Showing papers by "Naval Surface Warfare Center published in 1995"
18 Jun 1995
TL;DR: In this paper, design oriented criteria are developed for distributed power systems with constant power loads to guarantee stability during large disturbances, where design constraints on the input filter parameters, such as the Q factor, and the amount of "ideal" constant power load that a system can support are placed.
Abstract: Design oriented criteria are developed for distributed power systems with constant power loads to guarantee stability during large disturbances. The criteria place design constraints on the input filter parameters, such as the Q factor, and constraints on the amount of "ideal" constant power load that a system can support. The criteria are based on Lyapunov stability theory, mixed potential functions, and the existence of equilibrium points. The analytical criteria are validated by means of computer simulations. >
201 citations
TL;DR: A suboptimal approach to the fixed-interval smoothing problem for Markovian switching systems is examined and a smoothing algorithm is developed that uses two multiple-model filters, where one of the filters propagate in the forward-time direction and the other one propagates in the backward- time direction.
Abstract: A suboptimal approach to the fixed-interval smoothing problem for Markovian switching systems is examined. A smoothing algorithm is developed that uses two multiple-model filters, where one of the filters propagates in the forward-time direction and the other one propagates in the backward-time direction. A backward-time filtering algorithm based on the interacting multiple model concept is also developed. Results from a simulation example are given to illustrate the performance of the smoothing algorithm with respect to that of filtering. The example involves radar tracking of a Mach 1 aircraft.
136 citations
TL;DR: In this paper, a comparison of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNPs is presented, and the dose-rate dependence of current gain degradation is even stronger than the dependence previously reported for NPN BJTs.
Abstract: A comparison is presented of ionizing-radiation-induced gain degradation in lateral, substrate, and vertical PNPs. The dose-rate dependence of current gain degradation in lateral PNP BJTs is even stronger than the dependence previously reported for NPN BJTs. Various mechanisms are presented and their relative significance for gain degradation in the lateral, substrate, and vertical PNPs is discussed. A detailed comparison of the lateral and substrate PNP devices is given. The specific lateral and substrate devices considered here are fabricated in the same process and possess identical emitters. Even though these devices have identical emitters and undergo the same processing steps, the lateral devices degrade significantly more than the substrate devices.
120 citations
TL;DR: In this article, a physically based comparison between hot-carrier and ionizing radiation stress in BJTs is presented, where the physical mechanisms responsible for the degradation are quite different.
Abstract: A physically based comparison between hot-carrier and ionizing radiation stress in BJTs is presented. Although both types of stress lead to qualitatively similar changes in the current gain of the device, the physical mechanisms responsible for the degradation are quite different. In the case of hot-carrier stress the damage is localized near the emitter-base junction, which causes the excess base current to have an ideality factor of two. For ionizing radiation stress, the damage occurs along all oxide-silicon interfaces, which causes the excess base current to have an ideality factor between one and two for low total doses of ionizing radiation, but an ideality factor of two for large total doses. The different physical mechanisms that apply for each type of stress imply that improvement in resistance to one type of stress does not necessarily imply improvement in resistance to the other type of stress. Based on the physical model, implications for correlating and comparing hot-carrier-induced and ionizing-radiation-induced damage are discussed. >
107 citations
TL;DR: In this article, a flux-weakening control specifically designed for surface-mounted permanent magnet machines is presented. But the proposed method does not require knowledge of the machine or system parameters and is not suitable for high-speed machines.
Abstract: Permanent-magnet synchronous machines fed from current-regulated converters feature nearly ideal performance at low-to-moderate speeds. However, as rotor speed increases the back emf rises which results in loss of current regulation and decreased torque. In buried-magnet machine drives, flux weakening is often used to extend the speed range. This paper sets forth a flux-weakening control specifically designed for surface-mounted permanent-magnet machines which is simple and does not require knowledge of the machine or system parameters. The proposed method is demonstrated both experimentally and through the use of computer simulation. >
90 citations
TL;DR: The concepts of chaos and its control are reviewed from an experimental as well as a theoretical viewpoint in this article, and examples are given of the control of chaos in ad-hoc set of experimental systems.
83 citations
TL;DR: In this paper, the role of gate oxide thickness (T/sub ox/) plays on the gate and drain failure threshold voltages required to induce the onset of single-event gate rupture (SEGR).
Abstract: This paper investigates the role that the gate oxide thickness (T/sub ox/) plays on the gate and drain failure threshold voltages required to induce the onset of single-event gate rupture (SEGR). The impact of gate oxide thickness on SEGR is experimentally determined from vertical power metal-oxide semiconductor field-effect transistors (MOSFETs) having identical process and design parameters, except for the gate oxide thickness. Power MOSFETs from five variants were specially fabricated with nominal gate oxide thicknesses of 30, 50, 70, 100, and 150 nm. Devices from each variant were characterized to mono-energetic ion beams of Nickel, Bromine, Iodine, and Gold. Employing different bias conditions, failure thresholds for the onset of SEGR were determined for each oxide thickness. Applying these experimental test results, a previously published empirical expression is extended to include the effects of gate oxide thickness. In addition, observations of ion angle, temperature, cell geometry, channel conductivity, and curvature at high drain voltages are briefly discussed.
81 citations
TL;DR: The ionizing radiation tolerance of high performance SiGe HBTs, grown by UHV/CVD and optimized for 77 K, has been investigated for the first time in this article.
Abstract: The ionizing radiation tolerance of high-performance SiGe HBTs, grown by UHV/CVD and optimized for 77 K, has been investigated for the first time. Results at both 300 K and 77 K indicate that this SiGe technology is inherently radiation tolerant without additional processing steps. Perimeter-to-area analysis show parallel shifts in the collector and base current density for total radiation doses below 1.0 Mrad(Si). Relatively minor degradation in the current gain characteristics is observed for SiGe HBTs exposed to 1.0 Mrad(Si) of Co/sup 60/ gamma radiation, indicating that the technology is robust for many applications requiring a high degree of ionizing radiation tolerance. 1/f noise measurements made pre- and post-radiation show the appearance of a generation-recombination center in some of the SiGe HBTs after a total-dose exposure to 10.0 Mrad(Si).
78 citations
TL;DR: In this article, several hardness-assurance approaches are examined and compared to experimental results obtained at low dose rates, including irradiation at high dose rates while at elevated temperature and high-dose-rate irradiation followed by annealing.
Abstract: The dose-rate dependence of gain degradation in lateral PNP transistors is even stronger than the dependence previously reported for NPN BJTs. In this work, several hardness-assurance approaches are examined and compared to experimental results obtained at low dose rates. The approaches considered include irradiation at high dose rates while at elevated temperature and high-dose-rate irradiation followed by annealing. The lateral PNP transistors continue to degrade during post-irradiation annealing, in sharp contrast to NPN devices studied previously. High-temperature conditions significantly increase the degradation during high-dose-rate irradiation, with the amount of degradation continuing to increase with temperature throughout the range studied here (up to 125/spl deg/C). The high-temperature degradation is nearly as great as that observed at very low dose rates, and is even greater when differences between /sup 60/Co and X-ray irradiation are accounted for. Since high-temperature irradiation has previously been shown to enhance the degradation in NPN transistors, this appears to be a promising hardness-assurance approach for bipolar integrated circuits. Based on these results, preliminary testing recommendations are discussed.
74 citations
TL;DR: Using a recently formulated technique for in vivo cardiac transmembrane current estimation and a newly formulated measure of nonlinear determinism, ventricular fibrillation in vivo exhibits deterministic dynamics similar to those previously used in chaos control.
Abstract: Using a recently formulated technique for in vivo cardiac transmembrane current estimation, we examined ventricular fibrillation for evidence of deterministic linear and nonlinear structure. Both unstable fixed point analysis and a newly formulated measure of nonlinear determinism indicated that ventricular fibrillation in vivo exhibits deterministic dynamics similar to those previously used in chaos control.
73 citations
TL;DR: In this article, the upper shelf fracture toughness and tearing resistance of two structural steels, HY-100 and ASTM A533, Gr. B, were determined over a wide range of applied constraint.
Abstract: The upper shelf fracture toughness and tearing resistance of two structural steels, HY-100 and ASTM A533, Gr. B, were determined over a wide range of applied constraint. The constraint conditions were varied by changes in specimen geometry and loading mode. Bend specimens with shallow and deep cracks, compact specimens, and single and double edge notched tension specimens were used in this study. A rotation correction was developed for the single edge notch tension specimen which greatly improved the behavior of the J-R curves determined using this specimen. The experimental results were used to investigate the applicability of the Q and T stress parameters to the correlation of upper shelf initiation toughness, J{sub Ic}, and tearing resistance, T{sub mat}. The J-Q and J-T stress loci, and corresponding plots of material tearing resistance plotted against Q and T, were developed and compared with the expectations of the O`Dowd and Shih and the Betegon and Hancock analyses. The principle conclusions of this work are that J{sub Ic} does not appear to be dependent on T stress or Q while the material tearing resistance, T{sub mat}, is dependent on T stress and Q, with the tearing modulus increasing as constraint decreases.
21 Jun 1995
TL;DR: In this article, the effects of false alarms and ECM are considered in the beam pointing control of a phased array radar and multiple waveforms are included in the benchmark problem so that the radar energy can be coordinated with the tracking algorithm.
Abstract: This paper extends an earlier benchmark problem for beam pointing control of a phased array radar to include the effects of false alarms and ECM. Multiple waveforms are included in the benchmark problem so that the radar energy can be coordinated with the tracking algorithm. The ECM includes a standoff jammer broadcasting wideband noise and targets attempting range gate pull off. The paper presents the radar model, the ECM techniques, the target scenarios, and performance criteria for the benchmark problem.
TL;DR: In this article, the authors show that an increase in the disorder of an array of Josephson junctions can lead to significant improvement in the synchronization of the array and that this effect and the opposite expected behavior are seen over a broad parameter range.
TL;DR: In this paper, the authors present a method for the anticontrol or maintenance of chaos designed for easy application to physical and biological systems based on the return map of the experimental data and requires only small, very infrequently applied time-dependent perturbations of a single system parameter.
Abstract: We present a method for the anticontrol or maintenance of chaos designed for easy application to physical and biological systems. The method is based on the return map of the experimental data and requires only small, very infrequently applied time-dependent perturbations of a single system parameter and does not require any model equations for or a priori knowledge of the system dynamics. The method is shown to be able to reliably sustain chaos in a magnetomechanical ribbon experiment.
TL;DR: The drop weight impact test is the simplest and easiest test that can be performed on small quantities of explosives or propellants, and yet it has only a minimal role in assessing explosive sensitivity or performance as mentioned in this paper.
Abstract: The drop weight impact test is the simplest and easiest test that can be performed on small quantities of explosives or propellants, and yet it has only a minimal role in assessing explosive sensitivity or performance. This paper examines the drop weight impact test as it is currently used, describes its major flaw, and suggests an alternative test that holds the promise of providing the impact energy required to ignite an energetic material. Other impact tests are described. One of these, the Ballistic Impact Chamber Test, measures the rate of reaction and extent of reaction during impact. This test demonstrates that during impact there are two forms of initiation reactions that occur, one that is very fast and is likely due to direct impact-shear initiation of the crystalline solids in the sample. The other, a much slower component, is thought to arise due to burning of the sample.
20 Jun 1995
TL;DR: In this paper, the authors describe an algorithm for mapping the time rate of change of the gradient tensor measured by a sensor of known velocity into the dipole bearing vector and the diphole moment vector scaled by the inverse fifth power of the range.
Abstract: The use of the magnetic gradient tensor in the point-by-point localization of a magentic dipole was first demonstrated by Wynn in 1971, with a more explicit solution derived by Frahm in 1972. This algorithm maps the five independent components of the magnetic gradient tensor at a point into the dipole bearing vector and the dipole moment vector scaled by the inverse fourth power of the range to the dipole. This inversion produces four solutions, two of which are reflections through the origin of the bearing and scaled moment vectors of the other two. In the present paper, we describe an algorithm for mapping the time rate of change of the gradient tensor measured by a sensor of known velocity into the dipole bearing vector and the dipole moment vecot scaled by the inverse fifth power of the range. An extensive computer exercise with random position and moment vector geometries consistently produces at least one and at most four distinct solutions, with an equal number of additional solutions related to these by reflection of the bearing vector through the origin, for a total of at least two and at most eight solutions. In the same exercise, the solution common to this algorithm and the gradient equation iversion algorithm is consistently unique, and the two different moment vector scalings allow the range to be determined, resulting in a unique solution for dipole position and moment vectors. A general proof of uniqueness is not yet available.
TL;DR: In this paper, a model of abrupt magnetization jumps within individual domains driven by the applied stress was proposed to describe the qualitative behavior of the damping in the giant magnetostriction material Terfenol-D.
Abstract: Magnetomechanical damping in the giant magnetostriction material Terfenol-D has been investigated by quasi-static stress-strain measurements and modeled theoretically. The damping capacity is a strong function of applied stress amplitude, increasing to a maximum at some finite stress and then decreasing slowly at still larger applied stresses. Maximum damping capacities greater than 1.0 were observed for the lowest magnetic bias fields and prestresses at applied stress amplitudes of 4 MPa. Both the qualitative behavior of the damping and its magnitude are successfully described by a model of abrupt magnetization jumps within individual domains driven by the applied stress.
TL;DR: In this article, the authors compared three different starting strategies including one apparently neglected method-normal load commutation, and showed that depending on system parameters, it may be possible to start the system with no special provision for start up.
Abstract: Load-commutated inverter (LCI) synchronous machine drives are common in the high power range. However, the starting performance of these systems is a concern since load-commutation cannot occur at arbitrarily low speeds. This paper compares three different starting strategies including one apparently neglected method-normal load commutation. In particular, it is shown that, depending on system parameters, it may be possible to start the system with no special provision for start up. A method to determine whether a given system can be started using load commutation is presented. >
TL;DR: In this article, an interacting acceleration compensation (IAC) algorithm is proposed to overcome the requirement of explicit maneuver detection of the two-stage estimator, where the zero acceleration of the constant velocity model and a constant acceleration model are viewed as a bias vector.
Abstract: The two-stage Kalman estimator has been studied for state estimation in the presence of random bias and applied to the tracking of maneuvering targets by treating the target acceleration as a bias vector. Since the target acceleration is considered a bias, the first stage contains a constant velocity motion model and estimates the target position and velocity, while the second stage estimates the target acceleration when a maneuver is detected, the acceleration estimate is used to correct the estimates of the first stage. The interacting acceleration compensation (IAC) algorithm is proposed to overcome the requirement of explicit maneuver detection of the two-stage estimator. The IAC algorithm is viewed as a two-stage estimator having two acceleration models: the zero acceleration of the constant velocity model and a constant acceleration model. The interacting multiple model (IMM) algorithm is used to compute the acceleration estimates that compensate the estimate of the constant velocity filter. Simulation results indicate the tracking performance of the IAC algorithm approaches that of a comparative IMM algorithm while requiring approximately 50% of the computations. >
28 Apr 1995
TL;DR: Results from the circuit theory literature are applied to yield conditions on the network parameters ensuring complete stability of the dynamic model of the system and it is shown that if one of the conditions does not apply, then the model undergoes an Andronov-Hopf bifurcation to unstable limit cycles for some parameter values.
Abstract: A power electronic system in which a constant source supplies a load through an input filter and a regulated DC-DC converter is considered. Results from the circuit theory literature are applied to yield conditions on the network parameters ensuring complete stability (i.e., convergence of all trajectories to an equilibrium point) of the dynamic model of the system. It is also shown that if one of the conditions does not apply, then the model undergoes an Andronov-Hopf bifurcation to unstable limit cycles for some parameter values.
TL;DR: In this paper, the effects of packaging and burn-in on the post-irradiation performance of National Semiconductor 54AC02 Quad 2-input NOR gates were investigated.
Abstract: Results are reported from an investigation of the effects of packaging and burn-in on the post-irradiation performance of National Semiconductor 54AC02 Quad 2-input NOR gates. The test population was drawn from a single wafer fabricated in the National process qualified under Mil-Prf-38535 to an ionizing radiation hardness of 100 krads(Si). The test sample was divided between plastic and ceramic packages. Additionally, half of the plastic samples and half of the ceramic samples received a 168 hour/125/spl deg/C burn-in, Two irradiation schemes were used. The first followed Mil-Std-883 Method 1019.4 (dose rate=50 rads(Si)/s). The second used a low dose rate (0.1 rads(Si)/s). AC, DC, transfer function and functional behavior were monitored throughout the tests. Significant differences among the package types and burn-in variations were noted with the plastic, burned-in components demonstrating enhanced degradation. They show the worst post-irradiation parameter values as well as very broad post-irradiation parameter distributions. Degradation is highly dependent upon dose rate and anneal conditions. Two different radiation induced leakage paths have been identified, and their characteristics have been correlated to variations in high dose rate and low dose rate circuit performance. Caution is recommended for system developers to ensure that radiation hardness characterization is performed for the same package/burn-in configuration to be used in the system.
TL;DR: In this article, the authors use multiple linear regression with subset selection to optimize the locations of control actuators in a feed-forward active noise control system, and provide numerical results for a simple active structural-acoustic control problem.
TL;DR: The ability of the network to solve for constrained paths is illustrated with both a graph theoretic example and a scenario involving an unmanned vehicle that must travel a constrained path through a real terrain area containing artificially generated keep out zones.
TL;DR: In this article, a multizone, thin-layer Navier-Stokes method was used to simulate the air wake of a DD-963 ship configuration by using a multiscale Navier Stokes method.
Abstract: The ship airwake is defined as an arbitrary volume of air, namely an air burble, surrounding the ship. This note describes simulating the airwake of a DD-963 ship configuration by using a multizone, thin-layer Navier-Stokes method.
21 Jun 1995
TL;DR: In this paper, an alternative approach to improving interceptor performance is by improving the guidance law used to steer the missile, which substantially improves system performance, and demonstrates the advantages of using a weave guidance law.
Abstract: During re-entry the rolling velocity of the non-separating tactical ballistic missile caused by configurational asymmetries will normally pass through the missile pitch frequency. This may result in a large amplitude circular yaw and a severe spiraling of the vehicles center of mass. The presence of a static aerodynamic induced rolling moment may cause the roll rate to lock-in at the critical frequency in which case the severity of this spiraling motion is greatly increased. Both the amplitude and frequency of spiraling generally increase as the missile descends in altitude. The frequency of the motion is in the range 0.5 to 1 Hz which is the range of target weave frequencies most critical for fast-response proportional navigation interceptors. These motions can cause significant miss distance in a conventional proportional navigation guidance system. This paper demonstrates the advantages of using a weave guidance law. The paper shows that an alternative approach to improving interceptor performance is by improving the guidance law used to steer the missile. If the target weave frequency can be estimated the paper shows that the compensated weave guidance law substantially improves system performance.
TL;DR: In this paper, an oxide-trapped charge-induced inversion layer acting as an additional emitter was modeled by interpreting the inversion as an extension of the emitter.
Abstract: Excess collector current in irradiated NPN BJT's is linked to an oxide-trapped-charge-induced inversion layer acting as an additional emitter. Excess collector current is modeled by interpreting the inversion layer as an extension of the emitter. >
TL;DR: In this paper, the theory of bicoherence is explored to establish its utilization in the detection of bearing localized defects, and the proposed method is effective in bearing defect detection and sensitive to incipient defects.
Abstract: For automatic detection and diagnosis of localized defects in rolling element bearings, bicoherence spectra are used to derive features that signify the condition of a bearing. These features quantitatively describe the degree of phase correlation among any three harmonics of bearing characteristic defect frequencies. In this paper, theory of bicoherence is explored to establish its utilization in the detection of bearing localized defects. Experimental results show that the proposed method is effective in bearing defect detection and sensitive to incipient defects.
TL;DR: The Tank-Hopfield linear programming network is modified to solve mixed integer linear programming with the addition of step-function amplifiers to avoid the traditional problems associated with most Hopfield networks using quadratic energy functions.
TL;DR: In this paper, a highly accurate average-value reduced-order model of a hysteresis current-regulated brushless DC drive is presented and the physical cause of each of these modes is explained and a mathematical model for each mode is set forth.
Abstract: Current-regulated brushless DC machines are used in a wide variety of applications including robotics, actuators, electric vehicles, and ship propulsion systems. When conducting system analysis of this or any other type of drive, average-value reduced-order models are invaluable since they provide a means of rapidly predicting the electromechanical dynamics and are readily linearized for control system synthesis. In this paper, a highly accurate average-value reduced-order model of a hysteresis current-regulated brushless DC drive is set forth. In so doing it is demonstrated that the drive exhibits five distinct operating modes. The physical cause of each of these modes is explained and a mathematical model for each mode is set forth. The mathematical models are verified both experimentally and through the use of computer simulation. It has been found that the model set fourth herein is on the order of 300 times faster than a detailed computer simulation in calculating electromechanical transients. >