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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Filling the expertise gap

Aeroelasticity, structures, and stability-and-control specialists can work in concerted fashion during the early design phases of future aircraft to achieve active control of naturally unstable configurations. In order to take full advantage of active control, attention must be given by designers to control-law synthesis, and to tools for the efficient synthesis and analysis of complex flexible-aircraft control systems. Analysts must consider interfaces among unsteady aerodynamics, structures, and control theory, as explored by the theory of analytic continuation for unsteady aerodynamics.

Abel, Irving↗
NASA NTRS1993

Average-cost based robust structural control

A method is presented for the synthesis of robust controllers for linear time invariant structural systems with parameterized uncertainty. The method involves minimizing quantities related to the quadratic cost (H2-norm) averaged over a set of systems described by real parameters such as natural frequencies and modal residues. Bounded average cost is shown to imply stability over the set of systems. Approximations for the exact average are derived and proposed as cost functionals. The properties of these approximate average cost functionals are established. The exact average and approximate average cost functionals are used to derive dynamic controllers which can provide stability robustness. The robustness properties of these controllers are demonstrated in illustrative numerical examples and tested in a simple SISO experiment on the MIT multi-point alignment testbed.

Hagood, Nesbitt W.↗
NASA NTRS1999

Effect of Electrical Stimulation on Beta-Adrenergic Receptor Population and Coupling Efficiency in Chicken and Rat Skeleton Muscle Cell Cultures

Expression of the beta-adrenergic receptor (bAR) and its coupling to cyclic AMP (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy, and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the bAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically, chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for seven days in culture were subjected to electrical stimulation for an additional two days at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the bAR population was not significantly affected by electrical stimulation; however, the ability of these cells to synthesize cyclic AMP was reduced by approximately one-half. Thus, in chicken muscle cells an enhanced level of contraction reduced the coupling efficiency of bAR for cyclic AMP production by approximately 55% compared to controls. In contrast, the bAR population in rat muscle cells was increased by approximately 25% by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was also increased by almost two-fold. Thus, in rat muscle cells an enhanced level of contraction increased the coupling efficiency of bAR for cyclic AMP production by approximately 50% compared to controls. The basal levels of intracellular cyclic AMP in both rat muscle cells and chicken muscle cells were not affected by electrical stimulation.

Young, Ronald B.↗
NASA NTRS2000

Effect of Electrical Stimulation on Beta-Adrenergic Receptor Population and Cyclic AMP Production in Chicken and Rat Skeletal Muscle Cell Cultures

Expression of the beta-adrenergic receptor (PAR) and its coupling to Adenosine 3'5' Cyclic Monophosphate (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the PAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture, were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the PAR population was not significantly affected by electrical stimulation; however, the ability, of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the PAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

Young, Ronald B.↗
NASA NTRS2000

Effect of electrical stimulation on beta-adrenergic receptor population and cyclic amp production in chicken and rat skeletal muscle cell cultures

Expression of the beta-adrenergic receptor (betaAR) and its coupling to cyclic AMP (cAMP) synthesis are important components of the signaling system that controls muscle atrophy and hypertrophy, and the goal of this study was to determine if electrical stimulation in a pattern simulating slow muscle contraction would alter the betaAR response in primary cultures of avian and mammalian skeletal muscle cells. Specifically, chicken skeletal muscle cells and rat skeletal muscle cells that had been grown for 7 d in culture were subjected to electrical stimulation for an additional 2 d at a pulse frequency of 0.5 pulses/sec and a pulse duration of 200 msec. In chicken skeletal muscle cells, the betaAR population was not significantly affected by electrical stimulation; however, the ability of these cells to synthesize cyclic AMP was reduced by approximately one-half. In contrast, the betaAR population in rat muscle cells was increased slightly but not significantly by electrical stimulation, and the ability of these cells to synthesize cyclic AMP was increased by almost twofold. The basal levels of intracellular cyclic AMP in neither rat muscle cells nor chicken muscle cells were affected by electrical stimulation.

Muscle, Skeletal/cytology↗
NASA NTRS1997

Enhanced Attitude Control Experiment for SSTI Lewis Spacecraft

The enhanced attitude control system experiment is a technology demonstration experiment on the NASA's small spacecraft technology initiative program's Lewis spacecraft to evaluate advanced attitude control strategies. The purpose of the enhanced attitude control system experiment is to evaluate the feasibility of designing and implementing robust multi-input/multi-output attitude control strategies for enhanced pointing performance of spacecraft to improve the quality of the measurements of the science instruments. Different control design strategies based on modern and robust control theories are being considered for the enhanced attitude control system experiment. This paper describes the experiment as well as the design and synthesis of a mixed H(sub 2)/H(sub infinity) controller for attitude control. The control synthesis uses a nonlinear programming technique to tune the controller parameters and impose robustness and performance constraints. Simulations are carried out to demonstrate the feasibility of the proposed attitude control design strategy. Introduction

Maghami, Peoman G.↗
NASA NTRS1990

Stochastic Robustness: Towards a Comprehensive Robustness Tool

Stochastic robustness is a simple technique to determine the robustness of linear, time-invariant systems by Monte Carlo methods. Stochastic stability robustness has been described previously. Those results are extended here to provide insight into control system design for performance. Together, stochastic stability and performance robustness concepts constitute a comprehensive tool that can be used to analyze control system robustness properties. As well, they offer control system design insight that can set the stage for stochastic robustness synthesis. The concept of stochastic stability robustness is reviewed, stochastic performance robustness is introduced, and stochastic robustness synthesis is described qualitatively. Confidence intervals necessary for comparing control laws statistically are presented.

Ray, Laurie Ryan↗
NASA NTRS1995

Parallel Monte Carlo Simulation for control system design

The research during the 1993/94 academic year addressed the design of parallel algorithms for stochastic robustness synthesis (SRS). SRS uses Monte Carlo simulation to compute probabilities of system instability and other design-metric violations. The probabilities form a cost function which is used by a genetic algorithm (GA). The GA searches for the stochastic optimal controller. The existing sequential algorithm was analyzed and modified to execute in a distributed environment. For this, parallel approaches to Monte Carlo simulation and genetic algorithms were investigated. Initial empirical results are available for the KSR1.

Schubert, Wolfgang M.↗
NASA NTRS1987

Investigation of control law for active flutter suppression

Discussed is the technology of active flutter suppression research by the use of the wind-tunnel model of a delta wing with low aspect ratio. The research includes the establishment of a mathematical model for the servo-aeroelastic system, and the synthesis and analysis of sub-optimal output feedback control laws for active flutter suppression.

Wang, Weipeng↗
NASA NTRS2010

Analysis of Air Traffic Track Data with the AutoBayes Synthesis System

The Next Generation Air Traffic System (NGATS) is aiming to provide substantial computer support for the air traffic controllers. Algorithms for the accurate prediction of aircraft movements are of central importance for such software systems but trajectory prediction has to work reliably in the presence of unknown parameters and uncertainties. We are using the AutoBayes program synthesis system to generate customized data analysis algorithms that process large sets of aircraft radar track data in order to estimate parameters and uncertainties. In this paper, we present, how the tasks of finding structure in track data, estimation of important parameters in climb trajectories, and the detection of continuous descent approaches can be accomplished with compact task-specific AutoBayes specifications. We present an overview of the AutoBayes architecture and describe, how its schema-based approach generates customized analysis algorithms, documented C/C++ code, and detailed mathematical derivations. Results of experiments with actual air traffic control data are discussed.

Schumann, Johann Martin Philip↗
NASA NTRS1979

Practical optimal flight control system design for helicopter aircraft. Volume 2: Software user's guide

A method by which modern and classical control theory techniques may be integrated in a synergistic fashion and used in the design of practical flight control systems is presented. A general procedure is developed, and several illustrative examples are included. Emphasis is placed not only on the synthesis of the design, but on the assessment of the results as well. The first step is to establish the differences, distinguishing characteristics and connections between the modern and classical control theory approaches. Ultimately, this uncovers a relationship between bandwidth goals familiar in classical control and cost function weights in the equivalent optimal system. In order to obtain a practical optimal solution, it is also necessary to formulate the problem very carefully, and each choice of state, measurement and output variable must be judiciously considered. Once design goals are established and problem formulation completed, the control system is synthesized in a straightforward manner. Three steps are involved: filter-observer solution, regulator solution, and the combination of those two into the controller. Assessment of the controller permits and examination and expansion of the synthesis results.

Riedel, S. A.↗
NASA NTRS1984

Optimal cooperative control synthesis applied to a control-configured aircraft

A multivariable control augmentation synthesis method is presented that is intended to enable the designer to directly optimize pilot opinion rating of the augmented system. The approach involves the simultaneous solution for the augmentation and predicted pilot's compensation via optimal control techniques. The methodology is applied to the control law synthesis for a vehicle similar to the AFTI F16 control-configured aircraft. The resulting dynamics, expressed in terms of eigenstructure and time/frequency responses, are presented with analytical predictions of closed loop tracking performance, pilot compensation, and other predictors of pilot acceptance.

Schmidt, D. K.↗
NASA NTRS1985

Automation study for space station subsystems and mission ground support

An automation concept for the autonomous operation of space station subsystems, i.e., electric power, thermal control, and communications and tracking are discussed. To assure that functions essential for autonomous operations are not neglected, an operations function (systems monitoring and control) is included in the discussion. It is recommended that automated speech recognition and synthesis be considered a basic mode of man/machine interaction for space station command and control, and that the data management system (DMS) and other systems on the space station be designed to accommodate fully automated fault detection, isolation, and recovery within the system monitoring function of the DMS.

Source record↗
NASA NTRS1990

Structure/control synthesis with nonnegligible actuator mass

The simultaneous design of a structure/active control system is addressed in which the mass of the actuators required to implement the active control is considered. An algorithm for estimating the required actuator mass given the control law and the desired maneuver is presented. A nonlinear optimization algorithm is used to direct the design process. Results are given for the design of a L shaped structure where it is desired to minimize the line of sight pointing error after a worst case slew maneuver.

Zimmerman, David C.↗
NASA NTRS1992

Control of nonlinear systems using terminal sliding modes

The development of an approach to control synthesis for robust robot operations in unstructured environments is discussed. To enhance control performance with full model information, the authors introduce the notion of terminal convergence and develop control laws based on a class of sliding modes, denoted as terminal sliders. They demonstrate that terminal sliders provide robustness to parametric uncertainty without having to resort to high-frequency control switching, as in the case of conventional sliders. It is shown that the proposed method leads to greater guaranteed precision in all control cases discussed.

Venkataraman, S. T.↗
DOE OSTI2024

Rational sub-nanometer manipulation of polymer morphology for efficient chemical separations

The ability to control polymer morphology on the sub-nanometer length scale has broad implications for chemical separations. To achieve such control on easily processable systems, this proposal focuses on the synthesis and characterization of polymers containing appended labile moieties that are easily detached by thermolysis or UV irradiation deep within the glassy state. Once liberated, these moieties can diffuse from the polymer matrix as gaseous products, leaving behind templated pathways for selective diffusion and sorption of small molecules. With a specific target of creating polymeric membrane materials with unprecedented diffusion and (ad)sorption characteristics for chemical separations, synthesis of new materials will be complemented with advanced metrologies, simulations, and evaluation of thermodynamic and transport theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Identifying Opportunities at the Interface of Chemistry and Quantum Information Science (Final Technical Report)

This project convened a National Academies committee to identify opportunities and research priorities at the interface of chemistry and quantum information science (QIS). The work culminated in a consensus study report that (1) articulates three fundamental research areas to advance QIS (design and synthesis of molecular qubits; measurement and control of molecular quantum systems; and experimental and computational scaling of qubit design and function), and (2) underscores the importance of cross-disciplinary collaboration, access to facilities and instrumentation, FAIR-aligned data infrastructure, and workforce development initiatives to sustain U.S. leadership in QIS. The report and all other material associated with this project can be downloaded on the project webpage: https://www.nationalacademies.org/projects/DELS-BCST-21-01 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗