Home

HyDE Model-Based Diagnosis Engine for Stochastic Hybrid Systems

Model-based diagnosis deals with the problem of diagnosing faults in systems using a model of the system for guidance. This problem is complicated by the presence of hybrid dynamics in the system (continuous evolution of the system interspersed with discrete events like commands to change configuration), as well as uncertainties in the form of model approximations and sensor noise. Several model-based technologies have been developed and successfully demonstrated using discrete abstractions of the system as models. These techniques are severely restricted in model expressiveness due to the discrete nature of the models. Moreover, sophisticated model abstraction techniques, as well as algorithms to convert continuous data to discrete form, need to be developed for such an approach to work. Recently, there have been efforts to develop diagnostic engines for hybrid and stochastic systems. However, these techniques have either focused on parametric faults, or use a probabilistic approach to fault identification. Consistency-based approaches that have been successfully demonstrated using discrete models have not been extended to work with stochastic and hybrid models.

Posted in: Briefs, Electronics & Computers, Information Sciences, Software

Read More >>

Use of Beam Deflection to Control an Electron Beam Wire Deposition Process

NASA Langley Research Center researchers have a strong technology foundation in the use of electron-beam (e-beam) deposition for freeform fabrication of complex shaped metal parts. While e-beam wire deposition is of interest for rapid prototyping of metal parts, cost-effective near-net shape manufacturing, and potential use in space, it is also of intense interest for industrial welding and fabrication in a range of applications, from small components to large aerospace structures. Through significant advancements in techniques to improve control of the process, NASA greatly expands upon the capabilities of the e-beam fabrication and welding process.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Thermal Stir Welding Process

NASA's Marshall Space Flight Center is developing an improved joining technology called thermal stir welding that improves upon fusion welding and friction stir welding. This new technology enables a superior joining method by allowing manufacturers to join dissimilar materials and to weld at high rates. NASA's technology offers users an exciting alternative to state-of-the-art fusion and friction stir welding technologies.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Systems, Apparatuses, and Methods for Using Durable Adhesively Bonded Joints for Sandwich Structures

A preform insert enables redundant bond lines and mass efficient load transfer across the joint.NASA'S Langley Research Center has developed a new adhesively bonded joint concept for curved and flat panel sandwich architectures. A woven preform, inserted into the seam between sandwich panels, provides a larger total bonding area and multiple load paths for an improved distribution of load through the joint. NASA is able to create structures by joining sections of sandwich panels or curved shells. The new joint provides more durable load transfer and redundant load paths compared to current state-of-the-art adhesively bonded strap joints.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Preliminary Design of a Cryogenic Hydrogen Radiation Shield for Human Spaceflight

Liquid hydrogen is the most mass-efficient radiation shielding material.Human susceptibility to the harsh space radiation environment has been identified as a major hurdle for exploration beyond low-Earth orbit (LEO). High-energy protons and nuclei ions from Solar Energetic Particles (SEPs) and Galactic Cosmic Rays (GCRs) can result in radiation doses that are dangerous to astronaut health and even survivability if the astronauts are not adequately shielded. These high-energy particles also cause significant amounts of secondary radiation when they impinge on the spacecraft structure. Hydrogen or hydrogen-rich materials are ideal materials for radiation shielding because hydrogen does not easily break down to form a secondary radiation source.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Methods of Making and Using Tubular Solid Oxide Fuel Cells (SOFCs)

SOFCs have applications in vehicle auxiliary power units, and emergency backup power for telecom and cable repeaters.Human-occupied vehicles and autonomous vehicles such as rovers and landers may benefit from the fuel flexibility and high energy density of solid oxide fuel cells (SOFCs), compared to batteries and polymer electrolyte membrane (PEM) systems. Fuel systems greater than 1 kW are traditionally planar and exhibit high volumetric power density; however, due to large sealing areas, they have poor cycling characteristics. Recently, 250 cycles on a Tubular SOFC (T-SOFC) system (Protonex Technology Corp.) was demonstrated. Hot zones designed around T-SOFCs have a lower packing density, but significantly better cycle life and start times, making them an ideal solution. By increasing the power density of T-SOFCs, overall hot zone and system volumetric power densities can be greatly improved. Extending the methodology of freeze-casting to T-SOFCs will provide a system with the micro-structural advantages of their planar counterpart, but with the rapid thermal cycling capacity of traditional extruded SOFCs.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

Tool Designs for Friction Stir Welding

This repeatable, environmentally friendly, cost-effective weld method is able to weld traditionally “unweldable” alloys.Friction stir welding (FSW) is a solidstate welding process that shows promise in the aerospace industry. A new system of experimentation has been used to quickly make and screen new tool designs. After conducting a literature review, friction stir tools were designed to optimize material flow around the tool.

Posted in: Briefs, Manufacturing & Prototyping

Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.