliances, and the design and development philosophy to achieve reliability and long life in large turbine generators. Other topics discussed include an integrated management approach to long life in space, artificial heart reliability factors, and architectural concepts and redundancy techniques in fault-tolerant computers. Individual items are announced in this issue.

Schurmeier, H. M.↗
NASA NTRS1976

A forward view on reliable computers for flight control

The requirements for fault-tolerant computers for flight control of commercial aircraft are examined; it is concluded that the reliability requirements far exceed those typically quoted for space missions. Examination of circuit technology and alternative computer architectures indicates that the desired reliability can be achieved with several different computer structures, though there are obvious advantages to those that are more economic, more reliable, and, very importantly, more certifiable as to fault tolerance. Progress in this field is expected to bring about better computer systems that are more rigorously designed and analyzed even though computational requirements are expected to increase significantly.

Goldberg, J.↗
NASA NTRS1977

Flight test results of the Strapdown hexad Inertial Reference Unit (SIRU). Volume 1: Flight test summary

Flight test results of the strapdown inertial reference unit (SIRU) navigation system are presented. The fault-tolerant SIRU navigation system features a redundant inertial sensor unit and dual computers. System software provides for detection and isolation of inertial sensor failures and continued operation in the event of failures. Flight test results include assessments of the system's navigational performance and fault tolerance.

Hruby, R. J.↗
NASA NTRS1977

Fault tolerant computing: A preamble for assuring viability of large computer systems

The need for fault-tolerant computing is addressed from the viewpoints of (1) why it is needed, (2) how to apply it in the current state of technology, and (3) what it means in the context of the Phoenix computer system and other related systems. To this end, the value of concurrent error detection and correction is described. User protection, program retry, and repair are among the factors considered. The technology of algebraic codes to protect memory systems and arithmetic codes to protect memory systems and arithmetic codes to protect arithmetic operations is discussed.

Lim, R. S.↗
NASA NTRS1976

The unified data system - A distributed processing network for control and data handling on a spacecraft

This paper presents the results obtained in a continuing investigation of real-time distributed processing systems which is being conducted at the Jet Propulsion Laboratory. A distributed processor architecture has been developed for control and data handling on a planetary spacecraft. This system, designated the Unified Data System, has been implemented in a feasibility breadboard. The following aspects of the Unified Data System are described: (1) standardized building block elements and their configuration into microprocessor modules, (2) a highly redundant bus structure which connects the various modules and facilitates intercommunications with minimal software support, (3) the structure of software within the individual modules and its coordination between modules, and (4) the mechanisms by which fault-tolerance can be implemented within the network. Through the attributes of multilevel standardization, simplicity, and flexibility, this system is expected to result in significant cost savings to future spacecraft missions.

Rennels, D. A.↗
NASA NTRS1978

A maintenance model for k-out-of-n subsystems aboard a fleet of advanced commercial aircraft

Proposed highly reliable fault-tolerant reconfigurable digital control systems for a future generation of commercial aircraft consist of several k-out-of-n subsystems. Each of these flight-critical subsystems will consist of n identical components, k of which must be functioning properly in order for the aircraft to be dispatched. Failed components are recoverable; they are repaired in a shop. Spares are inventoried at a main base where they may be substituted for failed components on planes during layovers. Penalties are assessed when failure of a k-out-of-n subsystem causes a dispatch cancellation or delay. A maintenance model for a fleet of aircraft with such control systems is presented. The goals are to demonstrate economic feasibility and to optimize.

Miller, D. R.↗