Publications

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CMMs equipped with non-contact probes, such as video probes, are becoming popular for a variety of 2-D or 2.5-D objects. The advantages of a video (or vision) probe include the ability to measure features which are either too small or too delicate for a touch probe. Unfortunately, vision-based probing systems do not have the same measurement accuracy as touch probe equipped machines. For example, a Moore M48 coordinate measurement machine has an expected measurement uncertainty of 0.2 μm (plus a scale dependent term) when using a touch probe (the actual repeatability is on the order of 0.03 μm). When the probe is changed to a Leitz LS1 vision system, the expected measurement uncertainty is 1.2 μm plus a scale dependent term. The decreased accuracy is due entirely to the change in probing method. Components of the error budget include environmental effects, choice of lighting, lens distortions, and stage 2-D accuracy. Lighting is a major contributor to the measurement error budget, especially when a bidirectional measurement needs to be made (for example, the width of a line, rather than the center location of a line). We report on the effect of the sensitivity of vision probing on an OGP Avant Apex 200 to different lighting conditions, both for unidirectional and bidirectional measurements.

One of the challenges facing microrobotic manufacturing is the ability to sense interactions for force-guided assembly of small devices. There is a need for a force transducer with the ability to sense forces in multiple degrees-of-freedom in the mN range with resolution on the order of 10 μN for microassembly applications. This paper presents theoretical studies for developing a surface micromachined piezoresistive force transducer that can measure normal force in the z-direction and moments about the x and y-axes. The devices proposed here are based on a compliant platform design with integrated piezoresistive sensing elements fabricated in a modified SUMMiT process. Various configurations and sensor element layouts are explored to determine the relationship of the applied forces and moments experienced during assembly and the corresponding strain. Structural and finite element analysis is used to determine the elastic response of the device and establish the best locations and orientations of the sensing elements to effectively utilize the piezoresistive effect of the polysilicon sensors. Initial experiments show the polysilicon piezoresistors to have a gauge factor of approximately 25. The expected sensitivities for these devices are presented. Copyright © 2005 by ASME.

Sandia National Laboratories has developed a mesoscale wheeled hopping vehicle (WHV) to overcome the longstanding problems of mobility and power in small scale unmanned vehicles. The system provides mobility in situations such as negotiating obstacles in the vertical dimension and rough terrain that are prohibitive for other small ground base vehicles.

Sandia National Laboratories (SNL) has limited inventories of, and activities with, fissile-material. Personnel who perform nuclear criticality safety (NCS) assignments do so on a part-time basis. Sandia's "tailored approach" to training and qualification of these personnel can serve as a model for others with "small" NCS programs. SNL uses a single set of qualification cards for qualifying nuclear criticality safety engineers (NCSE). Provision is made for: (1) training and mentoring of new NCSE with testing or other verification of their skills and knowledge and (2) "qualification by documentation" for staff who historically have been performing NCSE-like duties. Key areas for evaluation include previous formal education and training; demonstrated success in writing Criticality Safety Assessments (CSA) and related documents; interaction with the SNL criticality safety committees; and overall knowledge (e.g., as judged against the objectives in DOE-STD-1135). Gaps of knowledge are filled through self-study, training, or mentoring. Candidate mastery of topics is confirmed primarily by evaluation of work products and interviews. Completion is approved by the Criticality Safety Officer (CSO) - the closest SNL comes to having an NCS manager - and then management. In applying the tailored approach, NCSE candidates are not required to be subject-matter experts for all NCS-related facilities and activities at SNL at the time of qualification. Familiarity with each of the facilities and activities is expected, along with the ability to "self-train" when needed (e.g., analogous just-in-time [JIT] procurement). The latter is supported by identification of applicable SNL-wide fissile-material facilities and activities along with resource organizations and personnel in NCS, safety analysis, accountability, etc. The capstone is a discussion with the CSO, or other experienced NCSE, demonstrating the ability to explain in some detail how a specific NCS assignment would be tackled (e.g., options for gaining facility/activity knowledge, performing analyses, using resource personnel, and traversing the required peer- and committee-review processes).

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