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NASA NTRS1992

Reliable vision-guided grasping

Automated assembly of truss structures in space requires vision-guided servoing for grasping a strut when its position and orientation are uncertain. This paper presents a methodology for efficient and robust vision-guided robot grasping alignment. The vision-guided grasping problem is related to vision-guided 'docking' problems. It differs from other hand-in-eye visual servoing problems such as tracking in that the distance from the target is a relevant servo parameter. The methodology described in this paper is a hierarchy of levels in which the vision/robot interface is decreasingly 'intelligent', and increasingly fast. Speed is achieved primarily by information reduction. This reduction exploits the use of region-of-interest windows in the image plane and feature motion prediction. These reductions invariably require stringent assumptions about the image. Therefore, at a higher level, these assumptions are verified using slower, more reliable methods. This hierarchy provides for robust error recovery in that when a lower-level routine fails, the next-higher routine will be called and so on. A working system is described which visually aligns a robot to grasp a cylindrical strut. The system uses a single camera mounted on the end effector of a robot and requires only crude calibration parameters. The grasping procedure is fast and reliable, with a multi-level error recovery system.

Nicewarner, Keith E.↗

DOE OSTI2015

Pressure-induced structures of Si-doped HfO{sub 2}

The effect of hydrostatic pressure on the structure of Si-doped HfO{sub 2} (Si:HfO{sub 2}) was studied by using a diamond anvil cell in combination with high-energy X-ray diffraction at a synchrotron source. Diffraction data were measured in situ during compression up to pressures of 31 GPa. Si:HfO{sub 2} with 3, 5, and 9 at. % Si were found to undergo a monoclinic to orthorhombic transition at pressures between 7 and 15 GPa. Whole pattern analysis was carried out using nonpolar (Pbca) and polar (Pca2{sub 1}) crystallographic models to investigate the symmetry of the observed high-pressure orthorhombic phase. Rietveld refinement results cannot discriminate a reliable difference between the Pbca and Pca2{sub 1} structures as they nearly equally model the measured diffraction data. The pressure dependent lattice parameters, relative volume, and spontaneous strain are reported.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2021

Finite-size correction for slab supercell calculations of materials with spontaneous polarization

Abstract The repeated slab approach has become a de facto standard to accurately describe surface properties of materials by density functional theory calculations with periodic boundary conditions. For materials exhibiting spontaneous polarization, we show that the conventional scheme of passivation with pseudo hydrogen is unable to realize a charge-neutral surface. The presence of a net surface charge induces via Gauss’s law a macroscopic electric field through the slab and results in poor size convergence with respect to the thickness of the slab. We propose a modified passivation method that accounts for the effect of spontaneous polarization, describes the correct bulk limits and boosts convergence with respect to slab thickness. The robustness, reliability, and superior convergence of energetics and electronic structure achieved by the proposed method are demonstrated using the example of polar ZnO surfaces.

Chemistry↗

DOE OSTI2016

Resilience Design Patterns - A Structured Approach to Resilience at Extreme Scale (version 1.0)

Reliability is a serious concern for future extreme-scale high-performance computing (HPC) systems. Projections based on the current generation of HPC systems and technology roadmaps suggest that very high fault rates in future systems. The errors resulting from these faults will propagate and generate various kinds of failures, which may result in outcomes ranging from result corruptions to catastrophic application crashes. Practical limits on power consumption in HPC systems will require future systems to embrace innovative architectures, increasing the levels of hardware and software complexities. The resilience challenge for extreme-scale HPC systems requires management of various hardware and software technologies that are capable of handling a broad set of fault models at accelerated fault rates. These techniques must seek to improve resilience at reasonable overheads to power consumption and performance. While the HPC community has developed various solutions, application-level as well as system-based solutions, the solution space of HPC resilience techniques remains fragmented. There are no formal methods and metrics to investigate and evaluate resilience holistically in HPC systems that consider impact scope, handling coverage, and performance & power eciency across the system stack. Additionally, few of the current approaches are portable to newer architectures and software ecosystems, which are expected to be deployed on future systems. In this document, we develop a structured approach to the management of HPC resilience based on the concept of resilience-based design patterns. A design pattern is a general repeatable solution to a commonly occurring problem. We identify the commonly occurring problems and solutions used to deal with faults, errors and failures in HPC systems. The catalog of resilience design patterns provides designers with reusable design elements. We define a design framework that enhances our understanding of the important constraints and opportunities for solutions deployed at various layers of the system stack. The framework may be used to establish mechanisms and interfaces to coordinate flexible fault management across hardware and software components. The framework also enables optimization of the cost-benefit trade-os among performance, resilience, and power consumption. The overall goal of this work is to enable a systematic methodology for the design and evaluation of resilience technologies in extreme-scale HPC systems that keep scientific applications running to a correct solution in a timely and cost-ecient manner in spite of frequent faults, errors, and failures of various types.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2016

Resilience Design Patterns - A Structured Approach to Resilience at Extreme Scale (version 1.1)

Reliability is a serious concern for future extreme-scale high-performance computing (HPC) systems. Projections based on the current generation of HPC systems and technology roadmaps suggest the prevalence of very high fault rates in future systems. The errors resulting from these faults will propagate and generate various kinds of failures, which may result in outcomes ranging from result corruptions to catastrophic application crashes. Therefore the resilience challenge for extreme-scale HPC systems requires management of various hardware and software technologies that are capable of handling a broad set of fault models at accelerated fault rates. Also, due to practical limits on power consumption in HPC systems future systems are likely to embrace innovative architectures, increasing the levels of hardware and software complexities. As a result the techniques that seek to improve resilience must navigate the complex trade-off space between resilience and the overheads to power consumption and performance. While the HPC community has developed various resilience solutions, application-level techniques as well as system-based solutions, the solution space of HPC resilience techniques remains fragmented. There are no formal methods and metrics to investigate and evaluate resilience holistically in HPC systems that consider impact scope, handling coverage, and performance & power efficiency across the system stack. Additionally, few of the current approaches are portable to newer architectures and software environments that will be deployed on future systems. In this document, we develop a structured approach to the management of HPC resilience using the concept of resilience-based design patterns. A design pattern is a general repeatable solution to a commonly occurring problem. We identify the commonly occurring problems and solutions used to deal with faults, errors and failures in HPC systems. Each established solution is described in the form of a pattern that addresses concrete problems in the design of resilient systems. The complete catalog of resilience design patterns provides designers with reusable design elements. We also define a framework that enhances a designer's understanding of the important constraints and opportunities for the design patterns to be implemented and deployed at various layers of the system stack. This design framework may be used to establish mechanisms and interfaces to coordinate flexible fault management across hardware and software components. The framework also supports optimization of the cost-benefit trade-offs among performance, resilience, and power consumption. The overall goal of this work is to enable a systematic methodology for the design and evaluation of resilience technologies in extreme-scale HPC systems that keep scientific applications running to a correct solution in a timely and cost-efficient manner in spite of frequent faults, errors, and failures of various types.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2019

Scalable Freeze-Tape-Casting Fabrication and Pore Structure Analysis of 3D LLZO Solid-State Electrolytes

Nonflammable solid-state electrolytes can potentially address the reliability and energy density limitations of lithium-ion batteries. Garnet-structured oxides such as Li 7 La 3 Zr 2 O 12 (LLZO) are some of the most promising candidates for solid-state devices. Here, three-dimensional (3D) solid-state LLZO frameworks with low tortuosity pore channels are proposed as scaffolds, into which active materials and other components can be infiltrated to make composite electrodes for solid-state batteries. To make the scaffolds, we employed aqueous freeze tape casting (FTC), a scalable and environmentally friendly method to produce porous LLZO structures. Using synchrotron radiation hard X-ray microcomputed tomography, we confirmed that LLZO films with porosities of up to 75% were successfully fabricated from slurries with a relatively wide concentration range. The acicular pore size and shape at different depths of scaffolds were quantified by fitting the pore shapes with ellipses, determining the long and short axes and their ratios, and investigating the equivalent diameter distribution. The results show that relatively homogeneous pore sizes and shapes were sustained over a long range along the thickness of the scaffold. Additionally, these pores had low tortuosity and the wall thickness distributions were found to be highly homogeneous. These are desirable characteristics for 3D solid electrolytes for composite electrodes, in terms of both the ease of active material infiltration and also minimization of Li diffusion distances in electrodes. The advantages of the FTC scaffolds are demonstrated by the improved conductivity of LLZO scaffolds infiltrated with poly(ethylene oxide)/lithium bis(trifluoromethanesulfonyl)imide (PEO/LITFSI) compared to those of PEO/LiTFSI films alone or composites containing LLZO particles.

36 MATERIALS SCIENCE↗

NASA NTRS1981

Reliability-based optimization under random vibration environment

A methodology of formulating the optimum design problem for structural systems with random parameters and subjected to random vibration as a mathematical programming problem is presented. The proposed method is applied to the optimum design of a cantilever beam with a tip mass and a truss structure supporting a water tank. The excitations are assumed to be Gaussian processes and the geometric and material properties are taken to be normally distributed random variables. The probabilistic constraints are specified for individual failure modes since it is easier to specify the reliability level for each failure mode keeping in view the consequences of failure in that particular mode. The time parameter appearing in the random vibration based constraints is eliminated by replacing the probabilities of failure by suitable upper bounds. The numerical results demonstrate the feasibility and effectiveness of applying the reliability-based design concepts to structures with random parameters and operating in random vibration environment.

Rao, S. S.↗

DOE OSTI2026

Performing Numerical Analysis of Cybersecurity Options Using Dynamic Risk Analysis Tool EMRALD

Cyberattacks can have many different attack paths, durations, and goals. There are also many different mitigation options involving hardware, software, and/or humans. Considering a cyber threat should involve defense-in-depth methods and a quantitative or numerical evaluation of overall effectiveness against dynamic, time-dependent attacks to make cost and risk-informed decisions. Typical cyberattack modeling methods only provide a qualitative evaluation. The main areas of cybersecurity are confidentiality, integrity, and availability. For companies with cyber-physical systems such as advanced nuclear reactors, cyber-related safety is a requirement set by North American Electric Reliability and the U.S. Nuclear Regulatory Commission. They are also concerned about availability or reliability as a business case. As cyber threats are evolving to a business-for-hire structure, more attacks may focus on disrupting business success and reliability, causing financial and economic stability risk. Companies want to know business reliability and recovery from those threats, and that requires modeling physical behavior of the targets. Dynamic-state-based and Markov-based modeling provides a method for better cyber scenario modeling with different tools having issues such as state-base explosion. Dynamic modeling enables time and conditional features not found in other numerical evaluation methods. EMRALD (Event Modeling Risk Assessment using Lined Diagrams) is a dynamic risk analysis modeling and simulation tool and has features that reduce modeling issues. It has been used to model different time-dependent events including plant behavior and operator procedures. As a general modeling tool, EMRALD can also be used to model cyberattack scenarios with varying mitigation options and quantify effectiveness, producing numerical data for risk-informed decisions. This paper uses EMRALD to demonstrate that dynamic numerical risk analysis can be used for cyber threat modeling to provide insights for design decision-making and optimize defense strategies. Keywords: cyber modeling; cyber-physical systems; numerical cyber modeling

97 - MATHEMATICS AND COMPUTING↗

NASA NTRS1991

Reliable fusion of control and sensing in intelligent machines

Although robotics research has produced a wealth of sophisticated control and sensing algorithms, very little research has been aimed at reliably combining these control and sensing strategies so that a specific task can be executed. To improve the reliability of robotic systems, analytic techniques are developed for calculating the probability that a particular combination of control and sensing algorithms will satisfy the required specifications. The probability can then be used to assess the reliability of the design. An entropy formulation is first used to quickly eliminate designs not capable of meeting the specifications. Next, a framework for analyzing reliability based on the first order second moment methods of structural engineering is proposed. To ensure performance over an interval of time, lower bounds on the reliability of meeting a set of quadratic specifications with a Gaussian discrete time invariant control system are derived. A case study analyzing visual positioning in robotic system is considered. The reliability of meeting timing and positioning specifications in the presence of camera pixel truncation, forward and inverse kinematic errors, and Gaussian joint measurement noise is determined. This information is used to select a visual sensing strategy, a kinematic algorithm, and a discrete compensator capable of accomplishing the desired task. Simulation results using PUMA 560 kinematic and dynamic characteristics are presented.

Mcinroy, John E.↗

NASA NTRS1989

Computational methods and software systems for dynamics and control of large space structures

The deployment, assembly and mission-oriented maneuvering of space structures in orbit will trigger large motions of flexible, truss-type structures. In addition, the presence of on-board controls both for attitude stabilization and specified vibration tolerance requirements may further complicate the dynamic behavior of the orbiting structures. Because of safety and cost considerations, the dynamic response of the combined structural and control systems must be predicted reliably. This need can only be met through the development of reliable and efficient simulation capabilities, since there is general agreement that on-orbit experiments should be limited because of cost, time and facility constraints. The long-term objective of this research effort is to develop a next-generation computer simulator for the dynamics and control of large space structures. The simulator will be based on integrating four research thrusts: a new multibody dynamics formulation methodology, modeling capabilities in long/slender truss-beam components with realistic joints, efficient computational procedures that can be implemented either in sequential or concurrent computers, and prototype simulation modules that can be easily processed into a modern large-scale engineering software system such as the NASA/Computational Structural Mechanics (CSM) testbed.

Park, K. C.↗

DOE OSTI2016

Controlling the stability of both the structure and velocity of domain walls in magnetic nanowires

For magnetic nanowire devices, the precise control of both domain wall (DW) motion and pinning behaviour is essential for reliable functional performance. The domain wall velocity and wall structure are typically sensitive to the driving field or spin-polarized current, and the pinning behaviour depends on the walls' structure and chirality, leading to variability in behaviour. Here, a systematic study combining experimental measurements and micromagnetic simulations of planar nanowires with small fixed-angle structural modulations on both edges was undertaken to study the domain wall reversal regime. A phase diagram for the reversal field as a function of modulation amplitude was obtained that shows that three DW reversal regime. A range of field and modulation amplitudes were identified in which stable DW reversal occurs, where the wall velocity is constant as a function of field and the wall structure is stable, which is well suited to applications.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2025

A Review on Building Resilient Power Networks: Emphasizing Adjacent Span Dynamics

This research article presents a comprehensive review of resilience in power transmission and distribution systems, focusing on key studies that examine structural integrity, mechanical stress distribution, and system reliability under various conditions. The article synthesizes findings across multiple studies, covering assumptions, system topologies, methodologies, and challenges that affect resilience in these networks. Particular attention is given to identifying studies that address the influence of adjacent spans and tower--line interactions, as these factors play a crucial role in the stress distribution and structural dynamics within poles, towers, and transmission lines. In addition to identifying critical factors contributing to system vulnerability, this review emphasizes the importance of continued research to better understand and mitigate risks from extreme events, such as high winds combined with ice storms. By consolidating knowledge on current challenges and future needs, this work outlines future directions to advance resilience studies and contributes to ongoing efforts to strengthen power transmission and distribution networks, reducing disruptions in electricity supply and improving overall system resilience in an evolving climate landscape.

Ahmad, Tawsif [Pacific Northwest National Laborato↗

NASA NTRS1997

Aerodynamic Synthesis of a Centrifugal Impeller Using CFD and Measurements

The performance and flow structure in an unshrouded impeller of approximately 4:1 pressure ratio is synthesized on the basis of a detailed analysis of 3D viscous CFD results and aerodynamic measurements. A good data match was obtained between CFD and measurements using laser anemometry and pneumatic probes. This solidified the role of the CFD model as a reliable representation of the impeller internal flow structure and integrated performance. Results are presented showing the loss production and secondary flow structure in the impeller. The results indicate that while the overall impeller efficiency is high, the impeller shroud static pressure recovery potential is underdeveloped leading to a performance degradation in the downstream diffusing element. Thus, a case is made for a follow-on impeller parametric design study to improve the flow quality. A strategy for aerodynamic performance enhancement is outlined and an estimate of the gain in overall impeller efficiency that might be realized through improvements to the relative diffusion process is provided.

Larosiliere, L. M.↗

NASA NTRS1994

Probabilistic assessment of space nuclear propulsion system nozzle

In assessing the reliability of a space nuclear propulsion system (SNPS) nozzle, uncertainties associated with the following design parameters were considered: geometry, boundary conditions, material behavior, and thermal and pressure loads. A preliminary assessment of the reliability was performed using NESSUS (Numerical Evaluation of Stochastic Structures Under Stress), a finite-element computer code developed at the NASA Lewis Research Center. The sensitivity of the nozzle reliability to the uncertainties in the random variables was quantified. With respect to the effective stress, preliminary results showed that the nozzle spatial geometry uncertainties have the most significant effect at low probabilities whereas the inner wall temperature has the most significant effect at higher probabilities.

Shah, Ashwin R.↗

NASA NTRS2000

2nd Generation RLV Airframe Structures and Materials

The goals and objectives of the project summarized in this viewgraph presentation are the following: (1) Develop and demonstrate verified airframe and cryotank structural design and analysis technologies, including damage tolerance, safety, reliability, and residual strength technologies, robust nonlinear shell and cryotank analysis technologies, high-fidelity analysis and design technologies for local structural detail features and joints, and high-fidelity analysis technologies for sandwich structures; (2) Demonstrate low cost, robust materials and processing, including polymeric matrix composite (PMC) and metallic materials and processing, and refractory composite and metallic hot structures materials and processing; (3) Develop and demonstrate robust airframe structures and validated integrated airframe structural concepts, including low cost fabrication and joining, operations efficient designs and inspection techniques (non-destructive evaluation), scale-up and integrated thermal structure tests, and airframe structures IVHM; (4) Demonstrate low cost, robust repair techniques; and (5) Develop verified integrated airframe structural concepts, including integrated structural concepts.

Johnson, Theodore F.↗

NASA NTRS1996

Rapid Inspection of Aerospace Structures - Is It Autonomous Yet?

The trend to increase the usage of aging aircraft added a great deal of urgency to the ongoing need for low-cost, rapid, simple-to-operate, reliable and efficient NDE methods for detection and characterization of flaws in aircraft structures. In many cases, the problem of inspection is complex due to the limitation of current technology and the need to disassemble aircraft structures and testing them in lab conditions. To overcome these limitations, reliable field inspection tools are being developed for rapid NDE of large and complex-shape structures, that can operate at harsh, hostal and remote conditions with minimum human interface. In recent years, to address the need for rapid inspection in field conditions, numerous portable scanners were developed using NDE methods, including ultrasonics, shearography, thermography. This paper is written with emphasis on ultrasonic NDE scanners, their evolution and the expected direction of growth.

Crawling System autonomous robotics↗

NASA NTRS1976

Design of a Mars entry 'aeroshell'

The external shell of the Project Viking capsule, which will provide atmospheric deceleration for the 1976 landing of an unmanned spacecraft on the surface of Mars, is a wide-angle, stiffened cone subject to buckling under entry aerodynamic pressure. Complex, highly optimized structural prototype and flight designs were evolved through the application of relatively advanced buckling analysis methodology. Both designs were evaluated through tests and analysis with improved shell-of-revolution computer programs. Deviations between the analyses and experiments were resolved only by modeling the thin-walled rings as shell branches. The results illustrate the great complexity of shell behavior and the designer's need for reliable analysis tools capable of representing detailed structural behavior with greater accuracy than is current practice.

Leonard, R. W.↗

NASA NTRS2012

Some Aspects of the Failure Mechanisms in BaTiO3-Based Multilayer Ceramic Capacitors

The objective of this presentation is to gain insight into possible failure mechanisms in BaTiO3-based ceramic capacitors that may be associated with the reliability degradation that accompanies a reduction in dielectric thickness, as reported by Intel Corporation in 2010. The volumetric efficiency (microF/cm3) of a multilayer ceramic capacitor (MLCC) has been shown to not increase limitlessly due to the grain size effect on the dielectric constant of ferroelectric ceramic BaTiO3 material. The reliability of an MLCC has been discussed with respect to its structure. The MLCCs with higher numbers of dielectric layers will pose more challenges for the reliability of dielectric material, which is the case for most base-metal-electrode (BME) capacitors. A number of MLCCs manufactured using both precious-metal-electrode (PME) and BME technology, with 25 V rating and various chip sizes and capacitances, were tested at accelerated stress levels. Most of these MLCCs had a failure behavior with two mixed failure modes: the well-known rapid dielectric wearout, and so-called 'early failures." The two failure modes can be distinguished when the testing data were presented and normalized at use-level using a 2-parameter Weibull plot. The early failures had a slope parameter of Beta >1, indicating that the early failures are not infant mortalities. Early failures are triggered due to external electrical overstress and become dominant as dielectric layer thickness decreases, accompanied by a dramatic reduction in reliability. This indicates that early failures are the main cause of the reliability degradation in MLCCs as dielectric layer thickness decreases. All of the early failures are characterized by an avalanche-like breakdown leakage current. The failures have been attributed to the extrinsic minor construction defects introduced during fabrication of the capacitors. A reliability model including dielectric thickness and extrinsic defect feature size is proposed in this presentation. The model can be used to explain the Intel-reported reliability degradation in MLCCs with respect to the reduction of dielectric thickness. It can also be used to estimate the reliability of a MLCC based on its construction and microstructure parameters such as dielectric thickness, average grain size, and number of dielectric layers. Measures for preventing early failures are also discussed in this document.

Liu, David Donhang↗