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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 1,333 records · Page 74
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

On actuator placement for robust time-optimal control of uncertain flexible spacecraft

The problem of computing open-loop, on-off jet firing logic for flexible spacecraft in the face of plant modeling uncertainty is investigated. The primary control objective is to achieve a fast maneuvering time with a minimum of structural vibrations during and/or after a maneuver. This paper is also concerned with the problem of selecting a proper pair of jets for practical trade-offs among the maneuvering time, fuel consumption, structural mode excitation, and performance robustness. A time-optimal control problem subject to parameter robustness constraints is formulated. A three-mass-spring model of flexible spacecraft with a rigid-body mode and two flexible modes is used to illustrate the concept.

Wie, Bong↗
NASA NTRS1993

Dual-Latching, Solenoid-Actuated Tube Valve

Tube-type shutoff valve electrically positioned to open or closed state by concentric solenoid. Solenoid dual latching: it holds position until changed electrically or manually. In tube valve, central tube slides axially, closing off flow when held against seat and allowing flow when backed away from seat. Simple to balance pressure on seal between seat and sharp edge of tube. With pressure-balanced seal, only small force needed to hold valve in position, regardless of pressure acting on valve.

Brudnicki, Myron J.↗
NASA NTRS1989

Electro-optic architecture for servicing sensors and actuators in advanced aircraft propulsion systems

A detailed design of a fiber optic propulsion control system, integrating favored sensors and electro-optics architecture is presented. Layouts, schematics, and sensor lists describe an advanced fighter engine system model. Components and attributes of candidate fiber optic sensors are identified, and evaluation criteria are used in a trade study resulting in favored sensors for each measurand. System architectural ground rules were applied to accomplish an electro-optics architecture for the favored sensors. A key result was a considerable reduction in signal conductors. Drawings, schematics, specifications, and printed circuit board layouts describe the detailed system design, including application of a planar optical waveguide interface.

Poppel, G. L.↗
NASA NTRS1989

Electro-optic architecture (EOA) for sensors and actuators in aircraft propulsion systems

Results of a study to design an optimal architecture for electro-optical sensing and control in advanced aircraft and space systems are described. The propulsion full authority digital Electronic Engine Control (EEC) was the focus for the study. The recommended architecture is an on-engine EEC which contains electro-optic interface circuits for fiber-optic sensors on the engine. Size and weight are reduced by multiplexing arrays of functionally similar sensors on a pair of optical fibers to common electro-optical interfaces. The architecture contains common, multiplex interfaces to seven sensor groups: (1) self luminous sensors; (2) high temperatures; (3) low temperatures; (4) speeds and flows; (5) vibration; (6) pressures; and (7) mechanical positions. Nine distinct fiber-optic sensor types were found to provide these sensing functions: (1) continuous wave (CW) intensity modulators; (2) time division multiplexing (TDM) digital optic codeplates; (3) time division multiplexing (TDM) analog self-referenced sensors; (4) wavelength division multiplexing (WDM) digital optic code plates; (5) wavelength division multiplexing (WDM) analog self-referenced intensity modulators; (6) analog optical spectral shifters; (7) self-luminous bodies; (8) coherent optical interferometers; and (9) remote electrical sensors. The report includes the results of a trade study including engine sensor requirements, environment, the basic sensor types, and relevant evaluation criteria. These figures of merit for the candidate interface types were calculated from the data supplied by leading manufacturers of fiber-optic sensors.

Glomb, W. L., Jr.↗
NASA NTRS1993

Design and application of electromechanical actuators for deep space missions

During the period 8/16/92 through 2/15/93, work has been focused on three major topics: (1) screw modeling and testing; (2) motor selection; and (3) health monitoring and fault diagnosis. Detailed theoretical analysis has been performed to specify a full dynamic model for the roller screw. A test stand has been designed for model parameter estimation and screw testing. In addition, the test stand is expected to be used to perform a study on transverse screw loading.

Haskew, Tim A.↗
NASA NTRS1993

Magnetic suspension actuator concepts and applications

The fundamental aspect which makes magnetic suspension systems possible is the magnetic phenomena by which significant forces can be generated. Each of these force-producing phenomena has unique characteristics and is implementable in a unique fashion, such that each performs the magnetic suspension task differently than the others. A practical overview of the force-producing concepts, their unique characteristics, and their typical methods of application is provided.

Kroeger, John↗
NASA NTRS1991

Active noise control - Piezoceramic actuators in fluid/structure interaction models

A model for a 2-D acoustic cavity with a flexible boundary (a beam) controlled via piezoceramic patches producing bending moments in the beam is considered. The associated control problem for this fluid/structure interaction system to reduce the acoustic pressure in the cavity involves unbounded control inputs. Approximation methods in the context of an LQR state space formulation are discussed, and numerical results are presented to demonstrate the effectiveness of this approach in computing feedback controls for noise reduction.

Banks, H. T.↗
NASA NTRS1993

Approximation methods for control of structural acoustics models with piezoceramic actuators

The active control of acoustic pressure in a 2-D cavity with a flexible boundary (a beam) is considered. Specifically, this control is implemented via piezoceramic patches on the beam which produces pure bending moments. The incorporation of the feedback control in this manner leads to a system with an unbounded input term. Approximation methods in this manner leads to a system with an unbounded input term. Approximation methods in this manner leads to a system with an unbounded input team. Approximation methods in the context of linear quadratic regulator (LQR) state space control formulation are discussed and numerical results demonstrating the effectiveness of this approach in computing feedback controls for noise reduction are presented.

Banks, H. T.↗
NASA NTRS1993

Development and test of electromechanical actuators for thrust vector control

A road map of milestones toward the goal of a full scale Redesigned Solid Rocket Motor/Flight Support Motor (RSRM/FSM) hot fire test is discussed. These milestones include: component feasibility, full power system demonstration, SSME hot fire tests, and RSRM hot fire tests. The participation of the Marshall Space Flight Center is emphasized.

Weir, Rae A.↗
NASA NTRS1923

The time lag and interval of discharge with a spring actuated fuel injection pump

Discussed here is research on a spring activated fuel pump for solid or airless injection with small, high speed internal combustion engines. The pump characteristics under investigation were the interval of fuel injection in terms of degrees of crank travel and in absolute time, the lag between the time the injection pump plunger begins its stroke and the appearance of the jet at the orifice, and the manner in which the fuel spray builds up to a maximum when the fuel valve is opened, and then diminishes.

Matthews, Robertson↗