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At least 1,387 records · Page 77
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Accuracy of an infrared marker-based patient positioning system (ExacTrac®) for stereotactic body radiotherapy in localizing the planned isocenter using fiducial markers

Stereotactic Body Radiation Therapy (SBRT) requires a controlled immobilization and position monitoring of patient and target. The purpose of this work is to analyze the performance of the imaging system ExacTrac® (ETX) using infrared and fiducial markers. Materials and methods: In order to assure the accuracy of isocenter localization, a Quality Assurance procedure was applied using an infrared marker-based positioning system. Scans were acquired of an inhouse-agar gel and solid water phantom with infrared spheres. In the inner part of the phantom, three reference markers were delineated as reference and one pellet was place internally; which was assigned as the isocenter. The iPlan® RT Dose treatment planning system. Images were exported to the ETX console. Images were acquired with the ETX to check the correctness of the isocenter placement. Adjustments were made in 6D the reference markers were used to fuse the images. Couch shifts were registered. The procedure was repeated for verification purposes. Results: The data recorded of the verifications in translational and rotational movements showed averaged 3D spatial uncertainties of 0.31 ± 0.42 mm respectively 0.82° ± 0.46° in the phantom and the first correction of these uncertainties were of 1.51 ± 1.14 mm respectively and 1.37° ± 0.61°. Conclusions: This study shows a high accuracy and repeatability in positioning the selected isocenter. The ETX-system for verifying the treatment isocenter position has the ability to monitor the tracing position of interest, making it possible to be used for SBRT positioning within uncertainty ≤1mm.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
NASA NTRS1994

The Virtual Mission Operations Center

Spacecraft management is becoming more human intensive as spacecraft become more complex and as operations costs are growing accordingly. Several automation approaches have been proposed to lower these costs. However, most of these approaches are not flexible enough in the operations processes and levels of automation that they support. This paper presents a concept called the Virtual Mission Operations Center (VMOC) that provides highly flexible support for dynamic spacecraft management processes and automation. In a VMOC, operations personnel can be shared among missions, the operations team can change personnel and their locations, and automation can be added and removed as appropriate. The VMOC employs a form of on-demand supervisory control called management by exception to free operators from having to actively monitor their system. The VMOC extends management by exception, however, so that distributed, dynamic teams can work together. The VMOC uses work-group computing concepts and groupware tools to provide a team infrastructure, and it employs user agents to allow operators to define and control system automation.

Moore, Mike↗
NASA NTRS1985

Design description of a microprocessor based Engine Monitoring and Control unit (EMAC) for small turboshaft

Research programs have demonstrated that digital electronic controls are more suitable for advanced aircraft/rotorcraft turbine engine systems than hydromechanical controls. Commercially available microprocessors are believed to have the speed and computational capability required for implementing advanced digital control algorithms. Thus, it is desirable to demonstrate that off-the-shelf microprocessors are indeed capable of performing real time control of advanced gas turbine engines. The engine monitoring and control (EMAC) unit was designed and fabricated specifically to meet the requirements of an advanced gas turbine engine control system. The EMAC unit is fully operational in the Army/NASA small turboshaft engine digital research program.

Baez, A. N.↗
DOE OSTI2016

SU-D-BRA-01: Feasibility Study for Swallowing Prediction Using Pressure Sensors

Purpose: To develop a swallowing prediction system (SPS) using force sensing sensors and evaluate its feasibility. Methods: The SPS developed consists of force sensing sensor units, a thermoplastic mask, a signal transport device and a control PC installed with an in-house software. The SPS is designed to predict the pharyngeal stage of swallowing because it is known that internal organ movement occurs in pharyngeal stage. To detect prediction signal in the SPS, the force sensing sensor units were attached on both the submental muscle region and thyroid cartilage region of the thermoplastic mask. While the signal from the thyroid cartilage region informs the action of swallowing, the signal from the submental muscle region is utilized as a precursor for swallowing. Since the duration of swallowing is relatively short, using such precursor (or warning) signals for machine control is considered more beneficial. A volunteer study was conducted to evaluate the feasibility of the system. In this volunteer study, we intended to verify that the system could predict the pharyngeal stage of the swallowing. We measured time gaps between obtaining the warning signals in the SPS and starting points of the pharyngeal stage of swallowing. Results: The measured data was examined whether the time gaps were in reasonable order to be easily utilized. The mean and standard deviation values of these time gaps were 0.550 s ± 0.183 s. in 8 volunteers. Conclusion: The proposed method was able to predict the on-set of swallowing of human subjects inside the thermoplastic mask, which has never been possible with other monitoring systems such as camera-based monitoring system. With the prediction ability of swallowing incorporated into the machine control mechanism (in the future), beam delivery can be controlled to skip swallowing periods and significant dosimetric gain is expected in head & neck cancer treatments. This work was supported by the Radiation Technology R&D program (No. 2015M2A2A7038291) and by the Mid-career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the Ministry of Science, ICT&Future Planning.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1989

Multidisciplinary Expert-aided Analysis and Design (MEAD)

The MEAD Computer Program (MCP) is being developed under the Multidisciplinary Expert-Aided Analysis and Design (MEAD) Project as a CAD environment in which integrated flight, propulsion, and structural control systems can be designed and analyzed. The MCP has several embedded computer-aided control engineering (CACE) packages, a user interface (UI), a supervisor, a data-base manager (DBM), and an expert system (ES). The supervisor monitors and coordinates the operation of the CACE packages, the DBM; the ES, and the UI. The DBM tracks the control design process. Models created or installed by the MCP are tracked by date and version, and results are associated with the specific model version with which they were generated. The ES is used to relieve the control engineer from tedious and cumbersome tasks in the iterative design process. The UI provides the capability for a novice as well as an expert to utilize the MCP easily and effectively. The MCP version 2(MCP-2.0) is fully developed for flight control system design and analysis. Propulsion system modeling, analysis, and simulation is also supported; the same is true for structural models represented in state-space form. The ultimate goal is to cover the integration of flight, propulsion, and structural control engineering, including all discipline-specific functionality and interfaces. The current MCP-2.0 components and functionality are discussed.

Hummel, Thomas C.↗
NASA NTRS2006

In-Flight Validation of a Pilot Rating Scale for Evaluating Failure Transients in Electronic Flight Control Systems

Engineering development and qualification of a Research Flight Control System (RFCS) for the Rotorcraft Aircrew Systems Concepts Airborne Laboratory (RASCAL) JUH-60A has motivated the development of a pilot rating scale for evaluating failure transients in fly-by-wire flight control systems. The RASCAL RFCS includes a highly-reliable, dual-channel Servo Control Unit (SCU) to command and monitor the performance of the fly-by-wire actuators and protect against the effects of erroneous commands from the flexible, but single-thread Flight Control Computer. During the design phase of the RFCS, two piloted simulations were conducted on the Ames Research Center Vertical Motion Simulator (VMS) to help define the required performance characteristics of the safety monitoring algorithms in the SCU. Simulated failures, including hard-over and slow-over commands, were injected into the command path, and the aircraft response and safety monitor performance were evaluated. A subjective Failure/Recovery Rating (F/RR) scale was developed as a means of quantifying the effects of the injected failures on the aircraft state and the degree of pilot effort required to safely recover the aircraft. A brief evaluation of the rating scale was also conducted on the Army/NASA CH-47B variable stability helicopter to confirm that the rating scale was likely to be equally applicable to in-flight evaluations. Following the initial research flight qualification of the RFCS in 2002, a flight test effort was begun to validate the performance of the safety monitors and to validate their design for the safe conduct of research flight testing. Simulated failures were injected into the SCU, and the F/RR scale was applied to assess the results. The results validate the performance of the monitors, and indicate that the Failure/Recovery Rating scale is a very useful tool for evaluating failure transients in fly-by-wire flight control systems.

Kalinowski, Kevin F.↗
NASA NTRS1994

Shared mission operations concept

Historically, new JPL flight projects have developed a Mission Operations System (MOS) as unique as their spacecraft, and have utilized a mission-dedicated staff to monitor and control the spacecraft through the MOS. NASA budgetary pressures to reduce mission operations costs have led to the development and reliance on multimission ground system capabilities. The use of these multimission capabilities has not eliminated an ongoing requirement for a nucleus of personnel familiar with a given spacecraft and its mission to perform mission-dedicated operations. The high cost of skilled personnel required to support projects with diverse mission objectives has the potential for significant reduction through shared mission operations among mission-compatible projects. Shared mission operations are feasible if: (1) the missions do not conflict with one another in terms of peak activity periods, (2) a unique MOS is not required, and (3) there is sufficient similarity in the mission profiles so that greatly different skills would not be required to support each mission. This paper will further develop this shared mission operations concept. We will illustrate how a Discovery-class mission would enter a 'partner' relationship with the Voyager Project, and can minimize MOS development and operations costs by early and careful consideration of mission operations requirements.

Spradlin, Gary L.↗
DOE OSTI2014

Quantifying the Impact of Unavailability in Cyber-Physical Environments

The Supervisory Control and Data Acquisition (SCADA) system discussed in this work manages a distributed control network for the Tunisian Electric & Gas Utility. The network is dispersed over a large geographic area that monitors and controls the flow of electricity/gas from both remote and centralized locations. The availability of the SCADA system in this context is critical to ensuring the uninterrupted delivery of energy, including safety, security, continuity of operations and revenue. Such SCADA systems are the backbone of national critical cyber-physical infrastructures. Herein, we propose adapting the Mean Failure Cost (MFC) metric for quantifying the cost of unavailability. This new metric combines the classic availability formulation with MFC. The resulting metric, so-called Econometric Availability (EA), offers a computational basis to evaluate a system in terms of the gain/loss ($/hour of operation) that affects each stakeholder due to unavailability.

Availability↗
NASA NTRS2005

Magnetically Attached Multifunction Maintenance Rover

A versatile mobile telerobot, denoted the magnetically attached multifunction maintenance rover (MAGMER), has been proposed for use in the inspection and maintenance of the surfaces of ships, tanks containing petrochemicals, and other large ferromagnetic structures. As its name suggests, this robot would utilize magnetic attraction to adhere to a structure. As it moved along the surface of the structure, the MAGMER would perform tasks that could include close-up visual inspection by use of video cameras, various sensors, and/or removal of paint by water-jet blasting, laser heating, or induction heating. The water-jet nozzles would be mounted coaxially within compressed-air-powered venturi nozzles that would collect the paint debris dislodged by the jets. The MAGMER would be deployed, powered, and controlled from a truck, to which it would be connected by hoses for water, compressed air, and collection of debris and by cables for electric power and communication (see Figure 1). The operation of the MAGMER on a typical large structure would necessitate the use of long cables and hoses, which can be heavy. To reduce the load of the hoses and cables on the MAGMER and thereby ensure its ability to adhere to vertical and overhanging surfaces, the hoses and cables would be paid out through telescopic booms that would be parts of a MAGMER support system. The MAGMER would move by use of four motorized, steerable wheels, each of which would be mounted in an assembly that would include permanent magnets and four pole pieces (see Figure 2). The wheels would protrude from between the pole pieces by only about 3 mm, so that the gap between the pole pieces and the ferromagnetic surface would be just large enough to permit motion along the surface but not so large as to reduce the magnetic attraction excessively. In addition to the wheel assemblies, the MAGMER would include magnetic adherence enhancement fixtures, which would comprise arrays of permanent magnets and pole pieces that could be adjusted to maximize or minimize the overall attractive magnetic force. Even with a paint thickness of 2 mm, a preliminary design provides a safety factor of 5 in the magnetic force in the upside- down, water-jets-operating condition, in which the total load (including the weight of the MAGMER and cables and the water-jet force) would be about 260 lb (the weight of 118 kg). Optionally, the MAGMER could carry magnetic shielding and/or could be equipped with a demagnetizing module to remove residual magnetism from the structure. The MAGMER would carry four charge-coupled-device cameras for visual inspection, monitoring of operation, navigation, and avoidance of collisions with obstacles. The control system of the MAGMER would include navigation and collision-avoidance subsystems that would utilize surface features as landmarks, in addition to direct images of obstacles.

Bar-Cohen, Yoseph↗
NASA NTRS2018

Antimicrobials for Water Systems in Manned Spaceflight - Past, Present, and Future Applications and Challenges

The use of antimicrobials to control microbiological growth in manned spaceflight water-based systems has and will continue to have a unique set of challenges and needs. The challenges are varied, and include antimicrobial effectiveness, crew health and safety, materials compatibility, optimal system functionality, antimicrobial shelf life, means to monitor antimicrobial concentration, and means to re-introduce biocides periodically in the case of depletion. Needs vary from application to application, and include control of pathogens for crew health, control of biofilm formation for optimal system functionality, inhibition and prevention of microbiologically influenced corrosion, optimization of wetted metallic material life, and general living quarter and consumable aesthetics with respect to odor and taste. This paper outlines and discusses the various antimicrobials used in prior and current manned spaceflight water-based applications with focus on pros, cons and lessons learned. Design factors such as minimum inhibitory concentration, minimum lethal concentration, required circulated concentrations, materials selection, means to introduce, means to monitor real-time, and concentration maintenance are discussed. The challenges associated with longer term missions, as well as long-term system dormancy as envisioned for exploration missions, lunar habitats, and a manned Mars mission are outlined with respect to anticipated needs and potential design solutions.

potable water↗
DOE OSTI2014

High spatial and temporal resolution charge exchange recombination spectroscopy on the HL-2A tokamak

A 32/64-channel charge exchange recombination spectroscopy (CXRS) diagnostic system is developed on the HL-2A tokamak (R = 1.65 m, a = 0.4 m), monitoring plasma ion temperature and toroidal rotation velocity simultaneously. A high throughput spectrometer (F/2.8) and a pitch-controlled fiber bundle enable the temporal resolution of the system up to 400 Hz. The observation geometry and an optimized optic system enable the highest radial resolution up to ~1 cm at the plasma edge. The CXRS system monitors the carbon line emission (C VI, n = 8–7, 529.06 nm) whose Doppler broadening and Doppler shift provide ion temperature and plasma rotation velocity during the neutral beam injection. The composite CX spectral data are analyzed by the atomic data and analysis structure charge exchange spectroscopy fitting (ADAS CXSFIT) code. First experimental results are shown for the case of HL-2A plasmas with sawtooth oscillations, electron cyclotron resonance heating, and edge transport barrier during the high-confinement mode (H-mode)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Texture analysis on the fluence map to evaluate the degree of modulation for volumetric modulated arc therapy

Purpose: Texture analysis on fluence maps was performed to evaluate the degree of modulation for volumetric modulated arc therapy (VMAT) plans. Methods: A total of six textural features including angular second moment, inverse difference moment, contrast, variance, correlation, and entropy were calculated for fluence maps generated from 20 prostate and 20 head and neck VMAT plans. For each of the textural features, particular displacement distances (d) of 1, 5, and 10 were adopted. To investigate the deliverability of each VMAT plan, gamma passing rates of pretreatment quality assurance, and differences in modulating parameters such as multileaf collimator (MLC) positions, gantry angles, and monitor units at each control point between VMAT plans and dynamic log files registered by the Linac control system during delivery were acquired. Furthermore, differences between the original VMAT plan and the plan reconstructed from the dynamic log files were also investigated. To test the performance of the textural features as indicators for the modulation degree of VMAT plans, Spearman’s rank correlation coefficients (r{sub s}) with the plan deliverability were calculated. For comparison purposes, conventional modulation indices for VMAT including the modulation complexity score for VMAT, leaf travel modulation complexity score, and modulation index supporting station parameter optimized radiation therapy (MI{sub SPORT}) were calculated, and their correlations were analyzed in the same way. Results: There was no particular textural feature which always showed superior correlations with every type of plan deliverability. Considering the results comprehensively, contrast (d = 1) and variance (d = 1) generally showed considerable correlations with every type of plan deliverability. These textural features always showed higher correlations to the plan deliverability than did the conventional modulation indices, except in the case of modulating parameter differences. The r{sub s} values of contrast to the global gamma passing rates with criteria of 2%/2 mm, 2%/1 mm, and 1%/2 mm were 0.536, 0.473, and 0.718, respectively. The respective values for variance were 0.551, 0.481, and 0.688. In the case of local gamma passing rates, the r{sub s} values of contrast were 0.547, 0.578, and 0.620, respectively, and those of variance were 0.519, 0.527, and 0.569. All of the r{sub s} values in those cases were statistically significant (p < 0.003). In the cases of global and local gamma passing rates, MI{sub SPORT} showed the highest correlations among the conventional modulation indices. For global passing rates, r{sub s} values of MI{sub SPORT} were −0.420, −0.330, and −0.632, respectively, and those for local passing rates were −0.455, −0.490 and −0.502. The values of r{sub s} of contrast, variance, and MI{sub SPORT} with the MLC errors were −0.863, −0.828, and 0.795, respectively, all with statistical significances (p < 0.001). The correlations with statistical significances between variance and dose-volumetric differences were observed more frequently than the others. Conclusions: The contrast (d = 1) and variance (d = 1) calculated from fluence maps of VMAT plans showed considerable correlations with the plan deliverability, indicating their potential use as indicators for assessing the degree of modulation of VMAT plans. Both contrast and variance consistently showed better performance than the conventional modulation indices for VMAT.

60 APPLIED LIFE SCIENCES↗
NASA NTRSDate not supplied

Defining a Global Lunar Position, Navigation, and Timing System

As NASA seeks to fulfill its mission of extending humanity’s reach through exploration as delineated in the Moon to Mars Strategy and Objectives Development and the Moon to Mars Architecture Definition Document, accurate and timely position, navigation, and timing (PNT) services are critical in the architecture, identifying a need to expand a PNT capability to the full lunar proximity service volume. This is echoed in the White House Office of Science, Technology, and Policy Cislunar Science and Technology Strategy, which pinpoints the fundamental need for PNT infrastructure to enable and sustain a vibrant cislunar ecosystem. While the Human Lunar Return segment seeks commercial services to provide a PNT service over a South Pole service volume for a limited period per Earth day, meeting the Sustained Lunar Evolution segment requires a Lunar Navigation System (LNS) focused on delivery of precise and resilient PNT services across the lunar globe and near-Moon space. This presentation describes the pre-Phase A system concept for an orbital constellation, the requisite lunar surface-based in-situ monitor and control segment, and an Earth control segment to provide lunar PNT services out to 200km altitude above the surface. The LNS leverages the foundational efforts on lunar reference system components such as the Lunar Geodetic System, Lunar Time System, and lunar ephemeris and orientation critical to safe, accurate, and seamless navigation.

navigation↗
NASA NTRS2001

Space Science Payloads Optical Properties Monitor (OPM) Mission Flight Anomalies Thermal Analyses

The OPM was the first space payload that measured in-situ the optical properties of materials and had data telemetered to ground. The OPM was EVA mounted to the Mir Docking Module for an eight-month stay where flight samples were exposed to the Mir induced and natural environments. The OPM was comprised of three optical instruments; a total hemispherical spectral reflectometer, a vacuum ultraviolet spectrometer, and a total integrated scatterometer. There were also three environmental monitors; an atomic oxygen monitor, solar and infrared radiometers, and two temperature-controlled quartz crystal microbalances (to monitor contamination). Measurements were performed weekly and data telemetered to ground through the Mir data system. This paper will describe the OPM thermal control design and how the thermal math models were used to analyze anomalies which occurred during the space flight mission.

Schmitz, Craig P.↗
NASA NTRS1989

A knowledge-based flight status monitor for real-time application in digital avionics systems

The Dryden Flight Research Facility of the National Aeronautics and Space Administration (NASA) Ames Research Center (Ames-Dryden) is the principal NASA facility for the flight testing and evaluation of new and complex avionics systems. To aid in the interpretation of system health and status data, a knowledge-based flight status monitor was designed. The monitor was designed to use fault indicators from the onboard system which are telemetered to the ground and processed by a rule-based model of the aircraft failure management system to give timely advice and recommendations in the mission control room. One of the important constraints on the flight status monitor is the need to operate in real time, and to pursue this aspect, a joint research activity between NASA Ames-Dryden and the Royal Aerospace Establishment (RAE) on real-time knowledge-based systems was established. Under this agreement, the original LISP knowledge base for the flight status monitor was reimplemented using the intelligent knowledge-based system toolkit, MUSE, which was developed under RAE sponsorship. Details of the flight status monitor and the MUSE implementation are presented.

Duke, E. L.↗
DOE OSTI2019

Using virtual sensors to accommodate industrial asset control systems during cyber attacks

In some embodiments, an industrial asset may be associated with a plurality of monitoring nodes, each monitoring node generating a series of monitoring node values over time that represent operation of the industrial asset. A threat detection computer may determine that an attacked monitoring node is currently being attacked. Responsive to this determination, a virtual sensor coupled to the plurality of monitoring nodes may estimate a series of virtual node values for the attacked monitoring node(s) based on information received from monitoring nodes that are not currently being attacked. The virtual sensor may then replace the series of monitoring node values from the attacked monitoring node(s) with the virtual node values. Note that in some embodiments, virtual node values may be estimated for a particular node even before it is determined that the node is currently being attacked.

20 FOSSIL-FUELED POWER PLANTS↗
DOE OSTI2020

Using virtual sensors to accommodate industrial asset control systems during cyber attacks

In some embodiments, an industrial asset may be associated with a plurality of monitoring nodes, each monitoring node generating a series of monitoring node values over time that represent operation of the industrial asset. A threat detection computer may determine that an attacked monitoring node is currently being attacked. Responsive to this determination, a virtual sensor coupled to the plurality of monitoring nodes may estimate a series of virtual node values for the attacked monitoring node(s) based on information received from monitoring nodes that are not currently being attacked. The virtual sensor may then replace the series of monitoring node values from the attacked monitoring node(s) with the virtual node values. Note that in some embodiments, virtual node values may be estimated for a particular node even before it is determined that the node is currently being attacked.

Mestha, Lalit Keshav↗