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System Theory, 2006. SSST '06. Proceeding of the Thirty-Eighth Southeastern Symposium on

Date 5-7 March 2006

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Displaying Results 1 - 25 of 110
  • Considering double frequency terms from phase detectors in synchronous master-slave networks

    Page(s): 453 - 456
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB) |  | HTML iconHTML  

    The main strategy used for distributing clock information along telecommunication synchronous networks is the master-slave (M-S), i.e., a well determined node provides a precise clock signal distributed to the other nodes that need to recover it using phase-locked loops (PLL). In spite of the PLLs being equipped with low pass filters, the recovered clock signal always contains second harmonic components that appear as phase jitter. Here we model how the amplitude of this double frequency jitter depends on PLL parameters for different types of topological arrangement of the M-S network View full abstract»

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  • Modeling and adaptive output feedback control for a flexible structure

    Page(s): 502 - 506
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    This paper presents the adaptive control scheme for vibration control problem. The dynamic model of the flexible cantilever beam using finite element modeling is derived. The adaptive control using output feedback for output tracking is developed to improve the tracking performance. The proposed adaptive control is numerically verified on a flexible beam model, showing that it has satisfactory performance and robustness in vibration suppression with respect to the system disturbance and parameter variation. Satisfactory simulation results verify that the effectiveness of proposed adaptive control scheme View full abstract»

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  • Optimal Vibration Suppression of a Flexible Structure Using Piezoceramic Actuators

    Page(s): 10 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB) |  | HTML iconHTML  

    This paper presents the optimal linear quadratic regulator control scheme for vibration suppression of a flexible structure using piezoceramic actuators. The PZT patches are bonded near the fixed end of flexible steel cantilever beam. The dynamic model of the flexible steel cantilever beam is derived. The optimal linear quadratic regulator control is experimentally verified on a flexible beam using xPC Target real-time system, showing that it has satisfactory performance in vibration suppression. Experimental results demonstrate that the proposed methods achieve effective vibration suppression results View full abstract»

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  • A real time automatic sign interpretation system for operator assistance

    Page(s): 11 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    This paper addresses the design of a system for automatic sign interpretation (ASI) with specific applications to road sign imagery for driver assistance. Other applications include intelligent highway systems, and sign inventory systems for transportation departments. This paper extends past work in which a prototype system for the detection of road signs was designed and tested on a limited set of images and sign types. The specific enhancements reported in this paper include the following: (i) enhanced dual-band spectral analysis in the hue-saturation-intensity (HSI) and RGB domains, (ii) the introduction of a relational analysis scheme to form the identification stage, (iii) the creation of a larger database of road sign images encompassing all road sign types encountered in the United States, and (iv) testing under adverse conditions with non-ideal road sign images. The proposed method can be adapted for implementation in real time as this was one of the design considerations. The human cognition of signs under adverse conditions is one of the basic research questions that is yet to be answered. The ASI system designed help to shed some light on the human cognitive process View full abstract»

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  • Study of pointing maneuvers for a spacecraft virtual structure formation

    Page(s): 99 - 103
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (185 KB) |  | HTML iconHTML  

    This paper describes a complex virtual simulation of three spacecraft in tight formation. Using rotational kinematics and rigid body dynamics, the virtual spacecraft structure is designed to perform calculated and synchronized maneuvers to point the formation in a desired direction. Modern control theories are applied to maintain the integrity of the tight formation and minimize errors as the entire system reorients to tracks the target object with its virtual boresight. This process involves determining the required independent orientation (Eulerian) angles using the target vector coordinates with respect to the initial orientation of the formation View full abstract»

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  • ASA: an adaptive space allocation algorithm for cache management in multi-level cache hierarchy

    Page(s): 524 - 528
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (146 KB) |  | HTML iconHTML  

    Multi-level cache hierarchies are widely used in high-performance storage systems to improve I/O performance. However, traditional cache management algorithms are not suited well for such cache organizations. Recently proposed exclusive caching works well with single or multiple-client, low-correlated workloads, but suffers serious performance degradation with multiple-client, high-correlated workloads. In this paper, we propose a new cache space management algorithm, Adaptive Space Allocation (ASA)7 which implements both exclusive and inclusive caching and manages storage caches by providing optimal inclusive cache space adaptively according to the characteristic of input workloads. Ours results show that ASA increases the cumulative cache hit ratios dramatically for both high and low-correlated workloads View full abstract»

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  • Formal Architectural Analysis of Complex Computer Systems

    Page(s): 29 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB) |  | HTML iconHTML  

    Today, most computer systems are designed using off the shelf hardware and software components. This significantly accelerates the system development process but does not guarantee the quality of the finished product. In this paper we consider quality as a compliance of the designed computer system with the requirements of potential users. We assume that there are limited cost and hardware/software restrictions during the development process of a computer system. To measure the quality of the developed system architecture we use a set of specified effectiveness criteria View full abstract»

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  • A general theory of set-point regulation for MIM0 linear dynamical systems; the case of state set-point regulation

    Page(s): 27 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB) |  | HTML iconHTML  

    This paper is the first in a series of papers in which a general mathematical theory of, and control design algorithms for, multivariable set-point regulation problems is developed for MIMO linear dynamical systems. In this paper, the class of "state" set-point regulation problems is considered View full abstract»

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  • A general theory of set-point regulation for MIMO linear dynamical systems; the case of output set-point regulation ["pointing control"] part 1: precise formulation as a subspace-stabilization problem

    Page(s): 38 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (217 KB) |  | HTML iconHTML  

    This paper is the second in a series of papers in which a general mathematical theory of, and control design algorithms for, multivariable set-point regulation problems for MIMO linear dynamical systems is developed. In this paper, the class of "output" setpoint regulation problems is considered and a unique formulation of the (output set-point) regulation problem as a "subspace-stabilization control" problem is developed View full abstract»

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  • A general theory of set-point regulation for MIMO linear dynamical systems; the case of output set-point regulation ["pointing control"] part II: precise solution as a subspace-stabilization problem

    Page(s): 48 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    This paper is a continuation of an earlier paper in which a general, multivariable output set-point regulation problem for a broad class of MIMO linear dynamic systems was formulated as a novel "subspace-stabilization control" problem. In this paper that formulation of the problem is used to develop a rather general linear-algebraic theory of, and an effective control-design algorithm for, multivariable output set-point regulation problems View full abstract»

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  • Performance Analysis of Discrete-Time Erlang Loss System

    Page(s): 54 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    We study a discrete-time Geom/Geom/c/c Erlang loss system. In this queueing system, we give the function equation that the generating function of the number of customers satisfies in steady-state system, and get the formula of stationary mean queue length. Furthermore, we derive recursive method to compute stationary queue length probability and loss probability. Finally, using a numerical example, we exemplify the relation between loss probability, the mean number of customers and various parameters View full abstract»

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  • An approximation of the pull-out frequency parameter in a second-order PLL

    Page(s): 75 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB) |  | HTML iconHTML  

    Consider a phase-lock loop (PLL) that is phase locked to a constant frequency reference. Under this condition, the PLL pull-out frequency is defined as the largest input reference frequency step that can be applied without the PLL slipping one or more cycles. The application of an input reference frequency step larger (alternatively, smaller) than the pull-out frequency will (alternatively, will not) cause the loop to break frequency lock and slip one or more cycles. In general, due to the complex nonlinear nature of the dynamics involved, the PLL pull-out frequency can only be approximated. For the second-order PLL containing a proportional-plus-integral loop filter and sinusoidal phase detector, only simulation results have been published, and a formula useful for approximating the pull-out frequency has been curve fitted to these results (an approximation to the pull-out frequency has not been derived analytically). In what follows, an approximation is derived to the pull-out frequency for the above-mentioned PLL. First, with the aid of a phase plane, the pull-out frequency is related to a phase plane separatrix. Next, an asymptotic approximation is developed for this separatrix. This is used in an integral of the nonlinear PLL equation to develop an approximation to the pullout frequency. The analytical results are shown to compare very favorably with numerical simulations View full abstract»

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  • A spectrum modification technique for embedding data in images

    Page(s): 231 - 234
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (141 KB) |  | HTML iconHTML  

    We propose a method of embedding data in images for secure communication of covert or sensitive information. The method employs an extension of the recent technique of imperceptible embedding in audio signals by inserting tones at perceptually masked frequencies. Instead of detecting visually masked frequencies in two-dimensions, a simpler approach was used by converting an image to a one-dimensional signal. Using the well-established audio frequency masking procedure, audibly masked frequencies at a chosen sampling frequency were determined for each segment or block. Embedding of given data was carried out by modifying the spectral power at a pair of commonly occurring masked frequencies. Preliminary results of embedding 1024 bits of random data in a 256 times 256 pixel black-and-white image show that the spectrum modification technique is viable and simple to process. The technique is useful for hiding a small amount of information on identification card images, credit card logos, etc. Payload can be increased at the cost of an acceptable level of image degradation View full abstract»

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  • Engineering System Theory: A New Idea on Artificial Systems

    Page(s): 67 - 71
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (203 KB) |  | HTML iconHTML  

    A new idea on "engineering system theory" is proposed and outlined in the paper. Both the characteristics and evolutional law of artificial systems is described concisely. Furthermore, some constructive suggestions on the analysis and design of the artificial system are also made View full abstract»

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  • Research on system theory of integrated numerical control

    Page(s): 6 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (381 KB) |  | HTML iconHTML  

    This paper introduces and analyses the system theory of INC (integrated/intelligent numerical control), which is a new type of CNC (computer numerical control) system. First it has a brief introduction of INC. And it makes a comparison and analysis about INC, ONC and DNC and describes some important characteristics of INC. Further it emphasizes on discussing the key technologies of INC, which includes CADoCNC (CAD technology oriented to CNC), CAPPoCNC (CAPP oriented to CNC), CNCbCAD&CNC (CNC technology based on CAD&CAPP). It discusses the basic theory of them. Finally, a case is given to illustrate how to realize INC in the engineering area View full abstract»

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  • Robust and Adaptable Job Shop Scheduling Using Multiple Agents: Further Experimental Justification

    Page(s): 77 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1125 KB) |  | HTML iconHTML  

    The work presented in this paper is a continuation for efforts to devise a complete multi-agent framework for dynamic job shop scheduling, which considers robustness and adaptability. Previous work reported in N. Liu, et al. (2004) and N. Liu et al. (2005), gave a theoretical basis and experimental justification of the framework. Computational experiments on dynamic job arrivals were provided for the experimental justification. It was concluded that the framework worked very good and stably both in static job shop scheduling and dynamic job shop scheduling with unpredictable job arrivals, and robustly in dynamic job shop scheduling with unpredictable job arrivals. The framework inherits the advantages of decentralized models, such as flexibility, robustness, and high fault tolerance. The framework is actually a job dispatching procedure - a completely reactive scheduling approach combining real time decision making with predictive decision-making based on optimization. It can solve various disruptions as flexibly as dispatching rules. This paper presents a further experimental justification of the arguments about the framework using computational experiments on processing time variations. By computational results, it is to show the effectiveness and efficiency of the framework and the effects of making full use of available information of disruptions on the framework View full abstract»

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  • Calibration of a pole-mounted camera using a neural network

    Page(s): 265 - 269
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    The intelligent soft arm control (ISAC) system is a robotic aid for the physically challenged. ISAC's current task is to feed the physically challenged. To accomplish this task ISAC needs to recognize the objects on the table, pick up the utensil it needs and bring it to the user's mouth. A camera is being used to recognize the objects on the table and a pair of cameras is being used to locate the user's mouth in real time. This report describes the calibration of the vision system dedicated to object recognition. The camera used in this system is mounted on a pole which is attached to the base of the robot. This setup makes the ISAC system compact as well as allowing the camera to view more than just one particular location, since it rotates with the base of the robot. Once an object is located in the image, the position of the object must be converted to robot coordinates so that the robot can use it. Unfortunately, the image plane is not parallel to the table in this setup. This causes the mapping from the image coordinates to the robot coordinates to be nonlinear. This nonlinearity was the motivation behind using a neural network to "learn" the mapping from image coordinates to robot coordinates View full abstract»

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  • Stiffness Matrix Analysis and Synthesis for Pre-Loaded Planar Structures

    Page(s): 87 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    The compliance/stiffness of a robotic mechanism is usually modeled by a 6 by 6 symmetric positive definite matrix at an equilibrium point using screw theory. When an external wrench is exerted on the mechanism and the mechanism moves away from its equilibrium, the modeled compliance/stiffness matrix becomes non-symmetric. In this article, the authors derive a non-symmetric stiffness matrix for a robotic mechanism and present a novel synthesis procedure for the desired non-symmetric stiffness matrix of a planar structure when the structure is not in equilibrium View full abstract»

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  • Maximum likelihood BPSK and QPSK classifier in fading environment using the EM algorithm

    Page(s): 313 - 317
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (179 KB) |  | HTML iconHTML  

    Modulation classification is to identify the modulation type of a received signal automatically. It is a promising technique that can increase the throughput of adaptive modulation systems such as IEEE 802.11 and HIPERLAN systems. While a variety of approaches have been proposed for modulation classification, most of them rely on the unrealistic assumption that the channel is additive white Gaussian noise channel. This paper presents an algorithm using hybrid likelihood ratio test for BPSK and QPSK classification in multipath fading environment. The unknown channel coefficients are first estimated blindly using the EM algorithm. The estimates are then used in likelihood ratio test for classification. Simulations show that the proposed classifier has high accuracy and is superior to the classifier that does not take the channel distortion into account. An added advantage of the proposed algorithm is that the maximum likelihood estimate of the channel coefficients can be used in equalization and data demodulation View full abstract»

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  • Comparison of adaptive systems for noise reduction in speech performance

    Page(s): 123 - 127
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB) |  | HTML iconHTML  

    An adaptive system is a well-known method for removing noise from noise-corrupted speech. The problem arises in many situations such as airplane cockpits and automobiles. The variable step size normalized least mean squares (VSS-NLMS) algorithm incorporating a variable step size parameter whose values are based on the ratio of signal-to-noise power has very good convergence speed and low steady-state misadjustment. This paper investigates the rate of convergence by the wavelet based LMS (WLMS) algorithm to the noise speech problem. Simulation results are presented to compare the performance of the variable step size NLMS algorithm, the wavelet based LMS Algorithm, and other commonly used fixed step size LMS algorithms View full abstract»

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  • Spatial focusing of time-reversed UWB electromagnetic waves in a hallway environment

    Page(s): 318 - 322
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (239 KB) |  | HTML iconHTML  

    Spatial focusing of time-reversed UWB electromagnetic waves is demonstrated in a hallway environment. Firstly, a general time domain channel model for the hallway environment has been built. This model takes into account the materials as well as the geometric configuration of the environment. Based on this model, spatial focusing of TR technique is investigated and simulation results show there is 10dB energy drop when the receiver is 1 m away from the intended receiver View full abstract»

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  • Optimal design of microelectromechanical systems via reversed polynomial programming

    Page(s): 137 - 138
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (211 KB) |  | HTML iconHTML  

    In this paper we describe an optimal design method for micro-electro-mechanical systems (MEMS). We observe that many MEMS device designs with a variety of design objects and constraints can be reformulated as reversed polynomial programs, which can be globally solved by, e.g., branch-and-bound methods; in consequence the optimal MEMS design can be obtained directly from specifications. In this paper, design optimization of a crab-leg resonator is formulated as a reversed polynomial program View full abstract»

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  • Kalman Filtering Based Chaotic System for Secure Communication

    Page(s): 109 - 112
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (186 KB) |  | HTML iconHTML  

    In this paper, a new chaos based secure communication system is proposed. In the proposed system, the process and measurement equations of the state space representation of Kalman filter are constructed based on the method which is used to generate chaotic sequence. The initial state vector for Kalman filtering algorithm is obtained using halving method of chaotic signal estimation. Then, the subsequent state vectors are estimated using Kalman filtering algorithm at every symbol duration. The performance of the proposed system is analyzed in additive white Gaussian noise (AWGN) environment. The simulation results show that the performance of the proposed system improves as the length of the state vector increases View full abstract»

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  • Interactive visualization tool for electrode placement and assessment of transthoracic defibrillation thresholds

    Page(s): 61 - 65
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (755 KB) |  | HTML iconHTML  

    In this paper, we describe the implementation of a scientific data visualization tool for rendering transthoracic defibrillation simulation results. The visualization tool includes a graphical user interface (GUI) that provides functionality for the interactive change of the shape, size and position of a defibrillator's electrodes. Also, an option for visualizing slices through the myocardium, such that the distribution of the magnitude of the electric field can be visually inspected is included in the tool. The goal of the tool is to enhance understanding of how electrode parameters relate to the change of the electric field values throughout the heart. The tool is significant in that it integrates simulation and visualization software, which previously required the execution of several independent software executables, into a single comprehensive software tool View full abstract»

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  • Detection of Physics-Based Ultra-Wideband Signals Using Generalized RAKE in Presence of Inter-Symbol Interference

    Page(s): 118 - 122
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB) |  | HTML iconHTML  

    The generalized rake receiver based on physics-based channel model is proposed for UWB outdoor application to estimate and compensate for the pulse distortion. The successive channel estimation is adopted to generate the per-path waveform as the template for the generalized rake receiver. The receiver can eliminate the effect of pulse distortion appearing in a lot of UWB channels. MMSE linear equalizer is used to handle intersymbol interference (ISI) for achieving high data rate View full abstract»

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