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Results for “SEQUENTIAL CONTROL”

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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Reliable VLSI sequential controllers

A VLSI architecture for synchronous sequential controllers is presented that has attractive qualities for producing reliable circuits. In these circuits, one hardware implementation can realize any flow table with a maximum of 2(exp n) internal states and m inputs. Also all design equations are identical. A real time fault detection means is presented along with a strategy for verifying the correctness of the checking hardware. This self check feature can be employed with no increase in hardware. The architecture can be modified to achieve fail safe designs. With no increase in hardware, an adaptable circuit can be realized that allows replacement of faulty transitions with fault free transitions.

Whitaker, S.↗
NASA NTRS1971

Sequential control chart methodology

A modification of the V mask sequential control chart is proposed. In this modified scheme, a parabolic section is included in the mask to provide better performance when the process undergoes a large change in the mean from goal conditions. It is shown that the modified V mask can be implemented either in conventional graphic form, or in an algorithmic form suitable for a digital computer. Average run lengths are given for a typical range of circumstances. It also is shown that the conventional Shewhart chart is better than a sequential chart for the specific purpose of promptly detecting very large shifts of the mean from goal conditions.

Source record↗
DOE OSTI2016

Sequential control of step-bunching during graphene growth on SiC (0001)

We have investigated the relation between the step-bunching and graphene growth phenomena on an SiC substrate. We found that only a minimum amount of step-bunching occurred during the graphene growth process with a high heating rate. On the other hand, a large amount of step-bunching occurred using a slow heating process. These results indicated that we can control the degree of step-bunching during graphene growth by controlling the heating rate. We also found that graphene coverage suppressed step bunching, which is an effective methodology not only in the graphene technology but also in the SiC-based power electronics.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

An electrostatic selection mechanism controls sequential kinase signaling downstream of the T cell receptor

The sequence of events that initiates T cell signaling is dictated by the specificities and order of activation of the tyrosine kinases that signal downstream of the T cell receptor. Using a platform that combines exhaustive point-mutagenesis of peptide substrates, bacterial surface-display, cell sorting, and deep sequencing, we have defined the specificities of the first two kinases in this pathway, Lck and ZAP-70, for the T cell receptor ζ chain and the scaffold proteins LAT and SLP-76. We find that ZAP-70 selects its substrates by utilizing an electrostatic mechanism that excludes substrates with positively-charged residues and favors LAT and SLP-76 phosphosites that are surrounded by negatively-charged residues. This mechanism prevents ZAP-70 from phosphorylating its own activation loop, thereby enforcing its strict dependence on Lck for activation. The sequence features in ZAP-70, LAT, and SLP-76 that underlie electrostatic selectivity likely contribute to the specific response of T cells to foreign antigens.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1975

Apollo experience report: Command and service module sequential events control subsystem

The Apollo command and service module sequential events control subsystem is described, with particular emphasis on the major systems and component problems and solutions. The subsystem requirements, design, and development and the test and flight history of the hardware are discussed. Recommendations to avoid similar problems on future programs are outlined.

Johnson, G. W.↗
NASA NTRS2009

Sequential Events Control System (SECS) Overview

This slide presentation will cover the Sequential Events Control System (SECS), which is the Apollo spacecraft subsystem that controls the automatically sequenced functions during the mission and during any a borts that could be performed. Included in this presentation are its general architecture, its integration into and use of the spacecraft' s other systems, and details on the functions it is responsible for c ontrolling during the mission. The objectives are to describe the system's architecture, the major components in the system, and the major system functions.

Interbartolo, Michael↗
DOE OSTI2017

Sequential Infiltration Synthesis for the Design of Low Refractive Index Surface Coatings with Controllable Thickness

Control over refractive index and thickness of surface coatings is central to the design of low refraction films used in applications ranging from optical computing to antireflective coatings. Here, we introduce gas-phase sequential infiltration synthesis (SIS) as a robust, powerful, and efficient approach to deposit conformal coatings with very low refractive indices. We demonstrate that the refractive indices of inorganic coatings can be efficiently tuned by the number of cycles used in the SIS process, composition, and selective swelling of the of the polymer template. We show that the refractive index of Al2O3 can be lowered from 1.76 down to 1.1 using this method. The thickness of the Al2O3 coating can be efficiently controlled by the swelling of the block copolymer template in ethanol at elevated temperature, thereby enabling deposition of both single-layer and graded-index broadband antireflective coatings. Using this technique, Fresnel reflections of glass can be reduced to as low as 0.1% under normal illumination over a broad spectral range.

Berman, Diana↗
NASA NTRS1991

Optimal uniform-damping ratio controller for sequential design of multivariable systems

An optimal uniform-damping ratio controller is developed for the sequential design of a multivariable control system so that the designed closed-loop poles of the respective multivariable system and reduced-order observer are exactly placed on the negative real axis and/or the boundaries of desired sectors with constant-damping ratios. The functions in the quadratic performance index to be minimized are chosen as a combination of the weighted outputs, reduced states and inputs. Also, the optimal uniform-damping ratio controller is a combination of optimal output-feedback and optimal reduced-order state-feedback controllers. A numerical example is given to demonstrate the design procedure.

Shieh, Leang G.↗
DOE OSTI2018

Sequential catalysis controls selectivity in electrochemical CO 2 reduction on Cu

Electrochemical reduction of CO 2 in aqueous media is a strategy for sustainable production of fuels and commodity chemicals. Cu is the only catalyst which converts CO 2 to significant quantities of hydrocarbons and oxygenates. Here we demonstrate that oxygenate products can be favored over hydrocarbons by positioning a local source of CO generated by a CO producing catalyst (Au or Ag) in close proximity to a Cu catalyst. Use of a bimetallic device comprising interdigitated and independently controllable lines of Au and Cu allows the local CO concentration to be modulated. Notably, diffusional simulations show that the saturation concentration of CO can be exceeded locally. Actuating both the Au and Cu lines increases the oxygenate to ethylene ratio compared to actuating Cu only. Increasing the relative area of CO-producing Au relative to Cu also increases this ratio. These insights are translated into a second bimetallic system comprising Cu dots/lines patterned directly onto a Ag substrate, allowing for the distance between Cu and the CO generating metal to be precisely controlled. Controlling the relative areas of Ag and Cu allows for tuning of the oxygenate to ethylene ratio from 0.59 to 2.39 and an increase in oxygenate faradaic efficiency from 21.4% to 41.4%, while maintaining the selectivity to C 2 /C 3 products in the 50–65% range. We attribute this change in selectivity to be due to an increased *CO coverage on Cu. Finally, by utilizing diffusional transport of CO to the Cu, a sequential catalysis pathway is created which allows for the control of oxygenate selectivity in aqueous CO 2 reduction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Connection stiffness and dynamical docking process of flux pinned spacecraft modules

This paper describes a novel kind of potential flux pinned docking system that consists of guidance navigation and control system, the traditional extrusion type propulsion system, and a flux pinned docking interface. Because of characteristics of passive stability of flux pinning, the docking control strategy of flux pinned docking system only needs a series of sequential control rather than necessary active feedback control, as well as avoidance of hazardous collision accident. The flux pinned force between YBaCuO (YBCO) high temperature superconductor bulk and permanent magnet is able to be given vent based on the identical current loop model and improved image dipole model, which can be validated experimentally. Thus, the connection stiffness between two flux pinned spacecraft modules can be calculated based on Hooke's law. This connection stiffness matrix at the equilibrium position has the positive definite performance, which can validate the passively stable connection of two flux pinned spacecraft modules theoretically. Furthermore, the relative orbital dynamical equation of two flux pinned spacecraft modules can be established based on Clohessy-Wiltshire's equations and improved image dipole model. The dynamical docking process between two flux pinned spacecraft modules can be obtained by way of numerical simulation, which suggests the feasibility of flux pinned docking system.

42 ENGINEERING↗
DOE OSTI2019

Zero-Cost Closed-Loop Discharging Method for Modular Multilevel Converter Submodules Without External Circuits

A novel submodule capacitor discharging control strategy is introduced and implemented for modular multilevel converters (MMCs). By sequentially controlling the arm currents of anMMC,all submodule capacitors are discharged rapidly through internal arm resistors without additional devices and circuits, resulting in improved performance and reduced cost. A closed-loop control method is explored for the effectiveness of the new control strategy.Acomparison study is evaluated between the proposed method and the traditional methods using bleeding resistors, auxiliary resistors, and load resistors. Confirmed by the simulation and experiment, the proposed method has the maximum benefits including zero hardware cost, fast discharging time, and negligible load current impact

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
NASA NTRS1992

Application of programmable logic controllers to space simulation

Incorporating a state-of-the-art process control and instrumentation system into a complex system for thermal vacuum testing is discussed. The challenge was to connect several independent control systems provided by various vendors to a supervisory computer. This combination will sequentially control and monitor the process, collect the data, and transmit it to color a graphic system for subsequent manipulation. The vacuum system upgrade included: replacement of seventeen diffusion pumps with eight cryogenic pumps and one turbomolecular pump, replacing a relay based control system, replacing vacuum instrumentation, and upgrading the data acquisition system.

Sushon, Janet↗
DOE OSTI2019

A Novel Discharging Control Strategy for Modular Multilevel Converter Submodules without Using External Circuit

A novel discharging control strategy is proposed and implemented for submodules in modular multilevel converters (MMCs). By sequentially controlling the arm currents of a MMC to the arm resistors, all submodule capacitors are discharged safely and rapidly without adding additional devices and circuits, resulting in improved performance and reduced cost. Both open- and closed-loop control methods are evaluated for effectiveness of the new control strategy. Simulation and experimental results are provided to validate the new control strategy.

Modular multilevel converter, discharging method, ↗