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Aerospace and Electronic Systems, IEEE Transactions on

Issue 4 • Date Oct. 1996

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Displaying Results 1 - 25 of 33
  • 1996 Index IEEE Transactions on Aerospace and Electronic Systems Vol. 32

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    Freely Available from IEEE
  • Monitoring the thermal condition of permanent-magnet synchronous motors

    Page(s): 1421 - 1429
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    This paper describes a novel approach to monitoring the condition of small permanent-magnet synchronous motors (PMSM) operating under thermal stress. The approach begins with the estimation of temperature-dependent motor parameters from measurements of line voltages and currents. The parameters are then used to derive estimates of motor temperatures. Next, the electrically estimated temperatures are combined with a surface measurement of motor temperature and a dynamic thermal model of the motor to yield an observer that is a Kalman filter. The temperatures estimated by the observer are used for failure prevention. Finally, by modifying the observer, it is tuned to use the geometric properties of its innovation for failure detection. The innovation, that is, the difference between the thermally and electrically estimated temperatures, is monitored and compared against appropriate thresholds to detect failures. Failure detection is demonstrated experimentally, and shown to be capable of distinguishing the conditions of normal operation, and operation with obstructed cooling View full abstract»

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  • An alternative closed-form solution to the GPS pseudo-range equations

    Page(s): 1430 - 1439
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    In the four satellite Global Positioning System (GPS) problem, the system of pseudo-range equations is shown to be equivalent to a system of two linear equations together with a range difference and pseudo-range equation. The formulation represents the user's position as the intersection of two planes and a hyperbola branch of revolution. The formulation is three-dimensional and includes almost all degenerate and special case geometries. It provides geometric insight into the characteristics of the solutions and resolves existence and uniqueness questions regarding solution of the pseudo-range equations View full abstract»

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  • Peformance of dynamic programming techniques for Track-Before-Detect

    Page(s): 1440 - 1451
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    “Track-Before-Detect” (TBD) is a target tracking technique where no threshold is applied at each measurement frame. Instead, data are processed over a number of frames before decisions on target existence are made. The track is returned simultaneously with the detection. A simple algorithm is presented and demonstrated via simulations. A detailed analysis enables detection and tracking performance to be predicted for particular algorithm parameters. Good performance is observed at low signal-to-noise ratio (SNR), with rapid degradation as SNR is reduced further. For some cases the detection performance does not improve regardless of how many frames of data are processed. Tracking performance may also be poor even though detection performance is good View full abstract»

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  • On the false alarm probability for an overlapped FFT processor

    Page(s): 1452 - 1456
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    A standard processor for detecting narrowband signals in noise applies the fast Fourier transform (FFT) to overlapped data blocks, and then sums the squared magnitudes of the bins from successive FFTs. The overlap of the data blocks causes these bins to be correlated, even when the noise is white. A simple expression is derived for the probability of false alarm when the covariance matrix of the FFT bins is tridiagonal View full abstract»

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  • Performance of the GLRT for adaptive vector subspace detection

    Page(s): 1473 - 1487
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    The problem of adaptively detecting a signal confined to a given vector subspace in interference modeled as a zero-mean complex Gaussian N-vector is considered. The correlation properties of interference are not known but are estimated from a given set of secondary (or reference) vectors. The dimension of the known signal subspace is Ns, where 1⩽Ns⩽N. The Generalized Likelihood Ratio Test (GLRT) is cast in a slightly different setting to show that it belongs to a class of invariant tests. The maximal invariants for the class of invariant tests are identified and the joint probability density function of the maximal invariants under both the null hypothesis H0 and the alternate hypothesis H1 are derived. These expressions are used to show that for 1⩽Ns<N, there exists no uniformly most powerful invariant (UMPI) test for the given signal detection problem. Expressions for characterizing the performance of the GLRT are derived and the detection performance of this test when the signal to be detected is a random vector confined to the given vector subspace is evaluated View full abstract»

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  • Current-mode control for multiple-output converters

    Page(s): 1412 - 1420
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    A small-signal model for multiple-output forward converter with current-mode control is derived. The model can accurately predict the small-signal characteristics for current-mode control. It is observed that the power stage pole-zero relative positions, which are critical to the compensator design, are not affected by introducing current-mode control View full abstract»

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  • Automatic recognition of ISAR ship images

    Page(s): 1392 - 1404
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    Inverse synthetic aperture radar (ISAR) produces images of ships at sea which human operators can be trained to recognize. Because ISAR uses the ship's own varying angular motions (roll, pitch, and yaw) for cross-range resolution, the viewing aspect and cross-range scale factor are continually changing on time scales of a few seconds. This and other characteristics of ISAR imaging make the problem of automatic recognition of ISAR images quite distinct from the recognition of optical images. The nature of ISAR imaging of ships, and single-frame and multiple-frame techniques for segmentation, feature extraction, and classification are described. Results are shown which illustrate a capability for automatic recognition of ISAR ship imagery View full abstract»

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  • Digital redesign for controlling the chaotic Chua's circuit

    Page(s): 1488 - 1500
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    We apply some successful digital redesign techniques, developed previously for the control of linear system, to controlling the nonlinear chaotic Chua's circuit. Chua's circuit is a simple autonomous physical device that exhibits very rich and complex nonlinear dynamics of bifurcation and chaos, and is hence very sensitive to digital controls. To apply advanced high-speed computer technology to the implementation, we show how to redesign a good digital controller, based on an existing successful analog controller, for controlling the chaotic trajectories of Chua's circuit, from anywhere within the chaotic attractor to a predesired unstable limit cycle of the circuit View full abstract»

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  • Nonlinear clutter cancellation and detection using a memory-based predictor

    Page(s): 1249 - 1256
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    In this paper, a nonlinear prediction (NLP) method is proposed as an alternative to the conventional linear prediction (LP) method for clutter cancellation. Because of the nonlinearity and non-Gaussianity of a clutter process, a nonlinear predictor is therefore needed to suppress clutter optimally. A memory-based predictor which uses a table look-up strategy to perform NLP is used in this work. The advantages of the memory-based approach are fast learning, algorithmic simplicity, robustness and suitability for parallel implementation. The memory-based predictor is then used as an adaptive detector for small surface target detection embedded in clutter. The effectiveness of the new method is demonstrated using real sea clutter data, and the results show improvement when compared with the conventional LP techniques View full abstract»

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  • Observability of target tracking with bearings-only measurements

    Page(s): 1468 - 1472
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    Observability requirements are obtained for three-dimensional maneuvering target tracking with bearings-only measurements. The approach taken here using pseudomeasurements is completely different from the previous work in this area in that it does not involve solutions of nonlinear differential equations resulting from complicated time differentiations and it can treat a more general class of target motions not restricted to N th-order target dynamics View full abstract»

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  • Efficient solution and performance analysis of 3-D position estimation by trilateration

    Page(s): 1239 - 1248
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    A new exact, explicit, and computationally efficient solution for three-dimensional (3-D) position estimation based on range measurements from three stations is proposed. The simple polynomial-type form of the new algorithm facilitates the performance analysis. Formulae are provided for both the variance and the bias of the position estimates. The systematic error is a joint effect of both the measurement noise and the system nonlinearity and its magnitude cannot be ignored if highly accurate localization is required. Performance evaluation results are presented for various conditions View full abstract»

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  • Stochastic stability theory for systems containing interval matrices

    Page(s): 1385 - 1391
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    Known conditions for the stability of stochastic, linear time-varying (LTV) dynamical systems based on Liapunov theory are applied to LTV dynamical systems containing interval matrices; both discrete and continuous time processes are considered. These conditions are sufficient for stability with probability 1 (wp1) and, in the case of discrete time, also necessary for stability in m.s. They lead to a simple, noniterative technique that involves the computation of eigenvalues of matrices whose elements often consist of first- and/or second-order moments. The results are useful in areas such as robust design, feedback control, perturbation analysis, and fault tolerant systems View full abstract»

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  • Estimation of singularities for intercept point forecasting

    Page(s): 1301 - 1310
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    In this paper, a recursive approach (an algorithm for estimation of singularity (AES)) is proposed to forecast the intercept point of a target and the pursuing interceptor recognized as the estimated singularity of a nodal cubic curve fitted to the data. The data comprises direction of arrival (DOA) estimates of both target and interceptor obtained at regular intervals of time using the maximum likelihood (ML) DOA estimation method. The estimates of coefficients of the cubic polynomial are given by a recursive least squares solution. From these coefficients, closed-form solutions for angle of interception and intercept time are obtained which are the forecasted coordinates of the intercept point. Experimental results demonstrate performance of the proposed algorithm View full abstract»

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  • Observability in passive target motion analysis

    Page(s): 1290 - 1300
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    The nature of observability of nonlinear systems encountered in passive target motion analysis (TMA) is carefully examined. The approach proposed here is based upon a well-chosen criterion which allows us to answer the major observability questions View full abstract»

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  • Strapdown INS error model for multiposition alignment

    Page(s): 1362 - 1366
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    The relationship between quaternion errors and tilt angles from true navigation frame to analytic platform frame is newly derived for strapdown inertial navigation system (SDINS). Using the relationship it is shown that the quaternion error model for attitude and velocity is equivalent to the conventional perturbation error model. Based upon the equivalency, the quaternion errors during a multiposition alignment are determined and analyzed. Furthermore, it is shown that the heading rotation of 180 deg achieves the minimal quaternion error for 2-position ground alignment View full abstract»

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  • Improved COSPAS-SARSAT locating with geostationary satellite data

    Page(s): 1405 - 1411
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    The COSPAS-SARSAT system locates distress beacons via Doppler analysis of beacon transmissions as observed by low Earth orbiting (LEO) satellites. By contrast, the 406 MHz search and rescue transponder on the geostationary satellites can measure only the transmitted frequency of the beacon, which is not currently being used in location determination. This report shows that a combined data approach can significantly improve the locating success rate, the time delay to the first solution, and the accuracy of location estimates View full abstract»

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  • Improved tracking of maneuvering targets: The use of turn-rate distributions for acceleration modeling

    Page(s): 1355 - 1361
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    Tactically maneuvering targets are difficult to track since acceleration cannot be observed directly and the accelerations are induced by human control or an autonomous guidance system therefore they are not subject to deterministic models. A common tracking system is the two-state Kalman filter with a Singer maneuver model where the second-order statistics of acceleration is the same as a first-order Markov process. The Singer model assumes a uniform probability distribution on the targets acceleration which is independent of the x and y direction. In practice, it is expected that targets have constant forward speed and an acceleration vector normal to the velocity vector, a condition not present in the Singer model. The work of Singer is extended by presenting a maneuver model which assumes constant forward speed and a probability distribution on the targets turn-rate. Details of the model are presented along with sample simulation results View full abstract»

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  • A fast initial alignment method for strapdown inertial navigation system on stationary base

    Page(s): 1501 - 1504
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    In this paper a strapdown inertial navigation system (SINS) error model is introduced, and the observability of the SINS error model is analyzed. Then, on the basis of this SINS error model and the analysis of computer simulation results, a fast estimation method of the azimuth error ΦD is proposed for the initial alignment of SINS on stationary base. Consequently, the time of initial alignment is reduced greatly. The computer simulation results illustrate the efficiency of this fast initial alignment method View full abstract»

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  • OS-CFAR thresholding in decentralized radar systems

    Page(s): 1257 - 1267
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    In a decentralized detection scheme, several sensors perform a binary (hard) decision and send the resulting data to a fusion center for the final decision. If each local decision has a constant false alarm rate (CFAR), the final decision is ensured to be CFAR. We consider the case that each local decision is a threshold decision, and the threshold is proportional, through a suitable multiplier, to a linear combination of order statistics (OS) from a reference set (a generalization of the concept of OS thresholding). We address the following problem: given the fusion rule and the relevant system parameters, select each threshold multiplier and the coefficients of each linear combination so as to maximize the overall probability of detection for constrained probability of false alarm. By a Lagrangian maximization approach, we obtain a general solution to this problem and closed-form solutions for the AND and OR fusion logics. A performance assessment is carried on, showing a global superiority of the OR fusion rule in terms of detection probability (for operating conditions matching the design assumptions) and of robustness (when these do not match). We also investigate the effect of the hard quantization performed at the local sensors, by comparing the said performance to those achievable by the same fusion rule in the limiting case of no quantization View full abstract»

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  • Chinese National Cumulative Index on Radar Systems: 1988-1994

    Page(s): 1523 - 1526
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    This “second edition” is a continuation of the series of National Cumulative Indexes on Radar Systems inaugurated in 1988. These National series augment the periodic International Cumulative Indexes on Radar Systems which are prepared by members of the IEEE AESS Radar Systems Panel. Information on both series is contained in IEEE AES Transactions vol. 27, no. 3 p. 581 (May 1991) View full abstract»

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  • Spacecraft telemetry link performance in a transfer orbit

    Page(s): 1321 - 1335
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    There are several critical periods early in the mission of a geo-stationary communication satellite. The first is the period from launch vehicle ignition until the upper stage final successful burn. The second is after the above span until the vehicle reaches its final altitude of a synchronous orbit. For a nominal low thrust apogee boost ascent subsystem during that later time, almost continuous telemetry is mandatory. This is especially true during the crucial periods of main engine burns and attitude correction phases. Maintaining a strong telemetry link throughout this phase requires an adequate RF signal link from the spacecraft to a ground station in the telemetry RF channel. An analysis of this link performance during each orbit until final position has two major aspects. One, the location of the spacecraft in relation to the ground tracking station at each moment in the mission is a matter of geometry and Keplerian physics. The other is the RF signal and its supporting subsystems, both on the ground and aboard the vehicle. The fundamental theoretical considerations or both the orbit parameters and radio link components are examined and then the individual parameter sensitivities are analyzed. Next, a nominal cast for a generic mission is studied. This survey considers the telemetry performance during each major stage of the flight from the launch through the transfer orbit to the postinjection period to the final orbit. Then abnormal situations due to both orbit and RF faults are examined. Finally, some design and operation concepts which may lessen the impact of the previous anomalies, are presented View full abstract»

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  • Maneuvering target tracking with colored noise

    Page(s): 1311 - 1320
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    It is known that colored noise may degrade the performance of a tracking algorithm. A common remedy is to model colored noise as an autoregressive (AR) process and apply the measurement difference method. One problem with the approach is that the AR parameters are usually unknown. In this work, we propose a new method to adaptively estimate the AR parameters. It is shown that this method is simple and practically feasible. We incorporate oar method into the interacting multiple model (IMM) tracking algorithm and show that the performance is almost as good as that in the known parameters case View full abstract»

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  • Low observable target motion analysis using amplitude information

    Page(s): 1367 - 1384
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    In conventional passive and active sonar system, target amplitude information (AI) at the output of the signal processor is used only to declare detections and provide measurements. We show that the AI can be used in passive sonar system, with or without frequency measurements, in the estimation process itself to enhance the performance in the presence of clutter where the target-originated measurements cannot be identified with certainty, i.e., for “low observable” or “dim” (low signal-to-noise ratio (SNR)) targets. A probabilistic data association (PDA) based maximum likelihood (ML) estimator for target motion analysis (TMA) that uses amplitude information is derived. A track formation algorithm and the Cramer-Rao lower bound (CRLB) in the presence of false measurements, which is met by the estimator even under low SNR conditions, are also given. The CRLB is met by the proposed estimator even at 6 dB in a cell (which corresponds to 0 dB for 1 Hz bandwidth in the case of a 0.25 Hz frequency cell) whereas the estimator without AI works only down to 9 dB. Results demonstrate improved accuracy and superior global convergence when compared with the estimator without AI. The same methodology can be used for bistatic radar View full abstract»

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  • Current ripple bounds of interleaved power converters

    Page(s): 1505 - 1508
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    We extend the main claims for more general waveforms. Specifically, we show that for any power converter module, if its input/output current ripple waveform is of full-sinusoidal-type or half-sinusoidal-type with peak-to-peak amplitude A(ΔI0), then the amplitude of the input/output current ripple of N (⩾1) parallelly interleaved such modules (with equal phase shift 2π/N) is always less than or equal to A(ΔI0 ) View full abstract»

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Aims & Scope

IEEE Transactions on Aerospace and Electronic Systems focuses on the equipment, procedures, and techniques applicable to the organization, installation, and operation of functional systems designed to meet the high performance requirements of earth and space systems.

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Meet Our Editors

Editor-in-Chief
Lance Kaplan
Army Research Laboratory