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Aerospace and Electronic Systems, IEEE Transactions on

Issue 5 • Date Sep 1989

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Displaying Results 1 - 20 of 20
  • Some early achievements in landing guidance using mechanically scanned pulse-encoded beams

    Page(s): 775 - 781
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    A microwave scanning beam landing system from the 1950s and 1960s is still operating routinely. It depends on airborne reception of pulse-coded signals from mechanically scanned antennas. Military versions include the US Navy's C-Scan for carrier landings and the Tactical Instrument Landing System used in Sweden. Other sets, called microwave scanning beam landing systems, serve Space Shuttle orbiters. System concepts and functional hardware requirements were tested extensively by on-ground and flight procedures. Both the US Navy and Sweden purchased operational equipments in 1969 View full abstract»

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  • A new quadrature sampling and processing approach

    Page(s): 733 - 748
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1096 KB)  

    A quadrature sampling and array signal processing technique that differs from earlier approaches in that is processes the data before the Hilbert transformation is presented. A fast Fourier transformation (FFT) technique that performs the discrete Fourier transformation (DFT) on the sampled data directly without Hilbert transformation is proposed for frequency-domain signal processing. For array signal processing, the proposed approach does not perform Hilbert transformation prior to signal combining. It features high processing speed, low distortion, and hardware simplicity. Error analyses, performance evaluation, and computer simulation results are included View full abstract»

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  • Processing of filtered GPS data

    Page(s): 711 - 728
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (912 KB)  

    General sufficiency conditions are developed for the stability of a discrete-time cascaded-filter architecture. An application of the result is in the filtering of prefiltered Global Positioning System (GPS) data during times in which the GPS receiver is tracking less than four satellites. Simulation results are presented for the case where the master filter processes the GPS filter estimate after the GPS filter attains uniform complete observability and controllability following its third filter cycle as well as the case where the observability condition is not met View full abstract»

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  • Nonlinear decoupling sliding mode control and attitude control of spacecraft

    Page(s): 621 - 633
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Control of a class of uncertain nonlinear systems which can be decoupled by state-variable feedback is considered. A variable-structure-control (VSC) law is derived so that in the closed-loop system the output variables asymptotically track given output trajectories in spite of any uncertainty in the system. On the basis of this result, a control law is derived for the attitude control of an orbiting spacecraft in the presence of uncertainty using reaction jets. The controlled outputs are the three Euler angles which describe the orientation of the spacecraft relative to an orbital frame. Simulation results are presented to show that, in the closed-loop system, precise attitude control is accomplished in spite of the uncertainty in the system View full abstract»

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  • Status of CR-like lower bounds for nonlinear filtering

    Page(s): 590 - 601
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    The motivation and mechanics of utilizing Cramer-Rao (CR) -type lower bounds to gauge the performance of filters being evaluated in nonlinear estimation applications such as in sonar, sonobuoy, and radar target tracking are reviewed. The status of several similar alternative CR-type lower bounds that have been considered or used for this purpose and certain limitations and/or caveats associated with their use are offered. These results should be of interest to sonar, sonobuoy, and radar practitioners and Kalman-filtering or nonlinear-filtering theorists View full abstract»

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  • Detection performance in K-distributed and correlated Rayleigh clutters

    Page(s): 634 - 642
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    Performance prediction for a detection system employing noncoherent integration is carried out for a chi-square family of fluctuating targets in K-distributed clutter plus noise. The detection performance for Swerling 11 targets in the K-distributed clutter plus noise is compared with that in exponentially correlated Rayleigh clutter. The results show that the performance prediction based on N pulses integrated in clutter plus noise using the K-distributed clutter model may be approximately equivalent to that using the exponentially correlated Rayleigh-distributed clutter model View full abstract»

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  • Lyapunov stability designs for switching regulator/low-pass filter system

    Page(s): 602 - 610
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    The second method of Lyapunov is employed to determine quantitatively accurate criteria for asymptotic stability of the fourth-order switching-regulator/low-pass filter system. Modeling the regulator as a linearized negative resistance, this analysis provides alternative stability relationships to those found in the literature and also reveals the limitations of the Routh stability criterion. Design examples are included which ensure system stability and reduce the amplitude of the filter resonant peak (audio-susceptibility constraint) View full abstract»

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  • Simulation and control of a 20-kHz spacecraft power system

    Page(s): 668 - 676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1136 KB)  

    A detailed computer representation of four Mapham inverters connected in a series-parallel arrangement has been implemented. System performance is illustrated by computer traces for the four Mapham inverters connected to a Litz cable with parallel resistance and DC receiver loads at the receiving end of the transmission cable. Methods of voltage control and load sharing between the inverters are demonstrated. The computer representation is used to design and demonstrate the advantages of a feedforward voltage-control strategy. It is shown that with a computer simulation of this type, the performance and control of spacecraft power systems can be investigated with relative ease and facility View full abstract»

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  • Decoding techniques in state estimation for dynamic systems with past histories

    Page(s): 765 - 768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    States of dynamic models with a higher order memory are estimated using both a stack sequential decoding algorithm and the Viterbi decoding algorithm (VDA), without higher dimensional dynamic system representation. This results in memory reduction for state estimate implementation. It is found that state estimation with a stack sequential decoding algorithm is faster and more practical than the state estimation with the Viterbi decoding algorithm, even though the estimates obtained by the Viterbi decoding algorithm are superior View full abstract»

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  • Decoupled ultimate boundedness control of systems and large aircraft maneuver

    Page(s): 677 - 688
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The robust trajectory control of a class of nonlinear systems which can be decoupled by state-variable feedback is considered. It is assumed that the system matrices are unknown but bounded. A nonlinear control law is derived so that the tracking error in the closed-loop system is uniformly bounded and tends to a certain small neighborhood of the origin. The error dynamics are asymptotically decoupled in an approximate sense. The controller includes a reference trajectory generator and uses the integral feedback of the tracking error. On the basis of this result, a flight control system is designed for the control of roll angle, angle of attack, and sideslip in rapid, nonlinear maneuvers of aircraft. Simulation results are presented to show that large, simultaneous lateral and longitudinal maneuvers can be performed in spite of the uncertainty in the stability derivatives View full abstract»

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  • Steady state analysis for discrete tracking filters

    Page(s): 768 - 771
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    An analysis of a discrete constant-gain α-β-γ tracking filter is presented. Steady-state tracking filter gains are determined without solving a discrete matrix Ricatti equation. Explicit closed-form gain solutions are found as a function of the roots to a cubic equation. Gain variations as a function of process noise, measurement noise, and sampling time are investigated View full abstract»

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  • A noise insensitive solution to an ambiguity problem in spectral estimation

    Page(s): 729 - 732
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB)  

    The instantaneous frequency measurement (IFM) receiver is capable of measuring the center frequency of single frequency pulses over a wide range (bandwidth) of center frequencies. Because of various constraints, the frequency resolution requirement results in long correlator delay times that reduce the single correlator bandwidth. A large bandwidth can be achieved only if two or more correlators are used. The problem of estimating frequency is then reduced to the simultaneous congruence problem of number theory. A design procedure is presented for solving the congruence problem for a given amount of noise protection, a stated frequency resolution, a minimum bandwidth, and a fixed level of precision (bits) in the IFM receiver View full abstract»

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  • MFDs of spinning satellite and attitude control using gyrotorquers

    Page(s): 611 - 620
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    Questions related to the matrix fraction descriptions (MFDs) and the minimal realizations of the transfer matrix of a spinning satellite system and control system design using output feedback are considered. The control torques are generated using gyrotorquers, and the output variables are the attitude angles. Two minimal state-space representations of the system, namely, a controller-form and an observer-form realization, are obtained from a right and left MFD of the transfer matrix, respectively. Using these canonical realizations, analytical expression for the feedback matrices of the controller and the observer as functions of the system parameters are obtained. The poles of the closed-loop system are invariant with respect to the spin rate of the satellite. Simulation results are presented to show that precise attitude control is accomplished in the closed-loop system using output feedback View full abstract»

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  • Three-dimensional atmospheric entry problem using method of matched asymptotic expansions

    Page(s): 660 - 667
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    A composite solution consisting of an outer solution, an inner solution, and a common solution is obtained. The outer solution arises from the gravitationally dominant region, whereas the aerodynamically dominant region contributes to the inner solution. The common solution accounts for the overlap between the outer and inner regions. In contrast to previous work, this simplified methodology yields explicit analytical expressions for various compounds of the composite solution without resorting to any type of transcendental equation that can be solved only by numerical methods. The present method is application for obtained autonomous guides and control strategies for a variety of aerospace vehicles View full abstract»

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  • Image-enhanced tracking

    Page(s): 701 - 710
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (712 KB)  

    Measurement of the angular orientation of the target or the target designation makes possible the design of high-accuracy tracking and prediction systems. Such measurements are best accomplished with an imaging sensor. A model is presented for the image-based observation link, along with the equations used to convert a sequence of image processor outputs into an estimate of target status. An example examines the interrelationship which exists between the rate of feature changes of a target, the frame rate of the imager, and the sensitivity of the sensor-image processor. It is shown that even at high frame rates, anomalous events may occur View full abstract»

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  • Optimal distributed decision fusion

    Page(s): 761 - 765
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The problem of decision fusion in distributed sensor systems is considered. Distributed sensors pass their decisions about the same hypothesis to a fusion center that combines them into a final decision. Assuming that the sensor decisions are independent of each other for each hypothesis, the authors provide a general proof that the optimal decision scheme that maximizes the probability of detection at the fusion for fixed false alarm probability consists of a Neyman-Pearson test (or a randomized N-P test) at the fusion and likelihood-ratio tests at the sensors View full abstract»

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  • Extensions and critique of minimum-relative-entropy spectral estimation

    Page(s): 650 - 659
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (884 KB)  

    Insight is provided into minimum-relative-entropy spectral estimation (MRESE), which has proved very successful in some applications. There are, however, shortcoming inherent in MRESE as it has so far developed; e.g. it would be desirable to incorporated objective, absolute (rather than subjective, relative) weighting for prior estimates. Such problems are pointed out, and solutions are offered for some of them. A few of these problems are common to MRESE and minimum-entropy spectral estimation. The unsolved problems are offered as topics for further research View full abstract»

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  • Geometric aspects of long-term noncoherent integration

    Page(s): 689 - 700
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    Long-term integration is defined as integration, perhaps interrupted, over time periods long enough for targets to move through volumes in space resolvable by the radar. Because the motion of the target is unknown prior to detection, long-term integration must be performed along multiple paths representing plausible target paths. The geometry of such a set of integration paths affects detection performance in several ways. The simplest implementation of long-term integration, using constant radial velocity paths, is investigated. The effects of path geometry on detection is quantified and optimized for a target whose motion is nearly radial but otherwise unknown View full abstract»

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  • Distributed sensor data fusion with binary decision trees

    Page(s): 643 - 649
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (524 KB)  

    A distributed sensor object recognition scheme that uses object features collected by several sensors is presented. Recognition is performed by a binary decision tree generated from a training set. The scheme does not assume the availability of any probability density functions, thus it is practical for nonparametric object recognition. Simulations have been performed for Gaussian feature objects, and some of the results are presented View full abstract»

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  • Two novel automatic frequency tracking loops

    Page(s): 749 - 760
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    Two automatic-frequency-control loops are introduced and analyzed in detail. The algorithms are generalizations of the well-known cross-product automatic-frequency-control loop with improved performance. The first estimator uses running overlapping discrete Fourier transforms (DFTs) to create a discriminator curve proportional to the frequency estimation error, whereas the second one preprocesses the received data and then uses an extended Kalman filter to estimate the input frequency. The algorithms are tested by computer simulations in a low carrier-to-noise-ratio (CNR) and highly dynamic environment. The algorithms are suboptimum tracking schemes with a larger frequency error variance compared to an optimum strategy, but they offer simplicity of mechanization and a CNR with a very low operating threshold 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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Editor-in-Chief
Lance Kaplan
Army Research Laboratory