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At least 217 records · Page 12

Combining Video Memory Operations

Designs of video random-access memory (VRAM) integrated circuits operating under control by external logic circuits simplified according to concept of combining two memory operations performed separately heretofore. Eliminates need for DRAM-refresh timers and counters, reducing amount of circuitry needed to control VRAM thereby reducing time needed to design VRAM. Simplification also reduces time needed to redesign DRAM-refresh logic circuitry when adapting VRAM design to another VRAM for which timing specifications different. Concept can be applied to VRAM clocking data out to display unit continuously.

Kania, Michael J.↗

RTSJ Memory Areas and Their Affects on the Performance of a Flight-Like Attitude Control System

The two most important factors in improving performance in any software system, but especially a real-time, embedded system, are knowing which components are the low performers and knowing what can be done to improve their performance. The word performance with respect to a real-time, embedded system does not necessarily mean fast execution, which is the common definition when discussing non real-time systems. It also includes meeting all of the specified execution dead-lines and executing at the correct time without sacrificing non real-time performance. Using a Java prototype of an existing control system used on Deep Space 1[1], the effects from adding memory areas are measured and evaluated with respect to improving performance.

Real-time Specification for Java2 (RTSJ)↗

Weaves as an Interconnection Fabric for ASIM's and Nanosatellites

Many of the micromachines under consideration require computer support, indeed, one of the appeals of this technology is the ability to intermix mechanical, optical, analog, and digital devices on the same substrate. The amount of computer power is rarely an issue, the sticking point is the complexity of the software required to make effective use of these devices. Micromachines are the nano-technologist's equivalent of 'golden screws'. In other words, they will be piece parts in larger assemblages. For example, a nano-satellite may be composed of stacked silicon wafers where each wafer contains hundreds to thousands of micromachines, digital controllers, general purpose computers, memories, and high-speed bus interconnects. Comparatively few of these devices will be custom designed, most will be stock parts selected from libraries and catalogs. The novelty will lie in the interconnections. For example, a digital accelerometer may be a component part in an adaptive suspension, a monitoring element embedded in the wrapper of a package, or a portion of the smart skin of a launch vehicle. In each case, this device must inter-operate with other devices and probes for the purposes of command, control, and communication. We propose a software technology called 'weaves' that will permit large collections of micromachines and their attendant computers to freely intercommunicate while preserving modularity, transparency, and flexibility. Weaves are composed of networks of communicating software components. The network, and the components comprising it, may be changed even while the software, and the devices it controls, are executing. This unusual degree of software plasticity permits micromachines to dynamically adapt the software to changing conditions and allows system engineers to rapidly and inexpensively develop special purpose software by assembling stock software components in custom configurations.

Gorlick, Michael M.↗

Waypoint Following Dynamics of a Quaternion Error Feedback Attitude Control System

Closed-loop attitude steering can be used to implement alternative attitude maneuvers by using a conventional attitude control system to track a non-standard attitude profile sampled as a series of sequential commands. The idea has been employed in practice to perform zero-propellant maneuvers on the International Space Station and minimum time maneuvers on NASA’s TRACE space telescope. A challenge for operational implementation of the idea is the finite capacity of a space vehicle’s command storage buffer. One approach to mitigate the problem is to downsample-and-hold the attitude commands so that the attitude control system to follows a set of waypoints. This paper explores the waypoint following dynamics of a quaternion error feedback control law for downsample-and-hold. It is shown that downsample-and-hold induces a ripple between downsamples that causes the satellite angular rate to significantly overshoot the desired limit. Analysis in the z-domain is carried out in order to understand the phenomenon. An interpolating Chebyshev-type filter is proposed that allows attitude commands to be encoded in terms of a small set of filter coefficients. Using the interpolating filter, commands can be issued at the ACS rate but with significantly reduced memory requirements. The attitude control system of NASA’s Lunar Reconnaissance Orbiter is used as an example to illustrate the behavior of a practical attitude control system.

Mark Karpenko↗

Shared memory for a fault-tolerant computer

A system is described for sharing a memory in a fault-tolerant computer. The memory is under the direct control and monitoring of error detecting and error diagnostic units in the fault-tolerant computer. This computer verifies that data to and from the memory is legally encoded and verifies that words read from the memory at a desired address are, in fact, actually delivered from that desired address. The means are provided for a second processor, which is independent of the direct control and monitoring of the error checking and diagnostic units of the fault-tolerant computer, and to share the memory of the fault-tolerant computer. Circuitry is included to verify that: (1) the processor has properly accessed a desired memory location in the memory; (2) a data word read-out from the memory is properly coded; and (3) no inactive memory was erroneously outputting data onto the shared memory bus.

Gilley, G. C.↗

Microprogrammed digital filters for strapdown guidance application.

Discussion of an approach for implementing digital filters using microprogrammed control logic with read only memory (ROM) for strapdown guidance applications, and description of a second-order multiplexed system using multiprogrammed control instruction. The microprogramming technique for control using ROM is shown to enhance higher order digital filter realization. The high speed of digital circuits reduces propagation time and facilitates multiplexing. Programmed ROM's can be altered easily for different algorithms.

Kapadia, K.↗

DARPA/AFRL/NASA Smart Wing Second Wind Tunnel Test Results

To quantify the benefits of smart materials and structures adaptive wing technology, Northrop Grumman Corp. (NGC) built and tested two 16% scale wind tunnel models (a conventional and a "smart" model) of a fighter/attack aircraft under the DARPA/AFRL/NASA Smart Materials and Structures Development - Smart Wing Phase 1. Performance gains quantified included increased pitching moment (C(sub M)), increased rolling moment (C(subl)) and improved pressure distribution. The benefits were obtained for hingeless, contoured trailing edge control surfaces with embedded shape memory alloy (SMA) wires and spanwise wing twist effected by SMA torque tube mechanisms, compared to conventional hinged control surfaces. This paper presents an overview of the results from the second wind tunnel test performed at the NASA Langley Research Center s (LaRC) 16ft Transonic Dynamic Tunnel (TDT) in June 1998. Successful results obtained were: 1) 5 degrees of spanwise twist and 8-12% increase in rolling moment utilizing a single SMA torque tube, 2) 12 degrees of deflection, and 10% increase in rolling moment due to hingeless, contoured aileron, and 3) demonstration of optical techniques for measuring spanwise twist and deflected shape.

Scherer, L. B.↗

Active control of buckling of flexible beams

Mathematical models are presented that simulate the dynamic characteristics of shape memory alloy actuators made of nickel-titanium alloy (Nitinol) controlling the buckling of compressive structural members. A closed-loop computer-controlled system has been designed, based on the proposed mathematical models, and has been implemented to control the buckling of simple beams. The performance of the computer-controlled system is evaluated experimentally and compared with the theoretical predictions to validate the developed models. The results emphasized the importance of buckling control and suggest the potential of shape memory alloy actuators as attractive means for controlling structural deformation in a simple and reliable way.

Baz, A.↗

Customizable Digital Receivers for Radar

Compact, highly customizable digital receivers are being developed for the system described in 'Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets' (NPO-43962), NASA Tech Briefs, Vol. 31, No. 7 (August 2007), page 72. The receivers are required to operate in unison, sampling radar returns received by the antenna elements in a digital beam-forming (DBF) mode. The design of these receivers could also be adapted to commercial radar systems. At the time of reporting the information for this article, there were no commercially available digital receivers capable of satisfying all of the operational requirements and compact enough to be mounted directly on the antenna elements. A provided figure depicts the overall system of which the digital receivers are parts. Each digital receiver includes an analog-to-digital converter (ADC), a demultiplexer (DMUX), and a field-programmable gate array (FPGA). The ADC effects 10-bit band-pass sampling of input signals having frequencies up to 3.5 GHz. The input samples are demultiplexed at a user-selectable rate of 1:2 or 1:4, then buffered in part of the FPGA that functions as a first-in/first-out (FIFO) memory. Another part of the FPGA serves as a controller for the ADC, DMUX, and FIFO memory and as an interface between (1) the rest of the receiver and (2) a front-panel data port (FPDP) bus, which is an industry-standard parallel data bus that has a high data-rate capability and multichannel configuration suitable for DBF. Still other parts of the FPGA in each receiver perform signal-processing functions. The digital receivers can be configured to operate in a stand-alone mode, or in a multichannel mode as needed for DBF. The customizability of the receiver makes it applicable to a broad range of system architectures. The capability for operation of receivers in either a stand-alone or a DBF mode enables the use of the receivers in an unprecedentedly wide variety of radar systems.

Moller, Delwyn↗

Thin-film lithium niobate on diamond as a platform for efficient spin-phonon coupling

Negatively charged silicon vacancy (SiV − ) centers in diamond are leading candidates for solid-state quantum memory that can be controlled using electromagnetic or acoustic waves. The latter are particularly promising due to the strong strain response of SiV − , enabling large spin-phonon interaction strengths. Indeed, coherent spin control via surface acoustic waves (SAWs) has been demonstrated and is essential for developing on-chip phononic quantum networks. However, the absence of piezoelectricity in diamond requires an interface with a piezoelectric material for efficient transduction and delivery of acoustic waves to spins in diamonds. Here, we demonstrate a heterogeneously integrated phononic platform that combines thin-film lithium niobate with diamond to enable acoustic control of single SiV − spins. Additionally, leveraging large SAW-induced strain at the location of SiV − , we achieve coherent acoustic control of an electron spin with more than twofold improvement in Rabi frequency compared to state-of-the-art devices based on aluminum nitride on diamond. Furthermore, this work represents a crucial step towards realizing phonon-based quantum information processing systems.

Optically detected magnetic resonance↗

Coherently coupled quantum oscillators for quantum reservoir computing

Here, we analyze the properties of a quantum system composed of two coherently coupled quantum oscillators and show through simulations that it fulfills the two properties required for reservoir computing: non-linearity and fading memory. We first show that the basis states of this system apply a set of nonlinear transformations on the input signals and thus can implement neurons. We then show that the system exhibits a fading memory that can be controlled by its dissipation rates. Finally we show that a strong coupling between the oscillators is important in order to ensure complex dynamics and to populate a number of basis state neurons that is exponential in the number of physical devices.

Dudas, Julien↗

Guidance and control research

Guidance and control research - Josephson junction memory elements, frequency response of thin film thermal detectors, gallium selenide barrier gate, and photoconductor metal contacts

Source record↗

Design of a modular digital computer system DRL 4 and 5

Design and development efforts for a spaceborne modular computer system are reported. An initial baseline description is followed by an interface design that includes definition of the overall system response to all classes of failure. Final versions for the register level designs for all module types were completed. Packaging, support and control executive software, including memory utilization estimates and design verification plan, were formalized to insure a soundly integrated design of the digital computer system.

Source record↗

Binary processing and display concepts for low-cost Omega receivers

A description is given of concepts related to plans for developing a low-cost, all-digital Omega receiver capable of offering to the small-aircraft pilot a reliable and accurate navigation aid. The receiver base considered includes a receiver front-end module, a receiver control module, a memory-aided phase-locked loop module, a housekeeping timer module, and a synthesizer module.

Lilley, R. W.↗

Conference on Advanced Technology for Future Space Systems, Hampton, Va., May 8-10, 1979, Technical Papers

Propulsion systems for spacecraft, satellite communications technology, the design of large light-weight erectable structures for assembly in space, electronics and information processing for spacecraft, and self-diagnostic, fault-tolerant controls based on high memory and processing capabilities are discussed. Topics of the papers include the design of large delta wings for earth-to-orbit transports, dual-fuel propulsion units, magnetoplasmadynamic thrusters, heating rates on blunt-nosed bodies at various angles of attack, remote manipulators for space assembly tasks, solar electric propulsion for planetary missions, deployable space platforms with multiple payloads, the design of large offset-fed antennas, a nonlinear stress-strain relationship for metallic meshes, and adaptive sensors for spacecraft.

Source record↗