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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 469 records · Page 26

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NASA NTRS1985

Techniques for accommodating control effector failures on a mildly statically unstable airplane

Commercial airplanes are becoming increasingly more sophisticated, placing an increasing burden on pilots to detect and resolve the exhaustive set of possible control effector failures. Automatic techniques are needed to either reconfigure an existing control law or restructure a new control law after failure. A discrete control law has been designed for the longitudinal channel of a mildly statically unstable commercial airplane, to track the glideslope during the approach to landing phase of flight. Single effector failures with time delays for failure detection and identification are analyzed for both the reconfigured and restructured control laws, and results are compared with those from previous research using a statically stable airplane. Strategies considered include reconfiguration and restructuring with new flight conditions. Validation of all cases is made using a 6 DOF nonlinear airplane simulation.

Ostroff, A. J.↗

NASA NTRS1987

Application of adaptive antenna techniques to future commercial satellite communication

The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further sub-divided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems.

Ersoy, L.↗

NASA NTRS1987

Application of adaptive antenna techniques to future commercial satellite communications. Executive summary

The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further subdivided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems.

Ersoy, L.↗

NASA NTRS1989

A variable-gain output feedback control design methodology

A digital control system design technique is developed in which the control system gain matrix varies with the plant operating point parameters. The design technique is obtained by formulating the problem as an optimal stochastic output feedback control law with variable gains. This approach provides a control theory framework within which the operating range of a control law can be significantly extended. Furthermore, the approach avoids the major shortcomings of the conventional gain-scheduling techniques. The optimal variable gain output feedback control problem is solved by embedding the Multi-Configuration Control (MCC) problem, previously solved at ICS. An algorithm to compute the optimal variable gain output feedback control gain matrices is developed. The algorithm is a modified version of the MCC algorithm improved so as to handle the large dimensionality which arises particularly in variable-gain control problems. The design methodology developed is applied to a reconfigurable aircraft control problem. A variable-gain output feedback control problem was formulated to design a flight control law for an AFTI F-16 aircraft which can automatically reconfigure its control strategy to accommodate failures in the horizontal tail control surface. Simulations of the closed-loop reconfigurable system show that the approach produces a control design which can accommodate such failures with relative ease. The technique can be applied to many other problems including sensor failure accommodation, mode switching control laws and super agility.

Halyo, Nesim↗

NASA NTRS1989

Design of a Thermal and Micrometeorite Protection System for an Unmanned Lunar Cargo Lander

The first vehicles to land on the lunar surface during the establishment phase of a lunar base will be unmanned lunar cargo landers. These landers will need to be protected against the hostile lunar environment for six to twelve months until the next manned mission arrives. The lunar environment is characterized by large temperature changes and periodic micrometeorite impacts. An automatically deployable and reconfigurable thermal and micrometeorite protection system was designed for an unmanned lunar cargo lander. The protection system is a lightweight multilayered material consisting of alternating layers of thermal and micrometeorite protection material. The protection system is packaged and stored above the lander common module. After landing, the system is deployed to cover the lander using a system of inflatable struts that are inflated using residual fuel (liquid oxygen) from the fuel tanks. Once the lander is unloaded and the protection system is no longer needed, the protection system is reconfigured as a regolith support blanket for the purpose of burying and protecting the common module, or as a lunar surface garage that can be used to sort and store lunar surface vehicles and equipment. A model showing deployment and reconfiguration of the protection system was also constructed.

Hernandez, Carlos A.↗

NASA NTRS1991

Redundancy management for efficient fault recovery in NASA's distributed computing system

The management of redundancy in computer systems was studied and guidelines were provided for the development of NASA's fault-tolerant distributed systems. Fault recovery and reconfiguration mechanisms were examined. A theoretical foundation was laid for redundancy management by efficient reconfiguration methods and algorithmic diversity. Algorithms were developed to optimize the resources for embedding of computational graphs of tasks in the system architecture and reconfiguration of these tasks after a failure has occurred. The computational structure represented by a path and the complete binary tree was considered and the mesh and hypercube architectures were targeted for their embeddings. The innovative concept of Hybrid Algorithm Technique was introduced. This new technique provides a mechanism for obtaining fault tolerance while exhibiting improved performance.

Malek, Miroslaw↗

NASA NTRS1995

A decentralized software bus based on IP multicas ting

We describe decentralized reconfigurable implementation of a conference management system based on the low-level Internet Protocol (IP) multicasting protocol. IP multicasting allows low-cost, world-wide, two-way transmission of data between large numbers of conferencing participants through the Multicasting Backbone (MBone). Each conference is structured as a software bus -- a messaging system that provides a run-time interconnection model that acts as a separate agent (i.e., the bus) for routing, queuing, and delivering messages between distributed programs. Unlike the client-server interconnection model, the software bus model provides a level of indirection that enhances the flexibility and reconfigurability of a distributed system. Current software bus implementations like POLYLITH, however, rely on a centralized bus process and point-to-point protocols (i.e., TCP/IP) to route, queue, and deliver messages. We implement a software bus called the MULTIBUS that relies on a separate process only for routing and uses a reliable IP multicasting protocol for delivery of messages. The use of multicasting means that interconnections are independent of IP machine addresses. This approach allows reconfiguration of bus participants during system execution without notifying other participants of new IP addresses. The use of IP multicasting also permits an economy of scale in the number of participants. We describe the MULITIBUS protocol elements and show how our implementation performs better than centralized bus implementations.

Callahan, John R.↗

NASA NTRS1996

Neural Networks for Flight Control

Neural networks are being developed at NASA Ames Research Center to permit real-time adaptive control of time varying nonlinear systems, enhance the fault-tolerance of mission hardware, and permit online system reconfiguration. In general, the problem of controlling time varying nonlinear systems with unknown structures has not been solved. Adaptive neural control techniques show considerable promise and are being applied to technical challenges including automated docking of spacecraft, dynamic balancing of the space station centrifuge, online reconfiguration of damaged aircraft, and reducing cost of new air and spacecraft designs. Our experiences have shown that neural network algorithms solved certain problems that conventional control methods have been unable to effectively address. These include damage mitigation in nonlinear reconfiguration flight control, early performance estimation of new aircraft designs, compensation for damaged planetary mission hardware by using redundant manipulator capability, and space sensor platform stabilization. This presentation explored these developments in the context of neural network control theory. The discussion began with an overview of why neural control has proven attractive for NASA application domains. The more important issues in control system development were then discussed with references to significant technical advances in the literature. Examples of how these methods have been applied were given, followed by projections of emerging application needs and directions.

Jorgensen, Charles C.↗

NASA NTRS1998

Assessment Study of the State of the Art in Adaptive Control and its Applications to Aircraft Control

Many papers relevant to reconfigurable flight control have appeared over the past fifteen years. In general these have consisted of theoretical issues, simulation experiments, and in some cases, actual flight tests. Results indicate that reconfiguration of flight controls is certainly feasible for a wide class of failures. However many of the proposed procedures although quite attractive, need further analytical and experimental studies for meaningful validation. Many procedures assume the availability of failure detection and identification logic that will supply adequately fast, the dynamics corresponding to the failed aircraft. This in general implies that the failure detection and fault identification logic must have access to all possible anticipated faults and the corresponding dynamical equations of motion. Unless some sort of explicit on line parameter identification is included, the computational demands could possibly be too excessive. This suggests the need for some form of adaptive control, either by itself as the prime procedure for control reconfiguration or in conjunction with the failure detection logic. If explicit or indirect adaptive control is used, then it is important that the identified models be such that the corresponding computed controls deliver adequate performance to the actual aircraft. Unknown changes in trim should be modelled, and parameter identification needs to be adequately insensitive to noise and at the same time capable of tracking abrupt changes. If however, both failure detection and system parameter identification turn out to be too time consuming in an emergency situation, then the concepts of direct adaptive control should be considered. If direct model reference adaptive control is to be used (on a linear model) with stability assurances, then a positive real or passivity condition needs to be satisfied for all possible configurations. This condition is often satisfied with a feedforward compensator around the plant. This compensator must be robustly designed such that the compensated plant satisfies the required positive real conditions over all expected parameter values. Furthermore, with the feedforward only around the plant, a nonzero (but bounded error) will exist in steady state between the plant and model outputs. This error can be removed by placing the compensator also in the reference model. Design of such a compensator should not be too difficult a problem since for flight control it is generally possible to feedback all the system states.

Kaufman, Howard↗

NASA NTRS2000

Internet Technology on Spacecraft

The Operating Missions as Nodes on the Internet (OMNI) project has shown that Internet technology works in space missions through a demonstration using the UoSAT-12 spacecraft. An Internet Protocol (IP) stack was installed on the orbiting UoSAT-12 spacecraft and tests were run to demonstrate Internet connectivity and measure performance. This also forms the basis for demonstrating subsequent scenarios. This approach provides capabilities heretofore either too expensive or simply not feasible such as reconfiguration on orbit. The OMNI project recognized the need to reduce the risk perceived by mission managers and did this with a multi-phase strategy. In the initial phase, the concepts were implemented in a prototype system that includes space similar components communicating over the TDRS (space network) and the terrestrial Internet. The demonstration system includes a simulated spacecraft with sample instruments. Over 25 demonstrations have been given to mission and project managers, National Aeronautics and Space Administration (NASA), Department of Defense (DoD), contractor technologists and other decisions makers, This initial phase reached a high point with an OMNI demonstration given from a booth at the Johnson Space Center (JSC) Inspection Day 99 exhibition. The proof to mission managers is provided during this second phase with year 2000 accomplishments: testing the use of Internet technologies onboard an actual spacecraft. This was done with a series of tests performed using the UoSAT-12 spacecraft. This spacecraft was reconfigured on orbit at very low cost. The total period between concept and the first tests was only 6 months! On board software was modified to add an IP stack to support basic IP communications. Also added was support for ping, traceroute and network timing protocol (NTP) tests. These tests show that basic Internet functionality can be used onboard spacecraft. The performance of data was measured to show no degradation from current approaches. The cost to implement is much less than current approaches due to the availability of highly reliable and standard Internet tools. Use of standard Internet applications onboard reduces the risk of obsolescence inherent in custom protocols due to extremely wide use across all domains. These basic building blocks provide the framework for building onboard software to support direct user communication with payloads including payload control. Other benefits are payload to payload communication from dissimilar spacecraft, constellations of spacecraft, and reconfigurability on orbit. This work is funded through contract with the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC).

Rash, James↗

NASA NTRS2001

International Space Station Radiation Shielding Model Development

The projected radiation levels within the International Space Station (ISS) have been criticized by the Aerospace Safety Advisory Panel in their report to the NASA Administrator. Methods for optimal reconfiguration and augmentation of the ISS shielding are now being developed. The initial steps are to develop reconfigurable and realistic radiation shield models of the ISS modules, develop computational procedures for the highly anisotropic radiation environment, and implement parametric and organizational optimization procedures. The targets of the redesign process are the crew quarters where the astronauts sleep and determining the effects of ISS shadow shielding of an astronaut in a spacesuit. The ISS model as developed will be reconfigurable to follow the ISS. Swapping internal equipment rack assemblies via location mapping tables will be one option for shield optimization. Lightweight shield augmentation materials will be optimally fit to crew quarter areas using parametric optimization procedures to minimize the augmentation shield mass. The optimization process is being integrated into the Intelligence Synthesis Environment s (ISE s) immersive simulation facility at the Langley Research Center and will rely on High Performance Computing and Communication (HPCC) for rapid evaluation of shield parameter gradients.

Qualls, G. D.↗

NASA NTRS2005

Temperature Tolerant Evolvable Systems Utilizing FPGA Boards and Bias-Controlled Amplifiers

Space missions often require radiation and extreme-temperature hardened electronics to survive the harsh environments beyond Earth's atmosphere. Traditional approaches to preserve electronics incorporate shielding, insulation and redundancy at the expense of power and weight. However, a novel way of bypassing these problems is the concept of evolutionary hardware. A reconfigurable device, consisting of several switches interconnected with analog/digital parts, is controlled by an evolutionary processor (EP). When the EP detects degradation in the circuit it sends signals to reconfigure the switches, thus forming a new circuit with the desired output. This concept has been developed since the mid-l990s, but one problem remains-the EP cannot degrade substantially. For this reason, extensive testing at extreme temperatures (-180 to 120 C) has been done on devices found on FPGA boards (taking the role of the EP), such as the Analog to Digital and the Digital to Analog Converter. The EP is used in conjunction with a bias-controlled amplifier and a new prototype relay board, which is interconnected with 6 G4-FETs, a tri-input transistor-like element developed at JPL. The greatest improvements to be made lie in the reconfigurable device, so future design and testing of the G4-FET chip is required.

Kumar, Nikhil R.↗

NASA NTRS2005

Modular Software Interfaces for Revolutionary Flexibility in Space Operations

To make revolutionary improvements in exploration, space systems need to be flexible, realtime reconfigurable, and able to trade data transparently among themselves and mission operations. Onboard operations systems, space assembly coordination and EVA systems in exploration and construction all require real-time modular reconfigurability and data sharing. But NASA's current exploration systems are still largely legacies from hastily-developed, one-off Apollo-era practices. Today's rovers, vehicles, spacesuits, space stations, and instruments are not able to plug-and-play, Lego-like: into different combinations. Point-to-point dominates - individual suit to individual vehicle, individual instrument to rover. All are locally optimized, all unique, each of the data interfaces has been recoded for each possible combination. This will be an operations and maintenance nightmare in the much larger Project Constellation system of systems. This legacy approach does not scale to the hundreds of networked space components needed for space construction and for new, space-based approaches to Earth-Moon operations. By comparison, battlefield information management systems, which are considered critical to military force projection, have long since abandoned a point-to-point approach to systems integration. From a system-of-systems viewpoint, a clean-sheet redesign of the interfaces of all exploration systems is a necessary prerequisite before designing the interfaces of the individual exploration systems. Existing communications and Global Information Grid and middleware technologies are probably sufficient for command and control and information interfaces, with some hardware and time-delay modifications for space environments. NASA's future advanced space operations must also be information and data compatible with aerospace operations and surveillance systems being developed by other US Government agencies such as the Department of Homeland Security, Federal Aviation Administration and Department of Defense. This paper discusses fundamental system-of-systems infrastructure: approaches and architectures for modular plug-and-play software interfaces for revolutionary improvements in flexibility, modularity, robustness, ease of maintenance, reconfigurability, safety and productivity. Starting with middleware, databases, and mobile communications technologies, our technical challenges will be to apply these ideas to the requirements of constellations of space systems and to implement them initially on prototype space hardware. This is necessary to demonstrate an integrated information sharing architecture and services. It is a bottom-up approach, one that solves the problem of space operations data integration. Exploration demands uniform software mechanisms for application information interchange, and the corresponding uniformly available software services to enhance these mechanisms. We will examine the issues in plug-and-play, real-time-configurable systems, including common definition and management and tracking of data and information among many different space systems. Different field test approaches are discussed, including the use of the International Space Station and terrestrial analog mission operations at field sites.

Glass, Brian↗

NASA NTRS2005

A Plug and Play GNC Architecture Using FPGA Components

The goal of Plug and Play, or PnP, is to allow hardware and software components to work together automatically, without requiring manual setup procedures. As a result, new or replacement hardware can be plugged into a system and automatically configured with the appropriate resource assignments. However, in many cases it may not be practical or even feasible to physically replace hardware components. One method for handling these types of situations is through the incorporation of reconfigurable hardware such as Field Programmable Gate Arrays, or FPGAs. This paper describes a phased approach to developing a Guidance, Navigation, and Control (GNC) architecture that expands on the traditional concepts of PnP, in order to accommodate hardware reconfiguration without requiring detailed knowledge of the hardware. This is achieved by establishing a functional based interface that defines how the hardware will operate, and allow the hardware to reconfigure itself. The resulting system combines the flexibility of manipulating software components with the speed and efficiency of hardware.

KrishnaKumar, K.↗

NASA NTRS2005

Evolvable hardware system at extreme low temperatures

This paper describes circuit evolutionary experiments at extreme low temperatures, including the test of all system components at this extreme environment (EE). In addition to hardening-by-process and hardening-by-design, 'hardening-by-reconfiguration ', when applicable, could be used to mitigate drifts, degradation, or damage on electronic devices (chips) in EE, by using re-configurable devices and an adaptive selfreconfiguration of their circuit topology. Conventional circuit design exploits device characteristics within a certain temperature/radiation range; when that is exceeded, the circuit function degrades. On a reconfigurable device, although component parameters change in EE, a new circuit design, suitable for new parameter values, may be mapped into the reconfigurable structure to recover the initial circuit function. This paper demonstrates this technique for circuit evolution and recovery at liquid nitrogen temperatures (-196.6 (deg)C). In addition, preliminary tests are performed to assess the survivability limitations of the evolutionary processor at extreme low temperatures.

evolvable harware↗

NASA NTRS2005

Characterization and recovery of Deep Sub Micron (DSM) technologies behavior under radiation

This paper serves a twofold purpose: characterize the behavior of a reconfigurable chip exposed to radiation; and demonstrate a method for functionality recovery due to Total Ionizing Dose (TID) effects. The experiments are performed using a PL developed reconfigurable device, a Field Programmable Transistor Array (FPTA). The paper initially describes experiments on the characterization of the NMOS transistor behavior for TID values up to 300krad. The behavior of analog and digital circuits downloaded onto the FPTA chip is also assessed for TID effects. This paper also presents a novel approach for circuit functionality recovery due to radiation effects based on Evolvable Hardware. The key idea is to reconfigure a programmable device, in-situ, to compensate, or bypass its degraded or damaged components. Experiments with total radiation dose up to 300kRad show that while the functionality of a variety of circuits, including digital gates, a rectifier and a Digital to Analog Converter implemented on a FPTA-2 chip is degraded/lost at levels before 200kRad, the correct functionality can be recovered through the proposed evolutionary approach and the chips are able to survive higher radiation, for several functions in excess of total radiation dose of 250kRad.

evolvable hardware↗

NASA NTRS2006

Electromagnetic energy coupling mechanism with matrix architecture control

The present invention relates generally to reconfigurable, solid-state matrix arrays comprising multiple rows and columns of reconfigurable secondary mechanisms that are independently tuned. Specifically, the invention relates to reconfigurable devices comprising multiple, solid-state mechanisms characterized by at least one voltage-varied parameter disposed within a flexible, multi-laminate film, which are suitable for use as magnetic conductors, ground surfaces, antennas, varactors, ferrotunable substrates, or other active or passive electronic mechanisms.

Knowles, Gareth↗

NASA NTRS2005

Transistor Level Circuit Experiments using Evolvable Hardware

The Jet Propulsion Laboratory (JPL) performs research in fault tolerant, long life, and space survivable electronics for the National Aeronautics and Space Administration (NASA). With that focus, JPL has been involved in Evolvable Hardware (EHW) technology research for the past several years. We have advanced the technology not only by simulation and evolution experiments, but also by designing, fabricating, and evolving a variety of transistor-based analog and digital circuits at the chip level. EHW refers to self-configuration of electronic hardware by evolutionary/genetic search mechanisms, thereby maintaining existing functionality in the presence of degradations due to aging, temperature, and radiation. In addition, EHW has the capability to reconfigure itself for new functionality when required for mission changes or encountered opportunities. Evolution experiments are performed using a genetic algorithm running on a DSP as the reconfiguration mechanism and controlling the evolvable hardware mounted on a self-contained circuit board. Rapid reconfiguration allows convergence to circuit solutions in the order of seconds. The paper illustrates hardware evolution results of electronic circuits and their ability to perform under 230 C temperature as well as radiations of up to 250 kRad.

self configuration↗