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ABSTRACT: A new method to estimate the rotor position of permanent magnet synchronous motor (PMSM) drives over a wide speed range, including zero frequency is introduced. The method measures the motor current derivative in response to the standard pulse width modulation (PWM) sequence to estimate rotor position. No additional signal injection or separate test vectors are required although modification is needed when narrow PWM voltage vectors occur. Three compensation techniques are proposed to improve the quality of the position estimation and reduce current distortion when narrow vectors are used for position estimation. Experimental results for sensorless speed and position control of a 4 kW PMSM verify the effectiveness of the proposed techniques.
IET Electric Power Applications 05/2011; · 1.17 Impact Factor
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ABSTRACT: For wireless/mobile ad hoc networks, researchers have developed many routing protocols. A typical problem setting is such that a packet of data is routed from a source to a destination without a prior knowledge of any existing route. To deal with unknown existing route, local flooding is required for each hop of the packet. Such an approach is appropriate for establishing a new route or forwarding infrequent data packets. However, for large volume data transmissions, the above approach is very inefficient. We believe that for many applications, mobile ad hoc networks must allow large volume data transmissions (in many separate packets) within a short period of time. For such applications, data forwarding policy should be based on a pre-established route. However, to combat random fluctuations of link qualities between nodes in dynamic environment, data forwarding policy should also exploit the spatial diversity of distributed nodes in a given route. It is from this perspective that we propose and analyze a one-to-many (1/M) data forwarding policy where each packet transmitted from a node is destined to multiple receiving nodes, and the node that receives the packet successfully and has the highest ranking becomes the next transmitting node. All nodes involved belong to a pre-established route, but the dynamic nature of each transmitting node of a packet makes the 1/M policy superior to the conventional one-to-one (1/1) policy for networks where transmission power dominates processing power
Military Communications Conference, 2005. MILCOM 2005. IEEE; 11/2005
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ABSTRACT: This paper analyses a simple method for iteratively computing the projection operator whose range space is the principal subspace of a given matrix. The iteration appears to be numerically very stable and is proven to converge at a quadratic rate. Several applications are briefly explored, as are extensions to Jordan algebras and C*-algebras.
Signals, Systems and Computers, 2004. Conference Record of the Thirty-Eighth Asilomar Conference on; 12/2004
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ABSTRACT: This letter introduces a novel class of linear precoders which explicitly add algebraic redundancy in the frequency domain. A procedure for designing robust precoders of the above form for transmission through unknown channels is derived. Such precoders guard against the adverse effects of narrowband interference and frequency selective fading channels. Their block nature also makes them suitable for quasi-stationary channels.
IEEE Communications Letters 03/2001; · 0.98 Impact Factor
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ABSTRACT: Blind identification and/or equalization of FIR MIMO channels
driven by unknown colored signals is useful in many applications
including in particular “smart” microphones. A technique
called blind identification via decorrelation (BID) can identify an FIR
MIMO channel using the second-order statistics of the channel output if
the channel transfer function is of full rank and column-wise coprime
and the channel input signals are mutually uncorrelated and of
sufficiently diverse power spectra. This identifiability condition is
much weaker than those required by other related techniques (which are
hence outperformed significantly by the BID). The BID first forms a bank
of MIMO subchannels and then constructs a decorrelator for each
subchannel. The decorrelators can then be used to form a bank of SIMO
channels, and each of the input signals is then estimated before the
channel transfer function is estimated (named BID-1). Alternatively, the
decorrelators can be used to estimate the channel transfer function
before the input signals are estimated (named BID-2), BID-2 is shown to
be more robust than BID-1
Neural Networks for Signal Processing X, 2000. Proceedings of the 2000 IEEE Signal Processing Society Workshop; 02/2000
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ABSTRACT: The reduced-rank Wiener filter (RRWF) can be utilized wherever a
desired signal needs to be extracted from random background noise or
deterministic interference. Common applications are echo cancellation,
equalization, neural network learning and spectral line enhancement.
This paper introduces a novel algorithm for the fast online computation
of the RRWF. The algorithm is derived by making a certain approximation
to the alternating power (AP) method to reduce its computational
complexity from O(m<sup>2</sup>r) to O[max(m<sup>2</sup>,mn)], or O(mn)
if the input is white. Simulations show that, somewhat surprisingly, the
computational saving does not come at the cost of estimation accuracy or
convergence speed
Neural Networks for Signal Processing X, 2000. Proceedings of the 2000 IEEE Signal Processing Society Workshop; 02/2000
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ABSTRACT: We introduce a novel information criterion (NIC) for searching for
the optimum weights of a two-layer linear neural network (NN). The NIC
exhibits a single global maximum attained if and only if the weights
span the (desired) principal subspace of a covariance matrix. The other
stationary points of the NIC are (unstable) saddle points. We develop an
adaptive algorithm based on the NIC for estimating and tracking the
principal subspace of a vector sequence. The NIC algorithm provides a
fast on-line learning of the optimum weights for the two-layer linear
NN. We establish the connections between the NIC algorithm and the
conventional mean-square-error (MSE) based algorithms such as Oja's
algorithm (Oja 1989), LMSER, PAST, APEX, and GHA. The NIC algorithm has
several key advantages such as faster convergence, which is illustrated
through analysis and simulation
IEEE Transactions on Signal Processing 08/1998; · 2.63 Impact Factor
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ABSTRACT: We address the problem of joint Schur decomposition (JSD) of
several matrices. This problem is of great importance for many signal
processing applications such as sonar, biomedicine, and mobile
communications. We first present a least-squares (LS) approach for
computing the JSD. The LS approach is shown to coincide with that
proposed intuitively by Haardt et al. (1996), thus establishing the
optimality of their criterion in the least-squares sense. Following the
LS criterion, we then propose new Jacobi-like algorithms that extend and
improve the existing JSD algorithms. An application of the new JSD
algorithm to multidimensional harmonic retrieval is also presented
Acoustics, Speech and Signal Processing, 1998. Proceedings of the 1998 IEEE International Conference on; 06/1998 · 4.63 Impact Factor
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ABSTRACT: Passive localization of narrowband sources in the spherical coordinates (azimuth, elevation, and range) is considered. A new method which proceeds in two steps and uses only the second order statistics (SOS) of the observations collected from a centro-symmetric cross-array is introduced. The first step is a signal pre-processing which consists in the computation of some properly chosen spatial correlation sequences of the observed signal. The correlation coefficients are shown to be superimposed exponential sequences and their frequencies are nonlinear functions of azimuths, elevations and the ranges of the source signals. The second step consists in the estimation of the frequency components using the subspace rotation invariance (also known as ESPRIT and matrix pencils) technique. This method, however requires a correct parameter pairing (or eigenvalue association) to achieve a consistent estimation of the signal parameters. Several pairing techniques are considered. The source azimuths, elevations, and ranges are then calculated from the estimated frequency components. The effectiveness of the proposed method is illustrated by some numerical simulations.
Signals, Systems & Computers, 1997. Conference Record of the Thirty-First Asilomar Conference on; 12/1997
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ABSTRACT: A new signal processing method is developed for solving the multi-line fitting problem in a two dimensional image. We first reformulate the former problem in a special parameter estimation framework such that a first order or a second order polynomial phase signal structure is obtained. Then, the previously developed algorithms in that formalism can be exploited to produce accurate estimates for line parameters. The signal representation employed in this formulation can be generalized to handle both problems of line fitting (in which a set of binary valued discrete pixels is given) and straight edge detection (in which one starts with a grey scale image). A main advantage of the proposed method is its ability to estimate the parameters of parallel lines with different offsets which can not be handled by the sensor array processing technique introduced by Aghajan and Kailath (1993). Simulation results are presented to demonstrate the usefulness of the proposed method.
Signals, Systems & Computers, 1997. Conference Record of the Thirty-First Asilomar Conference on; 12/1997
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ABSTRACT: We present the concepts and some applications of the minimum noise
subspace (MNS) technique. The MNS technique has been first introduced as
a computationally efficient subspace technique which exploits a minimum
number of noise vectors for multichannel blind system identification. It
is shown that a noise subspace basis can be obtained in a parallel
structure from a set of tuples (combinations) of system outputs that
form a properly connected sequence (PCS). The technique of the MNS and
particularly the concept of PCS turn out to be powerful tools that can
be applied for number of array processing problems. To illustrate the
potential of this technique, we present three successful applications
related to the problems of blind system identification, source
localization, and array calibration respectively
Information, Communications and Signal Processing, 1997. ICICS., Proceedings of 1997 International Conference on; 10/1997
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ABSTRACT: We present a new subspace-based method for blind identification of multichannel finite impulse response (FIR) systems. Instead of assuming spatially white additive noise as commonly used, we consider the case where the noise spatial covariance matrix is unknown. We show how a standard subspace method can be simply modified so that the channel estimate does not depend on the zero-lag correlation coefficient of the observation vector and, thus, is independent of the spatial covariance matrix of the additive noise.
IEEE Signal Processing Letters 06/1997; · 1.39 Impact Factor
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ABSTRACT: In this paper we present a new two-step maximum likelihood (TSML)
algorithm for estimating the impulse responses of multiple FIR channels
driven by an arbitrary unknown input. In Hua (1996), the original TSML
method was developed as a fast alternative to the direct maximum
likelihood approach. The TSML method exploits a novel orthogonal
complement (OC) matrix of the block Sylvester matrix. Despite its
high-SNR (signal-to-noise-ratio) efficiency, the TSML method is still
computationally expensive as it requires approximately O(q<sup>3</sup>N
<sup>3</sup>) flops, where N is the sample size and q is the number of
system outputs. The contribution in this paper consists in introducing a
new TSML method which exploits a non-redundant OC matrix whose column
vectors are shown to form a basis of the noise subspace. The new TSML
method is shown to require only O(q<sup>3</sup>N<sup>2</sup>) flops.
Like the original TSML method, the new TSML method requires no initial
estimates and is asymptotically (high SNR) optimum
Signal Processing Advances in Wireless Communications, 1997 First IEEE Signal Processing Workshop on; 05/1997
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ABSTRACT: The authors propose an algorithm for estimating the parameters of
multiple superimposed chirp signals in additive white noise. The
algorithm is based on a novel iterative approach that significantly
reduces the error propagation effect inherent in many existing
techniques. Moreover, it allows the estimation over a wider range of
phase parameter values while still maintaining a better estimation
accuracy
Electronics Letters 05/1997; · 0.96 Impact Factor
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ABSTRACT: This paper is concerned with the problem of estimating the parameters of multicomponent chirp signals from a finite number of noisy discrete time observations. A new transform called quadratic phase transform and its discrete version called discrete quadratic phase transform (DQPT) are introduced which jointly estimate the phase parameters of chirp signals. The DQPT is shown to result in maximum likelihood estimates for a single component chirp signal. A fast implementation of the DQPT is also proposed that results in substantial savings in the computational cost.
Signals, Systems and Computers, 1996. Conference Record of the Thirtieth Asilomar Conference on; 12/1996
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ABSTRACT: Second-order blind system identification has become an intense area of research. Recently, it has been shown that, by exploiting space diversity (i.e., multiple receivers) and/or time diversity (i.e., cyclostationarity) of communication signals, system identification using only the second order statistics (SOS) of the system output is possible. In this contribution, we propose to combine cyclostationarity and spatial diversity for the blind identification of p-input, q-output rational system. The basic idea consists in associating with each input signal a specific cyclo-frequency as a proper 'signature'. This will permit, in a first step, to separate the p input signals by selecting successively their respective cyclo-frequencies. In a second step, and thanks to the spatial diversity, we can estimate the channel transfer function using only the output SOS.
Signals, Systems and Computers, 1996. Conference Record of the Thirtieth Asilomar Conference on; 12/1996
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ABSTRACT: In this paper, we address the problem of the blind identification of linear-quadratic instantaneous mixture of statistically independent random variables. This problem consists in the identification of an unknown linear-quadratic transmission channel excited by temporally correlated and mutually independent source signals, using only statistical information on the observations received by an array of sensors. Herein we propose a new technique of blind identification of this non-linear mixture based on joint diagonalization of a set of data correlation matrices. Several numerical simulations are presented to demonstrate the effectiveness of the method in the case of a quadratic phase-coupling mixture
Acoustics, Speech, and Signal Processing, 1996. ICASSP-96. Conference Proceedings., 1996 IEEE International Conference on; 06/1996
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ABSTRACT: For detection and estimation of 2-D frequencies from a 2-D array
of data using a subspace decomposition method, one needs to construct a
block Hankel matrix. For reliable detection and estimation, the rank of
the block Hankel matrix should be made equal to the number of 2-D
frequencies inherent in the data in the absence of noise. In this work,
we provide the conditions for achieving the desired rank
IEEE Transactions on Signal Processing 05/1996; · 2.63 Impact Factor
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ABSTRACT: A phase fluorometer based on a low‐cost and versatile high‐frequency modulated light source and a fast gain‐modulated photomultiplier is described. The apparatus is particularly well‐suited to high‐sensitivity frequency‐domain fluorescence measurements requiring ultraviolet excitation. The system is very compact since it features a directly modulated light source, a miniature photomultiplier tube, and an rf synthesizer on a PC board. Equipped with a suitable fiber optic probe sensor, the device has potential as a portable unit for a wide range of remote sensing applications. The lamp can be modulated at frequencies up to 120 MHz and the phase fluorometer has been tested at up to 70 MHz with a range of fluorescent lifetime standards containing quinine sulfate quenched with sodium chloride. © 1996 American Institute of Physics.
Review of Scientific Instruments 02/1996; · 1.37 Impact Factor
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ABSTRACT: An exact and most revealing expression of the high signal-to-noise
(SNR) first-order perturbation variance of the single 2D frequency
estimate using the matrix enhancement and matrix pencil (MEMP) method is
provided. This expression is a general form consistent with several
previously reported expressions for the 1D frequency case. Based on this
expression, the statistical efficiency of the MEMP method is discussed.
The optimum efficiency of the MEMP method is shown to be achieved by its
1D specialized version
IEEE Transactions on Signal Processing 06/1995; · 2.63 Impact Factor
