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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Real-time control of the MIT vehicle emulation system

The MIT vehicle emulation system (VES) is an experimental facility designed to facilitate the study of controlling robots fixed to nonstationary bases. This includes assembly and repair manipulators attached to space vehicles, or to the space shuttle arm, as well as manipulators fixed to the bed of moving ground vehicles. Controlling manipulators under these conditions for endpoint force and positioning tasks requires both the development of new theory, and the development of a testbed for verifying theoretical results through experimentation. A description is presented of the technical details of the real-time controller for the second generation VES system.

Durfee, William K.↗
NASA NTRS1992

A methodology to emulate and evaluate a productive virtual workstation

The Advanced Display and Computer Augmented Control (ADCACS) Program at ACT is sponsored by NASA Ames to investigate the broad field of technologies which must be combined to design a 'virtual' workstation for the Space Station Freedom. This program is progressing in several areas and resulted in the definition of requirements for a workstation. A unique combination of technologies at the ACT Laboratory have been networked to effectively create an experimental environment. This experimental environment allows the integration of nonconventional input devices with a high power graphics engine within the framework of an expert system shell which coordinates the heterogeneous inputs with the 'virtual' presentation. The flexibility of the workstation is evolved as experiments are designed and conducted to evaluate the condition descriptions and rule sets of the expert system shell and its effectiveness in driving the graphics engine. Workstation productivity has been defined by the achievable performance in the emulator of the calibrated 'sensitivity' of input devices, the graphics presentation, the possible optical enhancements to achieve a wide field of view color image and the flexibility of conditional descriptions in the expert system shell in adapting to prototype problems.

Krubsack, David↗
NASA NTRS1992

A digitally implemented modem - Theory and emulation results

Theory and hardware emulation results are presented for a very flexible digitally implemented modem whose technology is useful over a broad class of terrestrial and in-flight satellite communications applications. The interdependent detection and tracking loop architectures based on the 'joint estimator-detector' approach is shown to perform well for various modulation techniques. The analysis is accurate in setting the loop parameters, and also predicting their transient behavior.

Poklemba, John J.↗
NASA NTRS1994

Large-displacement structural durability analyses of simple bend specimen emulating rocket nozzle liners

Large-displacement elastic and elastic-plastic, finite-element stress-strain analyses of an oxygen-tree high-conductivity (OFHC) copper plate specimen were performed using an updated Lagrangian formulation. The plate specimen is intended for low-cost experiments that emulate the most important thermomechanical loading and failure modes of a more complex rocket nozzle. The plate, which is loaded in bending at 593 C, contains a centrally located and internally pressurized channel. The cyclic crack initiation lives were estimated using the results from the analyses and isothermal strain-controlled low-cycle fatigue data for OFHC copper. A comparison of the predicted and experimental cyclic lives showed that an elastic analysis predicts a longer cyclic life than that observed in experiments by a factor greater than 4. The results from elastic-plastic analysis for the plate bend specimen, however, predicted a cyclic life in close agreement with experiment, thus justifying the need for the more rigorous stress-strain analysis.

Arya, Vinod K.↗
NASA NTRS2001

Synchronous Parallel System for Emulation and Discrete Event Simulation

A synchronous parallel system for emulation and discrete event simulation having parallel nodes responds to received messages at each node by generating event objects having individual time stamps, stores only the changes to the state variables of the simulation object attributable to the event object and produces corresponding messages. The system refrains from transmitting the messages and changing the state variables while it determines whether the changes are superseded, and then stores the unchanged state variables in the event object for later restoral to the simulation object if called for. This determination preferably includes sensing the time stamp of each new event object and determining which new event object has the earliest time stamp as the local event horizon, determining the earliest local event horizon of the nodes as the global event horizon, and ignoring events whose time stamps are less than the global event horizon. Host processing between the system and external terminals enables such a terminal to query, monitor, command or participate with a simulation object during the simulation process.

Jeffrey S Steinman↗
NASA NTRS2004

Aviation Communications Emulation Testbed

Aviation related applications that rely upon datalink for information exchange are increasingly being developed and deployed. The increase in the quantity of applications and associated data communications will expose problems and issues to resolve. NASA Glenn Research Center has prepared to study the communications issues that will arise as datalink applications are employed within the National Airspace System (NAS) by developing a aviation communications emulation testbed. The Testbed is evolving and currently provides the hardware and software needed to study the communications impact of Air Traffic Control (ATC) and surveillance applications in a densely populated environment. The communications load associated with up to 160 aircraft transmitting and receiving ATC and surveillance data can be generated in real time in a sequence similar to what would occur in the NAS.

Sheehe, Charles↗
NASA NTRS2004

Aviation Communications Emulation Testbed

Aviation related applications that rely upon datalink for information exchange are increasingly being developed and deployed. The increase in the quantity of applications and associated data communications will expose problems and issues to resolve. NASA s Glenn Research Center has prepared to study the communications issues that will arise as datalink applications are employed within the National Airspace System (NAS) by developing an aviation communications emulation testbed. The Testbed is evolving and currently provides the hardware and software needed to study the communications impact of Air Traffic Control (ATC) and surveillance applications in a densely populated environment. The communications load associated with up to 160 aircraft transmitting and receiving ATC and surveillance data can be generated in realtime in a sequence similar to what would occur in the NAS. The ATC applications that can be studied are the Aeronautical Telecommunications Network s (ATN) Context Management (CM) and Controller Pilot Data Link Communications (CPDLC). The Surveillance applications are Automatic Dependent Surveillance - Broadcast (ADS-B) and Traffic Information Services - Broadcast (TIS-B).

Sheehe, Charles↗
NASA NTRS2004

Integration of On-board EOS Schedule Revision with Space Communication Emulation System

The need for on-board decision-making for planning science observations on Earth Observing Satellites is based on the fact that the desirability of acquiring an image can change dynamically, because of changes in meteorological conditions (e.g. cloud cover), unforeseen events such as fires, floods, or volcanic eruptions, or unexpected changes in satellite or ground station capability. In such cases, satellite resources, such as power and SSR capacity can potentially be better utilized taking another image that is of higher quality. Currently, typical Earth observing satellites cannot communicate directly with each other, and can only communicate with ground stations about 5% to 10% of the time. Because of the limited communication windows, as well as the cost and effort that would need to be expended in revising a mission schedule, a ground-based scheduler would have little or no opportunity to revise the schedule in response to the contingencies that may arise. For this reason, a distributed science planning system combining a ground-based scheduler with on-board schedule revision capabilities is warranted. This paper will describe algorithms for on-board decision-making for science planning and their integration with the advanced satellite control and communications technology developed at the Space Communication Emulation Facility (SCEF) at NASA Glenn Research Center. Our objective of demonstrating how advanced communications and scheduling technology can be combined to improve the scientific utility of images acquired by Earth observing systems will be discussed via a description of a number of realistic flight scenarios.

Khatib, Lina↗
NASA NTRS1999

Reconfigurable Data Communications Packet-Switch Emulation Test Bed Demonstrated

The Communications Technology Division at the NASA Lewis Research Center has an ongoing program to develop advanced switching and routing technology concepts for future satellite onboard processing systems. Through a university grant as a part of this research, the Cleveland State University is using a flexible reconfigurable data communications packet switch emulation test bed to investigate packet switching techniques. Because of the switching speed and protocol complexity, implementing a data communications network is a tremendous task. Various alternatives should be carefully studied and evaluated in the development stage so that the optimal system configuration can be obtained and implemented later. Therefore, it is desirable to predict the performance of the network before it is actually constructed. This is especially true in the case of satellite systems. In the past, theoretical analysis, software simulation, and prototyping were used to evaluate performance. However, each method has its drawback. There are basic tradeoffs among accuracy, cost, and required evaluation time. No method is completely satisfactory.

Chu, Pong P.↗
NASA NTRS1995

Emulating the Lateral Dynamics of a Range of Vehicles Using a Four-Wheel-Steering Vehicle

The concept of Variable Dynamic Testbed Vehicle (VDTV) has been proposed as a tool to evaluate collision detection/avoidance systems, to perform vehicle-related human factors research, and to support other Automated HighWay System programs. The goal of this study is to analytically investigate to what extent a VDTV with four-wheel-steering can emulate the lateral dynamics of a broad range of vehicle models.

Four-wheel-steering varible dynamic testbed vehicl↗
NASA NTRS2010

MCCx C3I Control Center Interface Emulator

This slide presentation reviews the project to develop and demonstrate alternate Information Technologies and systems for new Mission Control Centers that will reduce the cost of facility development, maintenance and operational costs and will enable more efficient cost and effective operations concepts for ground support operations. The development of a emulator for the Control Center capability will enable the facilities to conduct the simulation requiring interactivity with the Control Center when it is off line or unavailable, and it will support testing of C3I interfaces for both command and telemetry data exchange messages (DEMs).

Mireles, James R.↗
NASA NTRS2014

Space Link Extension (SLE) Emulation for High-Throughput Network Communication

As the data rate requirements for space communications increases, signicant stressis placed not only on the wireless satellite communication links, but also on the groundnetworks which forward data from end-users to remote ground stations. These wide areanetwork (WAN) connections add delay and jitter to the end-to-end satellite communicationlink, eects which can have signicant impacts on the wireless communication link. It isimperative that any ground communication protocol can react to these eects such that theground network does not become a bottleneck in the communication path to the satellite.In this paper, we present our SCENIC Emulation Lab testbed which was developed to testthe CCSDS SLE protocol implementations proposed for use on future NASA communica-tion networks. Our results show that in the presence of realistic levels of network delay,high-throughput SLE communication links can experience signicant data rate throttling.Based on our observations, we present some insight into why this data throttling happens,and trace the probable issue back to non-optimal blocking communication which is sup-ported by the CCSDS SLE API recommended practices. These issues were presented aswell to the SLE implementation developers which, based on our reports, developed a newrelease for SLE which we show xes the SLE blocking issue and greatly improves the pro-tocol throughput. In this paper, we also discuss future developments for our end-to-endemulation lab and how these improvements can be used to develop and test future spacecommunication technologies.

Networking↗
NASA NTRS2018

Computer Controlled Solid State Lighting Assembly to Emulate Diurnal Cycle and Improve Circadian Rhythm Control

A light system can simultaneously emulate more than one different diurnal cycle to individually improve circadian rhythm control for more than one observer by having each light fixture autonomously self-controlled. Each light fixture is mountable in respective locations to individually treat respective observers. Each light fixture includes one or more light elements mounted to a housing and are controllable to emit a selected light intensity at a selected light temperature. A micro controller is contained in the housing and includes memory containing instructions for one or more automatic diurnal cycle protocols. The micro controller is in communication with the memory and the one or more light elements to execute the instructions to configure the light fixture to vary the light intensity and the light temperature of the emitted light.

Holbert, Eirik↗
NASA NTRS2021

In-Flight Turbulence Emulation for Fixed-Wing Aircraft using Equivalent Multisine Excitations

A procedure is discussed for designing control-equivalent turbulence input (CETI) excitations to emulate a fixed-wing aircraft response to turbulence while flying through calm air. These excitations are added to the actuator commands to produce the same motion of the aircraft that would have resulted from flying in actual turbulence. Although CETI models are usually shaping filters driven by white noise inputs, the equivalent control inputs in this report were constructed as multisine excitations, which enables mimicking the response to turbulence with arbitrary power spectra, within hardware limitations. Practical aspects of the approach are discussed, such as actuator dynamics, model uncertainty, actual in-flight turbulence, and others. The procedure is demonstrated using a flight dynamics simulation model of a subscale generic jet transport aircraft.

control-equivalent turbulence inputs (CETI)↗
NASA NTRSDate not supplied

Entry, Descent, and Landing GN&C System Evaluation via Cable-Driven Emulation Robotics

An innovative cable-driven parallel robot named the Six Degree-of-Freedom Tendon Actu- ated Robot (STAR), recently developed by researchers at NASA Johnson Space Center, was built to enable entry, descent, and landing (EDL) emulation experiments. Upon functional testing and system verification, STAR employed several simulated EDL trajectories to validate velocimeter LIDAR-based sensor models for cooperative terrain relative navigation applica- tions for its first testing campaign. The STAR lab also hosted researchers from Astrobotic to evaluate the real-time performance of a newly developed sensor payload, UltraNav, through hardware in-the-loop-testing (HWIL). This work introduces the STAR system along with its accompanying testing utilities and capabilities, and deliver the experimental methodology and results of test campaigns performed with the STAR facility to date.

navigation↗
NASA NTRSDate not supplied

Statistical Analysis of Fading Power Vectors for Real-Time Atmospheric Channel Emulation

The design and testing of a free-space optical communication system requires assessment of the impact of random fluctuations in received power from a laser beam transmitted over an atmospheric channel. A number of methods for generating fading power vectors for in-lab emulation of an atmospheric channel have previously been reported. These techniques include spectral shaping and filtering of a signal from a normally distributed pseudo-random number generator, full wave optics simulations with random phase screens, and pre-recorded measurements from experimental free-space links. In this work, a statistical analysis of atmospheric fading is presented with the goal of producing a practical engineering model for the fading channel suitable for generating synthetic fade vectors in real-time for long-duration receiver testing with channel interleaving. Specifically, a parametric model is developed for turbulence-induced fade on space-to-ground links with large-aperture receivers, including aperture-averaging and the effects of aperture size on the instantaneous coupling efficiency for mode- limited receivers. In particular, we analyze the probability density function and temporal power spectrum for fluctuations of the coupling efficiency for few-mode fibers in a range of turbulence conditions.

free-space optical communication↗
NASA NTRSDate not supplied

Statistical Analysis of Fading Power Vectors for Real-Time Atmospheric Channel Emulation

The design and testing of a free-space optical communication system requires assessment of the impact of random fluctuations in received power from a laser beam transmitted over an atmospheric channel. A number of methods for generating fading power vectors for in-lab emulation of an atmospheric channel have previously been reported. These techniques include spectral shaping and filtering of a signal from a normally distributed pseudo-random number generator, full wave optics simulations with random phase screens, and pre-recorded measurements from experimental free-space links. In this work, a statistical analysis of atmospheric fading is presented with the goal of producing a practical engineering model for the fading channel suitable for generating synthetic fade vectors in real-time for long-duration receiver testing with channel interleaving. Specifically, a parametric model is developed for turbulence-induced fade on space-to-ground links with large-aperture receivers, including aperture-averaging and the effects of aperture size on the instantaneous coupling efficiency for mode-limited receivers. In particular, we analyze the probability density function and temporal power spectrum for fluctuations of the coupling efficiency for few-mode fibers in a range of turbulence conditions.

free-space optical communication↗