Showing papers by "General Dynamics published in 1991"

Fuzzy min-max neural networks

Abstract: A supervised neural network classifier using a combination of min-max hyperboxes and fuzzy logic is described A min-max hyperbox and its membership function define a fuzzy set Each class in the neural network is a collection of labeled hyperboxes (fuzzy sets) The degree to which an input pattern belongs to a class is determined by the membership function of the winning hyperbox Using multiple hyperbox fuzzy sets to form classes allows arbitrary numbers and shapes of classes and their respective class boundaries The min-max classification learning procedure requires only a single pass through the data and allows online learning The author describes how the fuzzy min-max classifier is implemented as a neural network, explains how min-max classes are produced, and provides two examples of operation >

Solar concentrator array

Abstract: A solar concentrator panel having an array of off axis cylindrical parabolic mirrors with an optical design of relatively short focal length solar cells arranged in line that converts sunlight to electricity. The back surface of the mirrors are used as the solar cell mount and the heat sink for the adjacent mirror. By appropriate positioning of the adjacent mirror so that the focal line of the parabola falls within the boundary or rim of the mirror reflected solar light can be directed to the solar cell mounted on the back of the adjacent mirror and converted to electricity

Apparatus and method for the compression and transmission of multiformat data

Abstract: Video data is compressed, at a first site, by a transform scaling data compressor (12), and carrier signals are modulated with audio and digital data by a delta modulation data modulator (14) and a delta-sigma modulation data modulator (16) respectively. Their output signals are combined by a multichannel data compressor (18) and transmitted to a second site, where the procedures are essentially reversed to effectively regenerate the data as originally formatted.

Static Aeroelastic Control Using Strain Actuated Adaptive Structures

Abstract: In this study, the feasibility of using representative box wing adaptive structures for static aeroelastic control is examined. A deformable typical section is uti lized to derive the optimal and suboptimal relations for induced strain actuated adaptive wings, and the relations developed are used to design representative adaptive lifting sur faces which are assessed in trade studies. The optimal relations developed showed that op timal adaptive airfoil designs are possible for some realistic configurations, and effective sub-optimal designs can be achieved for others. In addition, the important parameters associated with inducing curvature and twist, thereby altering the lifting forces on the air foil, are determined. The most important of which were found to be the airfoil thickness ratio, the actuation strain produced by the induced strain actuators, and the relative stiff ness ratio of the actuator to the wing skin for both camber and twist control. The stiffness coupling parameter and the wing aspect ...

Depolyable retractable photovoltaic concentrator solar array assembly for space applications

Abstract: A deployable/retractable photovoltaic concentrator solar array assembly for space applications that includes a plurality of solar array panels that are carried by a pantograph arm arrangement that is deployable to position the panels in a predetermined canted arrangement for receipt of solar radiation. Each panel includes a plurality of spaced cylindrical off axis parabolic mirrors that concentrate the reflected light on a line that falls upon a series of photovoltaic cells arranged longitudinally along the back of each mirror. The cylindrical parabolic mirrors are aligned with the cylindrical axis perpendicular to the axis about which the panels are canted, so that such canting causes no loss of focus. The array panels may be hardened to resist perceived threats and the pantograph arm arrangement is operable to position the array panels in a preferred orientation according to the nature of the threat. A preferred method of making the parabolic concentrator mirrors and assembling them into array panels is disclosed.

Distortion compensation means and method

Abstract: Distortion introduced in phase modulated RF signals by amplifiers and other signal processors is substantially reduced by modifying complex modulating signals I,Q in a way that compensates for the amplifier phase error φ e as a function of amplifier power P. In a preferred embodiment, I, Q are combined to calculate the amplifier power level and scaled by a parameter, e.g., K1=-dφ e /dP, to provide factor B so that compensated signals I"=AQ+BI and Q"=AI-BQ, where A is a constant, can be determined. When an RF carrier modulated by I", Q" is passed through the distorting amplifier the amplifier induced distortion is cancelled. Substantial reduction in bit error probability is obtained. The method can also be used for post-distortion correction.

Performance evaluation methods for multiple-target-tracking algorithms

Abstract: Scoring methods are described for evaluating the performance of a multiple target tracking (MTT) algorithm fairly, without undue bias towards any particular type. The methods were initially developed by individuals and further developed and adapted by the members of the SDI panels on tracking. Ambiguous track-to-target truth association is the fundamental difficulty in MTT performance evaluation. The methods use a global nearest neighbor assignment algorithm to uniquely associate tracks to targets. With the track- to-target associations, the methods employ measures of effectiveness for track purity, data association, state estimation accuracy, and credibility of filter calculated covariance.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Uninterruptable fault tolerant data processor

Abstract: An apparatus for fault tolerant data processing has a plurality of data processors. The fault tolerant apparatus includes at least three data processors operating in tandem. The apparatus further has a plurality of fault tolerant comparators. Each fault tolerant comparator is connected to a corresponding one of the data processors for receiving data from the corresponding data processor. Each fault tolerant comparator is further connected to each of the other fault tolerant comparators, with each fault tolerant comparator comparing output signals from the other fault tolerant comparators in a pairwise fashion to eliminate data output signals from any faulty data processors. The apparatus finds application in uninterruptible multiprocessor synchronization as well as data encryption in secure telephony.

Method of manufacturing composite structures

Abstract: A method of making a composite structure, such as an aircraft wing, which has a foam core and at least one outer layer of fiber reinforced resin material. A shaped foam core is prepared by compressing a rigid, closed-cell foam to the desired shape in a closed mold under heat and pressure. A sheet of flexible open-cell foam is impregnated with a thermosetting resin. A sheet of dry fiber reinforcement material is placed on one or both sides of the impregnated foam sheet. The resulting sandwich is wrapped around the foam core and the assembly is placed in a corresponding tool cavity. The tool is heated to the curing temperature of the impregnating resin. As the temperature rises, the foam core expands, exerting pressure on the impregnated foam sheet, forcing resin into the fiber reinforcement, wetting all the fibers and forcing air out of the material. As the resin cures, void-free, strong skins are formed integral with the core foam. After the resin is cured, the part is cooled, removed from the tool and trimmed.

Ultraviolet marine anti-biofouling systems

Abstract: Biofouling of underwater surfaces by marine organisms is prevented by irradiating the surfaces or the adjacent water with ultraviolet light and adjusting the intensity of the ultraviolet light so as to kill or temporarily stun marine organisms to prevent their attachment to the underwater surface.

Method and apparatus for usage protection of data files using split key and unique variable

Abstract: A split key encryption system to crypto-seal a data file comprising a method for unique variable entry (eg, terminal serial number), random number generation, key storage device, encryption function for combining the unique variable and the random number to generate an encryption variable in an exclusive-OR function using a variable tap linear feedback shift register, and storage function for receiving the encryption variable and the unencrypted data file A split key decryption system to unseal the crypto-sealed data file comprises a key storage device, terminal, terminal input, and storage function, with decryption again using an exclusive-OR function using a variable tap linear feedback shift register A comparator allows use of the unencrypted data file only if the decrypted unique variable matches the terminal serial number

Direct-sequence spread-spectrum communication system with asynchronous despreading

Abstract: A direct-sequence spread-spectrum communication system having a receiver that despreads a received signal that has been modulated with a pseudonoise code generated by a linear feedback shift register. The receiver despreads the received signal by multiplying it with a limited number of delayed replicas of the received signal. Despreading is thus performed without need for a locally generated pseudonoise code or a synchronizing clock.

Efficient codebook search for CELP vocoders

Abstract: A new way of determining correlation coefficients for stochastic codebook vectors for CELP coding of speech takes advantage of the sparsely populated nature of stochastic codebook vectors. N valued input signals (e.g., convolution vectors) to be correlated with N valued codebook vectors are fed to an N by N multiplexer or other selection means and the signal values either passed to an accumulator or not according to the state of N select inputs or other identification means determined from a memory store (e.g., an EPROM) whose entries correspond to the non-zero values of the codebook vectors. The accumulator output is the correlation of the codebook vector with the input signal. A sequencer steps through the entire codebook to provide correlation values for each vectors. The results are used to determine the optimum stochastic codebook vector for replicating the particular speech frame being analyzed.

Open systems software backplane architecture for federated execution of independent application programs

Abstract: A plurality of computer application programs have respective display generation routines for generating respective program video displays onto a computer display screen. Backplane software operates all of the respective display generation routines to generate a overlayed, composite video display of the respective program video displays. The software system fuses the display outputs of each of a plurality of independent application programs into a single overlayed screen display. More particularly, the software backplane architecture interrupts the draw subroutine calling sequences of each independent application program, and redirects those sequences to the backplane software. The backplane software initiates a redraw command to the application program to in turn operate the display generation routines to cause a display. Since all of the independent application programs have draw sequences under control of the backplane software, the application programs remain independent of each other. A coordinates table provides offset coordinate and orientation data for each application program so that the program displays are offset by the correct amount and are oriented to like attitudes. The backplane software multiplexes the input devices to each subscribing independent application program integrated into the architecture. Each application program executes in the originally designed code and language and executes on input commands as if it were a stand-alone, un-integrated application program.

Filament wound composite structure, its tooling and method of manufacture

Abstract: A filament wound composite structure, its tooling and method of manufacture. The isogrid filament wound composite structure is formed having at least one or more pseudo-isotropic laminate zones in its joint regions. This structure is realized through the use of specialized tooling. The ribs of the isogrid filament wound composite structure are discontinued by tapering them out into a thin skin. This is accomplished by gradually widening the grooves in the mandrel while simultaneously decreasing the depth of the grooves. This gradual change in the tooling redistributes the material in the ribs into a thin skin. The fibers that are redistributed into this thin layer, coupled with the skin wound over the top of the ribs, provide the necessary reinforcement in the joints.

Spray nozzle cleaning apparatus and method

Abstract: Apparatus for cleaning paint spray gun nozzles automatically includes a housing having separate cleaning and reservoir chambers separated by a dividing wall, and a cleaning spray head in the cleaning chamber for directing a spray of cleaning fluid at a nozzle in the chamber. A supply of cleaning fluid in the reservoir is connected to the cleaning spray head by a supply tube. The cleaning chamber has an entrance for receiving a spray gun nozzle, and a supply of gas under pressure is connected to the reservoir chamber automatically on detection of entry of a spray gun nozzle through the entrance, to urge cleaning fluid from the reservoir into the supply tube. A passageway is provided in the dividing wall for returning used cleaning fluid to the reservoir. The supply of gas to the reservoir is cut off automatically at the end of a cleaning cycle on removal of the cleaned nozzle from the chamber.

Modular distributed concentrating collector using power bus to route power to centralized converter

Abstract: A modular distributed concentrating collector using a low loss power bus to route solar radiation collected from a plurality of concentrating and collecting dishes to a centralized converted for conversion into electricity in space. The power bus may utilize fiber optic bundles. The collector includes a plurality of adjustable solar collectors to provide optimum tracking of the sun. The arrangement can be folded for stowing in the payload bay of the Space Shuttle or other launch vehicle for transport to a location in space.

Low inductance circuit apparatus with controlled impedance cross-unders and connector for connecting to backpanels

Abstract: Circuit apparatus comprises an integral structure of first and second multilayer wiring board portions and a flexible circuit portion. The wiring board portions each have at least circuit trace planes, ground planes and insulator planes. The flexible circuit portion includes at least one signal trace plane and at least one ground plane separated by at least one insulator plane; the singal trace plane of the flexible circuit portion being integral with a signal trace plane of each of the wiring board portions, the ground plane of the flexible circuit portion being integral with a ground plane of each of the wiring board portions, and the insulator plane of the flexible circuit portion being integral with an insulator plane of each of the wiring board portions. Selected ones of a plurality of electric contacts are connected to selected ones of the circuit traces of the circuit trace plane of the flexible circuit portions; others of the contacts being connected to the ground plane. A pin connector is conencted to the plurality of contacts and is arranged to electrically connect selected circuits traces and the ground plane of the flexible circuit portion to an interconnect backpanel, thereby electrically connecting the wiring board portions to the backpanel with minimum inductance.

Adaptive control of propellant slosh for launch vehicles

Abstract: The use of adaptive system to stabilize a launch vehicle with sloshable fuel is discussed. The adaptive system is based on a laser sensor to measure fluid displacement in the tank, a recursive-least-squares estimator to assess the natural frequency of the sloshing fuel, and a linear filter to stabilize the unstable fuel slosh. The method is found to be promising for a pitch-plane, single pendulum model.

Thermostructural concepts for hypervelocity vehicles

Abstract: In the design of hypervelocity veh~cles (HVV). a key driving parameter is the structural mass fraction of the system. The mass fraction greatly influences the performance and payload capabilities of the vehicle. For example. a reduction of one pound of structural weight would effectively translate into an additional pound of payload, or alternatively, approximately ten fewer pounds of propellant. Through the optimization of thermostructural concepts. a significant increase in overall mission perfbrmance can be reallred. Such an optimiration requires not only good familiarity with the available material optlons and therrnostructural concepts. but also a thorough knowledge of the thermal. inertial, aerodynamic, and control loads on the vehicle as a consequence of hqpervelocity flight conditions. This optimiration process the establishment o l aeroheating and other critical loads, the consideration of material alternatives, and the formulation of thermostructural concep t wa the primary l'i~cus ol' t h ~ \ study. A suborbital vehicle (Figure I ) and the aswciated trajectory (Figure 2 ) a i described in Rckrence I were chosen as stud) baselines. These selections wcrc Idlowed b> a series of interrclated design and anal] tical tazks. during which a number of thcri~~ostructural trade \tudie\ \\el-c conducted. The primary results ol'the stud! include detailed w i g h t estlmates h r the candidate thernio~tructural concepts and the selecSUB-ORBITER SYNERGETIC PLANE CHANGE

Constant frequency power converter

Abstract: A constant frequency power converter which includes a system to switch a resonant capacitive or inductive element during the power transfer cycle in a clamped series resonant converter. A feedback control system generates a pulse width modulated signal to switch the resonant element at the appropriate time. A conventional power MOSFET can be used as the switching device. The resonant control elements may be operated in series or parallel depending on the basic resonant topology selected. Applications include high frequency power converters where small size is of prime concern.

Viscoelastic and Nonlinear Adherend Effects in Bonded Composite Joints

Abstract: An experimental and theoretical investigation is described on the effects of viscoelasticity and geometric and material nonlinearity in rubber-toughened graphite/epoxy adherends. Single-lap joints, with adherends of a matrix-dominated layup and a brittle epoxy adhesive layer, were tested under two constant loading rates to failure; axial strains were measured at several locations on the surface of the adherends. Aluminum and fiber-dominated laminate adherends were also studied for comparison. Finite element analyses of the adhesive joint were made using linear and nonlinear viscoelastic characterizations of the composite. The experimental work is discussed first. Then we describe the constitutive theory and its implementation in the finite element analysis, after which the theoretical ane experimental results are presented and compared.

Broadband optical power summer

Abstract: An optical power summing apparatus that allows a multiplicity of optical signals to be combined with minimal signal transmission loss. A single photodiode simultaneously receives all of the input signals to perform a summation of signal powers. Alternative embodiments of the apparatus use either a tightly packed bundle of etched optical fibers or a converging arrangement of optical waveguides on a dielectric substrate to focus the optical signals onto the base region of a single photodiode.

Key design selections for the 20.4 MWh SMES/ETM

Abstract: The 20.4-MWh superconducting magnetic energy storage engineering test model (SMES/ETM) will be the world's largest superconducting magnet by nearly two orders of magnitude in stored energy. Its size, Lorentz loads, and power delivery requirements dictate a number of fundamental design requirements. In addition, the SMES/ETM must fully accomplish its primary mission of demonstrating large-scale SMES technology, while at the same time minimizing technical, schedule, and cost risks. A discussion is presented of nine key design decisions that are fundamental to meeting these challenging goals. These are a conductor current of 200 kA, helium containment within the conductor, an operating temperature of 1.8 K, a CICC conductor with a hollow core, a conductor premanufactured in half-turn lengths, a circular and continuous coil pac structure, fiberglass-reinforced plastic pultrusion for the coil pack structure material, a coil pack operating position that is precompressed radially inward, and a liner for vacuum enclosure.

Fuzzy min-max classification with neural networks

Abstract: A feedforward neural network classifier that uses min-max vector pairs to define classes is described. This two-layer neural network utilizes a supervised learning rule to build a set of classes. Each node in the output layer of the network represents a class. During recall each class node produces an output value that represents the degree to which the input pattern fits within the represented classes. This fuzzy neural network is ideally suited to applications that have very little data available to define classes. The author provides a brief overview of fuzzy sets and fuzzy pattern classification, a description of fuzzy min-max classification and its neural network implementation, and an example of the classification operation. >

Fatigue crack growth through arall‐4 at ambient temperature

Abstract: Fatigue cracks were grown in the 5 layer aluminum alloy-Aramid fiber laminate composite ARALL-4 over the range of cyclic stress intensity factors (ΔK) from 3.5 to 91 MPa✓m. Near the threshold, crack growth rate was about the same as for unreinforced aluminum alloys, but at high ΔK, crack growth rates were significantly lower. Crack closure was measured over this range of growth rates and found to be different than for unreinforced aluminum alloys. The magnitude of closure was also dependent on crack length. Cracks opened progressively towards the tip with increasing load in much the same way as for unreinforced aluminum alloys. Removal of the aluminum outer layer and some of the epoxy revealed that fibers were intact close to the crack tip, but heavily damaged further away. By adjusting the fatigue crack growth curve of an unreinforced aluminum alloy for the closure exhibited by the composite, it was possible to approximate the crack growth rate for the composite over the lower to mid range of ΔK, but at higher values of ΔK, this model seriously overestimated measured crack growth rates. Therefore, fiber bridging affects both closure and maximum stress intensity factor at the crack tip. Standard fracture mechanics cannot be applied to describe these effects.

Reeding edge for securing in place fiber band during filament winding operation

Abstract: An improved mandrel for use in filament winding. Two embodiments are described for a new filament winding mandrel concept. The first embodiment comprises a plurality of spaced apart slots machined at an angle along the ends of the central mandrel section for use with machines of at least three degrees of motion. A second embodiment comprises a series of two circumferential rows of axial fins protruding along the circumference of the central section of the mandrel for use with machines having only two degrees of motion. A second configuration of the second embodiment is an addition of a strip of slots that are simply placed around and secured to the circumference of the mandrel at locations where fiber turn around is desired. This provides for fiber securing in place with minimal rather than requiring machining the axial fins into the tool.

Passive nonlinear interface strut (PNIS)

Abstract: A passive load limiting strut particularly useful in limiting loads between a spacecraft and an upper stage during booster first stage operation and thereby permit the launching of heavier spacecraft. The strut operates on the principle of snap through buckling of bar linkages. A tension shaft is telescoped into a compression shaft within a housing. A plurality of bar linkages are connected between each of the shafts and the housing, the bars being oriented at an acute angle in the direction of the tension shaft. In tension, the bar linkages connected to the tension shaft progressively buckle, absorbing tension loads. In compression, the bars connected to the compression shaft progressively buckle, absorbing compression loads. A compression spring intermediate the ends of the shafts further aids in load relief. Collars on the shafts prevent the shafts moving beyond preselected locations.

Computer and communications systems employing universal direct spherics processing architectures

Abstract: Communication and computer interconnecting systems using Universal Direct Spherics (Unidispherics) philosophy makes it possible to transmit and store data in an efficient and rapid manner. The system architecture embodies a plurality of communication sites (nodes) which interact with each other by a symmetrical arrangement of great circles on a sphere or their equivalent. Each intersection of two great circles can be a node for linking processors, bulk memories, and in/out units (IND). In addition to the insertion of two great circles on a sphere, there are five other links, four along each of the great circles connected to the nodes at the adjacent great circle intersections and one cross-link to the node diametrically opposite on the sphere.