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At least 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Limiter-aware adaptive excitation control for hydropower generators with legacy voltage regulation systems

Hydropower units often rely on legacy excitation systems with fixed automatic voltage regulator (AVR) settings, but parameter drift, changing operating conditions, and evolving grid-service demands can degrade terminal-voltage regulation over time. This problem should be addressed because poor voltage regulation affects reactive-power support, system stability, and reliable plant operation, and replacing installed AVR and limiter logic is costly and disruptive in practice. To address this issue, this paper proposes a retrofit-friendly enhancement for hydropower generator excitation systems that combines adaptive tuning of the AVR middle lead–lag branch with a small proportional-integral correction for removing steady bias and slow drift. The adaptive laws are normalized, projection-bounded, and equipped with leakage, while adaptation is enabled only in the middle branch. Thus, the intent of the underexcitation and overexcitation limiters, as well as legacy current and rate limits, remains unchanged. Stability is analyzed under incremental performance assumptions, yielding boundedness and asymptotic tracking in the absence of saturation. The method is evaluated using real operational data from a utility-scale hydropower unit at Rocky Reach Dam, Unit C-8. Compared with the fixed AVR baseline, the proposed method reduces terminal-voltage mean squared error by about 70%, removes long periods of steady-state bias, and improves transient tracking while coexisting with limiter actions. These results show that substantial voltage-control improvement can be achieved on existing hydropower units with minimal integration effort and without replacing the installed AVR structure.

ESST5B model↗
DOE OSTI2026

Advanced Mixed Mode Combustor for Hydrogen F-Class Retrofit (Final Report)

This objective of this project was to develop a retrofittable combustor module for the GE Vernova Operations LLC (GE Vernova, GEV) frame 7F gas turbine (GT) that would allow operation on blends of hydrogen in Natural Gas (NG) between 0% and 100%. The new system was to be part of a package that retained current cycle performance while limiting the increase in NOx emissions to the equivalent of 25ppm (parts per million by volume dry at 15% O2, ppmvd15) with consideration for the impact of hydrogen fuel on the O2 correction. The expectation was that with the addition of Axial Fuel Staging (AFS), turndown within emission compliance would be extended to below 20% GT load. The original project plan included three budget periods (BPs): BP1 spanning October 1, 2022 through August 31, 2024; BP2 spanning September 1, 2024 through December 31, 2025; and BP3 spanning January 1, 2026 through September 30, 2026. The project was terminated early by the DOE on October 10, 2025 about three months prior to the end of BP2. BP3 activities were therefore cancelled. The program was on track to meet all objectives prior to the DOE termination. This Final Report covers work completed during BP1 and BP2 prior to the program termination.

08 HYDROGEN↗
NASA NTRS1984

Autonomous Integrated Receive System (AIRS) requirements definition. Volume 1: Executive summary

Distributed processing in the design and operation of the augmented TDRSS and the succeeding TDAS in the 1990's is discussed with the emphasis on the development of the autonomous integrated receive system (AIRS) for the operation of the S-band single access (SSA) return link in the White Sands ground terminal. This receive system has the capability of self configuration, real-time operation, and self diagnostic. The tasks of Doppler correction, demodulation, detection, and decoding are performed in an integrated manner where useful information are shared and used by ALL portions of AIRS performing these tasks. Operating modes, maintenance, system architecture, and performance characteristics are described.

Chie, C. M.↗
NASA NTRS1994

Sliding mode control method having terminal convergence in finite time

An object of this invention is to provide robust nonlinear controllers for robotic operations in unstructured environments based upon a new class of closed loop sliding control methods, sometimes denoted terminal sliders, where the new class will enforce closed-loop control convergence to equilibrium in finite time. Improved performance results from the elimination of high frequency control switching previously employed for robustness to parametric uncertainties. Improved performance also results from the dependence of terminal slider stability upon the rate of change of uncertainties over the sliding surface rather than the magnitude of the uncertainty itself for robust control. Terminal sliding mode control also yields improved convergence where convergence time is finite and is to be controlled. A further object is to apply terminal sliders to robot manipulator control and benchmark performance with the traditional computed torque control method and provide for design of control parameters.

Venkataraman, Subramanian T.↗
NASA NTRS2010

Concept of Operation for Tactical Separation Assurance in Super-Density Operations

The Airspace Systems Program is committed to supporting the Next Generation Air Transportation System through research and development in select areas. One such area, referred to as Super Density Operations, is conducting research to develop technologies that will safely increase the throughput in busy terminal area environments. The purpose of this document is to develop a Concept of Operations for the Tactical Separation Assurance function, one of the functions included in Super Density Operations. A functional description of the technologies required for Super Density Operations is presented followed by a more detail description of the Tactical Separation Assurance function. Two story boards are presented to illustrate the operational use of the Tactical Separation Assurance function under different situations. The last section proposes a pathway to implementing the Tactical Separation Assurance function.

Denery, Dallas G.↗
DOE OSTI2026

High-Voltage DC MULTI-terminal SIMulation (HVDC MULTISIM): Technical Program Summary

Expansion of the power grid in the USA is essential to fulfilling the rising energy demand of the country. In particular, the transmission grid, a network of electrical energy corridors that enable the flow of large amounts of energy from the point of generation to the point of consumption, needs significant expansion to cater to this growth of electrification. The current infrastructure is also dated, and any new transmission corridor should be based on a vision of building a modern infrastructure that is futureproof. High voltage DC (HVDC) transmission technology falls in this category: it is the most economical way to build large transmission lines and relies on sophisticated electronics and flexible controls, rather than just passive components like switchgear and transformers. This project is aimed at establishing the technical and economic feasibility of a network of HVDC lines that are interconnected to form a multi-terminal DC network. HVDC transmission is not a new technology and United States has a number of such lines; however, these are point to point transmissions and do not form a DC grid. Modeling and analyzing DC grids is challenging since there are no established modeling tools and the traditional ways of modeling AC grids fall short of providing the fidelity required the fast dynamics of the DC grid. This project aims to build a software-in-the-loop simulator for a multi-terminal HVDC grid, called MULTISIM and, establish new control and protection algorithms to operate such a connected DC system. NLR, a key partner, established the core framework of the MULTISIM simulator and validated its functionality. The GE Vernova team, created a full-scale model of a four-terminal HVDC network using PSCAD (Power Systems Computer Aided Design) software and established the baseline performance of the system during normal and fault operation. The project was started on 10/12024 with a kick-off meeting held on 12/11/2024 and ran through two quarters till termination. All the tasks, milestones and deliverables during this period were met. Several interim reports detailing the various tasks were submitted. The following sections provide details on the completed tasks till the project pause and termination after Q2.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS2000

NASA's Subsonic Jet Transport Noise Reduction Research

Although new jet transport airplanes in today s fleet are considerably quieter than the first jet transports introduced about 40 years ago, airport community noise continues to be an important environmental issue. NASA s Advanced Subsonic Transport (AST) Noise Reduction program was begun in 1994 as a seven-year effort to develop technology to reduce jet transport noise 10 dB relative to 1992 technology. This program provides for reductions in engine source noise, improvements in nacelle acoustic treatments, reductions in the noise generated by the airframe, and improvements in the way airplanes are operated in the airport environs. These noise reduction efforts will terminate at the end of 2001 and it appears that the objective will be met. However, because of an anticipated 3-8% growth in passenger and cargo operations well into the 21st Century and the slow introduction of new the noise reduction technology into the fleet, world aircraft noise impact will remain essentially constant until about 2020 to 2030 and thereafter begin to rise. Therefore NASA has begun planning with the Federal Aviation Administration, industry, universities and environmental interest groups in the USA for a new noise reduction initiative to provide technology for significant further reductions.

Powell, Clemans A.↗
NASA NTRS1981

An evaluation of head-up displays in civil transport operations

To determine the advantages and disadvantages of head-up displays (HUD) in civil transport approach and landing operations, an operational evaluation was conducted on the flight simulator for advanced aircraft at Ames. A non-conformal HUD concept which contained raw data and Flight Director command information, and a conformal, flight path HUD concept was designed to permit terminal area maneuvering, intercept, final approach, flare, and landing operations. Twelve B-727 line pilots (Captains) flew a series of precision and non-precision approaches under a variety of environmental and operational conditions, including wind shear, turbulence and low ceilings and visibilities. A preliminary comparison of various system and pilot performance measures as a function of display type (Flight Director HUD, Flight Path HUD, or No HUD) indicates improvements in precision and accuracy of aircraft flight path control when using the HUDs. The results also demonstrated some potentially unique advantages of a flight path HUD during non-precision approaches.

Lauber, J. K.↗
NASA NTRS1980

NASA TLA workload analysis support. Volume 1: Detailed task scenarios for general aviation and metering and spacing studies

The techniques required to produce and validate six detailed task timeline scenarios for crew workload studies are described. Specific emphasis is given to: general aviation single pilot instrument flight rules operations in a high density traffic area; fixed path metering and spacing operations; and comparative workload operation between the forward and aft-flight decks of the NASA terminal control vehicle. The validation efforts also provide a cursory examination of the resultant demand workload based on the operating procedures depicted in the detailed task scenarios.

Sundstrom, J. L.↗
NASA NTRS1990

Simulator evaluation of the final approach spacing tool

The design and simulator evaluation of an automation tool for assisting terminal radar approach controllers in sequencing and spacing traffic onto the final approach course is described. The automation tool, referred to as the Final Approach Spacing Tool (FAST), displays speed and heading advisories for arrivals as well as sequencing information on the controller's radar display. The main functional elements of FAST are a scheduler that schedules and sequences the traffic, a 4-D trajectory synthesizer that generates the advisories, and a graphical interface that displays the information to the controller. FAST was implemented on a high performance workstation. It can be operated as a stand-alone in the Terminal Radar Approach Control (TRACON) Facility or as an element of a system integrated with automation tools in the Air Route Traffic Control Center (ARTCC). FAST was evaluated by experienced TRACON controllers in a real-time air traffic control simulation. Simulation results show that FAST significantly reduced controller workload and demonstrated a potential for an increase in landing rate.

Davis, Thomas J.↗
NASA NTRS1991

Design and evaluation of an air traffic control Final Approach Spacing Tool

This paper describes the design and simulator evaluation of an automation tool for assisting terminal radar approach controllers in sequencing and spacing traffic onto the final approach course. The automation tool, referred to as the Final Approach Spacing Tool (FAST), displays speed and heading advisories for arriving aircraft as well as sequencing information on the controller's radar display. The main functional elements of FAST are a scheduler that schedules and sequences the traffic, a four-dimensional trajectory synthesizer that generates the advisories, and a graphical interface that displays the information to the controller. FAST has been implemented on a high-performance workstation. It can be operated as a stand-alone in the terminal radar approach control facility or as an element of a system integrated with automation tools in the air route traffic control center. FAST was evaluated by experienced air traffic controllers in a real-time air traffic control simulation. simulation results summarized in the paper show that the automation tools significantly reduced controller work load and demonstrated a potential for an increase in landing rate.

Davis, Thomas J.↗
NASA NTRS1974

Management and control of Skylab missions

The flight operations task, as developed in support of the Skylab Program, was evolutionary in nature and, to a great extent, was an orderly extension of the flight control concepts used in the Apollo Program, tempered by the nature of the Skylab Program. During the terminal portion of the Apollo Program, many of the operating concepts proposed for Skylab were tested and used for Apollo support to obtain a realistic evaluation of these new techniques. The principal concept developed in the Apollo Program and augmented in support of the Skylab Program was one wherein a professional operations team would provide support to the scientists in the areas of mission integration, experiment, and experiment support systems, monitoring and control, and data retrieval.

Roach, J. W.↗
NASA NTRS1979

Capturing and tracking performance of the horizontal guidance and control systems of the terminal configured vehicle

A twin-jet commercial transport equipped with digital navigation, guidance, and control systems and advanced electronic display system was used for airborne operational research. The results of flight tests which evaluated a second-order horizontal-path guidance control law and the autopilot and airplane response are presented. This evaluation was accomplished through analysis of recorded flight data and through pilot opinion of the airplane maneuvers during automatic path-capture scenarios and path tracking. Four different path captures were flown at a ground speed of approximately 160 knots and repeated at approximately 300 knots. Path tracking tracking error was measured in terms of cross track error along two paths: one pat at cruise speeds and one at airport-terminal-area speeds. The path tracking accuracy and the smoothness of the airplane maneuvers were judged satisfactory for high speeds; however, at lower speeds the control law design should be improved so that tracking will be more accurate for operations in the airport terminal area.

Knox, C. E.↗
NASA NTRS1993

SCATHA mission termination report

The SCATHA (Spacecraft Charging at High Altitudes) satellite was operated from the Consolidated Space Test Center in Sunnyvale, California from February 1979 to May 1991. It was a spin stabilized vehicle in a highly eccentric orbit that collected data on spacecraft charging. The purpose of such data gathering was to predict and/or model the effects of the Earth's magnetic field on synchronous and near synchronous satellites. During the majority of its lifetime, attitude precession maneuvers were done every 10-15 days to maintain solar panel orientation. Maneuver planning was difficult due to the structural characteristics of SCATHA. It is cylindrically shaped and has seven booms ranging in length from 2 to 50 meters. These precession maneuvers induced predictable nutation that damped out after a few days. Eventually fuel began running low due to these frequent maneuvers. Experiments that had required the spin axis be in the orbit plane had already been turned off or had collected all their data. To increase the vehicle lifetime, the spin axis was moved to ecliptic normal. While this stopped the need for frequent attitude maneuvering (only two per year required now), this movement of the spin axis caused nutation that would not damp out for the remainder of the mission. This phase of the mission, with the ecliptic normal orientation, lasted for approximately three years. Although nutation never damped, data gathering was uninterrupted. In late 1990, when SCATHA's transmitter became seriously degraded, the Air Force decided to turn SCATHA off. This would only be done after the satellite was made 'safe'. The most difficult part of making the vehicle safe was quickly purging the fuel. Several plans were considered. The selected plan was to perform a series of 20 degree attitude precession maneuvers (3 days apart to allow for the worst nutation to damp) until the fuel was depleted. Although this sounded simple, the actual execution proved difficult. This was due to a nearly complete lack of available telemetry data, large undamped motion of the long booms, inadequacies in attitude determination software, and an error in the fuel level calculation software. This paper discusses the various proposed termination plans and execution of the selected one. Attitude determination methodologies, nutation from maneuvers, and effects of the flexible booms on the termination mission are presented and analyzed from a satellite analyst point of view.

Stakkestad, Kjell↗
NASA NTRS1990

Douglas flight deck design philosophy

The systems experience gained from 17 years of DC-10 operation was used during the design of the MD-11 to automate system operation and reduce crew workload. All functions, from preflight to shutdown at the termination of flight, require little input from the crew. The MD-11 aircraft systems are monitored for proper operation by the Aircraft Systems Controllers (ASC). In most cases, system reconfiguration as a result of a malfunction is automated. Manual input is required for irreversible actions such as engine shutdown, fuel dump, fire agent discharge, or Integrated Drive Generator (IDG) disconnect. During normal operations, when the cockpit is configured for flight, all annunciators on the overhead panel will be extinguished. This Dark Cockpit immediately confirms to the crew that the panels are correctly configured and that no abnormalities are present. Primary systems annunciations are shown in text on the Alert Area of the Engine and Alert Display (EAD). This eliminates the need to scan the overhead. The MD-11 aircraft systems can be manually controlled from the overhead area of the cockpit. The center portion of the overhead panel is composed of the primary aircraft systems panels, which include FUEL, AIR, Electrical (ELEC) and Hydraulic (HYD) systems, which are easily accessible from both flight crew positions. Each Aircraft Systems Controller (ASC) has two automatic channels and a manual mode. All rectangular lights are annunciators. All square lights are combined switches and annunciators called switch/lights. Red switch/lights on the overhead (Level 3 alerts) are for conditions requiring immediate crew action. Amber (Level 2 or Level 1 alerts) indicates a fault or switch out of position requiring awareness or crew interaction. Overhead switches used in normal operating conditions will illuminate blue when in use (Level 0 alerts) such as WING ANTI-ICE - ON. An overhead switch/light with BLACK LETTERING on an amber or red background indicates a system failure and that crew interaction is required. A switch/light with blue or amber lettering and a BLACK BACKGROUND indicates a switch out of normal position and that crew action is necessary only if the system is in manual operation.

Oldale, Paul↗
NASA NTRS2010

Preliminary Investigation of Civil Tiltrotor in NextGen Airspace

Presentation intro: Tiltrotor aircraft have long been envisioned as being a potentially viable means of commercial aviation transport. Preliminary results from an ongoing study into the operational and technological considerations of Civil Tiltrotor (CTR) operation in the Next Generation airspace, circa the 2025 time-frame, are presented and discussed. In particular, a fleet of CTR aircraft has been conceptually designed. The performance characteristics of this CTR fleet was subsequently translated into BADA (Base of Aircraft DAta) models that could be used as input to emulate CTR aircraft operations in the ACES and AvTerminal airspace and terminal area simulation tools. A network of nine North-Eastern corridor airports is the focus of the airspace simulation effort; the results from this airport network viII then be extrapolated to provide insights into systemic impact of CTRs on the National Airspace System (NAS). Future work will also be detailed as to attempts to model the systemic effects of noise and emissions from this fleet of new aircraft as well as assess their leveraged impact on public service missions, in time of need, such as major regional/national disaster relief efforts. The ideal outcome of this study is a set of results whereby Next Gen airspace CONOPs can be refined to reflect potential CTR capabilities and, conversely, CTR technology development efforts can be better informed as to key performance requirement thresholds needed to be met in order to successfully introduce these aircraft into civilian aviation operation.

Young, Larry A.↗
NASA NTRS2003

Major Impact of Fleet Renewal Over Airports Located in the Most Important Region of Brazil

The present article discusses and analyses the major impacts of the Brazilian carriers fleet renewal regarding Brazilian airport infrastructure in the most important region of the country, the Southeast (SE). A brief historical overview of the country's airline fleet will be presented, demonstrating the need for its renewal (m fact, Brazilian carriers started a major fleet renewal program m the last five years), while analyzing the periods in which a new breed of aircraft was put into service by the major carriers operating in the SE region. The trend of operating the classic regional jets plus the forthcoming entry into service of the "large regional jets" (LRJ, 70-115 seaters) in several point-to-point routes are presented along with the country's carriers" reality of operating these former aircraft in several high-capacity and medium-range routes. The article will focus on the ability of four of the major Southeast's airports to cope with the fleet modernization, mainly due to the fact that the region studied is the most socioeconomic developed, by far, with the largest demand for air transportation, thus making the impacts much more perceptible for the communities and the airport management involved. With the emergence of these impacts, several new projects and investments are being discussed and pushed forward, despite budgetary constrains being a reality in almost every Brazilian city, even in the SE region. In view of this, the paper presents how the general planning could be carried out in order to adapt the airports' infrastructures in function of the proposed (and in some cases, necessary) fleet renewal. Ultimately, we will present the present picture and two future scenarios m order to determine the level of service in the existent passenger terminal facilities in the wake of the possible operation of several new aircraft. Keywords: Airline fleet planning, Airport planning, Regional development, Regional Jets.

Maters, Rafael Waltz↗
NASA NTRS1987

Pressure-Transducer Simulator

Simulation circuit operates under remote, automatic, or manual control to produce electrical outputs similar to pressure transducer. Specific circuit designed for simulations of Space Shuttle main engine. General circuit concept adaptable to other simulation and control systems involving several operating modes. Switches and amplifiers respond to external control signals and panel control settings to vary differential excitation of resistive bridge. Output voltage or passive terminal resistance made to equal pressure transducer in any of four operating modes.

Simon, Richard A.↗