Showing papers in "Journal of The Franklin Institute-engineering and Applied Mathematics in 2008"
TL;DR: The historical context of early research is outlined and new directions for future research in the exciting interplay between electromagnetic propagation, signal processing, and knowledge-based reasoning algorithms are provided.
Abstract: Through-wall imaging approaches are highly desirable for a range of applications including police, fire and rescue, first responder, and military applications. The ultimate desire of such systems is to provide detailed information in areas that cannot be seen through conventional measures. Borrowing from successes in geological and medical imaging environments, researchers have attempted to apply radio frequency (RF) and other sensing modes to penetrate wall materials and optimally estimate the content and structure of rooms and buildings. There are many propagation differences that provide unique challenges that must be addressed to make through-wall penetration sensors operationally viable. This paper outlines the historical context of early research and provides new directions for future research in the exciting interplay between electromagnetic propagation, signal processing, and knowledge-based reasoning algorithms.
240 citations
TL;DR: An integrated approach of multi-attribute utility theory (MAUT) and linear programming (LP) is proposed for rating and choosing the best suppliers and defining the optimum order quantities among selected ones in order to maximize total additive utility.
Abstract: Supplier selection is a complex multi-criteria problem including both quantitative and qualitative factors. In order to select the best suppliers it is necessary to make a trade-off between these factors, some of which may be in conflict and may also be uncertain. In this problem if suppliers have capacity or other different constraints, two problems will exist: which suppliers are best and how much should be purchased from each selected supplier. In this paper an integrated approach of multi-attribute utility theory (MAUT) and linear programming (LP) is proposed for rating and choosing the best suppliers and defining the optimum order quantities among selected ones in order to maximize total additive utility. A numerical example is proposed to illustrate an application of the proposed method.
172 citations
TL;DR: It is found that chaos exists in the fractional order unified system with order less than 3.76 and the lowest order the authors found to have chaos in this system is 2.76.
Abstract: The chaotic behaviors in the fractional order unified system are numerically investigated. By utilizing the fractional calculus techniques, we found that chaos exists in the fractional order unified system with order less than 3. The lowest order we found to have chaos in this system is 2.76. Chaos synchronization of the fractional order unified system is theoretically and numerically studied using the one-way coupling method. The suitable conditions for achieving synchronization of the fractional order differential system are derived by using the Laplace transform theory. It is noticed that the time required for achieving synchronization of the drive system and the response system and the synchronization effect sensitively depend on the coupling strength. Numerical simulations are performed to verify the theoretical analysis.
158 citations
TL;DR: Image fusion techniques for combining synthetic aperture radar images acquired from multiple locations along two sides of an enclosed structure are presented and results are provided which demonstrate the improved performance of the multiple location scheme compared to operation from a single vantage point.
Abstract: The presence of significant multipath propagation and heavy clutter in indoor environments imposes severe limitations on imaging through walls, rendering through-the-wall radar imaging a difficult and complex proposition. It is highly desirable to properly interpret the radar images and determine the contents of the indoor scene with a high level of confidence. Data collected from multiple vantage points around a structure can be used to improve imaging visibility into the indoor scene, which, in turn, enhances indoor target detection and localization. In this paper, we consider multi-location radar imaging. Image fusion techniques for combining synthetic aperture radar images acquired from multiple locations along two sides of an enclosed structure are presented. Supporting results, based on real-data collected in a semi-controlled laboratory environment, are provided which demonstrate the improved performance of the multiple location scheme compared to operation from a single vantage point.
124 citations
TL;DR: This paper presents an effective quadratic time–frequency S-method-based approach in conjunction with the Viterbi algorithm to extract m-D features and contributes additional experimental m- D data and analysis, which should help in developing a better picture of the human gait m-d research and its applications to indoor and outdoor imaging and automatic gait recognition systems.
Abstract: In many cases, a target or a structure on a target may have micro-motions, such as vibrations or rotations. Micro-motions of structures on a target may introduce frequency modulation on the returned radar signal and generate sidebands on the Doppler frequency shift of the target's body. The modulation due to micro-motion is called the micro-Doppler (m-D) phenomenon. In this paper, we present an effective quadratic time–frequency S-method-based approach in conjunction with the Viterbi algorithm to extract m-D features. For target recognition applications, mainly those in military surveillance and reconnaissance operations, m-D features have to be extracted quickly so that they can be used for real-time target identification. The S-method is computationally simple, requiring only slight modifications to the existing Fourier transform-based algorithm. The effectiveness of the S-method in extracting m-D features is demonstrated through the application to indoor and outdoor experimental data sets such as rotating fan and human gait. The Viterbi algorithm for the instantaneous frequency estimation is used to enhance the weak human m-D features in relatively high noise environments. As such, this paper contributes additional experimental m-D data and analysis, which should help in developing a better picture of the human gait m-D research and its applications to indoor and outdoor imaging and automatic gait recognition systems.
121 citations
TL;DR: The nonlinear simulation results show that optimally located STATCOM improves the transient stability and coordinated design of STATCOM-based controller and PSSs improve greatly the system damping.
Abstract: The optimal location of a static synchronous compensator (STATCOM) and its coordinated design with power system stabilizers (PSSs) for power system stability improvement are presented in this paper First, the location of STATCOM to improve transient stability is formulated as an optimization problem and particle swarm optimization (PSO) is employed to search for its optimal location Then, coordinated design problem of STATCOM-based controller with multiple PSS is formulated as an optimization problem and optimal controller parameters are obtained using PSO A two-area test system is used to show the effectiveness of the proposed approach for determining the optimal location and controller parameters for power system stability improvement The nonlinear simulation results show that optimally located STATCOM improves the transient stability and coordinated design of STATCOM-based controller and PSSs improve greatly the system damping Finally, the coordinated design problem is extended to a four-machine two-area system and the results show that the inter-area and local modes of oscillations are well damped with the proposed PSO-optimized controllers
120 citations
TL;DR: The topics discussed include the micro-Doppler characteristics of humans, the azimuth, elevation and range tracking of humans using Doppler, spatial and frequency diversity, the effect of walls, and the characteristics of dynamic clutters from non-humans.
Abstract: In this paper, the principles of Doppler processing to detect and track human movers in indoor environments are presented. The topics discussed include the micro-Doppler characteristics of humans, the azimuth, elevation and range tracking of humans using Doppler, spatial and frequency diversity, the effect of walls, and the characteristics of dynamic clutters from non-humans. The studies are supported by simulation and measurement results.
116 citations
TL;DR: Manual segmentations of the blood-vessel structure for all images in the ARIA and STARE datasets were obtained by a retinal image interpretation expert and were taken to be the authors' gold standards.
Abstract: We employed multiscale line operators (MSLO) in order to segment blood vessels in digital fundus images. Separately, a median filter technique was used in order to provide results that were compared to those of the MSLO. The green channel of the colour image was used, and both sets of results were further enhanced by subsequently employing a simple “randomly seeded” region-growing algorithm. We applied this approach to two sets of retinal images, namely, the ARIA (www.eyecharity.com/aria_online/) and STARE (www.ces.clemson.edu/∼ahoover/stare/) retinal image archives. The ARIA dataset contained colour fundus images from healthy subjects, diabetic subjects, and age-related macular degeneration (AMD) subjects. Similarly, the STARE dataset contained images from both “normal” (i.e., healthy) and “abnormal” (i.e., diseased) eyes. Manual segmentations of the blood-vessel structure for all images in the ARIA and STARE datasets were obtained by a retinal image interpretation expert. These images were then taken to be our gold standards. Receiver–operator characteristic (ROC) curves were determined and the areas under the ROC curve (AZ) were obtained. A large increase in efficiency for our MSLO algorithm was observed for the entire datasets (ARIA AZ=0.899; STARE AZ=0.953) compared to basic thresholding alone (ARIA AZ=0.608; STARE AZ=0.753). Interestingly, the simple median filter algorithm followed by region growing also performed well (ARIA AZ=0.888; STARE AZ=0.947). Our results compared favourably to those results of previous segmentation procedures for the STARE dataset. As expected, the best results were found for the healthy control group for ARIA and for the normal subjects for STARE.
95 citations
TL;DR: Several simple sufficient conditions checking the global exponential stability and the existence of periodic solutions are obtained for the neural networks and the estimation for exponential convergence rate index is proposed.
Abstract: In this paper, the discrete-time fuzzy cellular neural network with variable delays and impulses is considered. Based on M -matrix theory and analytic methods, several simple sufficient conditions checking the global exponential stability and the existence of periodic solutions are obtained for the neural networks. Moreover, the estimation for exponential convergence rate index is proposed. The obtained results show that the stability and periodic solutions still remain under certain impulsive perturbations for the neural network with stable equilibrium point and periodic solutions. Some examples with simulations are given to show the effectiveness of the obtained results.
90 citations
TL;DR: The design of an adaptive sliding mode control (SMC) scheme is proposed in this paper for stabilizing a class of dynamic systems with matched and mismatched perturbations.
Abstract: The design of an adaptive sliding mode control (SMC) scheme is proposed in this paper for stabilizing a class of dynamic systems with matched and mismatched perturbations. Two methods for designing a novel sliding surface function are introduced first. By utilizing a pseudocontrol input in the sliding surface function, one cannot only suppress the mismatched perturbations in the sliding mode, but also obtain the property of asymptotical stability. Then a sliding mode controller is designed to drive the controlled systems to the designated sliding surface in a finite time. Adaptive mechanism is also embedded in the controller as well as in the sliding surface function designed from the second method to overcome the perturbations, so that the informations of upper bound of perturbations are not required. An application of flight control and experimental results of controlling a servomotor are also given for demonstrating the applicability of the proposed control scheme.
89 citations
TL;DR: A practical matrix method is presented to find an approximate solution of high-order linear Fredholm integro-differential equations with constant coefficients under the initial-boundary conditions in terms of Taylor polynomials.
Abstract: In this study, a practical matrix method is presented to find an approximate solution of high-order linear Fredholm integro-differential equations with constant coefficients under the initial-boundary conditions in terms of Taylor polynomials. The method converts the integro-differential equation to a matrix equation, which corresponds to a system of linear algebraic equations. Error analysis and illustrative examples are included to demonstrate the validity and applicability of the technique.
TL;DR: An adaptive feedback controller is designed to achieve complete synchronization of unidirectionally coupled delayed neural networks with stochastic perturbation to investigate the globally almost surely asymptotical stability of the error dynamical system.
Abstract: In this paper, an adaptive feedback controller is designed to achieve complete synchronization of unidirectionally coupled delayed neural networks with stochastic perturbation. LaSalle-type invariance principle for stochastic differential delay equations is employed to investigate the globally almost surely asymptotical stability of the error dynamical system. An example and numerical simulation are given to demonstrate the effectiveness of the theory results.
TL;DR: Noise radar technology combined with modern signal processing approaches is indeed a viable technique for covert high-resolution imaging of obscured stationary and moving targets and issues related to locating, detection, and tracking humans behind walls are addressed.
Abstract: This paper examines the results of our research on the use of ultrawideband noise waveforms for imaging objects behind walls. The advantages of using thermally generated noise as a probing signal are introduced. The technique of heterodyne correlation used to inject coherence in the random noise probing signal and to collapse the wideband reflected signal into a single frequency are presented. Central to successful imaging through building walls is the characterization of the wideband propagation properties of wall materials and these are discussed. The basic concepts of synthetic aperture radar image formation using noise waveforms and the unique problems associated with the random nature of the transmit waveform are analyzed. We also address issues related to locating, detection, and tracking humans behind walls, using new tools for human activity characterization, namely the Hilbert-Huang Transform approach. The results indicate that noise radar technology combined with modern signal processing approaches is indeed a viable technique for covert high-resolution imaging of obscured stationary and moving targets.
TL;DR: A vector comparison system whose solution is finite-time stable is constructed and related to the stability properties of a nonlinear dynamical system using a vector comparison principle to design a universal decentralized finite- time stabilizer for large-scale dynamical systems that is robust against full modeling uncertainty.
Abstract: Finite-time stability involves dynamical systems whose trajectories converge to an equilibrium state in finite time. Since finite-time convergence implies nonuniqueness of system solutions in reverse time, such systems possess non-Lipschitzian dynamics. Sufficient conditions for finite-time stability have been developed in the literature using Holder continuous Lyapunov functions. In this paper, we develop a general framework for finite-time stability analysis based on vector Lyapunov functions. Specifically, we construct a vector comparison system whose solution is finite-time stable and relate this finite-time stability property to the stability properties of a nonlinear dynamical system using a vector comparison principle. Furthermore, we design a universal decentralized finite-time stabilizer for large-scale dynamical systems that is robust against full modeling uncertainty. Finally, we present two numerical examples for finite-time stabilization involving a large-scale dynamical system and a combustion control system.
TL;DR: System design challenges and issues with sensing through walls at different standoff distances and wall types are presented through lessons learned and results from modeling and simulations performed by the Army Research Laboratory.
Abstract: This paper presents system design challenges and issues with sensing through walls at different standoff distances and wall types. Efforts for developing sense through the wall (STTW) systems, such as those undertaken by the US Army Technology Objective (ATO) program, aim at providing the soldier with situational awareness information before breaching a building in a military operations in urban terrain (MOUT) environment. STTW capabilities also support law enforcement and search and rescue applications. Since 2002, extensive evaluations of STTW technologies, most notably those performed by the Communications Electronics, Research, Development and Engineering Center (CERDEC) Intelligence and Information Warfare Directorate (I2WD), have been made to determine which technology could be the most viable solution. After conducting comprehensive studies, I2WD initiated several Phase I efforts and Phase II efforts. The purpose behind both efforts was to develop various STTW technology demonstrators under a 5 year ATO. Many lessons learned during the development of Phase I systems were incorporated into the considerations for Phase II developments. This paper discusses design challenges and issues with sensing through walls at different standoff distances and wall types through lessons learned and results from modeling and simulations performed by the Army Research Laboratory.
TL;DR: A new robust stability condition is proposed first for the sliding mode dynamics, then a sliding mode observer is designed, based on which an observer-based controller is synthesized by using the SMC theory combined with the reaching law technique.
Abstract: In this paper, the observer-based sliding mode control (SMC) problem is investigated for a class of uncertain nonlinear neutral delay systems. A new robust stability condition is proposed first for the sliding mode dynamics, then a sliding mode observer is designed, based on which an observer-based controller is synthesized by using the SMC theory combined with the reaching law technique. Then, a sufficient condition of the asymptotic stability is proposed in terms of linear matrix inequality (LMI) for the overall closed-loop system composed of the observer dynamics and the state estimation error dynamics. Furthermore, the reachability problem is also discussed. It is shown that the proposed SMC scheme guarantees the reachability of the sliding surfaces defined in both the state estimate space and the state estimation error space, respectively. Finally, a numerical example is given to illustrate the feasibility of the proposed design scheme.
TL;DR: Time and space splitting techniques are applied to the Burgers' equation and the modified Burgers’ equation, and then the quintic B-spline collocation procedure is employed to approximate the resulting systems.
Abstract: Time and space splitting techniques are applied to the Burgers’ equation and the modified Burgers’ equation, and then the quintic B-spline collocation procedure is employed to approximate the resulting systems. Some numerical examples are studied to demonstrate the accuracy and efficiency of the proposed method. Comparisons with both analytical solutions and some published numerical results are done in computational section.
TL;DR: In this work, a new delay-dependent stability criterion of the system is derived in terms of LMI (linear matrix inequality), and the interior-point algorithm is utilized in this work to solve effectively the LMI as a convex optimization problem.
Abstract: In this paper, the problem of stability of uncertain cellular neural networks with discrete and distribute time-varying delays is considered. Based on the Lyapunov function method and convex optimization approach, a new delay-dependent stability criterion of the system is derived in terms of LMI (linear matrix inequality). In order to solve effectively the LMI as a convex optimization problem, the interior-point algorithm is utilized in this work. A numerical example is given to show the effectiveness of our results.
TL;DR: Bohnenblust–Karlin's fixed point theorem combined with a strongly continuous operator semigroup is used to establish a sufficient condition for the controllability of semilinear mixed Volterra–Fredholm-type integro-differential inclusions in Banach spaces.
Abstract: The paper establishes a sufficient condition for the controllability of semilinear mixed Volterra–Fredholm-type integro-differential inclusions in Banach spaces. We use Bohnenblust–Karlin's fixed point theorem combined with a strongly continuous operator semigroup. Our main condition (A5) only depends upon the local properties of multivalued map on a bounded set. An example is also given to illustrate our main results.
TL;DR: Bicausal BG modelling proves to be a unified approach for sensor placement from the FDI and FTC viewpoint, identification of hardware redundancies for system reconfiguration, generation of fault indicators, estimation of fault parameters for fault accommodation, inversion of systems and actuator sizing for FTC, etc.
Abstract: Model-based fault detection and isolation (FDI) requires an analytical system model from which fault indicators can be derived by assigning proper computational causalities. Many bond graph (BG) model-based techniques for FDI have been developed in recent past. Furthermore, many other advances have been made in the field of control engineering applications of BG modelling. Supervision systems not only perform FDI, but also take the necessary steps for fault accommodation. Fault accommodation is done either through system reconfiguration or through fault tolerant control (FTC). In this paper, it is shown that bicausal BG modelling proves to be a unified approach for sensor placement from the FDI and FTC viewpoint, identification of hardware redundancies for system reconfiguration, generation of fault indicators, estimation of fault parameters for fault accommodation, inversion of systems and actuator sizing for FTC, etc. It is shown that the use of bicausalled BG helps to integrate many of the recently developed advances made in the field of control engineering into development of complex supervision systems.
TL;DR: This paper tackles the diagnosis problem in nonlinear systems under failure using differential algebra and numerical simulations of these examples are presented to illustrate the effectiveness of the suggested approach.
Abstract: In this paper we tackle the diagnosis problem in nonlinear systems under failure using differential algebra. Three examples are presented in order to apply the proposed methodology. Numerical simulations of these examples are presented to illustrate the effectiveness of the suggested approach.
TL;DR: It is demonstrated that inducing a relaxation type of dynamics in the models contributes to their successful generation of ECG like signals, and an interesting affinity is found, which associates the present models with a version of the well-known practical Wien Bridge oscillator.
Abstract: The present article deals with the development of an oscillatory model, which generates waveforms corresponding to ECG patterns. The present oscillatory system relies on coupling of oscillators derived from the famous VDP oscillator. We demonstrate that inducing a relaxation type of dynamics in the models contributes to their successful generation of ECG like signals. Furthermore, an interesting affinity is found, which associates the present models with a version of the well-known practical Wien Bridge oscillator. The presently discussed system relies on coupled elementary oscillator units. The present coupling is due to merely two units. The model, however, is likely to become even more realistic by coupling in the same manner an assembly of relatively many oscillators.
TL;DR: Time- and frequency-domain techniques for measuring the electromagnetic properties of construction materials in the UWB frequency range are examined and the modified model is helpful in estimating the link power budget.
Abstract: This paper addresses the potentials of ultra-wideband (UWB) through-wall imaging radars compared with conventional narrowband systems. The challenges that limit the utilization of high precision UWB systems are examined with the aim of mitigating them. These challenges include multi-path, pulse dispersion, and antenna effects on the pulse shape due to angles of transmission and arrival. The propagation of UWB signals through walls is a crucial factor in determining the success of UWB radar technology. UWB signals, when propagating through walls, not only suffer attenuation but also distortion due to dispersive properties of the walls. This paper examines time- and frequency-domain techniques for measuring the electromagnetic properties of construction materials in the UWB frequency range. The measured parameters provide valuable insights in appreciating the capabilities and limitations of the UWB technology. Special attention is paid to time gating as a mean to extract the direct-path signal from the multi-path components. Both single-pass and multi-pass models are discussed. Multi-pass models account for the multiple reflections within the wall while the single-pass model assumes the possibility of gating out a single transmission. The partition-dependent narrowband propagation model is modified to account for the ultra-wide bandwidth of the signal. The paper illustrates the application of the modified model in indoor environments. The modified model is helpful in estimating the link power budget. It is also useful in studying the performance of UWB systems for indoor communication and positioning applications.
TL;DR: This study develops a fuzzy multi-Objective linear programming (FMOLP) model for solving the multi-objective no-wait flow shop scheduling problem in a fuzzy environment that yields a compromised solution and the decision maker's overall levels of satisfaction.
Abstract: This study develops a fuzzy multi-objective linear programming (FMOLP) model for solving the multi-objective no-wait flow shop scheduling problem in a fuzzy environment. The proposed model attempts to simultaneously minimize the weighted mean completion time and the weighted mean earliness. A numerical example demonstrates the feasibility of applying the proposed model to no-wait flow shop scheduling problem. The proposed model yields a compromised solution and the decision maker's overall levels of satisfaction.
TL;DR: It is established that sufficient conditions for the existence of the mixed H 2 / H ∞ controller and the associated performance upper bound could be cast in the form of linear matrix inequalities.
Abstract: In this paper, we investigate a class of linear continuous-time systems with Markovian jump parameters. An integral part of the system dynamics is a delayed state with time-varying and bounded delays. The jumping parameters are modeled as a continuous-time, discrete-state Markov process. Employing norm-bounded parametric uncertainties and utilizing the second-method of Lyapunov, we examine the problem of designing a mixed H 2 / H ∞ controller which minimizes a quadratic H 2 performance measure while satisfying a prescribed H ∞ -norm bound on the closed-loop system. It is established that sufficient conditions for the existence of the mixed H 2 / H ∞ controller and the associated performance upper bound could be cast in the form of linear matrix inequalities.
TL;DR: By exploring the parameter-dependence condition on disturbance into the controller design algorithms based on linear matrix inequalities (LMIs), it is showed that a better performance can be achieved than simply considering it as an external disturbance.
Abstract: This paper presents a gain-scheduled control approach for the vertical takeoff and landing aircraft. The non-linear aircraft dynamics are formulated as a linear parameter varying (LPV) system with external parameter-dependent disturbance, which arisen from the equilibrating between gravity force and nozzles thrust. The disturbance is dependent on the system varying parameter, roll angle, and a constant parameter denoting the normalized gravity force. The controllers are designed in terms of mixed optimization of H ∞ performance for disturbance attenuation and relative stability for tracking position command in pitch-yaw plane. The characteristics of the parameter-dependent disturbance are described by an equality condition with a defined annihilation matrix. By exploring the parameter-dependence condition on disturbance into the controller design algorithms based on linear matrix inequalities (LMIs), it is showed that a better performance can be achieved than simply considering it as an external disturbance. The design results are demonstrated by time response simulations.
TL;DR: An efficient technique based on clonal selection algorithm (CLONALG) for linear antenna array pattern synthesis with null steering by controlling only the element excitation phases is presented.
Abstract: In this paper, an efficient technique based on clonal selection algorithm (CLONALG) for linear antenna array pattern synthesis with null steering by controlling only the element excitation phases is presented. The CLONALG is an evolutionary computation method inspired by the clonal selection principle of human immune system. To show the versatility and flexibility of the proposed CLONALG, some examples of Chebyshev array pattern with the imposed single, multiple and broad nulls are given. The sensitivity of the nulling patterns due to small variations of the element phases is also investigated.
TL;DR: It is shown that while the increase of the design parameters may be desirable to achieve a good transient performance, it harms the control signal as this increase introduces large high-frequency components due to the numerical errors.
Abstract: The backstepping-based adaptive tuning functions design is a control-scheme for uncertain systems that ensures reasonably good stability and performance properties of the closed loop. The complexity of the controller makes inevitable the use of digital computers to perform the calculation of the control signal. This paper addresses the issue of the numerical sensitivity of this control scheme. It is shown that while the increase of the design parameters may be desirable to achieve a good transient performance, it harms the control signal as this increase introduces large high-frequency components due to the numerical errors. The presented results suggest that it is necessary a certain compromise between the choice of the design parameters and the numerical precision of the tools involved in the control design. This compromise can be quantified by explicit expressions.
TL;DR: This paper presents the optimal LQG controller for linear systems with unknown parameters obtained using the separation principle, whose applicability to the considered problem is substantiated.
Abstract: This paper presents the optimal LQG controller for linear systems with unknown parameters. The optimal controller equations are obtained using the separation principle, whose applicability to the considered problem is substantiated. Performance of the obtained optimal controller is verified in the illustrative example against the conventional LQG controller that is optimal for linear systems with known parameters. Simulation graphs verifying overall performance and computational accuracy of the designed optimal controller are included.
TL;DR: Close-form expressions for the symbol error probability of decode and forward cooperative diversity systems, when operating over independent but not necessarily identically distributed Nakagami-m fading channels, are provided.
Abstract: In this paper, we provide closed-form expressions for the symbol error probability of decode and forward cooperative diversity systems, when operating over independent but not necessarily identically distributed Nakagami-m fading channels. The results hold for arbitrary number of relays, and refer to the M-ary QAM and M-ary PSK modulations.