Showing papers by "General Dynamics published in 2007"

Toward accurate dynamic time warping in linear time and space

Abstract: Dynamic Time Warping (DTW) has a quadratic time and space complexity that limits its use to small time series. In this paper we introduce FastDTW, an approximation of DTW that has a linear time and space complexity. FastDTW uses a multilevel approach that recursively projects a solution from a coarser resolution and refines the projected solution. We prove the linear time and space complexity of FastDTW both theoretically and empirically. We also analyze the accuracy of FastDTW by comparing it to two other types of existing approximate DTW algorithms: constraints (such as Sakoe-Chiba Bands) and abstraction. Our results show a large improvement in accuracy over existing methods.

A Bayesian Approach to Multiple Target Detection and Tracking

Abstract: This paper considers the problem of simultaneously detecting and tracking multiple targets. The problem can be formulated in a Bayesian framework and solved, in principle, by computation of the joint multitarget probability density (JMPD). In practice, exact computation of the JMPD is impossible, and the predominant challenge is to arrive at a computationally tractable approximation. A particle filtering scheme is developed for this purpose in which each particle is a hypothesis on the number of targets present and the states of those targets. The importance density for the particle filter is designed in such a way that the measurements can guide sampling of both the target number and the target states. Simulation results, with measurements generated from real target trajectories, demonstrate the ability of the proposed procedure to simultaneously detect and track ten targets with a reasonable sample size

Robotic driving system

Abstract: A system that enables a vehicle to follow a traffic rule when traveling in a road network includes a database that stores data relating to at least one feature of the road network, a location detector that detects a location of the vehicle relative to the road network, a sensor that senses at least one object in a vicinity of the vehicle, and a processing system that controls the vehicle to autonomously obey at least one traffic rule, or provides a notification to a driver of the vehicle to enable the driver to obey at least one traffic rule, based on the detected location of the vehicle, data retrieved from the database relating to at least one feature of the road network, and data relating to at least one object sensed by the sensor.

Neural interactions between flicker-induced self-organized visual hallucinations and physical stimuli.

Abstract: Spontaneous pattern formation in cortical activity may have consequences for perception, but little is known about interactions between sensory-driven and self-organized cortical activity. To address this deficit, we explored the relationship between ordinary stimulus-controlled pattern perception and the autonomous hallucinatory geometrical pattern formation that occurs for unstructured visual stimulation (e.g., empty-field flicker). We found that flicker-induced hallucinations are biased by the presentation of adjacent geometrical stimuli; geometrical forms that map to cortical area V1 as orthogonal gratings are perceptually opponent in biasing hallucinations. Rotating fan blades and pulsating circular patterns are the most salient biased hallucinations. Apparent motion and fractal (1/f) noise are also effective in driving hallucinatory pattern formation (the latter is consistent with predictions of spatiotemporal pattern formation driven by stochastic resonance). The behavior of these percepts suggests that self-organized hallucinatory pattern formation in human vision is governed by the same cortical properties of localized processing, lateral inhibition, simultaneous contrast, and nonlinear retinotopic mapping that govern ordinary vision.

PVDF corrugated transducer for ultrasonic ranging sensor

Abstract: This paper describes a method to design and build ultrasonic transceivers using low-cost polyvinylidene fluoride (PVDF) corrugated film. The corrugated transducer features multiple curved sections, which provide a higher acoustic output compared to traditional ultrasonic transducer design using a single curved PVDF film section. We have built and demonstrated a prototype 200 kHz transducer and found it to be practical for applications requiring short-range distance measurement (20–300 mm) with SNR of 20 dB for 200 mm target. The prototype uses a single transducer that operated as both an ultrasonic transmitter and a receiver and provides a beam directivity of ±7° at −6 dB point using a 160 Vpp drive pulse. The transmitter output is 6.6 Pa (rms) at 30 cm with relative bandwidth of 33% and the receiver sensitivity is 0.55 mV/Pa. A microprocessor provides the timing signals, measures the time of flight from the transmitted pulse to the received echo, and calculates the distance.

Safety Case Composition Using Contracts - Refinements based on Feedback from an Industrial Case Study

Abstract: Modular safety cases provide a means of organising large and/or complex safety cases into separate but interrelated component modules of argument and evidence. Safety case ‘contracts’ can be used to record the interdependencies that exist between safety case modules — e.g. to show how the claims of one module support the arguments of another. A number of techniques for structuring and describing modular safety cases using the Goal Structuring Notation were defined by Kelly in (Kelly 2001). The Industrial Avionics Working Group, (IAWG) has been using these techniques as part of a substantial industrial case study being funded by the UK Ministry of Defence. Based on this experience, and a number of issues encountered, modifications to the original approach have been defined. This paper presents some of these experiences of the IAWG in using’ modular’ GSN — in particular, those relating to capturing and recording safety case contracts — and proposes an enhanced approach.

High Performance Elliptic Curve Cryptographic Co-processor

Abstract: For an equivalent level of security, elliptic curve cryptography uses shorter key sizes and is considered to be an excellent candidate for constrained environments like wireless/mobile communications. In FIPS 186-2, NIST recommends several finite fields to be used in the elliptic curve digital signature algorithm (ECDSA). Of the ten recommended finite fields, five are binary extension fields with degrees ranging from 163 to 571. The fundamental building block of the ECDSA, like any ECC based protocol, is elliptic curve scalar multiplication. This operation is also the most computationally intensive. In many situations it may be desirable to accelerate the elliptic curve scalar multiplication with specialized hardware.

Operating condition modeling for ATR fusion assessment

Abstract: Real world Operating Conditions (OCs) influence sensor data that in turn affects the perf ormance of target detection and identification systems utilizing the collected information. The impact of operating conditions on collected data is widely accepted, but not fully characterized . OCs that affect data depend on sens or wavelength and associated scenario phenomenology, and can vary significantly between electro-optical (EO), infrared (IR), and radar sensors. This paper will discuss what operating cond itions might be modeled for each sensor type and how they could affect automatic target recognition (ATR) systems designed to exploit their respective sensory data. The OCs are broken out into four categories; sensor, environment, target, and ATR algorithm training. These main categories will further contain subcategories with varying levels of influence. The purpose of this work is to develop an OC distribution model for the “real world” that can be used to realistically represent the performance of multiple ATR systems, and ultimately the decision made from the fused ATR results. An accurate OC model will greatly enhance th e performance assessment of ATR and fusion systems by affording Bayesian conditioning in fusion performance analysis and aiding in the sensitivity analysis of fusion performance over different operational conditions. Accurate OC models will also be useful in the fusion algorithm operation. Keywords: EO, IR, SAR, radar, ATR, operating cond itions, OCs, fusion, detection, identification

Pilot Design for IEEE 802.16 OFDM and OFDMA

Abstract: In this paper we apply a new pilot design optimization technique to the IEEE 802.16a wireless MAN standard. Using the specifications from 802.16a, we demonstrate that significant SER improvements are possible for 802.16a in a Rayleigh fading channel by judiciously choosing where the pilots are placed and the power contained in each pilot. Specifically, for the OFDM mode, we show that up to 13 dB SNR improvement is possible by simply modifying the pilots. For the OFDMA mode we demonstrate that a more modest but still significant improvement of 1.8 dB is possible with proper pilot design.

Enhancement of Low-Contrast Curvilinear Features in Imagery

Abstract: A new method is described for enhancing low-contrast curvilinear features in imagery that combines directional filtering with Fischler, Tenenbaum and Wolf's F* algorithm for computing minimum cost paths. The method exploits a phenomenon called "the stability of lines over angle." The idea is that when a directionally filtered image contains a line plus noise, minimum cost paths tend to be aligned in the direction of the line with random jumps between parallel paths. When the input image contains noise only, the direction of minimum cost paths resemble random walks with drift. As the direction of the filter changes, minimum cost paths that follow true features persist and are more stable over angle than those that follow noise. Adding them up in an accumulator array over angle produces a larger number of votes along signal paths than along noise paths. This provides a means for enhancing trajectories of low-contrast features. Several examples illustrate the enhancement of forest trails in USGS aerial imagery, linear features on Mars, and roads in synthetic aperture radar imagery

Ship recognition using optical imagery for harbor surveillance

Abstract: Many military and homeland defense missions require automated situation awareness in maritime environments. A major element of these missions is automatic detection, tracking, and recognition of ships as they transit harbors. We advocate the use of optical sensors in an Automated Target Recognition (ATR) system to accomplish these missions. This paper reports on the development of maritime optical ATR systems that incorporate a new capability for recognition of known ships, using a database of previously acquired imagery. The approach investigated here uses the local interest point detector and descriptor known as SIFT (Scale Invariant Feature Transform) features. The SIFT interest point detector locates extrema in scale space of Difference-of-Gaussian functions, generating a set of distinctive image regions; the keypoint descriptor measures the orientation of local gradients in the region. The features are normalized, making them invariant to image scaling and rotation and partially invariant to changes in illumination and viewpoint. SIFT features are used in object recognition by matching features extracted from test images with those previously measured in database images. Following feature matching, a geometric verification process is used to eliminate false matches. This paper describes criteria developed to recognize ships using SIFT features and strategies employed to handle changes in camera viewpoint and cluttered backgrounds common in maritime environments.

Hyperion—Next-Generation Battlespace Information Services

Abstract: QinetiQ, Malvern Technology Centre, St Andrews Road, Malvern, Worcestershire WR14 3PS, UK*Corresponding author: robert.ghanea-hercock@bt.comThe future digital battlespace will be a fast-paced and frenetic environment that stresses informationcommunicationtechnologysystemstothelimit.Thechallengesaremostacuteinthetacticalandoper-ational domains where bandwidth is severely limited, security of information is paramount, thenetwork is under physical and cyber attack and administrative support is minimal. Hyperion is aclusterofresearchprojectsdesignedtoprovideanautomatedandadaptiveinformationmanagementcapability embeddedin defence networks. The overall system architecture isdesigned toimprove thesituational awareness of field commanders by providing the ability to fuse and compose informationservices in real time. The key technologies adopted to enable this include: autonomous softwareagents, self-organizing middleware, a smart data filtering system and a 3-D battlespace simulationenvironment. This paper reviews some of the specific techniques under development within theHyperion sub-projects and the results achieved to date.Keywords: agents; autonomous systems; middleware; data visualizationReceived 14 May 2007; revised 14 May 2007

Cryptographic key management in a communication network

Abstract: A communication network (22) includes a central node (30) loaded with a trusted key (26) and key material (56) corresponding to an asymmetric key agreement protocol (48). The network (22) further includes vulnerable nodes (32) loaded with key material (69) corresponding to the protocol (48). Successive secure connections (68, 70) are established between the central node (30) and the vulnerable nodes (32) using the key material (56, 69) to generate a distinct session key (52) for each of the secure connections (68, 70). The trusted key (26) and one of the session keys (52) are utilized to produce a mission key (39). The mission key (39) is transferred from the central node (30) to each of the vulnerable nodes (32) via each of the secure connections (68, 70) using the corresponding current session key (52). The mission key (39) functions for secure communication within the communication network (22).

Statistical Modeling and ML Parameter Estimation of Complex SAR Imagery

Abstract: Accurate statistical models for the complex pixels forming fine-resolution synthetic aperture radar (SAR) images are needed for several engineering applications, including coherent signal detection in SAR clutter, automatic target recognition, and automatic SAR RCS calibration without calibration targets We derive the maximum likelihood estimator for the parameters of a complex generalized Gaussian distribution and show that it can be efficiently computed Applying this to fine-resolution SAR images representing a wide variety of scene contents, we show that this model very accurately captures both the central regions and tails of the data distribution

Access-Control Method For Software Module And Programmable Electronic Device Therefor

Abstract: A programmable electronic device ( 10 ) stores a number of cipher-text software modules ( 14 ) to which access is granted after evaluating a user's token ( 55, 80, 82 ), a software-restriction class ( 58 ) for a requested software module ( 14 ), and/or a currently active access-control model ( 60 ). Access-control models ( 60 ) span a range from uncontrolled to highly restrictive. Models ( 60 ) become automatically activated and deactivated as users are added to and deleted from the device ( 10 ). A virtual internal user proxy that does not require users to provide tokens ( 80, 82 ) is used to enable access to modules ( 16 ) classified in a global software-restriction class ( 62 ) or when an uncontrolled-access-control model ( 68 ) is active. Both licensed modules ( 76 ) and unlicensed modules ( 18,78 ) may be loaded in the device ( 10 ). However, no keys are provided to enable decryption of unlicensed modules ( 18,78 ).

Remote setting for electronic systems in a projectile for chambered ammunition

Abstract: A fuze setting circuit in an artillery or tank shell having a case with a press-fitted head assembly is provided with an electromechanical fuze-wiring link that is completed electrically by mechanical assembly of a tracer-carrying projectile on the shell casing, and by the rotational attachment of a programmable fuze onto the projectile.

Dynamic Logic Applied to SAR Data for Parameter Estimation Behind Walls

Abstract: Identifying and localizing targets within buildings using exterior sensors will offer superior advantages to the military and law enforcement communities. Research on wall-penetrating radar has produced significant advances in recent years regarding this topic. However, wall parameter ambiguities, multiple reflections, clutter, and measurement noise pose significant challenges to developing robust detection and estimation methods. In the present work we demonstrate can be mitigated using dynamic logic (DL), an adaptive method for iterative maximum likelihood.

Safety process improvement with POSE and alloy

Abstract: Safety Standards demand that applications demonstrate they have the required safety integrity, starting with the initial requirements phase. This paper shows how the Problem Oriented Software Engineering (POSE) framework, in conjunction with the Alloy formal method, supports this task through its ability to elaborate, transform and analyse the project requirements. The results of applying this combination to an existing design showed that process improvement can be realised through its ability to detect anomalies early in the life cycle that had previously been detected by much later (and more costly) validation work.

EO/IR ATR performance modeling to support fusion experimentation

Abstract: The identification of a target from an electro-optical or thermal imaging sensor requires accurate sensor registration, quality sensor data, and an exploitation algor ithm. Combining the sensor data and exploitation, we are concerned with developing an electro-optical or infrared (EO/IR) performance model. To combat the registration issue, we need a detaile d list of operating conditions (i.e. colle ction position) so that the sensor exploitation results can be evaluated with sensitivities to these operating conditions or collection parameters. The focus of this p aper will build on the NVSED AQUIRE model 2 . We are also concerned with developing an EO/IR model that affords comparable operating condition parameters to a synthetic aperture radar (SAR) performance model. The choice of EO/IR modeling additions are focused on areas were Fusion Gain might be realized through an experiment tradeoff between mult iple EO/IR looks for ATR exploitation fusion. The two additions to known EO/IR models discussed in t he paper are (1) adjacency and (2) obscuration. The methods to account for these new operating conditions and the corresponding results on the modeled performance are presented in this paper. Keywords: EO, IR, performance model, ATR, fusion, operating conditions, OC s, identification, multiple looks

Detecting change in images with parallax

Abstract: The ability to detect significant change in images is reduced when there is parallax. Fixed objects above or below the ground plane displace from their true position by an amount that depends on their height and the look angle of the sensor, reducing background cancellation and limiting the effectiveness of change detection. A method for reducing the effect of parallax shifts using dynamic time warping (DTW) to align images along the epipolar direction is described. A performance model is developed for predicting the processing gain of change detection (CD) over single image object detection as a function of the parallax. The model is used to predict CD performance with, and without DTW. A 10x improvement in processing gain is demonstrated on optical imagery, which results in a significant reduction in the number of false alarms.

Resistivity and electric-field poling behaviors of DNA-based polymers compared to selected non-DNA polymers

Abstract: Resistivity studies were carried out on DNA-based polymer films and selected traditional polymer films, including PMMA and APC. The films were spin coated on glass slides configured for guarded electrode measurements of resistance. The measurements used the alternating polarity method to determine the applied-voltage-dependent current independent of charging and background currents. The data for the temperature dependence of all the polymers were fitted to a common Arrhenius-type expression plus a constant. The poling studies described various dependencies of the measured electro-optic coefficient on how the heating and electric field are applied to the films. The severe impact of poling DNA-based films with vacuum-deposited gold electrodes and the persistent problem of electrode burning and failure presumably due to the high electric fields at the electrode edges are described. How these problems were managed is discussed. The presence of an emf following poling of the DNA-based films is described.

Evaluation of an MHT-Enabled Tracker with Simulated Multistatic Sonar Data

Abstract: Multistatic sonar is an operational concept for jointly deploying and processing multiple sonar sources and receivers in order to obtain enhanced coverage of targets of interest in a volume of ocean. The enhanced performance is obtained through the diversity of "looks" at the targets of interest provided by the many source-target-receiver geometries available through multistatics. This increased probability of target detection by the sensor field is particularly significant in littoral operations, where a tracker must be able to hold the target in the presence of large numbers of random false alarms. This paper describes the performance results of a multiple hypothesis tracking (MHT) enabled tracker against three simulated multistatic data sets provided by the Multi Static Tracking Working Group (MSTWG). Using a set of MSTWG-defined tracking metrics, the tracker is demonstrated to successfully discriminate target contacts from large quantities of false alarms, and in doing so, successfully track the target(s) of interest in each scenario. These results lend credence to the idea that multistatic operations can significantly enhance the ability of a maritime defense force to localize and track targets of interest. Several valuable lessons regarding tracker configuration for multistatic tracking, learned as a result of this research, are presented.

Timing Synchronization in Distributed Mobile MISO Rayleigh Fading Channels

Abstract: This paper proposes a novel acquisition technique to improve single-antenna receiver detection performance of signals from multiple transmitters that are distributed spatially. We assume that the distributed transmissions occur simultaneously, but the start time of each of the respective transmissions are not synchronous due to imperfect coordination and non-synchronized clocks across distributed transmitters. First, we propose a robust combining method in mobile channels when there is no feedback or channel knowledge between the receiver and the distributed transmitters. Next, we propose a power control technique, given feedback (and partial channel knowledge) between the receiver and distributed transmitters, to improve the receiver operating characteristic (ROC) performance when re-acquiring multiple distributed transmitters. The ROC performance improvements are demonstrated for multiple distributed transmitter signal detection in a mobile Rayleigh fading channel. Analytical solutions are derived to predict the ROC performance when no channel knowledge is assumed, which is corroborated via simulation. For the power control method, simulation is used to demonstrate performance improvement (over the no feedback case) when the channel is estimated with error and feedback latency. The probability of missed detection is improved by at least a factor of 10 and 100, respectively.

Systems and methods for reliable message delivery over digital networks

Abstract: Systems and methods reliably transmit a message from a sender to a receiver via a network. A reliability module is configured to determine a probability of delivering a packet from the sender to the recipient via the network. Mode selection logic determines transmission mode from a number of options based upon the probability of delivering the packet from the sender to the recipient. A formatting module is configured to provide a first push that includes the message and, in at least one of the operating modes, a number of redundancy packets formulated as a function of the contents of the message. The receiver acknowledges the packets received so that any dropped packets can be re-transmitted. The redundancy packets can be created using Reed-Solomon or other forward error-correcting codes to further increase the reliability of the message transmission when network conditions warrant.

Towards normal design for safety-critical systems

Abstract: Normal design is, essentially, when an engineer knows that the design they are working on will work. Routine 'traditional' engineering works through normal design. Software engineering has more often been assessed as being closer to radical design, i.e., repeated innovation. One of the aims of the Problem Oriented Software Engineering framework (POSE) is to provide a foundation for software engineering to be considered an application of normal design. To achieve this software engineering must mesh with traditional, normal forms of engineering, such as aeronautical engineering. The POSE approach for normalising software development, from early requirements through to code (and beyond), is to provide a structure within which the results of different development activities can be recorded, combined and reconciled. The approach elaborates, transforms and analyses the project requirements, reasons about the effect of (partially detailed) candidate architectures, and audits design rationale through iterative development, to produce a justified (where warranted) fit-for-purpose solution. In this paper we show how POSE supports the development task of a safety-critical system. A normal 'pattern of development' for software safety under POSE is proposed and validated through its application to an industrial case study.

Overview of the Mars Science Laboratory Parachute Decelerator System

Abstract: In 2010 the Mars Science Laboratory (MSL) mission will deliver NASA's largest and most capable rover to the surface of Mars. MSL will explore previously unattainable landing sites due to the implementation of a high precision Entry, Descent, and Landing (EDL) system. The parachute decelerator subsystem (PDS) is an integral prut of the EDL system, providing a mass and volume efficient som·ce of aerodynamic drag to decelerate the entty vehicle fi·om Mach 2 to subsonic speeds prior to final propulsive descent to the sutface. The PDS for MSL is a mortru· deployed 19.7m Viking type Disk-Gap-Band (DGB) parachute; chosen to meet the EDL timeline requirements and to utilize the heritage parachute systems from Viking, Mars Pathfinder, Mars Exploration Rover, and Phoenix NASA Mars Lander Programs. The preliminruy design of the parachute soft goods including materials selection, stress analysis, fabrication approach, and development testing will be discussed. The preliminaty design ofmottru· deployment system including mortar system sizing and performance predictions, gas generator design, and development mottru· testing will also be presented.

A Comparsion of Acoustic and Psychoacoustic Measurements of Pass-Through Hearing Protection Devices

Abstract: In environments where listeners need to detect low-level sounds while being protected from high-level noises, electronic pass-through hearing protectors (EPHPs) offer an appealing alternative to traditional passive earplugs or earmuffs. In this paper, we compare acoustic measurements of the Head-Related Transfer Functions associated with eight different EPHPs to localization results measured on human listeners with the same devices. The results are discussed in terms of the insights they can provide for the design of improved EPHP systems.

Methods and systems for acquiring signals using coherent match filtering

Abstract: Embodiments include methods and apparatus for verifying the detection of a correlation peak, which may represent an acquisition of a received acquisition code symbol sequence. The method includes determining a series of coherently-aligned peaks from a series of correlation peaks. Determining the plurality of coherently-aligned peaks includes correcting a frequency offset and a phase offset for each of the plurality of correlation peaks. A coherent match filter process is performed on the plurality of coherently-aligned peaks. A detection of the correlation peak may be verified when the match filter result exceeds a threshold.