Backward assembly planning with DFA analysis

An assembly planning system that operates based on a recursive decomposition of assembly into subassemblies is presented. The planning system analyzes assembly cost in terms of stability, directionality, and manipulability to guide the generation of preferred assembly plans. The planning in this system incorporates the special processes, such as cleaning, testing, labeling, etc., that must occur during the assembly. Additionally, the planning handles nonreversible, as well as reversible, assembly tasks through backward assembly planning. In order to decrease the planning efficiency, the system avoids the analysis of decompositions that do not correspond to feasible assembly tasks. This is achieved by grouping and merging those parts that can not be decomposable at the current stage of backward assembly planning due to the requirement of special processes and the constraint of interconnection feasibility. The invention includes methods of evaluating assembly cost in terms of the number of fixtures (or holding devices) and reorientations required for assembly, through the analysis of stability, directionality, and manipulability. All these factors are used in defining cost and heuristic functions for an AO* search for an optimal plan

Phase calibration generator

A phase calibration system was developed for the Deep Space Stations to generate reference microwave comb tones which are mixed in with signals received by the antenna. These reference tones are used to remove drifts of the station's receiving system from the detected data. This phase calibration system includes a cable stabilizer which transfers a 20 MHz reference signal from the control room to the antenna cone. The cable stabilizer compensates for delay changes in the long cable which connects its control room subassembly to its antenna cone subassembly in such a way that the 20 MHz is transferred to the cone with no significant degradation of the hydrogen maser atomic clock stability. The 20 MHz reference is used by the comb generator and is also available for use as a reference for receiver LO's in the cone

Precedence relationship representations of mechanical assembly sequences

Two types of precedence relationship representations for mechanical assembly sequences are presented: precedence relationships between the establishment of one connection between two parts and the establishment of another connection, and precedence relationships between the establishment of one connection and states of the assembly process. Precedence relationship representations have the advantage of being very compact. The problem with these representations was how to guarantee their correctness and completeness. Two theorems are presented each of which leads to the generation of one type of precedence relationship representation guaranteeing its correctness and completeness for a class of assemblies

Spatial Aggregation: Theory and Applications

Visual thinking plays an important role in scientific reasoning. Based on the research in automating diverse reasoning tasks about dynamical systems, nonlinear controllers, kinematic mechanisms, and fluid motion, we have identified a style of visual thinking, imagistic reasoning. Imagistic reasoning organizes computations around image-like, analogue representations so that perceptual and symbolic operations can be brought to bear to infer structure and behavior. Programs incorporating imagistic reasoning have been shown to perform at an expert level in domains that defy current analytic or numerical methods. We have developed a computational paradigm, spatial aggregation, to unify the description of a class of imagistic problem solvers. A program written in this paradigm has the following properties. It takes a continuous field and optional objective functions as input, and produces high-level descriptions of structure, behavior, or control actions. It computes a multi-layer of intermediate representations, called spatial aggregates, by forming equivalence classes and adjacency relations. It employs a small set of generic operators such as aggregation, classification, and localization to perform bidirectional mapping between the information-rich field and successively more abstract spatial aggregates. It uses a data structure, the neighborhood graph, as a common interface to modularize computations. To illustrate our theory, we describe the computational structure of three implemented problem solvers -- KAM, MAPS, and HIPAIR --- in terms of the spatial aggregation generic operators by mixing and matching a library of commonly used routines.Comment: See http://www.jair.org/ for any accompanying file

Mariner Mars 1969 SCAN control subsystem design and analysis

Design and analysis of self correcting automatic navigation system for Mariner Mars spacecraf

Seismic Performance of Anchored Brick Veneer

A study was conducted on the out-of-plane seismic performance of anchored brick veneer with wood-frame backup wall systems, to evaluate prescriptive design requirements and current construction practices. Prescriptive requirements for the design and construction of anchored brick veneer are currently provided by the Masonry Standards Joint Committee (MSJC) Building Code, the International Residential Code (IRC) for Oneand Two-Family Dwellings, and the Brick Industry Association (BIA) Technical Notes. Laboratory tests were conducted on brick-tie-wood subassemblies, comprising two bricks with a corrugated sheet metal tie either nail- or screw-attached to a wood stud, permitting an evaluation of the stiffness, strength, and failure modes for a local portion of a veneer wall system, rather than just of a single tie by itself. Then, full-scale brick veneer wall specimens (two one-story solid walls, as well as a one-and-a-half story wall with a window opening and a gable region) were tested under static and dynamic out-of-plane loading on a shake table. The shake table tests captured the performance of brick veneer wall systems, including interaction and load-sharing between the brick veneer, corrugated sheet metal ties, and wood-frame backup. Finally, all of these test results were used to develop finite element models of brick veneer wall systems, including nonlinear inelastic properties for the tie connections. The experimental and analytical studies showed that the out-of-plane seismic performance of residential anchored brick veneer walls is generally governed by: tensile stiffness and strength properties of the tie connections, as controlled by tie installation details; overall grid spacing of the tie connections, especially for tie installation along the edges and in the upper regions of walls; and, overall wall geometric variations. Damage limit states for single-story residential brick veneer wall systems were established from the experimental and analytical studies as a function of tensile failure of key tie connections, and the seismic fragility of this form of construction was then evaluated. Based on the overall findings, it is recommended that codes incorporate specific requirements for tie connection installation along all brick veneer wall edges, as well as for tie connection installation at reduced spacings in the upper regions of wall panels and near stiffer regions of the backup. Residential anchored brick veneer construction should as a minimum be built in accordance with the current prescriptive code requirements and recommendations, throughout low to moderate seismicity regions of the central and eastern U.S., whereas non-compliant methods of construction commonly substituted in practice are generally not acceptable.published or submitted for publicatio

A design of resonant inelastic X-ray scattering (RIXS) spectrometer for spatial- and time-resolved spectroscopy.

The optical design of a Hettrick-Underwood-style soft X-ray spectrometer with Wolter type 1 mirrors is presented. The spectrometer with a nominal length of 3.1 m can achieve a high resolving power (resolving power higher than 10000) in the soft X-ray regime when a small source beam (<3 µm in the grating dispersion direction) and small pixel detector (5 µm effective pixel size) are used. Adding Wolter mirrors to the spectrometer before its dispersive elements can realize the spatial imaging capability, which finds applications in the spectroscopic studies of spatially dependent electronic structures in tandem catalysts, heterostructures, etc. In the pump-probe experiments where the pump beam perturbs the materials followed by the time-delayed probe beam to reveal the transient evolution of electronic structures, the imaging capability of the Wolter mirrors can offer the pixel-equivalent femtosecond time delay between the pump and probe beams when their wavefronts are not collinear. In combination with some special sample handing systems, such as liquid jets and droplets, the imaging capability can also be used to study the time-dependent electronic structure of chemical transformation spanning multiple time domains from microseconds to nanoseconds. The proposed Wolter mirrors can also be adopted to the existing soft X-ray spectrometers that use the Hettrick-Underwood optical scheme, expanding their capabilities in materials research

Planetary film reconnaissance system

Design, fabrication, assembly of planetary film reconnaissance syste

Spacesuit mobility knee joints

Pressure suit mobility joints are for use in interconnecting adjacent segments of an hermetically sealed spacesuit in which low torques, low leakage and a high degree of reliability are required. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics and includes linkages which restrain the joint from longitudinal distension and includes a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints

Spacesuit mobility joints

Joints for use in interconnecting adjacent segments of an hermetically sealed spacesuit which have low torques, low leakage and a high degree of reliability are described. Each of the joints is a special purpose joint characterized by substantially constant volume and low torque characteristics. Linkages which restrain the joint from longitudinal distension and a flexible, substantially impermeable diaphragm of tubular configuration spanning the distance between pivotally supported annuli are featured. The diaphragms of selected joints include rolling convolutions for balancing the joints, while various joints include wedge-shaped sections which enhance the range of motion for the joints