SEARCH · Engineering Papers

Results for “continuous 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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93

All sources NASA NTRS DOE OSTI

NASA NTRS2018

Microwave Radar Sensor Modules

Systems and methods for detecting biometrics using microwave radar sensor modules are disclosed. Integrated microwave sensor modules can include a transmitter unit configured to generate at least one continuous wave transmit signal based upon at least one frequency control signal, a receiver unit configured to utilize a cancellation path to cancel contributions to a return signal based upon at least one cancellation path control signal, and a microcontroller unit that includes a processor, a memory containing a microcontroller application, where the microcontroller application configures the processor to generate at least one frequency control signal to generate least one CW transmit signal having a plurality of frequencies, generate at least one cancellation path control signal to automatically adjust the cancellation path in real time, receive at least one demodulated signal, digitize the at least one demodulated signal, and update the at least one frequency control and cancellation path control signals.

Lux, James Paul↗

DOE OSTI2016

LONG TERM OPERATION ISSUES FOR ELECTRICAL CABLE SYSTEMS IN NUCLEAR POWER PLANTS

Nuclear power plants contain hundreds of kilometers of electrical cables including cables used for power, for instrumentation, and for control. It is essential that safety-related cable systems continue to perform following a design-basis event. Wholesale replacement of electrical cables in existing plants facing licensing period renewal is both impractical and cost-prohibitive. It is therefore important to understand the long term aging of cable materials to have confidence that aged cables will perform when needed. It is equally important in support of cable aging management to develop methods to evaluate the health of installed cables and inform selective cable replacement decisions. The most common insulation materials for electrical cables in nuclear power plants are cross-linked polyethylene and ethylene-propylene rubber. The mechanical properties of these materials degrade over time in the presence of environmental stresses including heat, gamma irradiation, and moisture. Mechanical degradation of cable insulation beyond a certain threshold is unacceptable because it can lead to insulation cracking, exposure of energized conductors, arcing and burning or loss of the ability of the cable system to function during a design-basis accident. While thermal-, radiation-, and moisture-related degradation of polymer insulation materials has been extensively studied over the last few decades, questions remain regarding the long-term performance of cable materials in nuclear plant-specific environments. Identified knowledge gaps include an understanding of the temperature-dependence of activation energies for thermal damage and an understanding of the synergistic effects of radiation and thermal stress on polymer degradation. Many of the outstanding questions in the aging behavior of cable materials relate to the necessity of predicting long-term field degradation using accelerated aging results from the laboratory. Materials degrade faster under more extreme conditions, but extension of behavior to long term degradation under more mild conditions, such as those experienced by most installed cables in nuclear power plants, is complicated by the fact that different degradation mechanisms may be involved in extreme and mild scenarios. The discrepancy in predicted results from short term, more extreme exposure and actual results from longer term, more mild exposures can be counter intuitive. For instance, due to the attenuation of oxidation penetration in material samples rapidly aged through exposure to high temperatures, the bulk of the samples may be artificially protected from thermal aging. In another example, simultaneous exposure of cable insulation material to heat and radiation may actually lead to less damage at higher temperatures than may be observed at lower temperatures. The Light Water Reactor Sustainability program of the United States (US) Department of Energy Office (DOE) of Nuclear Energy is funding research to increase the predictive understanding of electrical cable material aging and degradation in existing nuclear power plants in support of continued safe operation of plants beyond their initial license periods. This research includes the evaluation and development of methods to assess installed cable condition.

Fifield, Dr Leonard S↗

DOE OSTI2021

Data-Driven Adaptive Damping Controller for Wind Power Plants with Doubly-Fed Induction Generators: Preprint

This paper presents an adaptive damping controller for wind power plants in which the turbines are equipped with doubly-fed induction generators. The controller is designed to respond to an input control signal that is triggered according to the system operating conditions. A processing unit continuously estimates the electromechanical modes of oscillation based on real-time streaming data acquired from a phasor measurement unit that is strategically positioned on the grid. The decision to trigger (or not trigger) the control signal is automatic, based on the relative damping of the dominant mode. The modes are estimated using the dynamic mode decomposition algorithm with time-delay embedding. Numerical simulations performed on the two-area system demonstrate that the proposed controller enhances the rotor angle stability for both small-signal and large disturbances, and is adaptive to changing grid conditions.

61 RADIATION PROTECTION AND DOSIMETRY↗

DOE OSTI2024

Building Automation

In this chapter, we focus on both need-based and vision-based control innovation for building automation for HVAC systems. After providing a brief background that describes different HVAC architectures and products, we describe the control challenges and opportunities from a needs-based point of view, at the equipment level, the systems level, and the building level. At the equipment level, increased use of continuously variable actuation such as variable speed compressors and fans, requires application of robust multivariable control that must consider various types of nonlinear behavior across increasingly larger operating envelopes. The objective at this level is to achieve robust and energy efficient operation. At the system level, coupled and interactive dynamics among subsystems are increasingly important to consider, and functional integration of these subsystems, along with set points and operating schedules are designed to minimize energy consumption and improve occupant comfort. At the building level, issues such as integration among other building systems, such as the building envelope and the electric grid, offer opportunities to develop new types of demand response and grid-interactive behaviors and technologies. At the higher levels, system dynamics and robust stability are less of an issue, similar to process control applications, while optimization and integration are more important, although dynamic stability is increasing an issue at the higher levels too. From a vision-driven innovation point of view, we describe three areas that will require sustained research efforts and will eventually impact building automation: Digital Twins, Model Predictive Control, and Grid Interactive Buildings.

Bortoff, Scott↗

NASA NTRS2004

Flexible Microsensor Array for the Monitoring and Control of Plant Growth System

Testing for plant experiments in space has begun to explore active nutrient delivery concepts in which water and nutrients are replenished on a continuous basis for long-term growth. The goal of this study is to develop a novel microsensor array to provide information on the dissolved oxygen environment in the plant root zone for the optimum control of hydroponics and solid substrate plant cultivation systems in the space environment. Miniaturized polarographic dissolved oxygen sensors have been designed and fabricated on a flexible Kapton (trademark) (polyimide) substrate. Two capabilities of the new microsensor array were explored. First, measurements of dissolved oxygen in the plant root zone in hydroponics and solid substrate culture systems were made. The microsensor array was fabricated on a flexible substrate, and then cut out into a mesh type to make a suspended array that could be placed either in a hydroponics system or in a solid substrate cultivation system to measure the oxygen environments. Second, the in situ self-diagnostic and self-calibration capability (two-point for oxygen) was adopted by dynamically controlling the microenvironment in close proximity to the microsensors. With a built-in generating electrode that surrounds the microsensor, two kinds of microenvironments (oxygen-saturated and oxygen-depleted phases) could be established by water electrolysis depending on the polarity of the generating electrode. The unique features of the new microsensor array (small size, multiple sensors, flexibility and self-diagnosis) can have exceptional benefits for the study and optimization of plant cultivation systems in both terrestrial and microgravity environments. The in situ self-diagnostic and self-calibration features of the microsensor array will also enable continuous verification of the operability during entire plant growth cycles. This concept of automated control of a novel chemical monitoring system will minimize crew time required for maintenance, as well as reduce volume, mass, and power consumption by eliminating bulky diagnosis systems including calibrant (fluid and gas) reservoir and flow system hardware.

Kim, Chang-Soo↗

NASA NTRS2016

Intelligent (Autonomous) Power Controller Development for Human Deep Space Exploration

As NASAs Evolvable Mars Campaign and other exploration initiatives continue to mature they have identified the need for more autonomous operations of the power system. For current human space operations such as the International Space Station, the paradigm is to perform the planning, operation and fault diagnosis from the ground. However, the dual problems of communication lag as well as limited communication bandwidth beyond GEO synchronous orbit, underscore the need to change the operation methodology for human operation in deep space. To address this need, for the past several years the Glenn Research Center has had an effort to develop an autonomous power controller for human deep space vehicles. This presentation discusses the present roadmap for deep space exploration along with a description of conceptual power system architecture for exploration modules. It then contrasts the present ground centric control and management architecture with limited autonomy on-board the spacecraft with an advanced autonomous power control system that features ground based monitoring with a spacecraft mission manager with autonomous control of all core systems, including power. It then presents a functional breakdown of the autonomous power control system and examines its operation in both normal and fault modes. Finally, it discusses progress made in the development of a real-time power system model and how it is being used to evaluate the performance of the controller and well as using it for verification of the overall operation.

Power Systems↗

NASA NTRS1979

LSA Large Area Silicon Sheet Task. Continuous Liquid Feed Czochralski Growth

The design and development of equipment and processes to demonstrate continuous growth of crystals by the Czochralski method suitable for producing single silicon crystals for use in solar cells is presented. The growth of at least 150 kg of mono silicon crystal, 150 mm in diameter is continuous from one growth container. A furnace with continuous liquid replenishment of the growth crucible, accomplished by a meltdown system with a continuous solid silicon feed mechanism and a liquid transfer system, with associated automatic feedback controls is discussed. Due to the silicon monoxide build up in the furnace and its retarding effect on crystal growth the furnace conversion for operation in the low pressure range is described. Development of systems for continuous solid recharging of the meltdown chamber for various forms of poly silicon is described.

Fiegl, G.↗

NASA NTRS1985

Wind-tunnel investigation at supersonic speeds of a remote-controlled canard missile with a free-rolling-tail brake torque system

Wind tunnel tests were conducted at Mach numbers 1.70, 2.16, and 2.86 to determine the static aerodynamic characteristics of a cruciform canard-controlled missile with fixed or free rolling tailfin afterbodies. Mechanical coupling effects of the free-rolling-tail afterbody were investigated by using an electronic electromagnetic brake system providing arbitrary tail-fin brake torques with continuous measurements of tail-to-mainframe torque and tail roll rate. Remote-controlled canards were deflected to provide pitch, yaw, and roll control. Results indicate that the induced rolling moment coefficients due to canard yaw control are reduced and linearized for the free-rolling-tail (free-tail) configuration. The canards of the latter provide conventional roll control for the entire angle-of-attack test range. For the free-tail configuration, the induced rolling moment coefficient due to canard yaw control increased and the canard roll control decreased with increases in brake torque, which simulated bearing friction torque. It appears that a compromise in regard to bearing friction, for example, low-cost bearings with some friction, may allow satisfactory free-tail aerodynamic characteristics that include reductions in adverse rolling-moment coefficients and lower tail roll rates.

Blair, A. B., Jr.↗

NASA NTRS2012

Efficient Computation of Separation-Compliant Speed Advisories for Air Traffic Arriving in Terminal Airspace

A class of problems in air traffic management asks for a scheduling algorithm that supplies the air traffic services authority not only with a schedule of arrivals and departures, but also with speed advisories. Since advisories must be finite, a scheduling algorithm must ultimately produce a finite data set, hence must either start with a purely discrete model or involve a discretization of a continuous one. The former choice, often preferred for intuitive clarity, naturally leads to mixed-integer programs, hindering proofs of correctness and computational cost bounds (crucial for real-time operations). In this paper, a hybrid control system is used to model air traffic scheduling, capturing both the discrete and continuous aspects. This framework is applied to a class of problems, called the Fully Routed Nominal Problem. We prove a number of geometric results on feasible schedules and use these results to formulate an algorithm that attempts to compute a collective speed advisory, effectively finite, and has computational cost polynomial in the number of aircraft. This work is a first step toward optimization and models refined with more realistic detail.

Sadovsky, Alexander V.↗

NASA NTRS1997

Density and composition of microorganisms during long-term (418 day) growth of potato using biologically reclaimed nutrients from inedible plant biomass

A study evaluating alternative methods for long term operation of biomass production systems was recently completed at the Kennedy Space Center (KSC). The 418-day study evaluated repeated batch versus mixed-aged production of potato grown on either standard 1/2-strength Hoagland's nutrient solution or solutions including nutrients recycled from inedible plant material. The long term effects of closure and recycling on microbial dynamics were evaluated by monitoring the microbial communities associated with various habitats within the plant growth system (i.e., plant roots, nutrient solution, biofilms within the hydroponic systems, atmosphere, and atmospheric condensate). Plate count methods were used to enumerate and characterize microorganisms. Microscopic staining methods were used to estunate total cell densities. The primary finding was that the density and composition of microbial communities associated with controlled environmental plant growth systems are stable during long term operation. Continuous production resulted in slightly greater stability. Nutrient recycling, despite the addition of soluble organic material from the waste processing system, did not significantly increase microbial density in any of the habitats.

NASA Center KSC↗

DOE OSTI2019

Demonstration of High-Temperature Calcium-Based Thermochemical Energy Storage System for use with Concentrating Solar Power Facilities

Thermochemical energy storage (TCES) systems offer several advantages over sensible heat storage via molten salts for concentrating solar power (CSP) including: energy density, cost, indefinite storage time, and no risk of freezing. SR’s TCES system utilizes a CaO-based carbonation reaction at high temperature in a fixed bed heat exchanger reactor. The SunShot APOLLO project focuses on the validation of the calcium oxide sorbent for capacity, durability, system economics, and demonstration of the system at a small pilot scale, including system control and operation in simulated on-sun conditions, discharging at 720°C. Under phase I SR completed evaluation of the sorbent loaded in a single-channel heat exchanger reactor. The major accomplishments of phase II are: Design, fabrication and commissioning of a 4 kWhth pilot plant (50x capacity increase from previous bench scale) with a closed-loop CO 2 system, and a commercially relevant heat exchange reactor. The heat exchange reactor has been designed with state-of-the-art modeling tools to ensure 1) sufficient lifetime of the Incoloy body and 2) performance of the packed bed reactor will be adequate to meet the milestones. The rest of the pilot system has been designed with off-the shelf components to maximize reliability and cost effectiveness. The system is highly instrumented and capable of time resolved, independent measurements of the heat and mass balances respectively. Major developments in the technoeconomic analysis (TEA) include 1) reduction of the cost of membrane gas storage for the near-term and future systems and 2) integration with liquid metal receivers and particle receivers for higher decarbonation temperatures and pressures which reduced the cost of gas compression and increased system efficiency. The result are three scenarios with costs bases of 21.9 dollars, 14.3 dollars, and 10.9 dollars/kWh th corresponding to a real LCOE of 59, 57, 56 dollars/MW he , respectively. The basic operations of the energy storage system were demonstrated for carbonation (discharging) and decarbonation (charging) over short time periods. Excellent control of the CO 2 mass balance across the reactor was achieved with mass flow controllers and the basic operation of the level control of the CO 2 gas bladder was achieved. The system was apparently free from leaks and operated continuously for 18 days with no mechanical failures, thus meeting milestone 2.5.5. The major shortcomings of the system had to do with the controls which prevented us from deep cycling and or reaching high cycles. We were unable to decarbonate (charge) the system for more than a few minutes at a time, which was much shorter than the design target of 10 hrs. This issue could not be resolved due to facility availability and contract closure. One major finding is that CaO-based TCES is most cost efficient when charged with HTF (heat transfer fluid) temperatures >850°C to reach the round-trip exergy efficiency and system cost targets which are higher temperatures than those considered for Gen 3 CSP. Many of the balance of plant components do not exist today, however we are encouraged by our findings that in general with more work we are able to reduce the capital cost, for example with the membrane gas storage, which is an innovative component in itself. The CaO-based TCES system has potential to meet the latest SunShot 2030 goals of LCOE at 50 $/MW he with capital costs of <11/kWh th .

14 SOLAR ENERGY↗

DOE OSTI2019

Demonstration of High-Temperature Calcium-Based Thermochemical Energy Storage System for use with Concentrating Solar Power Facilities

Thermochemical energy storage (TCES) systems offer several advantages over sensible heat storage via molten salts for concentrating solar power (CSP) including: energy density, cost, indefinite storage time, and no risk of freezing. SR’s TCES system utilizes a CaO-based carbonation reaction at high temperature in a fixed bed heat exchanger reactor. The SunShot APOLLO project focuses on the validation of the calcium oxide sorbent for capacity, durability, system economics, and demonstration of the system at a small pilot scale, including system control and operation in simulated on-sun conditions, discharging at 720°C. Under phase I SR completed evaluation of the sorbent loaded in a single-channel heat exchanger reactor. The major accomplishments of phase II are: Design, fabrication and commissioning of a 4 kWhth pilot plant (50x capacity increase from previous bench scale) with a closed-loop CO 2 system, and a commercially relevant heat exchange reactor. The heat exchange reactor has been designed with state-of-the-art modeling tools to ensure 1) sufficient lifetime of the Incoloy body and 2) performance of the packed bed reactor will be adequate to meet the milestones. The rest of the pilot system has been designed with off-the shelf components to maximize reliability and cost effectiveness. The system is highly instrumented and capable of time resolved, independent measurements of the heat and mass balances respectively. Major developments in the technoeconomic analysis (TEA) include 1) reduction of the cost of membrane gas storage for the near-term and future systems and 2) integration with liquid metal receivers and particle receivers for higher decarbonation temperatures and pressures which reduced the cost of gas compression and increased system efficiency. The result are three scenarios with costs bases of 21.9 dollars, 14.3 dollars, and 10.9 dollars/kWhth corresponding to a real LCOE of 59, 57, 56 dollars/MWhe, respectively. The basic operations of the energy storage system were demonstrated for carbonation (discharging) and decarbonation (charging) over short time periods. Excellent control of the CO 2 mass balance across the reactor was achieved with mass flow controllers and the basic operation of the level control of the CO 2 gas bladder was achieved. The system was apparently free from leaks and operated continuously for 18 days with no mechanical failures, thus meeting milestone 2.5.5. The major shortcomings of the system had to do with the controls which prevented us from deep cycling and or reaching high cycles. We were unable to decarbonate (charge) the system for more than a few minutes at a time, which was much shorter than the design target of 10 hrs. This issue could not be resolved due to facility availability and contract closure. One major finding is that CaO-based TCES is most cost efficient when charged with HTF (heat transfer fluid) temperatures >850°C to reach the round-trip exergy efficiency and system cost targets which are higher temperatures than those considered for Gen 3 CSP. Many of the balance of plant components do not exist today, however we are encouraged by our findings that in general with more work we are able to reduce the capital cost, for example with the membrane gas storage, which is an innovative component in itself. The CaO-based TCES system has potential to meet the latest SunShot 2030 goals of LCOE at 50 dollars/MWhe with capital costs of <11/kWhth.

14 SOLAR ENERGY↗

NASA NTRS1961

Incipient- and Developed-Spin and Recovery Characteristics of a Modern High-Speed Fighter Design with Low Aspect Ratio as Determined from Dynamic-Model Tests

Incipient- and developed-spin and recovery characteristics of a modern high-speed fighter design with low aspect ratio have been investigated by means of dynamic model tests. A 1/7-scale radio-controlled model was tested by means of drop tests from a helicopter. Several 1/25-scale models with various configuration changes were tested in the Langley 20-foot free-spinning tunnel. Model results indicated that generally it would be difficult to obtain a developed spin with a corresponding airplane and that either the airplane would recover of its own accord from any poststall motion or the poststall motion could be readily terminated by proper control technique. On occasion, however, the results indicated that if a post-stall motion were allowed to continue, a fully developed spin might be obtainable from which recovery could range from rapid to no recovery at all, even when optimum control technique was used. Satisfactory recoveries could be obtained with a proper-size tail parachute or strake, application of pitching-, rolling-, or yawing-moment rockets, or sufficient differential deflection of the horizontal tail.

Lee, Henry A.↗

NASA NTRS1988

Overview of structural parameter identification for large space structures needs, concepts, limits, potential

Virtually all space structure mission requirements include control of vibration, position, and possibly shape. In order to satisfy their requirements it is necessary to know the dynamic characteristics of the structure. Therefore, a means must be developed to continuously determine a dynamic model, or changes in the model, and to appropriately adapt the controls to these changes. The detection and location of physical damage would also be a very beneficial characteristic of such a procedure. A discussion outlining the methods to perform On-Orbit Model Determination is presented.

Berman, Alex↗

DOE OSTI2022

CRADA Number NFE-19-07845 with American Nanotechnologies, Inc. (CRADA Final Report)

Cooperative Research and Development Agreement (CRADA) NFE-19-07845 between Oak Ridge National Laboratory (ORNL) and American Nanotechnologies, Inc. (ANI) focused on studying the use of dielectrophoresis as a mechanism to purify nanoparticles, particularly semiconducting carbon nanotubes (CNTs). The successful development of low-cost purification processes is a significant bottleneck in the adoption of semiconducting CNTs in commercial semiconducting devices. ANI is a startup company developing scalable systems for performing nanoparticle dielectrophoresis, which has previously been used only in microfluidic devices. The work done under this CRADA is exploring the use of ANI’s patent resonant dielectrophoresis (rDEP) technology and its ability to purify semiconducting CNTs at large scale. While continued work is on-going, r-DEP has proven to be a viable way to control nanoparticles in bulk dispersions. Optimization of the process is now underway to reach minimum viable product and begin material sales. Additionally, ANI and ORNL continue to collaborate on leveraging this technology to reach down the value chain and create new commercial devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

NASA NTRS1996

Development and status of data quality assurance program at NASA Langley research center: Toward national standards

As part of a continuing effort to re-engineer the wind tunnel testing process, a comprehensive data quality assurance program is being established at NASA Langley Research Center (LaRC). The ultimate goal of the program is routing provision of tunnel-to-tunnel reproducibility with total uncertainty levels acceptable for test and evaluation of civilian transports. The operational elements for reaching such levels of reproducibility are: (1) statistical control, which provides long term measurement uncertainty predictability and a base for continuous improvement, (2) measurement uncertainty prediction, which provides test designs that can meet data quality expectations with the system's predictable variation, and (3) national standards, which provide a means for resolving tunnel-to-tunnel differences. The paper presents the LaRC design for the program and discusses the process of implementation.

Hemsch, Michael J.↗

NASA NTRS1996

Characterizing photosynthesis and transpiration of plant communities in controlled environments

CO2 and water vapor fluxes of hydroponically grown wheat and soybean canopies were measured continuously in several environments with an open gas exchange system. Canopy CO2 fluxes reflect the photosynthetic efficiency of a plant community, and provide a record of plant growth and health. There were significant diurnal fluctuations in root and shoot CO2 fluxes, and in shoot water vapor fluxes. Canopy stomatal conductance (Gc) to water vapor was calculated from simultaneous measurements of canopy temperature (Tcan) and transpiration rates (Tr). Tr in the dark was substantial, and there were large diurnal fluctuations in both Gc and Tr. Canopy net Photosynthesis (Pnet), Tr, and Gc increased with increasing net radiation. Gc increased with Tr, suggesting that the stomata of plants in controlled environments (CEs) behave differently from field-grown plants. A transpiration model based on measurements of Gc was developed for CEs. The model accurately predicted Tr from a soybean canopy.

NASA Discipline Life Support Systems↗

NASA NTRS1985

Dynamic Considerations for Control of Closed Life Support Systems

Reliability of closed life support systems depend on their ability to continue supplying the crew's needs during perturbations and equipment failures. The dynamic considerations interact with the basic static design through the sizing of storages, the specification of excess capacities in processors, and the choice of system initial state. A very simple system flow model was used to examine the possibilities for system failures even when there is sufficient storage to buffer the immediate effects of the perturbation. Two control schemes are shown which have different dynamic consequences in response to component failures.

Babcock, P. S.↗