Showing papers by "General Electric published in 1985"

Selecting uncertainty calculi and granularity: an experiment in trading-off precision and complexity

Abstract: The management of uncertainty in expert systems has usually been left to ad hoc representations and rules of combinations lacking either a sound theory or clear semantics. The objective of this paper is to establish a theoretical basis for defining the syntax and semantics of a small subset of calculi of uncertainty operating on a given term set of linguistic statements of likelihood. Each calculus will be defined by specifying a negation, a conjunction and a disjunction operator. Families of Triangular norms and conorms will provide the most general representations of conjunction and disjunction operators. These families provide us with a formalism for defining an infinite number of different calculi of uncertainty. The term set will define the uncertainty granularity, i.e. the finest level of distinction among different quantifications of uncertainty. This granularity will limit the ability to differentiate between two similar operators. Therefore, only a small finite subset of the infinite number of calculi will produce notably different results. This result is illustrated by an experiment where nine different calculi of uncertainty are used with three term sets containing five, nine, and thirteen elements, respectively.

Edge-Based Data Structures for Solid Modeling in Curved-Surface Environments

Abstract: CAD/CAM applications need quick and easy access to topological information about objects. Here, four structures for representing this information are evaluated for sufficiency, efficiency, and ease of implementation.

Microcomputer Control of a Residential Photovoltaic Power Conditioning System

Abstract: Microcomputer-based control of a residential photovoltaic power conditioning system is described. The microcomputer is responsible for array current feedback control, maximum power tracking control, array safe zone steering control, phase-locked reference wave synthesis, sequencing control, and some diagnostics. The control functions are implemented using Intel 8751 single-chip microcomputer-based hardware and software. The controller has been tested in the laboratory with the prototype power conditioner and shows excellent performance.

Dynamic Models for Control System Design of Integrated Robot and Drive Systems

Abstract: The design of high performance motion controls for industrial robots is based on accurate models for the robot arm and drive systems. This paper presents analytical models and experimental data to show that interactions between electromechanical drives coupled with compliant linkages to arm link drive points are of fundamental importance to robot control system design. Flexibility in harmonic drives produces resonances in the 5 Hz to 8 Hz range. Flexibility in the robot linkages and joints connecting essentially rigid arm members produces higher frequency modes at 14 Hz and 40 Hz. The nonlinear characteristics of the drive system are modeled, and compared to experimental data. The models presented have been validated over the frequency range 0 to 50 Hz. The paper concludes with a brief discussion of the influence of model characteristics on motion control design.

Transmission Network Planning Using Linear Programming

Abstract: In long range transmission planning, where new load growth, new generation sites and perhaps a new voltage level are to be considered, a computer aided method of visualizing new circuits in a network context is needed. The new method presented meets this need by the combined use of a linear (dc) power flow transmission model and a transportation model (also known as a trans-shipment model). The dc transmission model is solved for the facilities network by obeying both of Kirchhoff's laws, flow conservation at each bus and voltage conservation around each loop. The transportation model is solved for the overloads by obeying only the bus flow conservation law while minimizing a cost objective function.

Load balancing for cellular radiotelephone system

Abstract: Balancing of loading of cells in a cellular mobile radio telephone system is performed by periodically determining the channel utilization of each cell, computing a representative voice channel occupancy level, and attempting to hand-off calls from cells with higher voice channels occupancy levels to adjacent cells with lower voice channel occupancy levels. Voice channel occupancy levels of cells are measured and compared with threshold values, and the results of the comparisons are used to direct cells to enter predetermined states. In one state, complete cell blockage is prevented by directing cells to hand-off calls to adjacent cells. In another state, voice channels are preserved for incoming hand-offs by directing the cell to deny access to mobile transceivers initiating new calls. Cells may assume a combined stage wherein both of these functions are performed simultaneously. Cells are selected as hand-off candidates for hand-offs initiated to more evenly distribute loading throughout the cellular system in accordance with cell state (i.e., voice channel occupancy level) and measured signal strength at the cells of the calls attempted to be handed off.

Loss Reduction in Axial-Flow Compressors Through Low-Speed Model Testing

Abstract: A systematic procedure for reducing losses in axial-flow compressors is presented. In this procedure, a large, low-speed, aerodynamic model of a high-speed core compressor is designed and fabricated based on aerodynamic similarity principles. This model is then tested at low speed where high-loss regions associated with three-dimensional endwall boundary layers flow separation, leakage, and secondary flows can be located, detailed measurements made, and loss mechanisms determined with much greater accuracy and much lower cost and risk than is possible in small, high-speed compressors. Design modifications are made by using custom-tailored airfoils and vector diagrams, airfoil endbends, and modified wall geometries in the high-loss regions. The design improvements resulting in reduced loss or increased stall margin are then scaled to high speed. This paper describes the procedure and presents experimental results to show that in some cases endwall loss has been reduced by as much as 10 percent, flow separation has been reduced or eliminated, and stall margin has been substantially improved by using these techniques.

Noninvasive study of high-energy phosphate metabolism in human heart by depth-resolved 31P NMR spectroscopy

Abstract: Phosphorus-31 nuclear magnetic resonance (NMR) spectra showing the relative concentrations of high-energy phosphate metabolites have been recorded noninvasively from the human heart in vivo. Spectral data were spatially localized by combining a pulsed magnetic field gradient with surface NMR excitation-detection coils. The location of the selected spectral region was determined by conventional proton NMR imaging immediately before examination by phosphorus-31 NMR spectroscopy.

Redefinition of the robot motion-control problem

Abstract: The objective of this paper is a redefinition of the robot control problem, based on (1) realistic models for the industrial robot as a controlled plant, (2) end-effector trajectories consistent with manufacturing applications, and (3) the need for end-effector sensing to compensate for uncertainties inherent to most robotic manufacturing applications. Based on extensive analytical and experimental studies, robot dynamic models are presented that have been validated over the frequency range 0 to 50 Hz. These models exhibit a strong influence of drive system flexibility, producing lightly damped poles in the neighborhood of 8 Hz, 14 Hz, and 40 Hz, all unmodeled by the conventional rigid-body multiple-link robot dynamic approach. The models presented also quantify the significance of non-linearities in the drive system, in addition to those well known in the linkage itself. Simulations of robot dynamics and motion controls demonstrate that existing controls coupled with effective path planning produce dynamic path errors that are acceptable for most manufacturing applications. Major benefits are projected, with examples cited, for use of end-effector sensors for position, force, and process control.

Numerical Recirculating Flow Calculation Using a Body-Fitted Coordinate System

Abstract: A finite-difference algorithm for recirculating flow problem! in a body-fitted coordinate system is presented. A fully staggered grid system is adopted for the velocity components and the scalar variables. The strong conservation law form of the governing equations is written in the general curvilinear coordinates. The SIMPLE calculation procedure originally developed in Cartesian coordinates is extended to the present curvilinear coordinates. Two methods of evaluating the metric derivatives are discussed. Although both methods are formally of the same order of accuracy, it is shown that one performs the physical conservation laws more accurately than the other. The relative merits of three schemes, i.e., hybrid, second-order upwinding, and QUICK, for approximating the convection terms in the momentum equations are compared and the results are quite different from those in Cartesian coordinates in both accuracy and efficiency aspects. The effects of the grid distribution are also studied. Results obtained...

NMR blood flow imaging using multiecho, phase contrast sequences.

Abstract: Moving nuclei, in contrast to stationary nuclei, experience a phase shift in the presence of a balanced gradient. Monitoring of this phase shift can be used to measure the flow velocity of moving nuclei. A specific scan sequence for blood flow imaging is presented. This sequence uses multiple echoes as well as a phase contrast approach to generate both conventional anatomical images and blood flow images from the same data. Images of a phantom and a human volunteer demonstrating the accuracy of the method are presented.

Motion Compensated Interframe Image Prediction

Abstract: Interframe motion estimation of subblocks based on improved search techniques is developed. These techniques are based on minimizing the mean difference between the subblock in question in the present frame and the displaced subblock in the previous frame. The performance of the motion compensated prediction developed here is investigated for various block sizes and is compared to other techniques.

Estimating radiofrequency power deposition in body NMR imaging.

Abstract: Simple theoretical estimates of the average, maximum, and spatial variation of the radiofrequency power deposition (specific absorption rate) during hydrogen nuclear magnetic resonance imaging are deduced for homogeneous spheres and for cylinders of biological tissue with a uniformly penetrating linear rf field directed axially and transverse to the cylindrical axis. These are all simple scalar multiples of the expression for the cylinder in an axial field published earlier (Med. Phys. 8, 510 (1981]. Exact solutions for the power deposition in the cylinder with axial (Phys. Med. Biol. 23, 630 (1978] and transversely directed rf field are also presented, and the spatial variation of power deposition in head and body models is examined. In the exact models, the specific absorption rates decrease rapidly and monotonically with decreasing radius despite local increases in rf field amplitude. Conversion factors are provided for calculating the power deposited by Gaussian and sinc-modulated rf pulses used for slice selection in NMR imaging, relative to rectangular profiled pulses. Theoretical estimates are compared with direct measurements of the total power deposited in the bodies of nine adult males by a 63-MHz body-imaging system with transversely directed field, taking account of cable and NMR coil losses. The results for the average power deposition agree within about 20% for the exact model of the cylinder with axial field, when applied to the exposed torso volume enclosed by the rf coil. The average values predicted by the simple spherical and cylindrical models with axial fields, the exact cylindrical model with transverse field, and the simple truncated cylinder model with transverse field were about two to three times that measured, while the simple model consisting of an infinitely long cylinder with transverse field gave results about six times that measured. The surface power deposition measured by observing the incremental power as a function of external torso radius was comparable to the average value. This is consistent with the presence of a variable thickness peripheral adipose layer which does not substantially increase surface power deposition with increasing torso radius. The absence of highly localized intensity artifacts in 63-MHz body images does not suggest anomalously intense power deposition at localized internal sites, although peak power is difficult to measure.

Converter Volt-Ampere Requirements of the Switched Reluctance Motor Drive

Abstract: An algebraic nonlinear analysis of the switched reluctance drive system is described. The analysis is intended to provide an understanding of the factors that determine the kVA requirements of the electronic power converter and to determine the fundamental nature of the torque/speed characteristics. The effect of saturation is given special attention. It is shown that saturation has the two main effects of increasing the motor size required for a given torque, and at the same time decreasing the kVA per horsepower (i.e., increasing the effective power factor by analogy with an ac machine). The kVA per horsepower is lower than predicted by simple linear analysis that neglects saturation. Necessary conditions are also developed for a flat-topped current waveform by correctly determining the motor back-EMF. The reason why it is desirable to allow the phase current to continue (though with much reduced magnitude) even after the poles have passed the aligned position is explained. The theory provides a formula for determining the required commutation angle for the phase current. The basis is provided for an estimation of the kVA requirements of the switched reluctance (SR) drive. These requirements have been measured and also calculated by a computer simulation program.

Time scale modeling of sparse dynamic networks

Abstract: This paper develops a time-scale approach to the decomposition and aggregation of dynamic networks with dense and sparse connections. Two parameters are used to characterize time-scale and weak coupling properties. Bounds in terms of these parameters determine when there are two time-scales in sparse networks. Simplified models of the slow and fast subsystems are proposed and physical interpretations are provided. The results are illustrated with a 2000-node power network.

Battery charger with three different charging rates

Abstract: A circuit for safely and rapidly charging batteries, with the charging occurring at three different rates. A first rate is used to bring a battery up to a level where it is determined to be safe for rapid rate charging. At this charge level the temperature of the battery may also be checked to be sure it is within a safe range for rapid charging. If safe, the battery is then rapidly charged at a second rate, until it is almost at its maximum capacity. At that point a third rate charge, lower than the first charge rate, is used to maintain the battery at nominally full charge. A microprocessor controller controls a plurality of rapid rate chargers and determines when the battery parameters are safe so that rapid charging can be safely employed. The rapid charger may be of a conventional charge pump type.

An equational approach to theorem proving in first-order predicate calculus

Abstract: A new approach for proving theorems in first-order predicate calculus is developed based on term rewriting and polynomial simplification methods. A formula is translated into an equivalent set of formulae expressed in terms of 'true', 'false', 'exclusive-or', and 'and' by analyzing the semantics of its top-level operator. In this representation, formulae are polynomials over atomic formulae with 'and' as multiplication and 'exclusive-or' as addition, and they can be manipulated just like polynomials using familiar rules of multiplication and addition. Polynomials representing a formula are converted into rewrite rules which are used to simplify polynomials. New rules are generated by overlapping polynomials using a critical-pair completion procedure closely related to the Knuth- Bendix procedure. This process is repeated until a contradiction is reached or it is no longer possible to generate new rules. It is shown that resolution is subsumed by this method.

Characteristics of Various F40 Fluorescent Systems at 60 Hz and High Frequency

Abstract: Recent improvements in both lamp and ballast technologies have resulted in substantial performance gains for fluorescent lighting systems. High-frequency electronic ballasts as well as high-efficiency 60-Hz electromagnetic ballasts have been designed to provide both better starting and operating conditions for the lamps under their control. At the same time, smaller diameter lamps and more efficient lamp phosphors have been developed to improve system performance further. How these improvements can be utilized in practical lighting systems is reviewed. Comparison characteristics, luminaire performance information, and application data are discussed.

A Review of Anode Phenomena in Vacuum Arcs

Abstract: This paper discusses arc modes at the anode, anode temperature measurments, anode ions, transitions of the arc into various modes (principally the anode-spot mode), and theoretical explanations of anode phenomena. A vacuum arc can exhibit five anode discharge modes: 1) a low-current mode in which the anode is basically passive, acting only as a collector of particles emitted from the cathode; 2) a second low-current mode that can occur if the electrode material is readily sputtered (a flux of sputtered atoms will be emitted by the anode); 3) a footpoint mode, characterized by the appearance of one or more luminous spots on the anode (footpoints are much cooler than the true anode spots present in the last two modes); 4) an anode-spot mode in which one large or several small anode spots are present (such spots are very luminous, have a temperature near the atmospheric boiling point of the anode material, and are a copious source of vapor and ions); and 5) an intense-arc mode where an anode spot is present, but accompanied by severe cathode erosion. The arc voltage is relatively low and quiet in the two low-current modes and the intense-arc mode. It is usually high and noisy in the footpoint mode, and it can be either in the anode-spot mode. Anode erosion is low, indeed negative, in the two low-current modes, and it is low to moderate in the footpoint mode. Severe anode erosion occurs in both the anode-spot and intense-arc modes.

Method of making high breakdown voltage semiconductor device

Abstract: A multiple-zone junction termination extension region is formed adjacent a reverse-blocking junction in a semiconductor device to increase the breakdown voltage of such device. A single mask is used to form the multiple-zone JTE region, with the mask having different patterns of openings in the different zones of the mask. Adjacent openings are maintained with a center-to-center spacing of less than 25 percent of the depletion width of the reverse-blocking junction in a voltage-supporting semiconductor layer adjoining the reverse-blocking junction at the ideal breakdown voltage of the junction. As a consequence, the resulting non-uniformities in doping of the various zones of the JTE region are negligibly small. An alternative JTE region is finely-graduated in dopant level from one end of the region to the other, as opposed to having multiple zones of discrete doping levels.

Frame synchronization of multiply redundant computers

Abstract: A frame synchronization method and apparatus wherein each computer system of a multiply redundant processing system periodically executes a frame synchronization procedure in which it sequentially assumes a plurality of different operating states during which it pauses in the execution of a task it was performing and readies itself for synchronization, determines which other computer systems are ready for synchronization, synchronizes itself with one or more of the systems, and then determines which of the other systems has also synchronized itself At a predetermined frame interval, the procedure is repeated and the computer systems resynchronize themselves with one another The invention is impervious to stuck-at type faults, and may be embodied either totally or partially in software within each computer system, or in a separate hardware device

Integrated range and luminance camera

Abstract: A three-dimensional range camera, which produces a range map of the distances from a reference to each of M×N points in a scene, is modified to generate registered luminance and range images. The same sensor detects range and luminance variations. A planar pattern projector generates sequential presentations of time/space coded light rays which are projected onto the object. A linear array camera images the points of light on the object surface, and a processor analyzes one-dimensional scan signals to determine range. To detect luminance there is an additional presentation, either constant illumination or no artificial illumination, and the other scan signal yields luminance along the same strip of the scene.