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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 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Communication-Constrained Expansion Planning for Resilient Distribution Systems

Distributed generation and remotely controlled switches have emerged as important technologies to improve the resiliency of distribution grids against extreme weather-related disturbances. Therefore it becomes important to study how best to place them on the grid in order to meet a resiliency criteria, while minimizing costs and capturing their dependencies on the associated communication systems that sustain their distributed operations. This paper introduces the Optimal Resilient Design Problem for Distribution and Communication Systems (ORDPDC) to address this need. The ORDPDC is formulated as a two-stage stochastic mixed-integer program that captures the physical laws of distribution systems, the communication connectivity of the smart grid components, and a set of scenarios that specifies which components are affected by potential disasters. The paper proposes an exact branch-and-price algorithm for the ORDPDC that features a strong lower bound and a variety of acceleration schemes to address degeneracy. The ORDPDC model and branch-and-price algorithm were evaluated on a variety of test cases with varying disaster intensities and network topologies. The results demonstrate the significant impact of the network topologies on the expansion plans and costs, as well as the computational benefits of the proposed approach.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Anomaly Detection and Mitigation for Wide-Area Damping Control using Machine Learning

In an interconnected multi-area power system, wide-area measurement based damping controllers are used to damp out inter-area oscillations, which jeopardize grid stability and constrain the power flows below to their transmission capacity. The effect of wide-area damping control (WADC) significantly depends on both power and cyber systems. At the cyber system layer, an adversary can inflict the WADC process by compromising either measurement signals, control signals or both. Stealthy and coordinated cyber-attacks may bypass the conventional cybersecurity measures to disrupt the seamless operation of WADC. This paper proposes an anomaly detection (AD) algorithm using supervised Machine Learning and a model-based logic for mitigation. The proposed AD algorithm considers measurement signals (input of WADC) and control signals (output of WADC) as input to evaluate the type of activity such as normal, perturbation (small or large signal faults), attack and perturbation-and-attack. Upon anomaly detection, the mitigation module tunes the WADC signal and sets the control status mode as either wide-area mode or local mode. The proposed anomaly detection and mitigation (ADM) module works inline with the WADC at the control center for attack detection on both measurement and control signals and eliminates the need for ADMs at the geographically distributed actuators. Here, we consider coordinated and primitive data-integrity attack vectors such as pulse, ramp, relay-trip and replay attacks. The performance of the proposed ADM algorithms was evaluated under these attack vector scenarios on a testbed environment for 2-area 4-machine power system. The ADM module shows effective performance with 96:5% accuracy to detect anomalies.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Automatic voltage regulation application for PV inverters in low-voltage distribution grids – A digital twin approach

This paper proposes a hierarchical coordinated control strategy for PV inverters to keep voltages in low-voltage (LV) distribution grids within specified limits. The top layer of the proposed architecture consists of the designed automatic voltage regulation (AVR) application, which has access to voltage measurements and grid parameters from the LV distribution grid, both current and historical. The AVR application solves a constrained optimization problem, which provides a set of local control set-points that bring the voltage across the grid within bounds. The middle layer consists of a local Volt/VAR controller, which is adjusted by the AVR app, while the bottom layer is the inner-loop controller of the PV inverter. The proposed method not only improves the voltage quality in the grid but also manages the reactive power outputs of PV inverters efficiently. Further, a digital twin of the cyber-physical system has also been employed that interacts with the control system to ensure its appropriate operation. The effectiveness of the proposed methodology is demonstrated on a representative low-voltage feeder located in Denmark.

24 POWER TRANSMISSION AND DISTRIBUTION↗
NASA NTRS1989

Shape control of high degree-of-freedom variable geometry trusses

Common static trusses are constrained to permit no relative motion between truss elements. A Variable Geometry Truss (VGT), however, is a truss which contains some number of variable length links. The extensible links allow the truss to change shape in a precise, controllable manner. These changes can also be used to control the vibrational response of a truss structure or to perform robotic tasks. Many geometric configurations, both planar and spatial, are possible candidates for VGT manipulators. Here, only two geometries are discussed; the three degree-of-freedom (DOF) spatial octahedral/octahedral truss and the three DOF planar tetrahedral truss. These truss geometries are used as the fundamental element in a repeating chain of trusses. This results in a highly dexterous manipulator with perhaps 30 to 60 degrees of freedom that retains the favorable stiffness properties of a conventional truss. From a fixed base, this type of manipulator could perform shape or vibration control while extending and snaking through complex passageways or moving around obstacles to perform robotic tasks. The approach taken here is to first concentrate on fully understanding the forward and inverse kinematics of the fundamental elements and then utilizing the insight thus gained to solve the more complex problem of the kinematic chains.

Salerno, R. J.↗
NASA NTRS1994

Semigroup approximation and robust stabilization of distributed parameter systems

Theoretical results that enable rigorous statements of convergence and exponential stability of Galerkin approximations of LQR controls for infinite dimensional, or distributed parameter, systems have proliferated over the past ten years. In addition, extensive progress has been made over the same time period in the derivation of robust control design strategies for finite dimensional systems. However, the study of the convergence of robust finite dimensional controllers to robust controllers for infinite dimensional systems remains an active area of research. We consider a class of soft-constrained differential games evolving in a Hilbert space. Under certain conditions, a saddle point control can be given in feedback form in terms of a solution to a Riccati equation. By considering a related LQR problem, we can show a convergence result for finite dimensional approximations of this differential game. This yields a computational algorithm for the feedback gain that can be derived from similar strategies employed in infinite dimensional LQR control design problems. The approach described in this paper also inherits the additional properties of stability robustness common to game theoretic methods in finite dimensional analysis. These theoretical convergence and stability results are verified in several numerical experiments.

Kurdila, A. J.↗
NASA NTRS2023

The Assembly, Test, and Integration of LOFTID (Low-Earth Orbit Flight Test of an Inflatable Decelera-tor)

R.J. Bodkin Biography Mr. Bodkin worked in industry for a rapid prototype company focusing on UAVs and manned experimental aircraft. Later he served as the Inflation System Lead on IRVE-II and 3 and the Re-Entry Vehicle Lead for LOFTID at NASA Langley Research Center. Introduction: The Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID), developed in partnership with United Launch Alliance (ULA) and flown in conjunction with the National Oceanic and Atmospheric Administration (NOAA) Joint Polar Satellite System-2 (JPSS-2) satellite, demonstrated Hypersonic Inflatable Aerodynamic Decelerator (HIAD) technology has progressed and is ready for mission infusion. LOFTID’s success demonstrates that aeroshells are not limited to the internal diame-ter of the launch vehicle payload fairing, allowing larger payloads to be deployed to the surfaces of planetary bodies with atmospheres. The challenges of assembling, integrating, and testing this revolutionary spacecraft will be dis-cussed as well as issues associated with doing this with a fixed launch date the project did not control. Assembly: Because LOFTID flew as a rideshare partner with JPSS-2, it was constrained with addi-tional schedule, milestone, and technical require-ments that were beyond the project’s control. As-sembly of the LOFTID hardware was challenged with the normal mechanical fit issues while also having to navigate the SARS-COVID-II pandemic. Challenges ranged from availability of team per-sonnel required on-site for vehicle assembly to dif-ficulties associated with team collaboration while working remotely and increased costs and lead times of components due to supply chain con-straints. Numerous additional challenges cascaded from the additional time required. Integration: LOFTID flew as a secondary pay-load to JPSS-2 in a mission-unique configuration, directly under JPSS-2 primary payload, inside the Payload Adapter that integrated JPSS-2 to the Atlas V launch vehicle. A mission unique Payload Adapt-er Separation System (PASS) was required to sepa-rate the Payload Adapter from the Launch Vehicle prior to the start of the LOFTID flight demonstra-tion. Development of this system was challenging due to a shortened development schedule resulting from the iterative nature of Payload Adapter devel-opment with the partners at ULA. Preparations to integrate the main segments of the LOFTID vehicle posed unique challenges of having to accommodate issues with a fixed launch date that led to some cre-ative solutions to the integration. The partnership agreement with ULA and JPSS-2 resulted in a mass simulator designed to be installed late in the inte-gration in the event the LOFTID vehicle was not ready in time.. Test: LOFTID testing was carried out in several phases. Some components were tested at the com-ponent level, others at the sub-system levels and then finally the integrated vehicle level. This culmi-nated with the Complete Systems Test (CST) per-formed in a vacuum chamber as one of the final checkouts prior to disassembly for re-packing of the aeroshell. CST challenges will be discussed as well as obstacles encountered post-CST. After CST, the vehicle was disassembled so the HIAD could be repacked, and the vehicle was reassembled for ac-ceptance vibration testing. Testing concluded with the fully assembled vehicle being shipped to the launch site for final testing and integrations with the Payload Adapter to JPSS-2 for launch and opera-tions. Conclusion: The challenges posed by the AI&T for LOFTID could inform the planetary community of some of the opportunities and challenges of de-veloping technologies on a rideshare with a rela-tively small budget.

R.J. Bodkin↗
NASA NTRS1997

Hybrid Damping System for an Electronic Equipment Mounting Shelf

The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-11. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

Voracek, David↗
NASA NTRS1997

Hybrid Damping System for an Electronic Equipment Mounting Shelf

The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-II. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

Voracek, David↗
NASA NTRS1989

Trajectory generation of space telerobots

The purpose is to review a variety of trajectory generation techniques which may be applied to space telerobots and to identify problems which need to be addressed in future telerobot motion control systems. As a starting point for the development of motion generation systems for space telerobots, the operation and limitations of traditional path-oriented trajectory generation approaches are discussed. This discussion leads to a description of more advanced techniques which have been demonstrated in research laboratories, and their potential applicability to space telerobots. Examples of this work include systems that incorporate sensory-interactive motion capability and optimal motion planning. Additional considerations which need to be addressed for motion control of a space telerobot are described, such as redundancy resolution and the description and generation of constrained and multi-armed cooperative motions. A task decomposition module for a hierarchical telerobot control system which will serve as a testbed for trajectory generation approaches which address these issues is also discussed briefly.

Lumia, R.↗
DOE OSTI2025

Insights Into Seismicity Associated With Flexibly Operating Enhanced Geothermal System From Real‐Time Distributed Acoustic Sensing

Enhanced Geothermal Systems (EGS) have the capacity to broaden the accessible resource pool for geothermal power generation. Traditionally viewed as a “baseload” resource, their flexible operation might also enable dispatchable load‐following generation and long‐term energy storage, aligning them with the evolving landscape of decarbonized electricity systems. However, increasing permeability and extracting energy during EGS operations can induce microseismic events; for many prior EGS efforts, some associated seismicity has been observed. While energetically beneficial, the flexibility of EGS operations prompts our inquiry into whether new types of operations will yield previously unseen seismicity patterns. We demonstrate the use of distributed acoustic sensing (DAS) with real‐time edge computing to monitor seismicity during a pilot test of a cyclically operated EGS facility at the Blue Mountain geothermal field. Our focus lies in uncovering seismicity insights from the real‐time microseismic catalog, particularly during load‐following dispatchability tests simulating flexible EGS operation. Here, we find that variations in pore pressure consistently correlate with seismicity, and that controlling pressure cycles during flexible operations appears to constrain microseismic activity during subsequent cycles. The spatio‐temporal evolution of microseismic clouds recorded during cyclic injection cycles fits diffusive models over our available observation period. Additionally, seismicity elevation lags behind pore pressure increases, likely due to pressure diffusion to the fracture system boundary. Through real‐time monitoring, we offer novel insights into seismicity associated with flexibly operating EGS. Our findings suggest that leveraging DAS and edge computing can inform EGS operations and help mitigate induced seismicity.

Chamarczuk, Michal [Rice Univ., Houston, TX (Unite↗
DOE OSTI2023

Dark Energy Survey Year 3 results: Constraints on extensions to Λ CDM with weak lensing and galaxy clustering

We constrain six possible extensions to the Λ cold dark matter (CDM) model using measurements from the Dark Energy Survey’s first three years of observations, alone and in combination with external cosmological probes. The DES data are the two-point correlation functions of weak gravitational lensing, galaxy clustering, and their cross-correlation. We use simulated data vectors and blind analyses of real data to validate the robustness of our results to astrophysical and modeling systematic errors. In many cases, constraining power is limited by the absence of theoretical predictions beyond the linear regime that are reliable at our required precision. The Λ CDM extensions are dark energy with a time-dependent equation of state, nonzero spatial curvature, additional relativistic degrees of freedom, sterile neutrinos with eV-scale mass, modifications of gravitational physics, and a binned σ 8 ( z ) model which serves as a phenomenological probe of structure growth. For the time-varying dark energy equation of state evaluated at the pivot redshift we find ( w p , w a ) = ( - 0.9 9 - 0.17 + 0.28 , - 0.9 ± 1.2 ) at 68% confidence with z p = 0.24 from the DES measurements alone, and ( w p , w a ) = ( - 1.0 3 - 0.03 + 0.04 , - 0. 4 - 0.3 + 0.4 ) with z p = 0.21 for the combination of all data considered. Curvature constraints of Ω k = 0.0009 ± 0.0017 and effective relativistic species N eff = 3.1 0 - 0.16 + 0.15 are dominated by external data, though adding DES information to external low-redshift probes tightens the Ω k constraints that can be made without cosmic microwave background observables by 20%. For massive sterile neutrinos, DES combined with external data improves the upper bound on the mass m eff by a factor of 3 compared to previous analyses, giving 95% limits of ( Δ N eff , m eff ) ≤ ( 0.28 , 0.20 eV ) when using priors matching a comparable Planck analysis. For modified gravity, we constrain changes to the lensing and Poisson equations controlled by functions Σ ( k , z ) = Σ 0 Ω Λ ( z ) / Ω Λ , 0 and μ ( k , z ) = μ 0 Ω Λ ( z ) / Ω Λ , 0 , respectively, to Σ 0 = 0. 6 - 0.5 + 0.4 from DES alone and ( Σ 0 , μ 0 ) = ( 0.04 ± 0.05 , 0.0 8 - 0.19 + 0.21 ) for the combination of all data, both at 68% confidence. Overall, we find no significant evidence for physics beyond Λ CDM .

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Search for Majorana neutrinos in same-sign WW scattering events from pp collisions at $\sqrt{s}=13$ TeV

A search for Majorana neutrinos in same-sign WW scattering events is presented. The analysis uses $\sqrt{s}=13$ TeV proton–proton collision data with an integrated luminosity of 140 fb -1 recorded during 2015–2018 by the ATLAS detector at the Large Hadron Collider. The analysis targets final states including exactly two same-sign muons and at least two hadronic jets well separated in rapidity. The modelling of the main backgrounds, from Standard Model same-sign WW scattering and WZ production, is constrained with data in dedicated signal-depleted control regions. The distribution of the transverse momentum of the second-hardest muon is used to search for signals originating from a heavy Majorana neutrino with a mass between 50 GeV and 20 TeV. No significant excess is observed over the background expectation. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. In addition, the sensitivity to the Weinberg operator is investigated. Upper limits at the 95% confidence level are placed on the squared muon-neutrino–heavy-neutrino mass-mixing matrix element |V μN | 2 as a function of the heavy Majorana neutrino’s mass m N , and on the effective μμ Majorana neutrino mass |m μμ |.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Enabling Real-Time Communication in Multi-Agent Systems: A Graph Neural Network Based Approach

Global connectivity enables effective coordination in Multi-Agent Systems (MAS). Solving these connection problems under hardware constraints is an NP-hard non-Euclidean Degree Constrained Minimum Spanning Tree (DCMST) problem. Prior MAS controllers coordinate team movement for task completion and collision avoidance; some considering Line-of-Sight (LOS) maintenance but prioritizing flexibility over guarantees. Evolutionary Algorithms (EA) have been shown to find good solutions for DCMST, but their performance degrades with larger populations required to support a large MAS. We present a method based on edge graph attention networks, trained offline to reduce online computation times. Empirical comparisons with greedy polynomial-time solvers and EA show that our method leverages latent graph information to consistently find constraint-satisfying solutions in less time.

connectivity maintenance↗
DOE OSTI2023

On the correlation between the stress exponent for creep determined by nanoindentation and the mechanism of action enabling stress relief in indium

Instrumented indentation performed at room temperature with a Berkovich and 10 μm radius sphere has been used to measure the stress exponent for creep before and after the strain burst observed in well-annealed, high-purity indium. Before the strain burst, the measured values are successfully rationalized using a new model based on stress directed diffusional flow along the interface between the indenter tip and test specimen. After the strain burst, the measured stress exponents are found to be representative of dislocation glide and climb assisted glide. Here these results are compared and contrasted to the previous experimental investigations and modeling efforts of Feng et al., Lucas et al., and Li et al. Collectively, the experimental observations and rationalization presented here provide significant new insight into the mechanisms of action that control the competition for stress relief in small, constrained volumes of crystalline metals subjected to high homologous temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A Regional Phase Amplitude Model of 2-D Attenuation for North America

We analyzed seismic attenuation patterns across the North America using over 70,000,000 Lg wave amplitudes recorded by the various networks at frequencies of 0.1-32 Hz. Our inversion solved for laterally varying attenuation, site terms, moments, and apparent stress following Phillips et al., (2016). The inversion was anchored by independently constrained: corner frequencies (via coda spectral ratios) to control the attenuation-stress tradeoff and moment measurements of teleseismic (GCMT, USGS) and regional (St. Louis University and UC Berkeley) earthquakes to provided absolute scaling. The quality factor (Q) shows clear regional patterns: low values in coastal, volcanic, and tectonically active regions, and high values in stable areas like the Great Plains and major plateaus throughout North America. These 2-D Q models enable improved regional source characterization, magnitude estimation, and yield determination.

58 GEOSCIENCES↗
NASA NTRS2005

The Effects of the Uncertainty of Departures on Multi-Center Traffic Management Advisor (TMA) Scheduling

The Multi-center Traffic Management Advisor (McTMA) provides a platform for regional or national traffic flow management, by allowing long-range cooperative time-based metering to constrained resources, such as airports or air traffic control center boundaries. Part of the demand for resources is made up of proposed departures, whose actual departure time is difficult to predict. For this reason, McTMA does not schedule the departures in advance, but rather relies on traffic managers to input their requested departure time. Because this happens only a short while before the aircraft's actual departure, McTMA is unable to accurately predict the amount of delay airborne aircraft will need to take in order to accommodate the departures. The proportion of demand which is made up by such proposed departures increases as the horizon over which metering occurs gets larger. This study provides an initial analysis of the severity of this problem in a 400-500 nautical mile metering horizon and discusses potential solutions to accommodate these departures. The challenge is to smoothly incorporate departures with the airborne stream while not excessively delaying the departures.' In particular, three solutions are reviewed: (1) scheduling the departures at their proposed departure time; (2) not scheduling the departures in advance; and (3) scheduling the departures at some time in the future based on an estimated error in their proposed time. The first solution is to have McTMA to automatically schedule the departures at their proposed departure times. Since the proposed departure times are indicated in their flight times in advance, this method is the simplest, but studies have shown that these proposed times are often incorrect2 The second option is the current practice, which avoids these inaccuracies by only scheduling aircraft when a confirmed prediction of departure time is obtained from the tower of the departure airport. Lastly, McTMA can schedule the departures at a predicted departure time based on statistical data of past departure time performance. It has been found that departures usually have a wheels-up time after their indicated proposed departure time, as shown in Figure 1. Hence, the departures were scheduled at a time in the future based on the mean error in proposed departure times for their airport.

Thipphavong, Jane↗
NASA NTRS2010

Absolute Stability Analysis of a Phase Plane Controlled Spacecraft

Many aerospace attitude control systems utilize phase plane control schemes that include nonlinear elements such as dead zone and ideal relay. To evaluate phase plane control robustness, stability margin prediction methods must be developed. Absolute stability is extended to predict stability margins and to define an abort condition. A constrained optimization approach is also used to design flex filters for roll control. The design goal is to optimize vehicle tracking performance while maintaining adequate stability margins. Absolute stability is shown to provide satisfactory stability constraints for the optimization.

Jang, Jiann-Woei↗