Publications

This report contains the results of a research effort on advanced robot locomotion. The majority of this work focuses on walking robots. Walking robot applications include delivery of special payloads to unique locations that require human locomotion to exo-skeleton human assistance applications. A walking robot could step over obstacles and move through narrow openings that a wheeled or tracked vehicle could not overcome. It could pick up and manipulate objects in ways that a standard robot gripper could not. Most importantly, a walking robot would be able to rapidly perform these tasks through an intuitive user interface that mimics natural human motion. The largest obstacle arises in emulating stability and balance control naturally present in humans but needed for bipedal locomotion in a robot. A tracked robot is bulky and limited, but a wide wheel base assures passive stability. Human bipedal motion is so common that it is taken for granted, but bipedal motion requires active balance and stability control for which the analysis is non-trivial. This report contains an extensive literature study on the state-of-the-art of legged robotics, and it additionally provides the analysis, simulation, and hardware verification of two variants of a proto-type leg design.

The Department of Energy has assigned to Sandia National Laboratories the responsibility of producing a Safety Analysis Report (SAR) for the plutonium-dioxide fueled Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) proposed to be used in the Mars Science Laboratory (MSL) mission. The National Aeronautic and Space Administration (NASA) is anticipating a launch in fall of 2009, and the SAR will play a critical role in the launch approval process. As in past safety evaluations of MMRTG missions, a wide range of potential accident conditions differing widely in probability and seventy must be considered, and the resulting risk to the public will be presented in the form of probability distribution functions of health effects in terms of latent cancer fatalities. The basic descriptions of accident cases will be provided by NASA in the MSL SAR Databook for the mission, and on the basis of these descriptions, Sandia will apply a variety of sophisticated computational simulation tools to evaluate the potential release of plutonium dioxide, its transport to human populations, and the consequent health effects. The first step in carrying out this project is to evaluate the existing computational analysis tools (computer codes) for suitability to the analysis and, when appropriate, to identify areas where modifications or improvements are warranted. The overall calculation of health risks can be divided into three levels of analysis. Level A involves detailed simulations of the interactions of the MMRTG or its components with the broad range of insults (e.g., shrapnel, blast waves, fires) posed by the various accident environments. There are a number of candidate codes for this level; they are typically high resolution computational simulation tools that capture details of each type of interaction and that can predict damage and plutonium dioxide release for a range of choices of controlling parameters. Level B utilizes these detailed results to study many thousands of possible event sequences and to build up a statistical representation of the releases for each accident case. A code to carry out this process will have to be developed or adapted from previous MMRTG missions. Finally, Level C translates the release (or ''source term'') information from Level B into public risk by applying models for atmospheric transport and the health consequences of exposure to the released plutonium dioxide. A number of candidate codes for this level of analysis are available. This report surveys the range of available codes and tools for each of these levels and makes recommendations for which choices are best for the MSL mission. It also identities areas where improvements to the codes are needed. In some cases a second tier of codes may be identified to provide supporting or clarifying insight about particular issues. The main focus of the methodology assessment is to identify a suite of computational tools that can produce a high quality SAR that can be successfully reviewed by external bodies (such as the Interagency Nuclear Safety Review Panel) on the schedule established by NASA and DOE.

Sandia National Laboratories has developed a Near Real Time Range Safety Analysis Tool named PREDICT that is based upon a probabilistic range safety analysis process. Probabilistic calculations of risk may be used in place of the total containment of potentially hazardous debris during a missile launch operation. Impact probabilities are computed based upon probabilistic density functions, Monte Carlo trajectories of dispersion events, and missile failure scenarios. Impact probabilities are then coupled with current demographics (land populations, commercial and military ship traffic, and aircraft traffic) to produce expected casualty predictions for a particular launch window. Historically, these calculations required days of computer time to finalize. Sandia has developed a process that utilizes the IBM SP machines at the Maui High Performance Computing Center and at the Arctic Region Supercomputing Center to reduce the computation time from days to as little as an hour or two. This analysis tool then allows the Missile Flight Safety Officer to make launch decisions based on the latest information (winds, ship, and aircraft movements) utilizing an intelligent risk management approach. This report provides a user's manual for PREDICT version 3.3.

Engineers at Sandia National Laboratories are combining entertainment industry software with traditional data collection techniques to create an interactive visualization tool. By replacing the usual flight simulator joystick with a telemetry data stream, experimental data is combined with existing three-dimensional (3D) engineering models. Users are immersed in their experiment, allowing interaction with and comprehension of complex data sets. Software tools are currently under development for post flight data visualization, and their usefulness and reusability have been demonstrated on numerous spaced-based programs within Sandia. However, data from remote sensors are subject to transmission errors that yield nonphysical behavior in real-time data visualization applications. We propose to investigate the applicability of real-time processing algorithms and estimation theories, such as Kalman filters, that have been successfully applied in other fields. Results will be integrated into existing postflight visualization tools for Proof-of-Concept validation and for potential integration of real-time applications.

This paper is an overview of the wafer and reticle positioning system of the Extreme Ultraviolet Lithography (EUVL) Engineering Test Stand (ETS). EUVL represents one of the most promising technologies for supporting the integrated circuit (IC) industry's lithography needs for critical features below 100 nm. EUVL research and development includes development of capabilities for demonstrating key EUV technologies. The ETS is under development at the EUV Virtual National Laboratory, to demonstrate EUV full-field imaging and provide data that supports production-tool development. The stages and their associated metrology operate in a vacuum environment and must meet stringent outgassing specifications. A tight tolerance is placed on the stage tracking performance to minimize image distortion and provide high position repeatability. The wafer must track the reticle with less than ±3 nm of position error and jitter must not exceed 10 nm rms. To meet these performance requirements, magnetically levitated positioning stages utilizing a system of sophisticated control electronics will be used. System modeling and experimentation have contributed to the development of the positioning system and results indicate that desired ETS performance is achievable.